Collection Number S005
Collection Type Series
This series consists of talks in the area of Quantum Gravity.

Getting hot without accelerating: vacuum thermal effects from conformal quantum mechanics

Michele Arzano Università degli Studi di Napoli Federico II

In this talk I will discuss how the generators of radial conformal symmetries in Minkowski space-time are related to the generators of time evolution in conformal quantum mechanics. Within this correspondence I will show that in conformal quantum mechanics the state corresponding to the inertial vacuum for a conformally invariant field in Minkowski space-time has the structure of a thermofield double. The latter is built from a bipartite "vacuum state" corresponding to the ground state of the generators of hyperbolic time evolution, which cover only a portion of the time domain.

Underground tests of Quantum Mechanics: Gravity-related and CSL wave function collapse models

Catalina Curceanu Istituto Nazionale di Fisica Nucleare (INFN)

We are experimentally investigating possible departures from the standard quantum mechanics’  predictions at the Gran Sasso underground laboratory in Italy. In particular, with radiation detectors we are searching signals predicted by the collapse models (spontaneous emission of radiation) which were proposed to solve the “measurement problem” in quantum physics and signals coming from a possible violation of the Pauli Exclusion Principle. 

Debate on Asymptotically Safe Quantum Gravity

Asymptotically safe gravity is one of the most conservative approaches to quantum gravity. It relies on the framework of quantum field theory and the Wilsonian renormalization group. Recently, questions and open issues have been discussed both within and outside its community.

Interplay of quantum gravity and matter: Role of symmetries

Astrid Eichhorn University of Southern Denmark

Across different scales, symmetries shape physical systems: for example, in effective theories in condensed matter, various global symmetries are realized; at higher energy scales, the local symmetries of the Standard Model of particle physics take over. But what is the fate of symmetries at the Planck scale, where quantum gravity fluctuations kick in?

A Generalized Hartle-Hawking State

Stephon Alexander Brown University

The Hartle-Hawking-Vilenkin state is defined on mini-superspace and is semiclassically related to inflationary theory.  However, the state suffers a few problems connected to the path integral of Euclidean or the Lorentzian measure of metrics.  In this talk, we will explore a way around these issues by working in the (Ashtekar) connection representation, a real Kodama-Chern-Simons state.  We find a generalized "Fourier Transform" that related the Chern-Simons-Kodama state to the Hartle-Hawking state beyond mini-superspace.  We end with some discussion and open ended questions for cosmology

Null infinity from quasi-local phase space

I will consider the phase space at null-infinity from the r\rightarrow\infty limit of a quasi-local phase space for a finite box with a boundary that is null. This box will serve as a natural IR regulator. To remove the IR regulator, I will consider a double null foliation together with an adapted Newman--Penrose null tetrad. The limit to null infinity (on phase space) is obtained in the limit where the boundary is sent to infinity. I will introduce various charges and explain the role of the corresponding balance laws. The talk is based on the paper: arXiv:2012.01889.

 

Deformations of General Relativity, Geometrodynamics and reality conditions

Ermis Mitsou Universität Zürich

A remarkable aspect of 4-dimensional complexified General Relativity (GR) is that it can be non-trivially deformed: there exists an infinite-parameter set of modifications with the same degree of freedom count. It is trivial to impose reality conditions that lead to real theories with Euclidean or split signature, but the situation is more complicated and not yet fully understood in the Lorentzian case, which is the subject of this talk.

Galilean and Carrollian relativities in noncommutative spacetime models

Giulia Gubitosi Universidad de Burgos

I describe the non-relativistic c→∞ and ultra-relativistic c→0 limits of the kappa-deformed symmetries, with and without a cosmological constant.  The corresponding kappa-Newtonian and kappa-Carrollian noncommutative spacetimes are also obtained. These constructions show the non-trivial interplay between the quantum deformation parameter kappa, the curvature parameter Lambda and the speed of light parameter c.

 

What happens at the end of Hawking's evaporation?

Carlo Rovelli Centre de Physique Théorique (CPT)

There are three distinct regions where quantum gravity becomes non-negligible in a black hole spacetime.  There is a precise sense in which these three regions are causally disconnected, and therefore arguably independent.   I illustrate a number of indications we have about what happens in each of them, coming both from the classical Einstein equations and from loop quantum gravity.  These point all to an interesting scenario: long living remnants stabilized by quantum gravity, formed by a large and slowly decreasing interior enclosed into a small anti-trapping horizon.