BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CERN//INDICO//EN
BEGIN:VEVENT
SUMMARY:Positivity bounds in Effective Field Theories
DTSTART;VALUE=DATE-TIME:20220725T070000Z
DTEND;VALUE=DATE-TIME:20220725T074500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-588@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Scott Melville ()\nhttps://indico.tpi.uni-jena.de/ev
ent/199/contributions/588/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/588/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Information theory and real space RG
DTSTART;VALUE=DATE-TIME:20220725T090000Z
DTEND;VALUE=DATE-TIME:20220725T094500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-590@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Zohar Ringel ()\nhttps://indico.tpi.uni-jena.de/even
t/199/contributions/590/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/590/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Precision calculation with FRG: the planar Bose gas as an example
DTSTART;VALUE=DATE-TIME:20220725T141500Z
DTEND;VALUE=DATE-TIME:20220725T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-595@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nicolas Dupuis ()\nhttps://indico.tpi.uni-jena.de/ev
ent/199/contributions/595/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/595/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The O(N) models in the vicinity of d=2
DTSTART;VALUE=DATE-TIME:20220728T090000Z
DTEND;VALUE=DATE-TIME:20220728T093000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-646@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Pawel Jakubczyk ()\nhttps://indico.tpi.uni-jena.de/e
vent/199/contributions/646/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/646/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Non-equilibrium Properties of Berezinskii-Kosterlitz-Thouless Phas
e Transitions
DTSTART;VALUE=DATE-TIME:20220728T093000Z
DTEND;VALUE=DATE-TIME:20220728T100000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-647@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Dante Kennes ()\nhttps://indico.tpi.uni-jena.de/even
t/199/contributions/647/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/647/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Information theoretic regulators for complex systems with multiple
notions of scale
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-683@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Adam Kline ()\nhttps://indico.tpi.uni-jena.de/event/
199/contributions/683/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/683/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional RG for strongly interacting Hubbard model'
DTSTART;VALUE=DATE-TIME:20220725T145500Z
DTEND;VALUE=DATE-TIME:20220725T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-597@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Demetrio Vilardi ()\nhttps://indico.tpi.uni-jena.de/
event/199/contributions/597/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/597/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional Renormalization Group and 2PI Effective Action Formalis
m
DTSTART;VALUE=DATE-TIME:20220726T100000Z
DTEND;VALUE=DATE-TIME:20220726T103000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-627@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Urko Reinosa ()\nhttps://indico.tpi.uni-jena.de/even
t/199/contributions/627/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/627/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Critical behaviour at thermal m-axial Lifshitz point and stability
of the FFLO superfluid phases
DTSTART;VALUE=DATE-TIME:20220726T143500Z
DTEND;VALUE=DATE-TIME:20220726T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-616@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Mateusz Homenda ()\nWe apply nonperturbative renorma
lization group method to critical exponents of m-axial Lifshitz point as a
function of dimensionality d\, anisotropy m and the number of order param
eter components N. Basing on the results we consider the stability of the
Fulde-Ferrell-Larkin-Ovchinnikov states in cold atom system.\n\nhttps://in
dico.tpi.uni-jena.de/event/199/contributions/616/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/616/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Structure functions in shell models of turbulence
DTSTART;VALUE=DATE-TIME:20220728T100000Z
DTEND;VALUE=DATE-TIME:20220728T103000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-648@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Léonie Canet ()\nShell models are simplified models
of turbulence\, describing discrete Fourier modes of velocity coupled via
purely local interactions in spectral space. Yet these simple models repr
oduce all characteristic features of Navier-Stokes turbulence\, including
intermittency. I will present a FRG analysis of these models\, and show th
at the turbulent regime corresponds to a non-trivial fixed-point. I will e
xplain its specific properties and present the results for the structure f
unctions.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/648/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/648/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Operator Product Expansion
DTSTART;VALUE=DATE-TIME:20220728T070000Z
DTEND;VALUE=DATE-TIME:20220728T074500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-626@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Stefan Hollands ()\nWith the help of the renormaliza
tion group flow equations a la Wilson-Wegner-Polchinski-Wetterich several
hitherto conjectural properties and several new properties of the operato
r product expansion (OPE) have been established in recent times such as 1)
its convergence properties 2) its algebraic properties ("associativity")\
, or 3) a functional master equation for the OPE coefficients. With the he
lp of the master equation\, a differential equation for the flow of the co
nformal data (OPE coefficients and anomalous dimensions) in $d$-dimensiona
l CFTs under a marginal perturbation can be established. In this talk\, I
give an \noverview over such results.\n\nhttps://indico.tpi.uni-jena.de/e
vent/199/contributions/626/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/626/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Towards quantitative precision for non-smooth interaction potentia
ls in FRG flows
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-693@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Franz Richard Sattler ()\nhttps://indico.tpi.uni-je
na.de/event/199/contributions/693/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/693/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Phase Transitions in Yukawa Models
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-694@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Richard Schmieden ()\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/694/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/694/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lifetimes of the Fermi polaron and molecule at finite momentum fro
m fRG
DTSTART;VALUE=DATE-TIME:20220726T145500Z
DTEND;VALUE=DATE-TIME:20220726T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-618@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jonas von Milczewski ()\nWe study theoretically the
lifetimes of the attractive and the repulsive Fermi Polaron and the molecu
le at finite momentum in both two and three dimensions. To this end we dev
eloped a new technique that allows for the computation of Green's function
s in the whole complex frequency plane using exact analytical continuation
within the functional renormalization group. While conventional approache
s like the NSCT method cannot determine these lifetimes\, we are able to f
ind the momentum dependent lifetime at different interaction strengths of
both the attractive and repulsive polaron as well as the molecule. In our
talk we discuss our findings and talk about possible experiments which cou
ld be conducted.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions
/618/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/618/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The predictive power of asymptotic safety for an ALP model
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-687@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Rafael Robson Lino dos Santos ()\nAn asymptoticall
y-safe theory of quantum gravity could render a non-perturbative renormali
zation of general relativity\, restoring its predictive power at higher en
ergies. The asymptotic-safety community has been finding indications for t
hat\, mainly using the functional renormalization group framework. In this
poster\, I will explore the predictive power of asymptotically-safe quant
um gravity and the interplay between gravity and matter\, focusing on a to
y model inspired by dark-matter axion-like particles.\n\nhttps://indico.tp
i.uni-jena.de/event/199/contributions/687/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/687/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum Gravity Amplitudes From First Principles
DTSTART;VALUE=DATE-TIME:20220725T125500Z
DTEND;VALUE=DATE-TIME:20220725T132000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-598@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Benjamin Knorr ()\nhttps://indico.tpi.uni-jena.de/ev
ent/199/contributions/598/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/598/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum discontinuity fixed point and renormalization group flow o
f the SYK model
DTSTART;VALUE=DATE-TIME:20220726T123000Z
DTEND;VALUE=DATE-TIME:20220726T125500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-608@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Peter Kopietz ()\nWe determine the global renormaliz
ation group (RG) flow of the Sachdev-Ye-Kitaev (SYK) model. From a control
led truncation of the infinite hierarchy of the exact functional RG flow e
quations we identify several fixed points: Apart from a stable fixed point
\, associated with the celebrated non-Fermi liquid state of the model\, we
find another stable fixed point related to an integer-valence state. Thes
e stable fixed points are separated by a discontinuity fixed point with on
e relevant direction\, describing a quantum first-order transition. Most n
otably\, the fermionic spectrum continues to be quantum critical even at t
he discontinuity fixed point. This rules out a description of the transiti
on in terms of a local effective Ising variable as is established for clas
sical transitions. We propose an entangled quantum state at phase coexiste
nce as a possible physical origin of this critical behavior.\n\nhttps://in
dico.tpi.uni-jena.de/event/199/contributions/608/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/608/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Clock models from second order of the derivarive expansion of the
functional renormalization group
DTSTART;VALUE=DATE-TIME:20220728T125500Z
DTEND;VALUE=DATE-TIME:20220728T132000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-650@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Carlos Sánchez ()\nhttps://indico.tpi.uni-jena.de/e
vent/199/contributions/650/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/650/
END:VEVENT
BEGIN:VEVENT
SUMMARY:SU(4) symmetry in Dirac materials - Application to twisted bilayer
graphene
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-688@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nikolaos Parthenios ()\nhttps://indico.tpi.uni-jena.
de/event/199/contributions/688/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/688/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The lower critical dimension of phi4 theory from Functional RG
DTSTART;VALUE=DATE-TIME:20220728T132000Z
DTEND;VALUE=DATE-TIME:20220728T134500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-651@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Lucija Nora Farkas ()\nThe lower critical dimension
$d_l$ is the spatial dimension on which fluctuations destroy the phase tra
nsition. In the scalar phi4 theory\, this happens due to the proliferation
of kinks. This differs for example from the O(N) case where it is a resul
t of Goldstone modes and where $d_l=2$ is well understood in the RG formal
ism. We explore whether the Functional Renormalization Group methods can b
e used to capture those localized excitations and investigate the phase tr
ansition just above the lower critical dimension. We have studied the fixe
d point solutions and discovered that the effective potential develops a b
oundary layer near its minimum as one approaches the $d_l$ limit\, a featu
re that was not identified in previous works. We explain how the boundary
layer determines the critical behavior in the vicinity of the lower critic
al dimension.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/65
1/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/651/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Second order chiral phase transition in three flavor quantum chrom
odynamics?
