Gravity and Black Holes - Moving beyond the paradigm

11 Apr 2023, 09:30 → 12 Apr 2023, 16:05 Europe/Berlin

Main Auditorium (Max Planck Institute for Physics (MPP))

Tuesday 11 April

1 A road to the UV properties of gravity and back

In this opening talk I will first underline why it's useful to work with a UV complete theory of gravity and illustrate why we don't need experiments at the Planck scale to understand its predictions on our Universe. In particular, we will illustrate with a couple of examples how black holes in string theory can be used to probe the validity of the EFT.

Speaker: Alessandra Gnecchi (INFN Padua)

2 The massless limit and tension in massive gauge theories

We study massive non-linear gauge theories with mass added by hand. First, we consider the massive Yang-Mills theory. The standard perturbative approach suggests that the massless limit of this theory is not smooth. Nevertheless, we show that the longitudinal modes - the source of this discontinuity – become strongly coupled at the Vainshtein scale. Beyond it, we show that the massless theory is recovered up to small corrections and that the massless limit of the massive Yang-Mills theory is smooth. We then extend our study to the theories of massive Kalb-Ramond and Proca fields modified by a quartic self-interaction and show that the same strong coupling scale is present in both theories. In the Proca theory, the longitudinal mode enters the strongly coupled regime beyond this scale, while the two transverse modes propagate further and survive in the massless limit. In contrast, in the case of the massive Kalb-Ramond field, the two transverse modes become strongly coupled beyond the Vainshtein scale, while the pseudo-scalar mode remains in the weak coupling regime and survives in the massless limit. This indicates a contradiction with numerous claims in the literature that state that the massive Kalb-Ramond and Proca theories are dual to each other.

Speaker: Anamaria Hell (LMU / ASC)

11:30 Lunch break

3 Hawking effect with a thermal input: Entanglement quantification and the role of superradiance

ORIGINS Guest Talk.
In this talk we will discuss how to quantify the entanglement generated in the Hawking process of a Kerr or an analog rotating black hole when the input radiation is in an arbitrary gaussian state. We will see how, when the input is a thermal state, such as CMB radiation, or thermal noise in the lab, the amount of entanglement generated between interior and exterior decreases with its temperature. We will pay special attention to the interplay between the Hawking emission and superradiance, showing how the entanglement generated between interior and exterior in the rotating case will be larger or equal than in its non-rotating couterpart, depending on the relation between the Hawking temperature and that of the thermal input.

Speaker: Adrià Delhom I Latorre (Louisiana State University )

14:00 Coffee break

4 Black hole basics

Speaker: Gia Dvali (LMU / MPP / ASC)

Wednesday 12 April

5 Restrictions in quadratic metric-affine gravity from the stability of the vector sector

ORIGINS Guest Talk.
In this talk we will revise the stability of the four vector irreducible pieces of the torsion and the nonmetricity tensors in the general quadratic metric-affine Lagrangian in 4 dimensions. This analysis highly constrains the theory and reduces the parameter space of the quadratic curvature part from 16 to 5 parameters. We will also mention the case of Weyl-Cartan gravity, proving that the stability of the vector sector completely fixes the dynamics of the full Lagrangian to just an Einstein-Proca theory or pure General Relativity.

Speaker: Alejandro Jiménez Cano (Tartu University)

6 Quantum networks as a beacon for physics in curved spacetimes

We propose quantum networks as a novel approach to investigate phenomena in arbitrary curved spacetimes, with the potential to address longstanding problems, where usual QFT approaches have failed. Its new framework confines quantum fields onto networks which are then imbedded in a spacetime of interest. The essential physical information about the full, higher dimensional phenomenon can be captured by the graph.

As a first example, we investigated the entanglement entropy for a massive scalar field on a generic network imbedded in Minkowski spacetime, confirming the famous area scaling for the entanglement entropy.

Due to their simplicity, quantum networks emerge as powerful devices able to describe and predict phenomena -such as entanglement entropy- on arbitrary complex curved backgrounds.

Speaker: Cecilia Giavoni (LMU / ASC)

11:30 Lunch break

7 Averaged energy conditions for vector fields

ORIGINS Guest Talk.
In this talk I will present the sufficient conditions for the appearance of singularities in gravitational theories which propagate an extra vector degree of freedom, based on the known relaxations of the singularity theorems. I will also show specific cases of singular behavior that usually would be considered as potentially singularity-free, since they violate the usual point-like energy conditions.

Speaker: Francisco José Maldonado Torralba (Tartu University)

8 Small black holes in the universe and as probes of quantum gravity

Astrophysical black holes are typically solar mass or much heavier objects. Primordial black holes are much lighter and smaller objects. We will discuss the role of small black holes
as dark matter candidates in the dark dimension scenario, with an extra dimension of micron size. In addition I will discuss how small black holes of string size can be used as probes of string theory and quantum gravity

Speaker: Dieter Lüst (LMU / MPP)

15:00 Coffee break