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25/07/2022, 08:55
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Scott Melville25/07/2022, 09:00
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Razvan Gurau25/07/2022, 09:45
The latest addition to the family of 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 large N limit but more amenable to analytic computations that the planar one. 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...
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Zohar Ringel25/07/2022, 11:00
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Volker Meden25/07/2022, 11:45
I present an overview of our recent applications of funtional RG for zero- and one-dimensional many-fermion systems. The vertex expansion scheme with the two-particle interaction U being the small parameter is used. Equilibrium as well as nonequilibrium situations are considered. Several questions are tackled. Can one describe phase transitions which occur at finite U? If so, what is the role...
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Stefan Floerchinger25/07/2022, 14:30
Extended symmetry transformations do not leave the action fully invariant, but change it by a term linear in field expectation values or known composite fields. I will discuss how this leads to a modified version of Noethers theorem with currents that are conserved up to known terms. I will also discuss how an extended version of Galilei boost symmetry allows to close and solve renormalization...
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Pietro Maria Bonetti25/07/2022, 14:30
We present a SU(2) gauge theory of fluctuating magnetic order in the two-dimensional Hubbard model. The theory is based on a fractionalization of electrons in fermionic chargons and bosonic spinons. The chargons undergo Néel or spiral magnetic order below a density dependent transition temperature $T^∗$. Fluctuations of the spin orientation are described by a non-linear sigma model obtained...
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Benjamin Knorr25/07/2022, 14:55
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Ivan Balog25/07/2022, 14:55
Authors: Ivan Balog, Adam Rançon, Bertrand Delamotte; The question of probabilistic interpretation of the renormalization 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 constituents of the system are strongly correlated, e.g. approaching...
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Aaron Held25/07/2022, 15:20
Renormalization-Group (RG) improvement has been applied to capture the effect of gravitational quantum corrections on cosmological and black-hole spacetimes. In this talk, I will use an 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...
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Nicolo Defenu25/07/2022, 15:20
The 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 Berezinskii - Kosterlitz - Thouless (BKT) phenomenology. We will discuss the deformation of the BKT scaling caused by the inclusion of power-law decaying couplings, yielding a coexistence of spontaneously symmetry broken...
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Chris Ripken25/07/2022, 16:15
One of the goals of the Asymptotic Safety program for gravity is to compute the effective action at k=0. However, given such an action, what are the concrete physical predictions that we can derive from it? Generically, the renormalization group will generate an infinite number of interactions in the effective action. It is therefore an interesting question which interactions can arise, and...
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Nicolas Dupuis25/07/2022, 16:15
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Johannes Thürigen25/07/2022, 16:35
Combinatorially non-local interactions are at the heart of matrix and tensor theories as well as non-commutative field theory. Interestingly, for theories on a compact domain their renormalization group equations are non-autonomous in the momentum scale. 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...
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Jonas Hauck25/07/2022, 16:35
Describing the emergence of phases of matter is one of the central challenges in physics. The main complication is the tremendous computational effort required to investigate real materials. Therefore, approximations to enable accurate and fast calculations are of central importance to deepening our understanding of phases of matter. Here, we present a new truncated unity (TU) approach...
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25/07/2022, 16:55
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Demetrio Vilardi25/07/2022, 16:55
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Côme Fontaine25/07/2022, 17:20
The functional renormalisation group has already been successfully used to study turbulence and it appears as a very natural tool for this problem. However, there remains an unsolved problem related to the calculation of the structure functions in the turbulent state, which is hard to tackle directly from the Navier-Stokes equations. In this work, we study a simpler model: the Sabra shell...
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Saswato Sen25/07/2022, 17:20
We compute non-perturbative flow equations for the couplings of quantum gravity in fourth order of a derivative expansion. The gauge invariant functional flow equation for arbitrary metrics allows us to extract β-functions for all couplings. In our truncation we find two fixed points. One corresponds to asymptotically free higher derivative gravity, the other is an extension of the...
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Abdol Sabor Salek25/07/2022, 17:20
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Dimitrios Gkiatas25/07/2022, 17:20
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Athanasios Kogios25/07/2022, 17:20
In this presentation, I will talk about asymptotically safe dilaton gravity. To that end we solve the coupled set of flow equations for the field dependent Newton constant F(phi), cosmological constant or dilaton potential V(phi) and dilaton wave function K(phi), including the physical vanishing cutoff scale. At vanishing dilaton field we recover classical general relativity, while we approach...
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Sarah Heinzelmann25/07/2022, 17:20
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Andreas Geissel25/07/2022, 17:20
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Jian Wang25/07/2022, 17:20
The exact renormalization group is a powerful 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 way to incorporate the necessary structures in the presence of a fluctuating spacetime is the Arnowitt-Deser-Misner decomposition of the...
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Hannes Braun25/07/2022, 17:20
We apply the functional renormalisation group to the two-dimensional Hubbard model to investigate the pseudogap opening. Extending previous applications at half filling [Phys. Rev. Research 2, 033068 (2020)], we here explore the physics in the more relevant finite-doping regime. In particular, we present a systematic analysis of the different contributions to the self-energy by performing a...
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Kilian Fraboulet25/07/2022, 17:20
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Francesco Vercesi25/07/2022, 17:20
In one dimension, the stochastic Burgers’ equation, describing a randomly forced viscous fluid, can be obtained from the Kardar-Parisi-Zhang (KPZ) equation for a stochastically growing interface through an exact mapping. Since its introduction, the KPZ equation has been studied broadly, and found to successfully describe the universal dynamics of a wide range of systems out of equilibrium,...
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Carlos I. Perez Sanchez25/07/2022, 17:20
In this poster we report recent progress in understanding the algebraic structure underlying Wetterich Equation for multimatrix models (this sort of model is inspired by noncommutative geometry and contains interactions indexed by the free algebra, i.e. words in the random matrices). The tools can be useful in discretization approaches to quantum gravity and combinatorics of maps. Based on...
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Benedikt Schneider25/07/2022, 17:20
Rydberg-Atom arrays are a versatile platform to simulate interesting physics from spin liquids to lattice gauge theories. We develop a one-loop functional renormalization group approach based on Kitaev's pseudo-Majorana spin representation that produces quantitative accurate data for Rydberg type Hamiltonians at finite temperature. By using the convenient symmetries of the Majorana...
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Pavan Dharanipragada25/07/2022, 17:20
Holographic RG is the interpretation 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, the precise regularisation of the boundary theory that allows this interpretation hasn't been looked at. I will show one such regularisation using...
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Lukas Debbeler25/07/2022, 17:20
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Adam Kline25/07/2022, 17:20
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Aiman Al-Eryani25/07/2022, 17:20
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Marcel Gievers25/07/2022, 17:20
Imbalanced mixtures of strongly correlated fermions have been investigated both theoretically and experimentally for several decades. A single impurity immersed in a Fermi gas is subject to a transition from a bound molecule of two different fermion species to a so-called ‘Fermi polaron’ where the impurity forms a quasiparticle with the surrounding fermions [1]. We study the Fermi polaron...
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Richard Schmieden25/07/2022, 17:20
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Max Oberon Hansen, Niklas Cichutek25/07/2022, 17:20
The Holstein model with dispersionless Einstein phonons is one of the simplest models describing electron-phonon interactions in condensed matter. A naive extrapolation of perturbation theory in powers of the relevant dimensionless electron-phonon coupling suggests that at zero temperature the model exhibits
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a Pomeranchuk instability characterized by a divergent uniform compressibility at a... -
Johannes Roth25/07/2022, 17:20
Real-time quantities such as spectral functions and transport coefficients can serve to examine the real-time evolution of a system close to equilibrium, as they encode the possible excitations in the medium and show universal static and dynamic scaling behaviour near a critical point. The functional renormalization group (FRG) formulated on the Schwinger-Keldysh closed-time path provides an...
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Fabian Wagner25/07/2022, 17:20
Horndeski theories are widely considered extensions of general relativity, intended to explain the dark sector dynamically as well as alleviate the existing cosmological tensions. In this poster, I present a first renormalisation group analysis of the subclass of shift-symmetric kinetic braiding models, which still holds up to observation after GW170817. In particular, I show the four arising...
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Jonas Wessely25/07/2022, 17:20
We derive renormalized Callan-Symanzik Flowequations in the FRG setup and apply the framework of spectral renormalisation to compute the full, nonperturbative spectral function of a \phi^4 theory in (2+1) dimensions
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Nikolaos Parthenios25/07/2022, 17:20
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Sebastian Töpfel25/07/2022, 17:20
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Jonas Stoll25/07/2022, 17:20
We investigate the Gross-Neveu model for a finite number of fermions $N$. The solution of the Gross-Neveu model 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 precisely the Wetterich equation. By using the local potential approximation the resulting flow equation for the scale dependent effective...
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Niklas Zorbach25/07/2022, 17:20
We investigate the Gross-Neveu model for a finite number of fermions $N$. The solution of the Gross-Neveu model 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 precisely the Wetterich equation. By using the local potential approximation the resulting flow equation for the scale dependent effective...
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Davide Lettera25/07/2022, 17:20
The F-theorem states that in three dimensions the sphere free energy of a field theory must decrease between ultraviolet and infrared fixed points of the renormalization group flow, and it has been proven for unitary conformal field theories (CFTs). We consider 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...
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Rafael Robson Lino dos Santos25/07/2022, 17:20
An asymptotically-safe theory of quantum gravity could render a non-perturbative renormalization of general relativity, restoring its predictive power at higher energies. The asymptotic-safety community has been finding indications for that, mainly using the functional renormalization group framework. In this poster, I will explore the predictive power of asymptotically-safe quantum gravity...
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Franz Richard Sattler25/07/2022, 17:20
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ravn henkel25/07/2022, 17:20
The functional renormalization group is a powerful tool to analyze many-body instabilities in strongly-correlated electron systems. In a simple but handy truncation scheme, i.e. the level-two truncation, it resolves the RG evolution of the two-particle interaction vertex. Thereby it manages to detect the leading instability of the electron system while taking into account all competing...
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Tilman Enss25/07/2022, 17:20
Many open quantum systems are well described by an effective non-hermitian Hamiltonian generating a time evolution that allows eigenstates to decay and dissipate to the environment. In this framework, quantum coherent scaling is traditionally tied to the appearance of dark states, where the effect of dissipation becomes negligible. Here we discuss the universal dynamical scaling after a sudden...
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Nahzaan Riyaz25/07/2022, 17:20
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Emanuel Gull26/07/2022, 09:00
Simulations of finite temperature quantum systems provide imaginary frequency Green's functions that correspond one-to-one to experimentally measurable real-frequency spectral functions. However, due to the bad conditioning of the continuation transform from imaginary to real frequencies, established methods tend to either wash out spectral features at high frequencies or produce spectral...
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Jens Braun26/07/2022, 09:45
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Renata Ferrero26/07/2022, 11:00
Within the functional renormalization 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 modified spectral flow of the metric dependent d'Alembertian, or of similar hyperbolic kinetic operators. The corresponding one-parameter family...
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Manuel Reichert26/07/2022, 11:30
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Urko Reinosa26/07/2022, 12:00
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Frederike Ihssen26/07/2022, 14:30
In my talk I will present a general functional renormalisation group framework for the computation of complex actions. Resolving the complex structure of quantum theories, such as QCD or condensed matter systems such as graphene or spin-imbalanced fermionic gases, may shed light on their phase structure. Restrictions on the phase structure come from exploring complex external fields such as a...
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Peter Kopietz26/07/2022, 14:30
We determine the global renormalization group (RG) flow of the Sachdev-Ye-Kitaev (SYK) model. From a controlled truncation of the infinite hierarchy of the exact functional RG flow equations 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...
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Takeru Yokota26/07/2022, 14:55
The development of theoretical methods for classical liquids is a longstanding problem in statistical mechanics. Accurate and efficient methods for classical liquids benefit, for instance, 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...
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Juergen Eser26/07/2022, 14:55
I present calculations of the S-wave isospin-zero and isospin-two pion-pion scattering lengths within a nucleon-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...
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Masatoshi Yamada26/07/2022, 15:20
The Yang-Mills gauge theory in 5 dimensional spacetime is perturbatively non-renormalizable, but could be asymptotically safe. We study the fixed point structure by using the functional renormalization group.
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Diego Buccio26/07/2022, 15:20
A scalar theory can have many Gaussian (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 derivatives (k = 1), in the presence of a shift-invariant interaction.
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Marcel Gievers26/07/2022, 16:15
The recently introduced single-boson exchange (SBE) decomposition [2] of the four-point vertex of interacting fermionic many-body systems is a conceptually and computationally appealing parametrization of the vertex. It relies on the notion of reducibility of vertex diagrams with respect to the bare interaction U, instead of a classification based on two-particle reducibility within the...
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Jan Horak26/07/2022, 16:15
We investigate timelike correlation functions in QCD via spectral functional renormalisation group and Dyson-Schwinger equations. Within the spectral formulation, direct access to the full complex structure of the theory is obtained. Studying the propagation of non-holomorphicities through the coupled system of DSEs in Yang-Mills theory, we obtain consistency conditions which constrain the...
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31. Critical behaviour at thermal m-axial Lifshitz point and stability of the FFLO superfluid phasesMateusz Homenda26/07/2022, 16:35
We apply nonperturbative renormalization group method to critical exponents of m-axial Lifshitz point as a function of dimensionality d, anisotropy m and the number of order parameter components N. Basing on the results we consider the stability of the Fulde-Ferrell-Larkin-Ovchinnikov states in cold atom system.
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Gergely Fejos26/07/2022, 16:35
We calculate the renormalization group flows of all renormalizable interactions in the three dimensional Ginzburg--Landau potential for the chiral phase transition of three flavor quantum 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 transition in the infrared. This shows that longstanding assumptions on...
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Jonas von Milczewski26/07/2022, 16:55
We study theoretically the lifetimes of the attractive and the repulsive Fermi Polaron and the molecule at finite momentum in both two and three dimensions. To this end we developed a new technique that allows for the computation of Green's functions in the whole complex frequency plane using exact analytical continuation within the functional renormalization group. While conventional...
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Yannick Kluth26/07/2022, 16:55
The question of unitarity in perturbatively non-renormalisable field theories such as asymptotically safe quantum gravity is notoriously difficult to answer. A possible way to make progress lies in analysing spectral functions given by the Källén-Lehmann representation of the propagator. For spectral functions of scalar quantities, unitarity requires positive definiteness as well as...
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Chiu Fan Lee26/07/2022, 17:15
A hallmark of living organisms is the ability to move around in their environments. In the fluid state, i.e., when the motile agents can exchange neighbours freely, the equations of 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...
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Alaric Erschfeld26/07/2022, 17:15
The formation of cosmic large-scale structures can be described with a statistical field theory for the dynamics of dark matter. The functional renormalisation group is on the one hand studied using the underlying symmetries of the theory and in particular using an extended version of Galilean invariance. The corresponding generalised Ward identities allow to close and solve the flow equations...
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Cristóbal Laporte26/07/2022, 17:35
In this work, a cosmological 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 quantities are understood as a result of effective, and thus scale-dependent, couplings. In the approach where the scale–dependence appears as a...
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Patrick Jentsch26/07/2022, 17:35
Active matter describes the collective properties of particles that either possess internal energy or harness energy from the environment to actively self-propel. Diverse biological 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 active fluids. Since these nonequilibrium systems break conservative laws that...
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George Savvidy26/07/2022, 17:55
We examine the phenomena of the chromomagnetic gluon condensation in Yang-Mills theory and the problem of stability of the vacuum state. The stability of the vacuum state is analysed 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...
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Andreas Pithis26/07/2022, 17:55
The Barrett-Crane spin foam and GFT model is a state-sum model which provides a quantization of first order Lorentzian Palatini gravity. Its complete formulation has only recently been accomplished. It is conjectured that the collective dynamics of the quanta of this model, which correspond to discrete building blocks of spacetime with spacelike, timelike and lightlike components, gives rise...
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Stephanie Palmer27/07/2022, 09:00
Biological systems must selectively encode partial information about the environment, as dictated by the capacity constraints at work in all living organisms. For example, we cannot see every feature of the light field that reaches our eyes; temporal resolution is limited by transmission noise and delays, and spatial resolution is limited by the finite number of photoreceptors and output cells...
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Valerio Lucarini27/07/2022, 09:45
The climate system is a complex, chaotic system with many degrees of freedom and variability on a vast range of temporal and spatial scales. Attaining a deeper level of understanding of its dynamical processes is a scientific challenge of great urgency, especially given the ongoing climate change and the evolving climate crisis. In statistical physics, complex, many-particle systems are...
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Kevin Falls27/07/2022, 11:00
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Luca Zambelli27/07/2022, 11:30
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Nicolás Wschebor27/07/2022, 12:00
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Reinhard Alkofer27/07/2022, 16:15
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Sabine Harribey27/07/2022, 16:15
Tensor models admit a melonic large 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 with a long-range propagator and a purely imaginary coupling constant....
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Junichi Haruna27/07/2022, 16:35
Gradient Flow Exact Renormalization 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 of gauge theories or quantum gravity. On the other hand, some scalar models (such as the CP^N-1 model or the O(N) non-linear sigma model) share...
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Marc Schiffer27/07/2022, 16:35
In this talk I will discuss the weak-gravity bound, which has been discovered in asymptotically safe gravity-matter systems. It limits the maximum strength of the gravitational fluctuations. Specifically, I will discuss the weak-gravity bound in gauge-gravity systems with more than one gauge field, to discover whether systems with 12 gauge fields (like the Standard Model) exhibit such a bound...
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Gustavo de Brito27/07/2022, 16:55
In this talk, I will explore the effect of quantum gravity on matter couplings within a Renormalization Group framework. In particular, I will focus on results obtained from a class of interpolating regulators that allow us to extract certain universal pieces from non-universal quantities. I will discuss an explicit example of how misleading conclusions can be drawn by analyzing the...
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Félix Rose27/07/2022, 16:55
Using the nonperturbative functional renormalization group (FRG) within the Blaizot-Méndez-Galain-Wschebor approximation, we compute the operator product expansion (OPE) coefficient c112 associated with the operators O1∼φ and O2∼φ2 in the three-dimensional O(N) universality class and in the Ising universality class (N=1) in dimensions 2≤d≤4. When available, exact results and estimates from the...
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Charlie Cresswell-Hogg27/07/2022, 17:15
Using functional RG for fermions, we study new fixed points of 3d Gross-Neveu theories beyond chiral symmetry. At large N we find that the sextic coupling becomes exactly marginal, 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...
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Nobuyoshi Ohta27/07/2022, 17:15
We discuss the quantum improvement of black hole solutions in the context of asymptotic safety. The Newton coupling in this formulation depends on an energy scale, which must be identified with some length scale in order to study physical consequences to black holes. However, no physical principle has so far been known for the identification. Here we propose that the consistency of the first...
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Johanna Borissova27/07/2022, 17:35
Quantum counterparts to classical black holes provide an exciting ground for phenomenology of quantum gravity. Within the functional renormalization group approach to quantum gravity, we propose a novel method to account for quantum effects in classical spacetimes. At the core of our construction is the decoupling mechanism: when a physical infrared scale overcomes the effect of the artificial...
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Shouryya Ray27/07/2022, 17:35
The Gross-Neveu SO(3) universality class in three spacetime dimensions describes a quantum critical point between 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 magnets with strong exchange frustration. Here, I shall report on...
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27/07/2022, 17:55
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Oleg Melichev27/07/2022, 17:55
The Essential Functional Renormalisation Group, applied to quantum gravity, allows the metric to be reparametrised along the RG trajectory, such that only the essential couplings are renormalised. This allows to simplify the study of the properties of the fixed points. It is of interest to investigate the behaviour of the solutions with respect to a change of the gauge fixing parameters. In...
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Stefan Hollands28/07/2022, 09:00
With the help of the renormalization group flow equations a la Wilson-Wegner-Polchinski-Wetterich several hitherto conjectural properties and several new properties of the operator 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...
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Laura Classen28/07/2022, 09:45
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Pawel Jakubczyk28/07/2022, 11:00
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Dante Kennes28/07/2022, 11:30
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Léonie Canet28/07/2022, 12:00
Shell models are simplified models of turbulence, describing discrete Fourier modes of velocity coupled via purely local interactions in spectral space. Yet these simple models reproduce all characteristic features of Navier-Stokes turbulence, including intermittency. I will present a FRG analysis of these models, and show that the turbulent regime corresponds to a non-trivial fixed-point. I...
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David Campbell28/07/2022, 14:30
We summarize recent work with Nahom YIrga on the development of a generalized functional Renormalization Group (fRG) approach to condensed matter systems. Our approach combines momentum 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...
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Alessia Platania28/07/2022, 14:30
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Carlos Sánchez28/07/2022, 14:55
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Gonzalo De Polsi28/07/2022, 14:55
In the context of the Functional Renormalization Group, the Derivative Expansion is one of the most employed approximation schemes. In the last decade, this scheme has been pushed up to order $\mathcal{O}(\partial^6)$ for the Ising model universality class and to order $\mathcal{O}(\partial^4)$ for the $O(N)$ models. This allowed us to comprehend better the properties and behaviour of this...
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Adrian Koenigstein28/07/2022, 15:20
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Lucija Nora Farkas28/07/2022, 15:20
The lower critical dimension $d_l$ is the spatial dimension on which fluctuations destroy the phase transition. 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 result of Goldstone modes and where $d_l=2$ is well understood in the RG formalism. We explore whether the Functional Renormalization Group methods can...
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Markus Fröb28/07/2022, 16:15
Employing the RG flow equations for 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 corrections in the CFT. I derive recursion relations for CFT correlation functions which generalize existing results in the large-N limit to all...
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Björn Sbierski28/07/2022, 16:15
Frustrated three-dimensional quantum magnets bear a rich phenomenology but are notoriously hard to treat theoretically. We show how a SO(3) Majorana representation of spin operators, in combination with the functional renormalization group allows for quantitative simulations at finite temperatures. Focusing on Heisenberg magnets, we establish a finite-size scaling approach and extract critical...
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Jobst Ziebell28/07/2022, 16:35
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Andreas Rückriegel28/07/2022, 16:35
We investigate dimerized quantum 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 dimers as initial condition for the renormalization group flow equations, we...
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Andrzej Chlebicki28/07/2022, 16:55
We investigate the low-temperature behaviour of the O(N) models for 1<d,N<2. We identify a phase with algebraic correlations similar to the Kosterlitz-Thouless phase but characterized by a universal anomalous dimension. We sketch the region of the (d,N)-plane where the algebraic low-temperature phase is present and calculate the anomalous dimension as a function of (d,N).
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Dario Zappala28/07/2022, 16:55
We analyse some aspects of higher derivative Lifshitz-type field theories that exhibit anisotropic scaling laws near the Lifshitz fixed point, with explicit breaking of Lorentz symmetry. Specifically, anisotropic models in 3+1 dimension with dynamical exponent z=3 and with all momentum dependent vertex operators discarded, show restoration of Lorentz symmetry in the infrared region. At the...
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Antonio Pereira28/07/2022, 17:15
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Shunsuke Yabunaka28/07/2022, 17:15
We study the tetracritical fixed point in O(N) models with NPRG. Increasing N, we find that the tetracritical FP continues to exist up to N=\infty, which is a different scenario 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 FP potential at the special point becomes singular in a way that the FP...
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Maximilian Becker28/07/2022, 17:35
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Peter Millington28/07/2022, 17:35
We can define various quantum effective actions, each of which may have particular utility or convenience, in analogy to the Routhians of classical mechanics. In this talk, we provide an update on efforts to provide pedagogical and explicit illustrations of the construction and subtleties of various effective actions and, in particular, the one-particle-irreducible, average...
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Johanna Erdmenger29/07/2022, 09:00
I will give a brief overview of the holographic RG in the context of the AdS/CFT correspondence, considering both flows to IR fixed points as well as to confining dual field theories. I will highlight recent developments on relating information-theory concepts such as entanglement entropy to geometric objects in dual hyperbolic spaces. Moreover, I will present recent results on the analogy...
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Christof Wetterich29/07/2022, 09:45
Functional renormalization for quantum gravity with a scalar field computes at the fixed point the scaling solution for the effective scalar potential for the whole range of the scalar field. Similarly, one investigates the scaling solution for the scalar-field-dependent effective Planck mass ( coefficient function of the curvature scalar). The solution of the field equations derived from the...
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Nicolas Wink29/07/2022, 11:00
The 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 connection between RG flows and convection-diffusion equations is given. These properties, as well as the connection to phase transitions, are made explicit at the example of O(N) theories in various variations. Finally,...
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Marcello Porta29/07/2022, 11:30
We consider the edge transport properties of a generic class of interacting quantum Hall systems on a cylinder, in the infinite volume and zero temperature limit. We prove that the large-scale behavior of the edge correlation functions is effectively described by the multi-channel Luttinger model. In particular, we prove that the edge conductance is universal, and equal to the sum of the...
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Sabine Andergassen29/07/2022, 12:00
The Hubbard model is the simplest model of interacting fermions on a lattice and is of similar importance to correlated electron physics as the Ising model is to statistical mechanics. Despite its simplicity, the model exhibits a rich physical behavior and has been proposed as an effective model for electrons moving in the copper-oxygen planes of cuprate high-temperature superconductors. The...
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Diego Buccio
A scalar theory can have many Gaussian (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 derivatives (k = 1), in the presence of a shift-invariant interaction.
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Alessia Platania
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Andreas Pithis
The Barrett-Crane spin foam and GFT model is a state-sum model which provides a quantization of first order Lorentzian Palatini gravity. Its complete formulation has only recently been accomplished. It is conjectured that the collective dynamics of the quanta of this model, which correspond to discrete building blocks of spacetime with spacelike, timelike and lightlike components, gives rise...
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