DTSTART;VALUE=DATE-TIME:20220726T143500Z
DTEND;VALUE=DATE-TIME:20220726T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-617@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Gergely Fejos ()\nWe calculate the renormalization g
roup flows of all renormalizable interactions in the three dimensional Gin
zburg--Landau potential for the chiral phase transition of three flavor qu
antum chromodynamics. On the contrary to the common belief we find a fixed
point in the system that is able to describe a second order phase transit
ion in the infrared. This shows that longstanding assumptions on the trans
ition order might be false. If the transition is indeed of second order\,
our results can also be interpreted as indirect evidence that the axial an
omaly restores at the transition temperature.\n\nhttps://indico.tpi.uni-je
na.de/event/199/contributions/617/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/617/
END:VEVENT
BEGIN:VEVENT
SUMMARY:UV Conformal Window and Loss of Asymptotic Safety
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-690@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nahzaan Riyaz ()\nhttps://indico.tpi.uni-jena.de/eve
nt/199/contributions/690/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/690/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Constructing CFTs from AdS flows
DTSTART;VALUE=DATE-TIME:20220728T141500Z
DTEND;VALUE=DATE-TIME:20220728T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-653@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Markus Fröb ()\nEmploying the RG flow equations fo
r weakly coupled quantum field theories in AdS\, I show how one can apply
the AdS/CFT correspondence to obtain flow equations for the dual CFTs. In
this duality\, loop corrections in the AdS bulk are mapped to 1/N correcti
ons in the CFT. I derive recursion relations for CFT correlation functions
which generalize existing results in the large-N limit to all orders in t
he 1/N expansion\, and show how these translate directly into recursion re
lations for the corresponding Mellin amplitudes.\n\nhttps://indico.tpi.uni
-jena.de/event/199/contributions/653/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/653/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Asymptotically safe Einstein-Palatini gravity
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-692@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Abdol Sabor Salek ()\nhttps://indico.tpi.uni-jena.d
e/event/199/contributions/692/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/692/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Renormalization group and probability theory: distribution of the
order parameter at criticality
DTSTART;VALUE=DATE-TIME:20220725T125500Z
DTEND;VALUE=DATE-TIME:20220725T132000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-593@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Ivan Balog ()\nAuthors: Ivan Balog\, Adam Rançon\,
Bertrand Delamotte\; The question of probabilistic interpretation of the r
enormalization group has been around since the beginning of the subject of
the renormalization group in the '70 [1]\, yet to this day no systematic
approach exists for making practical calculations in cases when constituen
ts of the system are strongly correlated\, e.g. approaching criticality. U
sing functional renormalization group and the effective average action for
malism [2]\, we write down a flow equation for the rate function $I(m)$\,
which determines the scaling function of the critical distribution of the
order parameter $P(m)$\, $I(m)=-ln(P(m))$. We show that $I$ is a universal
function parametrized by $\\zeta=\\xi/L$ characterizing the approach to c
riticality. Monte Carlo results for different $\\zeta=\\xi/L$ collapse clo
sely to the rate functions for different $\\zeta$ determined from the reno
rmalization group. For all cases when $\\zeta>1$ the shape of the rate fun
ction is largely similar\, yet not identical\, to the shape of the fixed p
oint (dimensionless) effective potential\, featuring concavity near the or
igin. [1] G. Jona-Lasinio: Il Nuovo Cimento\, 26\, 99 (1975) [2] J. Berges
\, N. Tetradis\, and C. Wetterich\, Phys. Rep. 363\, 223 (2002).\n\nhttps:
//indico.tpi.uni-jena.de/event/199/contributions/593/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/593/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spin functional renormalization group for dimerized quantum spin s
ystems
DTSTART;VALUE=DATE-TIME:20220728T143500Z
DTEND;VALUE=DATE-TIME:20220728T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-654@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Andreas Rückriegel ()\nWe investigate dimerized qua
ntum spin systems using the spin functional renormalization group approach
proposed by Krieg and Kopietz which directly focuses on the physical spin
correlation functions and avoids the representation of the spins in terms
of fermionic or bosonic auxiliary operators. Starting from decoupled dime
rs as initial condition for the renormalization group flow equations\, we
obtain the spectrum of the triplet excitations as well as the magnetizatio
n in the quantum paramagnetic\, ferromagnetic\, and thermally disordered p
hases at all temperatures. Moreover\, we compute the full phase diagram of
a weakly coupled dimerized spin system in three dimensions\, including th
e correct mean field critical exponents at the two quantum critical points
.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/654/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/654/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The long-range XY model and other examples of exotic BKT scaling
DTSTART;VALUE=DATE-TIME:20220725T132000Z
DTEND;VALUE=DATE-TIME:20220725T134500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-594@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nicolo Defenu ()\nThe two dimensional classical $XY$
model is characterised by the the presence\, in the short-range regime\,
of a line of RG fixed points\, which gives rise to the celebrated Berezins
kii - Kosterlitz - Thouless (BKT) phenomenology. We will discuss the defor
mation of the BKT scaling caused by the inclusion of power-law decaying co
uplings\, yielding a coexistence of spontaneously symmetry broken (SSB) an
d BKT phases in the phase diagram. Perturbative RG arguments imply that th
e SSB phenomenology observed in this model is described by a novel form of
universality. Finally\, in the last part of the talk\, we are gonna exten
d our description of BKT scaling outside of the equilibrium world and cons
ider the BKT scaling generated by the inclusion of non-Hermitian terms in
the model Hamiltonian.\n\nhttps://indico.tpi.uni-jena.de/event/199/contrib
utions/594/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/594/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A Rigorous Treatment of the Wetterich Equation
DTSTART;VALUE=DATE-TIME:20220728T143500Z
DTEND;VALUE=DATE-TIME:20220728T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-655@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jobst Ziebell ()\nhttps://indico.tpi.uni-jena.de/eve
nt/199/contributions/655/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/655/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The low-temperature phase of the O(N) models below two dimensions
DTSTART;VALUE=DATE-TIME:20220728T145500Z
DTEND;VALUE=DATE-TIME:20220728T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-656@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Andrzej Chlebicki ()\nWe investigate the low-tempera
ture behaviour of the O(N) models for 1\n\nhttps://indico.tpi.uni-jena.de/
event/199/contributions/656/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/656/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Benchmarking effective actions and their flow equations in zero di
mensions
DTSTART;VALUE=DATE-TIME:20220728T153500Z
DTEND;VALUE=DATE-TIME:20220728T155500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-660@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Peter Millington ()\nWe can define various quantum e
ffective actions\, each of which may have particular utility or convenienc
e\, in analogy to the Routhians of classical mechanics. In this talk\, we
provide an update on efforts to provide pedagogical and explicit illustrat
ions of the construction and subtleties of various effective actions and\,
in particular\, the one-particle-irreducible\, average one-particle-irred
ucible and two-particle-irreducible effective actions. By focussing on zer
o-dimensional “QFTs”\, we are able to make concrete one-to-one compari
sons in terms of analytic expressions for the effective actions\, and the
relevant n-point functions and sources\, and to benchmark various approach
es to the derivation of exact flow equations.\n\nhttps://indico.tpi.uni-je
na.de/event/199/contributions/660/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/660/
END:VEVENT
BEGIN:VEVENT
SUMMARY:From holographic RG to information flows
DTSTART;VALUE=DATE-TIME:20220729T070000Z
DTEND;VALUE=DATE-TIME:20220729T074500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-662@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Johanna Erdmenger ()\nI will give a brief overview o
f the holographic RG in the context of the AdS/CFT correspondence\, consid
ering both flows to IR fixed points as well as to confining dual field the
ories. I will highlight recent developments on relating information-theory
concepts such as entanglement entropy to geometric objects in dual hyperb
olic spaces. Moreover\, I will present recent results on the analogy betwe
en the RG and deep neural networks\, wherein subsequent layers of neurons
are analogous to successive steps along the RG. In particular\, we quantif
y the flow of information by explicitly computing the relative entropy or
Kullback-Leibler divergence in both the one- and two-dimensional Ising mod
els under decimation RG\, as well as in a feedforward neural network as a
function of depth. We observe qualitatively identical behavior characteriz
ed by the monotonic increase to a parameter-dependent asymptotic value.\n\
nhttps://indico.tpi.uni-jena.de/event/199/contributions/662/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/662/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional renormalisation group for cosmic large-scale structure
formation
DTSTART;VALUE=DATE-TIME:20220726T151500Z
DTEND;VALUE=DATE-TIME:20220726T153500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-621@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Alaric Erschfeld ()\nThe formation of cosmic large-s
cale structures can be described with a statistical field theory for the d
ynamics of dark matter. The functional renormalisation group is on the one
hand studied using the underlying symmetries of the theory and in particu
lar using an extended version of Galilean invariance. The corresponding ge
neralised Ward identities allow to close and solve the flow equations for
two-point correlation functions and relate to the so-called ‘sweeping ef
fect’ known in fluid turbulence. On the other hand the flow equations ar
e solved using an ansatz that corresponds to time-local effective dynamics
for dark matter and can be understood as a vertex and derivative expansio
n of the effective action.\n\nhttps://indico.tpi.uni-jena.de/event/199/con
tributions/621/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/621/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cosmological constant problem and Hubble tension in scale-dependen
t cosmology
DTSTART;VALUE=DATE-TIME:20220726T153500Z
DTEND;VALUE=DATE-TIME:20220726T155500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-623@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Cristóbal Laporte ()\nIn this work\, a cosmologica
l model based on the scale-dependent scenario of gravity is presented. We
argue that the discrepancy between the Planck mass scale and the observed
value of the cosmological constant can be largely attenuated if those quan
tities are understood as a result of effective\, and thus scale-dependent\
, couplings. In the approach where the scale–dependence appears as a cor
rection to the classical ΛCDM evolution\, the potential to address the te
nsions between early and late time measurements of H0 is studied. Our resu
lts are compared to the renormalization group flow obtained within the asy
mptotic safety program\, which reveals a stunning agreement. The work is b
ased on JCAP 01 (2020) 021\, JCAP 06 (2021) 019\, and arXiv:2205.05592.\n\
nhttps://indico.tpi.uni-jena.de/event/199/contributions/623/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/623/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Large Deviations in the Climate System: Extreme Events and Metasta
bility
DTSTART;VALUE=DATE-TIME:20220727T074500Z
DTEND;VALUE=DATE-TIME:20220727T083000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-629@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Valerio Lucarini ()\nThe climate system is a complex
\, chaotic system with many degrees of freedom and variability on a vast r
ange of temporal and spatial scales. Attaining a deeper level of understan
ding of its dynamical processes is a scientific challenge of great urgency
\, especially given the ongoing climate change and the evolving climate cr
isis. In statistical physics\, complex\, many-particle systems are studied
successfully using the Large Deviation Theory (LDT). In the spirit of Has
selmann's programme\, a great potential exists for applying LDT to problem
s relevant for climate science. In particular\, LDT allows for understandi
ng the fundamental properties of persistent deviations of climatic fields
from the long-term averages and for associating them to low-frequency\, la
rge scale patterns of variability. This allows one to introduce a notion o
f typicality with regard to extreme events. These applications are of key
importance to improve our understanding of high-impact weather and climate
events. We will present several applications to the case of recent heatwa
ves (2010 Russian Heatwave\, 2021 Western North America Heatwave) and cold
spells (2010 Mongolian Dzud\, 2019 Canadian Cold Spell). Furthermore\, ta
king advantage of the formalism of Graham's quasipotential\, LDT provides
powerful tools for evaluating the probability of noise-induced transitions
between competing metastable states of the climate system and for underst
anding the multiscale\, hierarchical properties of the so-called dynamical
landscape. We will show how this framework can be used to better understa
nd the - arguably - most important critical transition of the Earth system
\, associated with the dichotomy between Snowball and Warm climate. The fi
nal transition to the Warm state that occurred about 600 Mya has been key
for the eventual emergence of multicellular life in our planet. References
: V.M. Galfi\, V. Lucarini\, Fingerprinting Heatwaves and Cold Spells and
Assessing Their Response to Climate Change using Large Deviation Theory\,
Phys. Rev. Lett. 127\, 058701 (2021) V.M. Galfi\, V. Lucarini\, F. Ragone\
, J. Wouters\, Applications of Large Deviation Theory in Climate Science a
nd Geophysical Fluid Dynamics\, Riv. Nuovo Cimento 44\, 291–363 (2021) G
. Margazoglou\, T. Grafke\, A. Laio\, V. Lucarini\, Dynamical Landscape an
d Multistability of the Earth's Climate\, Proc. R. Soc. A 477\, 2021001920
210019 V. Lucarini\, T. Bodai\, Global Stability Properties of the Climate
: Melancholia States\, Invariant Measures\, and Phase Transitions\, Nonlin
earity 33\, R59 (2020) V. Lucarini\, T. Bodai\, Transitions across Melanch
olia States in a Climate Model: Reconciling the Deterministic and Stochast
ic Points of View\, Phys. Rev. Lett. 122\,158701 (2019)\n\nhttps://indico.
tpi.uni-jena.de/event/199/contributions/629/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/629/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dimensional reduction along the RG flow in combinatorially non-loc
al field theories
DTSTART;VALUE=DATE-TIME:20220725T143500Z
DTEND;VALUE=DATE-TIME:20220725T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-603@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Johannes Thürigen ()\nCombinatorially non-local int
eractions are at the heart of matrix and tensor theories as well as non-co
mmutative field theory. Interestingly\, for theories on a compact domain t
heir renormalization group equations are non-autonomous in the momentum sc
ale. We show that this should be regarded not as an issue but as a feature
of such theories leading to a reduction of the effective dimension of the
field theory along the renormalization group flow. We illustrate this wit
h the example of a field theory with tensorial symmetry using the function
al renormalization group in the cyclic-melonic potential approximation. Wh
ile this yields a dimensional flow on compact domain\, we also find a new
phase structure with hints for an asymptotic safe fixed point in the large
-volume limit.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/6
03/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/603/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Spectral Geometry of de Sitter Space in Asymptotic Safety
DTSTART;VALUE=DATE-TIME:20220726T090000Z
DTEND;VALUE=DATE-TIME:20220726T093000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-606@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Renata Ferrero ()\nWithin the functional renormaliza
tion group approach to Background Independent quantum gravity\, we explore
the scale dependent effective geometry of the de Sitter solution dS4. The
investigation employs a novel approach whose essential ingredient is a mo
dified spectral flow of the metric dependent d'Alembertian\, or of similar
hyperbolic kinetic operators. The corresponding one-parameter family of s
pectra and eigenfunctions encodes information about the nonperturbative ba
ckreaction of the dynamically gravitating vacuum fluctuations on the mean
field geometry of the quantum spacetime. Used as a diagnostic tool\, the p
ower of the spectral flow method resides in its ability to identify the sc
ale dependent subsets of field modes that supply the degrees of freedom wh
ich participate in the effective field theory description of the respectiv
e scale. A central result is that the ultraviolet of Quantum Einstein Grav
ity comprises far less effective degrees of freedom than predicted (incorr
ectly) by background dependent reasoning. Exploring the quantum spacetime'
s spatial geometry carried by physical fields\, we find that 3-dimensional
space disintegrates into a collection of coherent patches which individua
lly can\, but in their entirety cannot be described by one of the effectiv
e average actions occurring along the renormalization group trajectory.\n\
nhttps://indico.tpi.uni-jena.de/event/199/contributions/606/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/606/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Active matter: A treasure trove of novel universality classes
DTSTART;VALUE=DATE-TIME:20220726T151500Z
DTEND;VALUE=DATE-TIME:20220726T153500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-620@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Chiu Fan Lee ()\nA hallmark of living organisms is t
he ability to move around in their environments. In the fluid state\, i.e.
\, when the motile agents can exchange neighbours freely\, the equations o
f motion that describes the system are called the Toner-Tu (TT) equations.
The TT equations govern active fluids the same way that the Navier-Stokes
equations govern simple fluids. Since the inception of the TT equations i
n 1995\, dynamic renormalization group (DRG) analyses on the TT equations
have led to the discovery of diverse novel nonequilibrium states of matter
(or phases)\, and novel critical phenomena. In this talk\, I will focus o
n the incompressible limit of the TT equations and elucidate the associate
d universal behaviour [1–5]. I will also discuss how exact RG may enable
us to solve some key open questions in active matter physics. References:
[1] Chen L\, Lee C F\, Maitra A and Toner J 2022 Packed swarms on dirt: t
wo dimensional incompressible flocks with quenched and annealed disorder a
rXiv:2202.02865 [2] Chen L\, Lee C F\, Maitra A and Toner J 2022 Incompres
sible polar active fluids with quenched disorder in dimensions d > 2 arXiv
:2203.01892 [3] Chen L\, Lee C F and Toner J 2018 Incompressible polar act
ive fluids in the moving phase in dimensions d > 2 New J. Phys. 20 113035
[4] Chen L\, Lee C F and Toner J 2016 Mapping two-dimensional polar active
fluids to two-dimensional soap and one-dimensional sandblasting Nat. Comm
un. 7 12215 [5] Chen L\, Toner J and Lee C F 2015 Critical phenomenon of t
he order–disorder transition in incompressible active fluids New J. Phys
. 17 042002\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/620/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/620/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luttinger Liquids at the Edge of Quantum Hall Systems
DTSTART;VALUE=DATE-TIME:20220729T093000Z
DTEND;VALUE=DATE-TIME:20220729T100000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-665@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Marcello Porta ()\nWe consider the edge transport pr
operties of a generic class of interacting quantum Hall systems on a cylin
der\, in the infinite volume and zero temperature limit. We prove that the
large-scale behavior of the edge correlation functions is effectively des
cribed by the multi-channel Luttinger model. In particular\, we prove that
the edge conductance is universal\, and equal to the sum of the chiraliti
es of the non-interacting edge modes. The proof is based on rigorous renor
malization group methods\, that allow to fully take into account the effec
t of backscattering at the edge. Universality arises as a consequence of t
he vanishing of the beta function for the emergent multi-channel Luttinger
liquid\, combined with lattice Ward identities for the microscopic 2d the
ory and with the non-renormalization of the chiral anomaly for the emergen
t QFT. Joint work with Vieri Mastropietro.\n\nhttps://indico.tpi.uni-jena.
de/event/199/contributions/665/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/665/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gross-Neveu SO(3) criticality in spin-orbital liquids: FRG vs high
er-order perturbation theory
DTSTART;VALUE=DATE-TIME:20220727T153500Z
DTEND;VALUE=DATE-TIME:20220727T155500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-641@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Shouryya Ray ()\nThe Gross-Neveu SO(3) universality
class in three spacetime dimensions describes a quantum critical point bet
ween a Dirac semimetal and a long-range-ordered phase in which the fermion
spectrum is only partially gapped out. Such a quantum critical point has
recently been predicted to be realizable in two-dimensional spin-orbital m
agnets with strong exchange frustration. Here\, I shall report on our effo
rts to characterize the quantum critical behaviour of the Gross-Neveu-SO(3
) universality class using the functional renormalization group in the imp
roved local potential approximation\, and compare with our three-loop and
second-order large-N results. Time permitting\, I shall also discuss some
of the qualitative behaviour for general spactime dimension and flavour nu
mber\, which shows some distinctive features that are absent in the corres
ponding Gross-Neveu-Ising and -Heisenberg incarnations.\n\nhttps://indico.
tpi.uni-jena.de/event/199/contributions/641/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/641/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Essential Renormalisation Group
DTSTART;VALUE=DATE-TIME:20220727T090000Z
DTEND;VALUE=DATE-TIME:20220727T093000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-630@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Kevin Falls ()\nhttps://indico.tpi.uni-jena.de/event
/199/contributions/630/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/630/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Asymptotically safe scalar-tensor theories
DTSTART;VALUE=DATE-TIME:20220728T151500Z
DTEND;VALUE=DATE-TIME:20220728T153500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-659@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Antonio Pereira ()\nhttps://indico.tpi.uni-jena.de/e
vent/199/contributions/659/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/659/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Extended symmetries
DTSTART;VALUE=DATE-TIME:20220725T123000Z
DTEND;VALUE=DATE-TIME:20220725T125500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-669@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Stefan Floerchinger ()\nExtended symmetry transforma
tions do not leave the action fully invariant\, but change it by a term li
near in field expectation values or known composite fields. I will discuss
how this leads to a modified version of Noethers theorem with currents th
at are conserved up to known terms. I will also discuss how an extended ve
rsion of Galilei boost symmetry allows to close and solve renormalization
group equations for cosmological large-scale structure formation in certai
n regimes.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/669/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/669/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Computational fluid dynamics and the fRG
DTSTART;VALUE=DATE-TIME:20220729T090000Z
DTEND;VALUE=DATE-TIME:20220729T093000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-664@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nicolas Wink ()\nThe talk reviews the application of
computational fluid dynamics techniques to flow equations\, explored in a
recent series of paper. Hereby\, a detailed explanation of the deep conne
ction between RG flows and convection-diffusion equations is given. These
properties\, as well as the connection to phase transitions\, are made exp
licit at the example of O(N) theories in various variations. Finally\, the
extension beyond such simple models and truncations of the effective acti
on will be discussed.\n\nhttps://indico.tpi.uni-jena.de/event/199/contribu
tions/664/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/664/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Background Effective Action with Nonlinear Massive Gauge Fixing
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-672@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Dimitrios Gkiatas ()\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/672/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/672/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nevanlinna Analytical Continuation
DTSTART;VALUE=DATE-TIME:20220726T070000Z
DTEND;VALUE=DATE-TIME:20220726T074500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-604@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Emanuel Gull ()\nSimulations of finite temperature q
uantum systems provide imaginary frequency Green's functions that correspo
nd one-to-one to experimentally measurable real-frequency spectral functio
ns. However\, due to the bad conditioning of the continuation transform fr
om imaginary to real frequencies\, established methods tend to either wash
out spectral features at high frequencies or produce spectral functions w
ith unphysical negative parts. Here\, we show that explicitly respecting t
he analytic `Nevanlinna' structure of the Green's function leads to intrin
sically positive and normalized spectral functions\, and we present a cont
inued fraction expansion that yields all possible functions consistent wit
h the analytic structure. Application to synthetic trial data shows that s
harp\, smooth\, and multi-peak data is resolved accurately. Application to
the band structure of silicon demonstrates that high energy features are
resolved precisely. Continuations in a realistic correlated setup reveal a
dditional features that were previously unresolved. By substantially incre
asing the resolution of real frequency calculations our work overcomes one
of the main limitations of finite-temperature quantum simulations.\n\nhtt
ps://indico.tpi.uni-jena.de/event/199/contributions/604/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/604/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gravity-mediated matter scattering amplitudes from the effective a
ction
DTSTART;VALUE=DATE-TIME:20220725T141500Z
DTEND;VALUE=DATE-TIME:20220725T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-601@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Chris Ripken ()\nOne of the goals of the Asymptotic
Safety program for gravity is to compute the effective action at k=0. Howe
ver\, given such an action\, what are the concrete physical predictions th
at we can derive from it? Generically\, the renormalization group will gen
erate an infinite number of interactions in the effective action. It is th
erefore an interesting question which interactions can arise\, and how the
y affect physical observables. In this talk\, I will present a classificat
ion scheme to parameterize the infinitely many interactions using form fac
tors. These take into account the full momentum-dependence of propagators
and vertices. Using 2-to-2 scattering processes involving scalars and phot
ons as a starting point\, I will show how to derive the most general scatt
ering amplitudes and cross-sections from the effective action. Taking the
