Seminars

Title: “Five little stories about liquids”

Abstract:
There are two famous italian sayings about water: ‘perdersi in un bicchiere d’acqua’ (get lost in a glass of water) and ‘facile come bere un bicchiere d’acqua’ (simple as drinking a glass of water). Both of them suggest the extreme simplicity of water and liquids in general. And both of them are totally wrong! Contrary to solids and gases, fluids are very poorly understood. In this talk, I will present five little stories to prove the above statement and I will discuss with you the reasons behind, and possible recent scenarios to overcome them.

Slides:

Time: 15:00 instead of the usual 13:00

Title:
“Holography abhors visible trapped surfaces”

Abstract:
One of the main consequences of the weak cosmic censorship conjecture is that trapped surfaces are hidden by event horizons. We prove that the holographic dictionary implies this result. In particular, we show that the existence of a trapped surface implies the existence of an event horizon, and that this event horizon must be outside of the trapped surface. We make few assumptions beyond the absence of evaporating singularities in the strictly classical gravity limit: thus our result provides a holographic derivation of a hallmark consequence of the longstanding weak cosmic censorship conjecture. We discuss the possibility that a classical gravity theory that admits AdS solutions with trapped surfaces outside of a horizon is not holographic and possibly has no consistent UV completion. We comment on a connection to chaos and holographic complexity.

Slides:

Title:
“TTbar-deformed conformal field theories out of equilibrium”

Abstract:
In the seminar I will discuss out-of-equilibrium properties of conformal field theories that are deformed by the TTbar-deformation from two perspectives: integrability and holography. I will focus on the energy and momentum Drude weights and diffusion constants, as well as the nonequilibrium steady states, which emerge after the inhomogeneous quench. Surprisingly, the transport coefficients and nonequilibrium steady states admit a universal closed form expressions, which do not depend on the field content of the conformal field theory. The matching of the results between the two methods serves as the first check of the TTbar-deformed holographic correspondence from the dynamical standpoint, and establishes the connection between the generalized hydrodynamics and holography.

Slides:

Time: 15:00 instead of the usual 13:00

Title:
“Transasymptotics, dynamical systems and far from equilibrium fluid dynamics”

Abstract:
Hydrodynamics is a physical theory which describes long wavelength phenomena.  Any introductory physics textbook indicates that the applicability of hydrodynamics is restricted to be near to local thermal equilibrium. This assumption seems to be very restrictive given the overwhelming experimental evidence of fluid behavior seen in nucleus-nucleus collisions and cold atoms systems. The fact that hydrodynamics can be applied to these non-equilibrated physical systems calls for a better understanding of the foundations of hydrodynamics. 

In this talk I will discuss the most recent developments of the theory for in and out of equilibrium fluids. I shall present new theoretical results related to the emergence of hydrodynamic attracting behavior, non-hydrodynamic transport and its relation with transasymptotics and trasseries. I shall also introduce in a pedagogical manner a new set of mathematical tools used frequently to analyze dynamical systems in the context of hydrodynamics. I will conclude by discussing new possibilities for future research directions.

Slides:

Title:
“Stress tensor sector of Holographic CFTs”

Abstract:
The stress tensor sector in holographic CFTs corresponds to multi-graviton contributions to correlation functions in dual AdS theory. In this talk, we will show how one can use the lightcone bootstrap to fix all dynamical data of multi-stress tensors with spin greater then 2, i.e. their operator product expansion (OPE) coefficients. We will show that a subset of stress tensor sector that consists of operators with minimal twist, have OPE coefficients that do not depend on the particular choice of holographic CFT and are therefore universal. 

Slides:

Title: “Hydrodynamics of 2-group global symmetry” part 2

Title: “Hydrodynamics of 2-group global symmetry”

Abstract:
Can one always construct hydrodynamics descriptions out of global symmetry? Even if that symmetry is not a group?

2-group is a genuine symmetry structure resulting from extending the ordinary symmetry by one-form symmetry. A QFT with 2-group shares similar features with anomalous QFT, despite being anomaly free. I will give a few example of QFTs with 2-group global symmetry, particularly those obtained by gauging non-anomalous subgroup of a QFT with anomaly. I will outline how to construct hydrodynamic description of an interacting QFT with 2-group global symmetry in the IR.

If time allows, I will also briefly discussed the holographic dual of 2-group global symmetry.

Slides: