Giulia Gubitosi: Planck-scale deformations of relativistic symmetries
Nikolaos Mavromatos: Anomalies and Torsion in Quantum Gravity and Lorentz Violation in the Universe
In search for a consistent theory of Quantum Gravity, I explore the possibility that Riemannian geometry might be abandoned, at the expense of introducing torsion as a fundamental quantum field. In string inspired theories, such a quantum torsion is linked to spin-one antisymmetric-tensor fields in the massless string gravitational multiplet, which in (3+1)-dimensions, after extra-dimensional compactification, corresponds to a fully dynamical massless pseudoscalar (axion-like) field. The latter can couple to gravitational anomalies in a way consistent with general covariance. In other settings, such as Loop Quantum Gravity, these axions may be thought of as somewhat analogous to field theoretic extensions of the Barbero-Immirzi parameter, which accompany torsional topological invariants in the corresponding effective gravitational actions.
In such modified theories of gravity, which could be viewed as effective low-energy theories of mathematically consistent quantum gravity models, including, but also going beyond, string theory, there are solutions for the axion background field which violate spontaneously Lorentz symmetry, as a result of condensation of gravitational anomalies induced by primordial gravitational waves. The low-energy theory with matter resembles then the Standard Model Extension (SME) with terms that Violate Lorentz (LV) and CPT symmetries (CPTV). Apart from theoretical considerations, the talk will also explore the phenomenology of the resulting cosmological models, paying particular attention to demonstrating a link with a running-vacuum-model inflationary cosmology, the emergence of matter antimatter asymmetry as a result of the aforesaid LV and CPTV, and the connection of the torsion-induced axion field to dark matter, upon appropriate mass generation at post inflationary epochs.
Zoom-Meeting:
https://uni-jena-de.zoom.us/j/69556470634
Meeting-ID: 695 5647 0634
Kenncode: QG-AA