low-energy limit\, this allows to parameterize the smoking gun signals for
quantum gravity in these observables.\n\nhttps://indico.tpi.uni-jena.de/e
vent/199/contributions/601/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/601/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vanishing regulators
DTSTART;VALUE=DATE-TIME:20220727T093000Z
DTEND;VALUE=DATE-TIME:20220727T100000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-631@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Luca Zambelli ()\nhttps://indico.tpi.uni-jena.de/eve
nt/199/contributions/631/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/631/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Background Independent Field Quantization with Sequences of Gravit
y-Coupled Approximants
DTSTART;VALUE=DATE-TIME:20220728T153500Z
DTEND;VALUE=DATE-TIME:20220728T155500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-661@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Maximilian Becker ()\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/661/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/661/
END:VEVENT
BEGIN:VEVENT
SUMMARY:mfRG analysis of the Attractive Hubbard Model
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-673@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Aiman Al-Eryani ()\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/673/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/673/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Towards a microscopic understanding of macroscopic properties of s
trong-interaction matter
DTSTART;VALUE=DATE-TIME:20220726T074500Z
DTEND;VALUE=DATE-TIME:20220726T083000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-605@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jens Braun ()\nhttps://indico.tpi.uni-jena.de/event/
199/contributions/605/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/605/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pion-pion scattering from nucleon-meson fluctuations
DTSTART;VALUE=DATE-TIME:20220726T125500Z
DTEND;VALUE=DATE-TIME:20220726T132000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-611@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Juergen Eser ()\nI present calculations of the S-wav
e isospin-zero and isospin-two pion-pion scattering lengths within a nucle
on-meson model with parity doubling. Both scattering lengths are computed
in various approximations\, ranging from a mean-field calculation towards
the inclusion of loop corrections by means of the FRG. I thereby elucidate
subtleties concerning the truncation of the effective action w.r.t. highe
r-derivative pion interactions. As the main result\, simultaneous agreemen
t for the isospin-zero and isospin-two scattering lengths with experimenta
l data within the LPA'-truncation is found. The isoscalar sigma-mass is dy
namically generated by the FRG integration\, and is a prediction of the mo
del. It ends being of the order of 500 MeV\, i.e.\, much lower than the va
lue (> 1 GeV) found in mean-field or one-loop treatment of this or related
models. Finally\, the convergence of the corresponding low-energy expansi
on of the quantum effective action in terms of pion momenta is discussed.\
n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/611/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/611/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional RG for zero- and one-dimensional Fermi systems
DTSTART;VALUE=DATE-TIME:20220725T094500Z
DTEND;VALUE=DATE-TIME:20220725T103000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-591@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Volker Meden ()\nI present an overview of our recent
applications of funtional RG for zero- and one-dimensional many-fermion s
ystems. The vertex expansion scheme with the two-particle interaction U be
ing the small parameter is used. Equilibrium as well as nonequilibrium sit
uations are considered. Several questions are tackled. Can one describe ph
ase transitions which occur at finite U? If so\, what is the role of the s
elf-energy feedback and that of the two-particle vertex? Does the breaking
of current conservation in nonequilibrium situations with a frequency dep
endent self-energy render the corresponding results useless right away? Ca
n one use functional RG to study interacting (topological) insulators? Is
it possible to extend functional RG to the realm of pseudo-Hermitian quant
um many-body problems?\n\nhttps://indico.tpi.uni-jena.de/event/199/contrib
utions/591/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/591/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Glory and misery of the Derivative Expansion: Ten years later
DTSTART;VALUE=DATE-TIME:20220727T100000Z
DTEND;VALUE=DATE-TIME:20220727T103000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-632@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nicolás Wschebor ()\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/632/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/632/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Multiloop flow equations for single-boson exchange fRG
DTSTART;VALUE=DATE-TIME:20220726T141500Z
DTEND;VALUE=DATE-TIME:20220726T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-614@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Marcel Gievers ()\nThe recently introduced single-bo
son exchange (SBE) decomposition [2] of the four-point vertex of interacti
ng fermionic many-body systems is a conceptually and computationally appea
ling parametrization of the vertex. It relies on the notion of reducibilit
y of vertex diagrams with respect to the bare interaction U\, instead of a
classification based on two-particle reducibility within the widely-used
parquet decomposition. We re-derived the SBE decomposition in a generalize
d framework (suitable for extensions to\, e.g.\, inhomogeneous systems or
real-frequency treatments) following from the parquet equations. We then d
erived multiloop functional renormalization group (mfRG) flow equations [3
] for the ingredients of this SBE decomposition\, both in the parquet appr
oximation\, where the fully two-particle irreducible vertex is treated as
an input\, and in the more restrictive SBE approximation\, where this role
is taken by the fully U-irreducible vertex. Moreover\, we give mfRG flow
equations for the popular parametrization of the vertex in terms of asympt
otic classes [4] of the two-particle reducible vertices. Since the parquet
and SBE decompositions are closely related\, their mfRG flow equations ar
e very similar in structure. [1] E. Walter\, M. Gievers\, A. Ge\, J. von D
elft\, F. B. Kugler\, aXiv:2201.04878 (2022). [2] F. Krien\, A. Valli\, M.
Capone\, PRB 100\, 155149 (2019). [3] F. B. Kugler\, J. von Delft\, Phys.
Rev. Lett. 120\, 057403 (2018). [4] N. Wentzell\, G. Li\, A. Tagliavini\,
C. Taranto\, G. Rohringer\, K. Held\, A. Toschi\, S. Andergassen PRB 102\
, 085106 (2020)\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/
614/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/614/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spins\, pseudo-Majoranas and the functional RG
DTSTART;VALUE=DATE-TIME:20220728T141500Z
DTEND;VALUE=DATE-TIME:20220728T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-652@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Björn Sbierski ()\nFrustrated three-dimensional qua
ntum magnets bear a rich phenomenology but are notoriously hard to treat t
heoretically. We show how a SO(3) Majorana representation of spin operator
s\, in combination with the functional renormalization group allows for qu
antitative simulations at finite temperatures. Focusing on Heisenberg magn
ets\, we establish a finite-size scaling approach and extract critical tem
peratures and -exponents. For the Pyrochlore lattice\, we discuss the impr
ovements introduced by two-loop contributions in the flow equations. We al
so show how the method can be applied so meet some challenges of long-rang
e interacting spin Hamiltonians arising in the context of Rydberg atom arr
ay quantum simulators.\n\nhttps://indico.tpi.uni-jena.de/event/199/contrib
utions/652/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/652/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tetracriticality in O(N) models
DTSTART;VALUE=DATE-TIME:20220728T151500Z
DTEND;VALUE=DATE-TIME:20220728T153500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-658@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Shunsuke Yabunaka ()\nWe study the tetracritical fix
ed point in O(N) models with NPRG. Increasing N\, we find that the tetracr
itical FP continues to exist up to N=\\infty\, which is a different scenar
io from what we found for the tricritical FP. The FP approaches the WF FP
except at a field value. We actually find that higher derivatives of the F
P potential at the special point becomes singular in a way that the FP can
not be found with conventional large N analysis.\n\nhttps://indico.tpi.uni
-jena.de/event/199/contributions/658/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/658/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ultraviolet properties of Lifshitz-type field theories
DTSTART;VALUE=DATE-TIME:20220728T145500Z
DTEND;VALUE=DATE-TIME:20220728T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-657@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Dario Zappala ()\nWe analyse some aspects of higher
derivative Lifshitz-type field theories that exhibit anisotropic scaling l
aws near the Lifshitz fixed point\, with explicit breaking of Lorentz symm
etry. Specifically\, anisotropic models in 3+1 dimension with dynamical ex
ponent z=3 and with all momentum dependent vertex operators discarded\, sh
ow restoration of Lorentz symmetry in the infrared region. At the same tim
e\, ultraviolet divergences are strongly smoothened and\, in particular\,
models with Liouville-like potential show asymptotic freedom. Generalisati
on of this picture\, that includes fermionic and gauge degrees of freedom\
, is discussed.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/
657/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/657/
END:VEVENT
BEGIN:VEVENT
SUMMARY:FRG analysis of the pseudogap opening in the 2D Hubbard model at f
inite doping
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-674@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Hannes Braun ()\nWe apply the functional renormali
sation group to the two-dimensional Hubbard model to investigate the pseud
ogap opening. Extending previous applications at half filling [Phys. Rev.
Research 2\, 033068 (2020)]\, we here explore the physics in the more rele
vant finite-doping regime. In particular\, we present a systematic analysi
s of the different contributions to the self-energy by performing a fluctu
ation diagnostics. Besides the quasiparticle weight\, we show results for
the correlation-induced shape of the Fermi surface. We identify the (incom
mensurate) antiferromagnetic fluctuations to be responsible for the pseudo
gap opening also at finite doping and provide a physical understanding of
the observed momentum-selective behavior.\n\nhttps://indico.tpi.uni-jena.d
e/event/199/contributions/674/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/674/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Holographic RG from Exact RG
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-677@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Pavan Dharanipragada ()\nHolographic RG is the inter
pretation of the AdS-CFT correspondence as RG evolution of boundary theory
. The radial coordinate is interpreted as the scale of the boundary theory
. This allows a new physical way of looking at the correspondence. But\, t
he precise regularisation of the boundary theory that allows this interpre
tation hasn't been looked at. I will show one such regularisation using ER
G formalism. I will write down the ERG equation for the scalar\, vector an
d tensor of boundary O(N) theory. I will explicitly redefine the Exact RG
evolution operator that corresponds to this equation as the bulk AdS actio
n\, thus making the connection precise.\n\nhttps://indico.tpi.uni-jena.de/
event/199/contributions/677/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/677/
END:VEVENT
BEGIN:VEVENT
SUMMARY:From Random Tensors to Tensor Field Theory
DTSTART;VALUE=DATE-TIME:20220725T074500Z
DTEND;VALUE=DATE-TIME:20220725T083000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-589@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Razvan Gurau ()\nThe latest addition to the family o
f large N field theories is tensor field theory built on the melonic large
N limit of random tensors. This large N limit is richer than the vector l
arge N limit but more amenable to analytic computations that the planar on
e. In this talk I will present an overview of the main results obtained on
tensor field theories over the past several years and comment on their im
plications for the future.\n\nhttps://indico.tpi.uni-jena.de/event/199/con
tributions/589/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/589/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Analysis of classical liquids using functional renormalization gro
up
DTSTART;VALUE=DATE-TIME:20220726T125500Z
DTEND;VALUE=DATE-TIME:20220726T132000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-610@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Takeru Yokota ()\nThe development of theoretical met
hods for classical liquids is a longstanding problem in statistical mechan
ics. Accurate and efficient methods for classical liquids benefit\, for in
stance\, analysis of chemical reactions. In this talk\, I will present an
application of the functional renormalization group to classical liquids.
