Talks by Stefano Liberati

Gravity, an unexpected journey: from thermodynamics to emergent gravity, Lorentz breaking and back...

Stefano Liberati SISSA Scuola Internazionale Superiore di Studi Avanzati
Thermodynamical aspects of gravity have been a tantalising puzzle for more than forty years now and are still at the center of much activity in semiclassical and quantum gravity. We shall explore the possibility that they might hint toward an emergent nature of gravity exploring the possible implications of such hypothesis. Among these we shall focus on the possibility that Lorentz invariance might be only a low energy/emergent feature by discussing viable theoretical frameworks, present constraints and open issues which make this path problematic.

Analogue Models of Gravity: The ubiquitous space-time

Stefano Liberati SISSA Scuola Internazionale Superiore di Studi Avanzati
Analogies have played a very important role in physics and mathematics, as they provide new ways of looking at problems that permit cross-fertilization of ideas among different branches of science. An analogue gravity model is a generic dynamical system (typically but not always based on condensed matter physics) where the propagation of excitations/perturbations can be described via hyperbolic equations of motion possibly characterized be one single metric element for all the perturbations.

Lorentz symmetry: Broken, intact or deformed?

Is aether technically natural?
I will discuss whether higher energy Lorentz violation should be considered a natural expectation in theories of quantum gravity with a preferred frame.

If spacetime is a causal set then Lorentz symmetry is unbroken

Quantum superpositions of the speed of light

An analogue model lesson for the cosmological constant

Stefano Liberati SISSA Scuola Internazionale Superiore di Studi Avanzati
Analogue models of gravity have been a test field for many phenomena in quantum field theory on curved spacetimes.  It was recently recognized that in some situations they can also provide toy models of emergent gravity.  We shall review here such a model and address within it the nature and scale of the cosmological constrant trying to draw general lessons for emergent gravity scenarios.

The emergent gravity challenge: a few lessons from analogue gravity

Stefano Liberati SISSA Scuola Internazionale Superiore di Studi Avanzati
Emergent gravity scenarios have become increasingly popular in recent times. In this talk I will review some evidence in this sense and discuss some lessons from toy models based on condensed matter analogues of gravity. These lessons suggest some (possibly) general features of the emergent gravity framework which not only can be tested with current astrophysical observations but can also improve our understanding of cosmological puzzles such as the dark energy one.