We develop a formulation suitable for a hard-core repulsion and introduce
the Kirkwood superposition approximation to truncate the hierarchy of the
flow equations in the vertex expansion. In a numerical test on a one-dimen
sional solvable model\, the functional renormalization group shows more ac
curate results than the integral-equation methods such as the hypernetted
chain and the Percus-Yevick equation\, which are conventional methods for
classical liquids.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributio
ns/610/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/610/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Coupling fermions to unimodular gravity
DTSTART;VALUE=DATE-TIME:20220727T141500Z
DTEND;VALUE=DATE-TIME:20220727T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-634@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Reinhard Alkofer ()\nhttps://indico.tpi.uni-jena.de/
event/199/contributions/634/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/634/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Fixed Point Structure of Gradient Flow Exact Renormalization Group
for Scalar Field Theories
DTSTART;VALUE=DATE-TIME:20220727T143500Z
DTEND;VALUE=DATE-TIME:20220727T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-635@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Junichi Haruna ()\nGradient Flow Exact Renormalizati
on Group (GFERG) is a framework to define the Wilson action via a gradient
flow equation proposed by Ref.[1]. Because it preserves gauge symmetries
obviously\, it is a promising approach to study non-perturbative aspects o
f gauge theories or quantum gravity. On the other hand\, some scalar model
s (such as the CP^N-1 model or the O(N) non-linear sigma model) share simi
lar properties with these theories and have been investigated as their toy
models. In this talk\, we study the fixed point structure of the GFERG eq
uation associated with a general gradient flow equation for scalar field t
heories. We show that the fixed point structure is the same as that of the
conventional Wilson-Polchinski (WP) equation in general. Furthermore\, we
discuss that the GFERG equation has a similar RG flow structure around a
fixed point to the WP equation. We illustrate these results with the O(N)
non-linear sigma model in 4-epsilon dimensions and the Wilson-Fisher fixed
point. This talk is based on Ref. [2]. [1] H. Sonoda and H. Suzuki\, PTEP
2021 No.2\, (2021) 023B05 [arXiv:2012.03568 [hep-th]] [2] Y.Abe\, Y.Hamada
and J.Haruna\, [arXiv:2201.04111 [hep-th]]\n\nhttps://indico.tpi.uni-jena
.de/event/199/contributions/635/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/635/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Asymptotic safety of Yang-Mills gauge theory in 5 dimensional spac
etime
DTSTART;VALUE=DATE-TIME:20220726T132000Z
DTEND;VALUE=DATE-TIME:20220726T134500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-643@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Masatoshi Yamada ()\nThe Yang-Mills gauge theory in
5 dimensional spacetime is perturbatively non-renormalizable\, but could b
e asymptotically safe. We study the fixed point structure by using the fun
ctional renormalization group.\n\nhttps://indico.tpi.uni-jena.de/event/199
/contributions/643/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/643/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Running Newton Coupling\, Scale Identification and Black Hole Ther
modynamics
DTSTART;VALUE=DATE-TIME:20220727T151500Z
DTEND;VALUE=DATE-TIME:20220727T153500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-640@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nobuyoshi Ohta ()\nWe discuss the quantum improvemen
t of black hole solutions in the context of asymptotic safety. The Newton
coupling in this formulation depends on an energy scale\, which must be id
entified with some length scale in order to study physical consequences to
black holes. However\, no physical principle has so far been known for th
e identification. Here we propose that the consistency of the first law of
thermodynamics is the principle that should determine physically sensible
scale identification\, at least close to the horizon. We show that this l
eads to a natural solution that the Newton coupling should be a function o
f the horizon area and find a universal formula for the quantum entropy\,
which agrees with the standard Bekenstein-Hawking entropy for constant New
ton coupling\, for Kerr black holes and other higher-dimensional black hol
es. This suggests that the Newton coupling is a function of the area at fi
xed radius near the horizon\, and also away to infinity\, where the quantu
m effects may not be so important.\n\nhttps://indico.tpi.uni-jena.de/event
/199/contributions/640/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/640/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sextic tensor field theories
DTSTART;VALUE=DATE-TIME:20220727T141500Z
DTEND;VALUE=DATE-TIME:20220727T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-633@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Sabine Harribey ()\nTensor models admit a melonic la
rge N limit. In d dimensions\, they give rise to a new family of conformal
field theories. Such melonic CFTs were studied for tensor models in rank
3 with quartic interactions. However\, a non-trivial infrared fixed point
with a real spectrum of conformal dimensions was only found for a model wi
th a long-range propagator and a purely imaginary coupling constant. We wi
sh to understand how this depends on the rank of the tensors and on the or
der of the interactions. I will present here the renormalization group flo
w of two tensor models with sextic interactions in rank 3 and 5 with eithe
r short or long-range propagators. In rank 3\, we found non-trivial IR fix
ed points for both the short-range and the long-range models\, with precur
sors at next-to-leading order in short range. We also found a real spectru
m of bilinear operators in both cases. Surprisingly\, in rank 5\, we only
found a non-interacting fixed point.\n\nhttps://indico.tpi.uni-jena.de/eve
nt/199/contributions/633/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/633/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional Renormalization for Multimatrix Models
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-689@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Carlos I. Perez Sanchez ()\nIn this poster we repo
rt recent progress in understanding the algebraic structure underlying Wet
terich Equation for multimatrix models (this sort of model is inspired by
noncommutative geometry and contains interactions indexed by the free alge
bra\, i.e. words in the random matrices). The tools can be useful in discr
etization approaches to quantum gravity and combinatorics of maps. Based o
n Ann. Henri Poincaré 22 (9) [arXiv 2007.10914] and [arXiv:2111.02858]\n\
nhttps://indico.tpi.uni-jena.de/event/199/contributions/689/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/689/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Operator product expansion coefficients from the nonperturbative f
unctional renormalization group
DTSTART;VALUE=DATE-TIME:20220727T145500Z
DTEND;VALUE=DATE-TIME:20220727T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-637@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Félix Rose ()\nUsing the nonperturbative functional
renormalization group (FRG) within the Blaizot-Méndez-Galain-Wschebor ap
proximation\, we compute the operator product expansion (OPE) coefficient
c112 associated with the operators O1∼φ and O2∼φ2 in the three-dimen
sional O(N) universality class and in the Ising universality class (N=1) i
n dimensions 2≤d≤4. When available\, exact results and estimates from
the conformal bootstrap and Monte-Carlo simulations compare extremely well
to our results\, while FRG is able to provide values across the whole ran
ge of d and N considered.\n\nhttps://indico.tpi.uni-jena.de/event/199/cont
ributions/637/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/637/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Formation and evaporation of quantum black holes from the decoupli
ng mechanism
DTSTART;VALUE=DATE-TIME:20220727T153500Z
DTEND;VALUE=DATE-TIME:20220727T155500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-642@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Johanna Borissova ()\nQuantum counterparts to classi
cal black holes provide an exciting ground for phenomenology of quantum gr
avity. Within the functional renormalization group approach to quantum gra
vity\, we propose a novel method to account for quantum effects in classic
al spacetimes. At the core of our construction is the decoupling mechanism
: when a physical infrared scale overcomes the effect of the artificial re
gulator implementing the Wilsonian integration of fluctuating modes\, the
effective average action freezes out and approximates the standard quantum
effective action. Starting from the Einstein-Hilbert truncation\, we use
the decoupling mechanism to explore the dynamics of quantum black holes in
the phases of collapse and evaporation.\n\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/642/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/642/
END:VEVENT
BEGIN:VEVENT
SUMMARY:--
DTSTART;VALUE=DATE-TIME:20220727T155500Z
DTEND;VALUE=DATE-TIME:20220727T161500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-644@indico.tpi.uni-jena.de
DESCRIPTION:https://indico.tpi.uni-jena.de/event/199/contributions/644/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/644/
END:VEVENT
BEGIN:VEVENT
SUMMARY:TU^2FRG - a scalable approach for TUFRG in generic fermionic model
s
DTSTART;VALUE=DATE-TIME:20220725T143500Z
DTEND;VALUE=DATE-TIME:20220725T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-596@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jonas Hauck ()\nDescribing the emergence of phases o
f matter is one of the central challenges in physics. The main complicatio
n is the tremendous computational effort required to investigate real mate
rials. Therefore\, approximations to enable accurate and fast calculations
are of central importance to deepening our understanding of phases of mat
ter. Here\, we present a new truncated unity (TU) approach unifying real-
and momentum-space TUFRG in a symmetry-preserving fashion\, called TU$^2$F
RG. This formalism significantly improves the scaling compared to conventi
onal momentum (TU)FRG when applied to large unit-cell models and models wi
thout translational symmetry. To showcase its predictive power\, we study
the topological edge modes in the superconducting phase of graphene.\n\nht
tps://indico.tpi.uni-jena.de/event/199/contributions/596/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/596/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Invariant Renormalization-Group improvement in General Relativity
DTSTART;VALUE=DATE-TIME:20220725T132000Z
DTEND;VALUE=DATE-TIME:20220725T134500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-600@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Aaron Held ()\nRenormalization-Group (RG) improvemen
t has been applied to capture the effect of gravitational quantum correcti
ons on cosmological and black-hole spacetimes. In this talk\, I will use a
n algebraically complete set of curvature invariants to establish that (i)
RG improvement at the level of the metric (or the equations of motion) is
coordinate-dependent\, while (ii) RG improvement at the level of curvatur
e invariants (or the action) is coordinate-independent. Spherically-symmet
ric and axially-symmetric black-hole spacetimes serve as concrete and phys
ically relevant examples.\n\nhttps://indico.tpi.uni-jena.de/event/199/cont
ributions/600/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/600/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lorentzian quantum gravity and the graviton spectral function
DTSTART;VALUE=DATE-TIME:20220726T093000Z
DTEND;VALUE=DATE-TIME:20220726T100000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-607@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Manuel Reichert ()\nhttps://indico.tpi.uni-jena.de/e
vent/199/contributions/607/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/607/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nonvanishing gravitational contribution to matter beta functions f
or vanishing regulators
DTSTART;VALUE=DATE-TIME:20220727T145500Z
DTEND;VALUE=DATE-TIME:20220727T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-638@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Gustavo de Brito ()\nIn this talk\, I will explore t
he effect of quantum gravity on matter couplings within a Renormalization
Group framework. In particular\, I will focus on results obtained from a c
lass of interpolating regulators that allow us to extract certain universa
l pieces from non-universal quantities. I will discuss an explicit example
of how misleading conclusions can be drawn by analyzing the gravitational
contributions to beta functions instead of analyzing universal quantities
\, such as critical exponents\, that can be extracted from the beta functi
ons. This could be key to explaining the differences between perturbative
studies and Functional Renormalization Group studies.\n\nhttps://indico.tp
i.uni-jena.de/event/199/contributions/638/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/638/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Incommensurate 2kF density wave quantum criticality
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-676@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Lukas Debbeler ()\nhttps://indico.tpi.uni-jena.de/ev
ent/199/contributions/676/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/676/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Timelike properties of QCD from functional methods
DTSTART;VALUE=DATE-TIME:20220726T141500Z
DTEND;VALUE=DATE-TIME:20220726T143500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-615@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jan Horak ()\nWe investigate timelike correlation fu
nctions in QCD via spectral functional renormalisation group and Dyson-Sch
winger equations. Within the spectral formulation\, direct access to the f
ull complex structure of the theory is obtained. Studying the propagation
of non-holomorphicities through the coupled system of DSEs in Yang-Mills t
heory\, we obtain consistency conditions which constrain the analytic stru
cture of possible solutions. We also present spectral functions in the Phi
^4 theory from the spectral renormalization group. Finally\, results for Q
CD transport coefficients are presented\, obtained via closed diagrammatic
representations in terms of timelike correlation functions.\n\nhttps://in
dico.tpi.uni-jena.de/event/199/contributions/615/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/615/
END:VEVENT
BEGIN:VEVENT
SUMMARY:FRG based on the single boson exchange decomposition
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-680@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Kilian Fraboulet ()\nhttps://indico.tpi.uni-jena.de/
event/199/contributions/680/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/680/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spectral functions from renormalised flow equations
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-701@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jonas Wessely ()\nWe derive renormalized Callan-Syma
nzik Flowequations in the FRG setup and apply the framework of spectral re
normalisation to compute the full\, nonperturbative spectral function of a
\\phi^4 theory in (2+1) dimensions\n\nhttps://indico.tpi.uni-jena.de/even
t/199/contributions/701/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/701/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Interacting fixed points of fermionic field theories
DTSTART;VALUE=DATE-TIME:20220727T151500Z
DTEND;VALUE=DATE-TIME:20220727T153500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-639@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Charlie Cresswell-Hogg ()\nUsing functional RG for f
ermions\, we study new fixed points of 3d Gross-Neveu theories beyond chir
al symmetry. At large N we find that the sextic coupling becomes exactly m
arginal\, leading to a line of UV fixed points. We discuss the generation
of mass in these theories\, the phase diagram and the Bardeen-Moshe-Bander
phenomenon for fermions. Similarities with critical scalar theories are h
ighlighted. We also discuss aspects of four-fermion interactions in four d
imensions.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/639/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/639/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional Flows for Complex Actions
DTSTART;VALUE=DATE-TIME:20220726T123000Z
DTEND;VALUE=DATE-TIME:20220726T125500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-609@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Frederike Ihssen ()\nIn my talk I will present a gen
eral functional renormalisation group framework for the computation of com
plex actions. Resolving the complex structure of quantum theories\, such a
s QCD or condensed matter systems such as graphene or spin-imbalanced ferm
ionic gases\, may shed light on their phase structure. Restrictions on the
phase structure come from exploring complex external fields such as a com
plex magnetic field in spin systems\, or\, more generally\, complex coupli
ngs. The latter gives rise to Lee-Yang zeros in the complex (magnetisation
) plane. For the explicit computations we consider both flows of the Wilso
nian effective action and the 1PI effective action. In the present formula
tions the flow of the Wilsonian effective action has a general range of ap
plicability and we obtain results for a $\\phi^4$ theory in d=0\,1\,2\,3\,
4 dimensions. These results are also compared with that for the 1PI effect
ive action within its range of applicability. Computations are performed u
sing the Discontinious Galerkin Methods. These advanced numerical methods
enable us to solve these highly dynamic equations to very high proximity o
f the ensuing Lee-Yang singularities\, and are reminiscent of reaction-dif
fusion equations (with an RG-kernel).\n\nhttps://indico.tpi.uni-jena.de/ev
ent/199/contributions/609/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/609/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Coarse graining to capture "relevant" information in biological sy
stems
DTSTART;VALUE=DATE-TIME:20220727T070000Z
DTEND;VALUE=DATE-TIME:20220727T074500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-628@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Stephanie Palmer ()\nBiological systems must selecti
vely encode partial information about the environment\, as dictated by the
capacity constraints at work in all living organisms. For example\, we ca
nnot see every feature of the light field that reaches our eyes\; temporal
resolution is limited by transmission noise and delays\, and spatial reso
lution is limited by the finite number of photoreceptors and output cells
in the retina. Classical efficient coding theory describes how sensory sys
tems can maximize information transmission given such capacity constraints
\, but it treats all input features equally. Not all inputs are\, however\
, of equal value to the organism. Our work quantifies whether and how the
brain selectively encodes stimulus features\, specifically predictive feat
ures\, that are most useful for fast and effective movements. We have show
n that efficient predictive computation starts at the earliest stages of t
he visual system\, in the retina. We borrow techniques from statistical ph
ysics and information theory to assess how we get terrific\, predictive vi
sion from these imperfect (lagged and noisy) component parts. In broader t
erms\, we aim to build a more complete theory of efficient encoding in the
brain\, and along the way have found some intriguing connections between
formal notions of coarse graining in biology and physics.\n\nhttps://indic
o.tpi.uni-jena.de/event/199/contributions/628/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/628/
END:VEVENT
BEGIN:VEVENT
SUMMARY:EOS of QCD Matter
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-681@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Andreas Geissel ()\nhttps://indico.tpi.uni-jena.de/e
vent/199/contributions/681/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/681/
END:VEVENT
BEGIN:VEVENT
SUMMARY:RG flows between Gaussian fixed points
DTSTART;VALUE=DATE-TIME:20220726T132000Z
DTEND;VALUE=DATE-TIME:20220726T134500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-613@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Diego Buccio ()\nA scalar theory can have many Gauss
ian (free) fixed points\, corresponding to Lagrangians of the form \\phi\\
box^k\\phi. We use the non-perturbative RG to study the flow from the free
theory with four derivatives (k = 2) to the free theory with two derivati
ves (k = 1)\, in the presence of a shift-invariant interaction.\n\nhttps:/
/indico.tpi.uni-jena.de/event/199/contributions/613/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/613/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Welcome
DTSTART;VALUE=DATE-TIME:20220725T065500Z
DTEND;VALUE=DATE-TIME:20220725T070000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-586@indico.tpi.uni-jena.de
DESCRIPTION:https://indico.tpi.uni-jena.de/event/199/contributions/586/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/586/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Fluid dynamic aspects of the exact renormalization group
DTSTART;VALUE=DATE-TIME:20220728T132000Z
DTEND;VALUE=DATE-TIME:20220728T134500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-671@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Adrian Koenigstein ()\nhttps://indico.tpi.uni-jena.d
e/event/199/contributions/671/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/671/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Novel critical phenomena in compressible polar active fluids
DTSTART;VALUE=DATE-TIME:20220726T153500Z
DTEND;VALUE=DATE-TIME:20220726T155500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-622@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Patrick Jentsch ()\nActive matter describes the coll
ective properties of particles that either possess internal energy or harn
ess energy from the environment to actively self-propel. Diverse biologica
l many-body systems\, like tissue\, or swarms of birds\, fish or bacteria\
, are thus of this type\, and many of which can be modelled as polar activ
e fluids. Since these nonequilibrium systems break conservative laws that
are intrinsic to thermal systems\, such as energy and momentum conservatio
n\, diverse novel nonequilibrium phenomena are expected. In this talk\, I
will describe the use of the functional renormalization group to discover
for the first time new universality classes in compressible polar active f
luids that correspond to a multicritical point of these active systems. ar
Xiv:2205.01610\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/6
22/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/622/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spectral Functions in Banks-Zaks QCD
DTSTART;VALUE=DATE-TIME:20220726T145500Z
DTEND;VALUE=DATE-TIME:20220726T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-619@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Yannick Kluth ()\nThe question of unitarity in pertu
rbatively non-renormalisable field theories such as asymptotically safe qu
antum gravity is notoriously difficult to answer. A possible way to make p
rogress lies in analysing spectral functions given by the Källén-Lehmann
representation of the propagator. For spectral functions of scalar quanti
ties\, unitarity requires positive definiteness as well as normalisability
. Such properties or even the existence of the Källén-Lehmann representa
tion are however not clear for gauge fields or the graviton. To address th
ese difficulties\, we consider QCD in the Banks-Zaks phase which allows st
udying spectral functions of all elementary fields analytically using pert
urbative methods. In particular\, this gives access to the propagator in t
he whole complex plane\, which is difficult to achieve using conventional
ERG methods. We analyse existence properties of spectral functions and tes
t whether they fulfil positive definiteness and normalisability due to uni
tarity. Implications for spectral functions of conventional QCD or quantum
gravity are discussed.\n\nhttps://indico.tpi.uni-jena.de/event/199/contri
butions/619/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/619/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Symmetry constraints for Callan-Symanzik flows in chiral models
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-705@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Sebastian Töpfel ()\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/705/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/705/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stability of the Yang-Mills theory vacuum and Cosmological Inflati
on.
DTSTART;VALUE=DATE-TIME:20220726T155500Z
DTEND;VALUE=DATE-TIME:20220726T161500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-625@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: George Savvidy ()\nWe examine the phenomena of the c
hromomagnetic gluon condensation in Yang-Mills theory and the problem of s
tability of the vacuum state. The stability of the vacuum state is analyse
d in the nonlinear regime. It is shown that an apparent instability of the
Yang Mills vacuum is a result of quadratic approximation. In the case of
(anti)self-dual fields the interaction of chromomagnetic modes of the quan
tised field in the direction of zero modes is calculated by using a new me
thod of infrared regularisation as well as by the integration over the col
lective variables of self-interacting zero modes. The deformation of (anti
)self-dual fields is also considered in the nonlinear regime by the integr
ation\, in this case\, over the collective variables of self-interacting u
nstable modes. All these vacuum field configurations are stable and indica
te that the vacuum is stable and is a superposition of many states. The de
ep interrelation between elementary particle physics and cosmology manifes
ts itself when one considers the contribution of quantum fluctuations of v
acuum fields to the dark energy and the effective cosmological constant. T
he contribution of zero-point energy exceeds by many orders of magnitude t
he observational cosmological upper bound on the energy density of the uni
verse. Therefore it seems natural to expect that vacuum fluctuations of th
e fundamental fields would influence the cosmological evolution in any way
. Our aim is to describe a recent investigation of the influence of the Ya
ng-Mills vacuum polarisation and of the chromomagnetic condensation on the
evolution of Friedmann cosmology\, on inflation and on primordial gravita
tional waves.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/62
5/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/625/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The weak-gravity bound in asymptotically safe gauge-gravity system
s
DTSTART;VALUE=DATE-TIME:20220727T143500Z
DTEND;VALUE=DATE-TIME:20220727T145500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-636@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Marc Schiffer ()\nIn this talk I will discuss the we
ak-gravity bound\, which has been discovered in asymptotically safe gravit
y-matter systems. It limits the maximum strength of the gravitational fluc
tuations. Specifically\, I will discuss the weak-gravity bound in gauge-gr
avity systems with more than one gauge field\, to discover whether systems
with 12 gauge fields (like the Standard Model) exhibit such a bound and w
hether the gravitational fixed point evades it. Furthermore\, I will highl
ight that the existence of the weak-gravity bound in gauge-gravity systems
also has important phenomenological consequences: it is key to a proposed
mechanism that bounds the spacetime dimensionality from above to four or
five dimensions. I will discuss strengthened evidence for this mechanism\,
which indicates that the predictive power of the asymptotic safety paradi
gm could extend to parameters of the spacetime geometry. Finally\, I will
present first steps towards investigating the weak-gravity bound beyond po
lynomial truncations.\n\nhttps://indico.tpi.uni-jena.de/event/199/contribu
tions/636/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/636/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Unconventional superconductivity in moiré transition metal dichal
cogenides
DTSTART;VALUE=DATE-TIME:20220728T074500Z
DTEND;VALUE=DATE-TIME:20220728T083000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-645@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Laura Classen ()\nhttps://indico.tpi.uni-jena.de/eve
nt/199/contributions/645/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/645/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A Generalized fRG Solver for Material Systems
DTSTART;VALUE=DATE-TIME:20220728T123000Z
DTEND;VALUE=DATE-TIME:20220728T125500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-649@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: David Campbell ()\nWe summarize recent work with Nah
om YIrga on the development of a generalized functional Renormalization Gr
oup (fRG) approach to condensed matter systems. Our approach combines mome
ntum decoupling (as in standard RG calculations) with frequency decoupling
(as in the dynamical mean field theories) and band decoupling (necessary
to study the multiband models that apply to various high temperature super
conductors and related materials). Importantly\, we are able to include bo
th electron-electron interactions and electron-phonon interactions in our
solver. We give examples of applications of two- and three-band models for
the Cuprate superconductors and of the effects of both Holstein and Su-Sc
hrieffer-Heeger phonons on the phase diagrams of two-dimensional Hubbard m
odels of strongly correlated systems.\n\nhttps://indico.tpi.uni-jena.de/ev
ent/199/contributions/649/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/649/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Universal scaling at a pre-thermal dark state
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-679@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Tilman Enss ()\nMany open quantum systems are well d
escribed by an effective non-hermitian Hamiltonian generating a time evolu
tion that allows eigenstates to decay and dissipate to the environment. In
this framework\, quantum coherent scaling is traditionally tied to the ap
pearance of dark states\, where the effect of dissipation becomes negligib
le. Here we discuss the universal dynamical scaling after a sudden quench
of the non-hermitian O(N) model Hamiltonian. While universality is general
ly spoiled by non-hermiticity\, we find that for a given set of internal p
arameters short-time scaling behaviour is restored with an initial slip ex
ponent different from that of closed quantum systems. This result is tied
to the compensation of dissipation by interaction effects at short times l
eading to a pre-thermal dark state\, where coherent many-body dynamics can
be observed (arXiv:2112.14180). Separately\, for hermitian systems we fin
d a new class of analytical quench solutions by scaling in complex space a
nd time (arXiv:2203.06098).\n\nhttps://indico.tpi.uni-jena.de/event/199/co
ntributions/679/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/679/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Multiloop functional renormalization group study of the Fermi pola
ron problem
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-682@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Marcel Gievers ()\nImbalanced mixtures of strongly c
orrelated fermions have been investigated both theoretically and experimen
tally for several decades. A single impurity immersed in a Fermi gas is su
bject to a transition from a bound molecule of two different fermion speci
es to a so-called ‘Fermi polaron’ where the impurity forms a quasipart
icle with the surrounding fermions [1]. We study the Fermi polaron problem
theoretically in three dimensions in an experimentally more realistic set
up where there is a finite density of the impurity particles. For this\, w
e apply the recently developed multi-loop functional renormalization group
(mfRG) which is an extension of the conventional functional renormalizati
on group equivalent to the diagrammatic parquet formalism [2]. To handle t
he complexity of the four-point vertex\, we make use of a decomposition in
to processes mediated by single-boson exchanges (SBE) [3]. With this elabo
rate numerical method\, we aim to provide more reliable theoretical predic
tions such as the lifetime of the polaron. [1] R. Schmidt\, T. Enss\, Phys
. Rev. A 83\, 063620 (2011). [2] F. B. Kugler\, J. von Delft\, Phys. Rev.
Lett. 120\, 057403 (2018). [3] E. Walter\, M. Gievers\, A. Ge\, J. von Del
ft\, F. B. Kugler\, aXiv:2201.04878 (2022).\n\nhttps://indico.tpi.uni-jena
.de/event/199/contributions/682/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/682/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entangled magnetic\, charge\, and superconducting pairing correlat
ions in the 2-D Hubbard model
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-684@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Sarah Heinzelmann ()\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/684/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/684/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Truncated-unity FRG approach to minimal models of correlated moir
é materials
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-685@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: ravn henkel ()\nThe functional renormalization group
is a powerful tool to analyze many-body instabilities in strongly-correla
ted electron systems. In a simple but handy truncation scheme\, i.e. the l
evel-two truncation\, it resolves the RG evolution of the two-particle int
eraction vertex. Thereby it manages to detect the leading instability of t
he electron system while taking into account all competing interaction cha
nnels on equal footing. The truncated unity (TU) variant of the channel de
composed FRG scheme facilitates to decrease the numerical effort of such c
alculations considerably. Compared to cubic scaling in the conventional pa
tching scheme\, it has the advantage of linear scaling in the number of co
nsidered exchange momenta. In our work\, we put forward a numerically effi
cient implementation of the TU-FRG and apply it to minimal models for the
newly discovered correlated moiré materials. We carefully explore the num
erical convergence of our scheme in form factors and momentum resolution t
o provide the basis for future applications of realistic models of correla
ted moiré materials.\n\nhttps://indico.tpi.uni-jena.de/event/199/contribu
tions/685/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/685/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The F-theorem in the melonic limit
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-686@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Davide Lettera ()\nThe F-theorem states that in thre
e dimensions the sphere free energy of a field theory must decrease betwee
n ultraviolet and infrared fixed points of the renormalization group flow\
, and it has been proven for unitary conformal field theories (CFTs). We c
onsider here the long-range bosonic O(N)3 model on a spherical background\
, at next-to-next-to-leading order of the 1/N expansion. The model display
s four large-N fixed points and we test and confirm the F-theorem holds in
this case. This is non-trivial as one of the couplings is imaginary\, and
therefore the model is non-unitary at finite N. Despite this\, several te
sts indicating that the large-N CFTs are in fact unitary have been perform
ed: for instance all the OPE coefficients computed so far in the large-N l
imit are real\, and the spectrum of bilinear operators is real and above u
nitarity bounds. Our result\, namely that the F theorem holds at large N\,
can be viewed as further indication that such theories are unitary. As an
added bonus\, we show how conformal partial waves expansions in conformal
field theory can be used to resum infinite classes of vacuum diagrams. No
n-perturbatively\, the jump in the value of the free energy has the interp
retation of the inclusion at the ultraviolet fixed point of an extra non-n
ormalizable contribution in the conformal partial wave expansion. This can
be seen in perturbation theory as the reversal of the sign of an infinite
class of diagrams due to the flow of a coupling constant.\n\nhttps://indi
co.tpi.uni-jena.de/event/199/contributions/686/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/686/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Real-time functional renormalization group for critical dynamics
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-691@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Johannes Roth ()\nReal-time quantities such as spect
ral functions and transport coefficients can serve to examine the real-tim
e evolution of a system close to equilibrium\, as they encode the possible
excitations in the medium and show universal static and dynamic scaling b
ehaviour near a critical point. The functional renormalization group (FRG)
formulated on the Schwinger-Keldysh closed-time path provides an excellen
t calculational tool for such real-time correlations. In this talk I will
present a novel approach for the systematic construction of causal regulat
ors for the FRG\, which comply with the analytic structure of the propagat
ors\, and demonstrate that they can be interpreted as a coupling to a fict
itious external heat bath with FRG scale dependent spectral distribution.
As particular applications I will discuss the relaxational Models A\, B an
d C according to the classification scheme by Halperin and Hohenberg\, and
show how they can be implemented in the real-time FRG. With this setup I
will then present results which demonstrate the generation of dynamic scal
ing behaviour in spectral functions obtained from one and two-loop self-co
nsistent truncation schemes. Our results for the different dynamic critica
l exponents z in both d=2 and 3 spatial dimensions compare favorably with
existing results from the literature.\n\nhttps://indico.tpi.uni-jena.de/ev
ent/199/contributions/691/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/691/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional Spin RG for Rydberg Array Spin Hamiltonians
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-695@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Benedikt Schneider ()\nRydberg-Atom arrays are a ver
satile platform to simulate interesting physics from spin liquids to latti
ce gauge theories. We develop a one-loop functional renormalization group
approach based on Kitaev's pseudo-Majorana spin representation that produc
es quantitative accurate data for Rydberg type Hamiltonians at finite temp
erature. By using the convenient symmetries of the Majorana representation
\, treatment of magnetic fields becomes feasible. The implementation of in
finite lattices with long-range interactions and complicated lattice geome
tries is straightforward.\n\nhttps://indico.tpi.uni-jena.de/event/199/cont
ributions/695/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/695/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Asymptotic freedom and safety in quantum gravity
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-696@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Saswato Sen ()\nWe compute non-perturbative flow equ
ations for the couplings of quantum gravity in fourth order of a derivativ
e expansion. The gauge invariant functional flow equation for arbitrary me
trics allows us to extract β-functions for all couplings. In our truncati
on we find two fixed points. One corresponds to asymptotically free higher
derivative gravity\, the other is an extension of the asymptotically safe
fixed point in the Einstein-Hilbert truncation or extensions thereof. Fur
thermore we describe the flow trajectories to different fixed points for a
subtruncation of Higher derivative gravity. Based on arxiv:2111.04696\n\n
https://indico.tpi.uni-jena.de/event/199/contributions/696/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/696/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The $( 1 + 1 )$-dimensional Gross-Neveu model at non-zero $\\mu$\,
$T$ and finite $N$
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-697@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jonas Stoll ()\nWe investigate the Gross-Neveu model
for a finite number of fermions $N$. The solution of the Gross-Neveu mode
l is well known in the large-$N$ limit ($N \\to \\infty$) but unknown for
finite $N$. We approach the finite-$N$ case with a FRG method\, more preci
sely the Wetterich equation. By using the local potential approximation th
e resulting flow equation for the scale dependent effective potential can
be transformed into a non-linear diffusion equation. This equation is solv
ed numerically by applying a finite volume method. No discrete chiral symm
etry breaking is observed for any finite number of fermions\, arbitrary ch
emical potentials as long as the temperature is non-zero.\n\nhttps://indic
o.tpi.uni-jena.de/event/199/contributions/697/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/697/
END:VEVENT
BEGIN:VEVENT
SUMMARY:From KPZ to Inviscid Burgers universality : a FRG approach
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-698@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Francesco Vercesi ()\nIn one dimension\, the stochas
tic Burgers’ equation\, describing a randomly forced viscous fluid\, can
be obtained from the Kardar-Parisi-Zhang (KPZ) equation for a stochastica
lly growing interface through an exact mapping. Since its introduction\, t
he KPZ equation has been studied broadly\, and found to successfully descr
ibe the universal dynamics of a wide range of systems out of equilibrium\,
from classical interfaces to driven dissipative polariton condensates. In
1D\, the rough KPZ interface is described by a fully attractive fixed-poi
nt corresponding to a finite value of its non-linear coupling g. In a rece
nt numerical work\, a crossover to a different dynamical regime with diffe
rent scaling exponents has been found from numerical simulations of the st
ochastic Burgers equation\, in the limit of zero viscosity. This limit cor
responds in the KPZ equation to the limit of infinite g\, which has not be
en explored so far. In this work\, we present a FRG approach to this regim
e\, revealing a new universal behaviour.\n\nhttps://indico.tpi.uni-jena.de
/event/199/contributions/698/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/698/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shift-symmetric Horndeski models in the asymptotically safe swampl
and?
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-699@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Fabian Wagner ()\nHorndeski theories are widely cons
idered extensions of general relativity\, intended to explain the dark sec
tor dynamically as well as alleviate the existing cosmological tensions. I
n this poster\, I present a first renormalisation group analysis of the su
bclass of shift-symmetric kinetic braiding models\, which still holds up t
o observation after GW170817. In particular\, I show the four arising fixe
d points of which only the shifted Gaussian one is deemed reliable. As the
investigated couplings are all irrelevant at this fixed point\, I conclud
e that these kind of kinetic braiding models are likely not in the asympto
tically safe landscape.\n\nhttps://indico.tpi.uni-jena.de/event/199/contri
butions/699/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/699/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Fluctuation computation of gravitational RG flows on foliated spac
etime
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-700@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jian Wang ()\nThe exact renormalization group is a p
owerful tool to explore the renormalization group fixed points in gravity
and gravity-matter systems. An important open question in this context is
the extension of the formalism to Lorentzian signature computations. One w
ay to incorporate the necessary structures in the presence of a fluctuatin
g spacetime is the Arnowitt-Deser-Misner decomposition of the metric degre
es of freedom. In this talk\, I will present the first analysis of the res
ulting fixed point structure at the level of a fluctuation computation\, r
eading off the flow of the gravitational couplings from the graviton two-p
oint function.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/7
00/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/700/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The $( 1 + 1 )$-dimensional Gross-Neveu model at non-zero $\\mu$\,
$T$ and finite $N$
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-702@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Niklas Zorbach ()\nWe investigate the Gross-Neveu mo
del for a finite number of fermions $N$. The solution of the Gross-Neveu m
odel is well known in the large-$N$ limit ($N \\to \\infty$) but unknown f
or finite $N$. We approach the finite-$N$ case with a FRG method\, more pr
ecisely the Wetterich equation. By using the local potential approximation
the resulting flow equation for the scale dependent effective potential c
an be transformed into a non-linear diffusion equation. This equation is s
olved numerically by applying a finite volume method. No discrete chiral s
ymmetry breaking is observed for any finite number of fermions\, arbitrary
chemical potentials as long as the temperature is non-zero.\n\nhttps://in
dico.tpi.uni-jena.de/event/199/contributions/702/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/702/
END:VEVENT
BEGIN:VEVENT
SUMMARY:SU(2) gauge theory of the pseudogap phase in the two-dimensional H
ubbard model
DTSTART;VALUE=DATE-TIME:20220725T123000Z
DTEND;VALUE=DATE-TIME:20220725T125500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-592@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Pietro Maria Bonetti ()\nWe present a SU(2) gauge th
eory of fluctuating magnetic order in the two-dimensional Hubbard model. T
he theory is based on a fractionalization of electrons in fermionic chargo
ns and bosonic spinons. The chargons undergo Néel or spiral magnetic orde
r below a density dependent transition temperature $T^∗$. Fluctuations o
f the spin orientation are described by a non-linear sigma model obtained
from a gradient expansion of the spinon action. The spin stiffnesses are c
omputed from a renormalization group improved random phase approximation.
Our approximations are applicable for a weak or moderate Hubbard interacti
on. The spinon fluctuations prevent magnetic long-range order of the elect
rons at any finite temperature. The phase with magnetic chargon order exhi
bits many features characterizing the pseudogap regime in high-Tc cuprates
: a strong reduction of charge carrier density\, a spin gap\, Fermi arcs\,
and electronic nematicity.\n\nhttps://indico.tpi.uni-jena.de/event/199/co
ntributions/592/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/592/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A study of a toy model of hydrodynamic turbulence using the NPRG
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-703@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Côme Fontaine ()\nThe functional renormalisation gr
oup has already been successfully used to study turbulence and it appears
as a very natural tool for this problem. However\, there remains an unsolv
ed problem related to the calculation of the structure functions in the tu
rbulent state\, which is hard to tackle directly from the Navier-Stokes eq
uations. In this work\, we study a simpler model: the Sabra shell model. S
hell models form a family of toy models that reproduce key properties of h
ydrodynamic turbulence\, and in particular the anomalous exponents of the
structure functions. In this work\, we present a FRG approach to the Sabra
model and the results obtained from this method for the structure functio
ns of this model.\n\nhttps://indico.tpi.uni-jena.de/event/199/contribution
s/703/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/703/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dilaton Quantum Gravity
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-706@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Athanasios Kogios ()\nIn this presentation\, I will
talk about asymptotically safe dilaton gravity. To that end we solve the c
oupled set of flow equations for the field dependent Newton constant F(phi
)\, cosmological constant or dilaton potential V(phi) and dilaton wave fun
ction K(phi)\, including the physical vanishing cutoff scale. At vanishing
dilaton field we recover classical general relativity\, while we approach
an asymptotically safe regime for large field amplitudes. In addition\, t
he dilaton potential at physical vanishing cutoff scale is essential for t
he study of the slow-roll-inflation scenario.\n\nhttps://indico.tpi.uni-je
na.de/event/199/contributions/706/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/706/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Non perturbative strings\, asymptotic safety\, and the swampland
DTSTART;VALUE=DATE-TIME:20220728T123000Z
DTEND;VALUE=DATE-TIME:20220728T125500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-708@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Alessia Platania ()\nhttps://indico.tpi.uni-jena.de/
event/199/contributions/708/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/708/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Universal quantities at high orders of the derivative expansion
DTSTART;VALUE=DATE-TIME:20220728T125500Z
DTEND;VALUE=DATE-TIME:20220728T132000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-670@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Gonzalo De Polsi ()\nIn the context of the Functiona
l Renormalization Group\, the Derivative Expansion is one of the most empl
oyed approximation schemes. In the last decade\, this scheme has been push
ed up to order $\\mathcal{O}(\\partial^6)$ for the Ising model universalit
y class and to order $\\mathcal{O}(\\partial^4)$ for the $O(N)$ models. Th
is allowed us to comprehend better the properties and behaviour of this sc
heme and enabled the introduction of error bars for the computed quantitie
s. As a consequence\, in the last few years not only critical exponents bu
t also universal amplitude ratios were computed with a precision and accur
acy comparable with the most precise results in the literature and\, in so
me cases\, they are the reference results. In this talk I will discuss the
se recent results in view of the new developments of the derivative expans
ion.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/670/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/670/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Functional renormalization for the beginning and the present Unive
rse
DTSTART;VALUE=DATE-TIME:20220729T074500Z
DTEND;VALUE=DATE-TIME:20220729T083000Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-663@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Christof Wetterich ()\nFunctional renormalization fo
r quantum gravity with a scalar field computes at the fixed point the scal
ing solution for the effective scalar potential for the whole range of the
scalar field. Similarly\, one investigates the scaling solution for the s
calar-field-dependent effective Planck mass ( coefficient function of the
curvature scalar). The solution of the field equations derived from the co
rresponding effective action determines the cosmology. The region of small
scalar field values leads to an inflationary cosmology at the beginning o
f the Universe. The large field region describes dynamical dark energy in
the present Universe\, with a cosmological constant that vanishes in the i
nfinite future. Between the two limits the field-dependent couplings of th
e scaling solution account for the running couplings in the scale invarian
t standard model of particle physics. No flow away from the scaling soluti
on may be needed.\n\nhttps://indico.tpi.uni-jena.de/event/199/contribution
s/663/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/663/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gauge dependence of Essential Quantum Einstein Gravity
DTSTART;VALUE=DATE-TIME:20220727T155500Z
DTEND;VALUE=DATE-TIME:20220727T161500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-709@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Oleg Melichev ()\nThe Essential Functional Renormali
sation Group\, applied to quantum gravity\, allows the metric to be repara
metrised along the RG trajectory\, such that only the essential couplings
are renormalised. This allows to simplify the study of the properties of t
he fixed points. It is of interest to investigate the behaviour of the sol
utions with respect to a change of the gauge fixing parameters. In this wo
rk we compute the flow up to the fourth order in derivative expansion usin
g a generic class of gauges for which the kinetic operator becomes nonmini
mal. To this end we implement the off-diagonal heat kernel technique also
known as the Universal RG Machine. We compute the position of the fixed po
ints using Landau and Feynman gauges and discuss the applicability of used
approximations.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions
/709/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/709/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Towards the phase structure of the complete Lorentzian Barrett-Cra
ne model
DTSTART;VALUE=DATE-TIME:20220726T155500Z
DTEND;VALUE=DATE-TIME:20220726T161500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-624@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Andreas Pithis ()\nThe Barrett-Crane spin foam and G
FT model is a state-sum model which provides a quantization of first order
Lorentzian Palatini gravity. Its complete formulation has only recently b
een accomplished. It is conjectured that the collective dynamics of the qu
anta of this model\, which correspond to discrete building blocks of space
time with spacelike\, timelike and lightlike components\, gives rise to co
ntinuum spacetime at criticality via phase transition. In this talk\, we d
iscuss how phase transitions for this and related models can be studied us
ing Landau-Ginzburg mean-field theory. To this aim\, we restrict the build
ing blocks of the complete model such that the Feynman diagrams are dual t
o spacelike triangulations. We also include degrees of freedom which may b
e interpreted as discretized scalar fields on the lattice typically employ
ed in quantum gravity to furnish a matter reference frame. This setting la
ys the groundwork to study the critical behavior when arbitrary Lorentzian
building blocks are incorporated and represents a crucial advance to unde
rstand how phase transitions to continuum spacetime can be achieved in thi
s setting. It also paves the way for the analysis of the phase structure o
f such models via functional renormalization group techniques in the futur
e.\n\nhttps://indico.tpi.uni-jena.de/event/199/contributions/624/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/624/
END:VEVENT
BEGIN:VEVENT
SUMMARY:--
DTSTART;VALUE=DATE-TIME:20220725T145500Z
DTEND;VALUE=DATE-TIME:20220725T151500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-710@indico.tpi.uni-jena.de
DESCRIPTION:https://indico.tpi.uni-jena.de/event/199/contributions/710/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/710/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A functional RG perspective on the 2D Hubbard model
DTSTART;VALUE=DATE-TIME:20220729T100000Z
DTEND;VALUE=DATE-TIME:20220729T104500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-666@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Sabine Andergassen ()\nThe Hubbard model is the simp
lest model of interacting fermions on a lattice and is of similar importan
ce to correlated electron physics as the Ising model is to statistical mec
hanics. Despite its simplicity\, the model exhibits a rich physical behavi
or and has been proposed as an effective model for electrons moving in the
copper-oxygen planes of cuprate high-temperature superconductors. The fun
ctional RG stability analysis\, originally developed for the 2D Hubbard mo
del describing tight-binding fermions with a local interaction on a square
lattice\, provided the first conclusive evidence for the existence of d-w
ave superconductivity with a sizable energy gap at moderate interaction st
rength. Since then large progress has been achieved in its treatment with
various theoretical and numerical methods. We here present recent advancem
ents in the functional RG showing that the flow can be brought to a quanti
tative level for two-dimensional problems\, which opens the route towards
the realistic numerical investigations of more general systems.\n\nhttps:/
/indico.tpi.uni-jena.de/event/199/contributions/666/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/666/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Phonon renormalization and Pomeranchuk instability in the Holstein
model
DTSTART;VALUE=DATE-TIME:20220725T152000Z
DTEND;VALUE=DATE-TIME:20220725T163500Z
DTSTAMP;VALUE=DATE-TIME:20240302T125350Z
UID:indico-contribution-199-704@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Max Oberon Hansen ()\, Niklas Cichutek ()\nThe Holst
ein model with dispersionless Einstein phonons is one of the simplest mode
ls describing electron-phonon interactions in condensed matter. A naive e
xtrapolation of perturbation theory in powers of the relevant dimensionles
s electron-phonon coupling suggests that at zero temperature the model exh
ibits \na Pomeranchuk instability characterized by a divergent uniform com
pressibility at a critical value where the dimensionless electron-phonon c
oupling is of order unity. In this work\, we re-examine this problem using
modern functional renormalization group (RG) methods. For dimensions d >
3 we find that the RG flow of the Holstein model indeed exhibits a tricrit
ical fixed point\nassociated with a Pomeranchuk instability. This non-Gaus
sian fixed point is ultraviolet stable and is closely related to the well-
known ultraviolet stable fixed point of phi^3-theory above six dimensions.
To realize the Pomeranchuk critical point in the Holstein model at fixed
density both the dimensionless electron-phonon coupling and the adiabatic
ratio (phonon frequency divided by Fermi Energy) have to be fine-tuned to
assume critical values of order unity. On the other hand\, for dimensions
d=3 or smaller we find that the RG flow of the Holstein model does not hav
e any critical fixed points. This rules out a quantum critical point assoc
iated with a Pomeranchuk instability in d=3 or smaller.\n\nhttps://indico.
tpi.uni-jena.de/event/199/contributions/704/
LOCATION:
URL:https://indico.tpi.uni-jena.de/event/199/contributions/704/
END:VEVENT
END:VCALENDAR