Holographic Entanglement Entropy and Topological Terms

We consider the renormalization of holographic entanglement entropy (HEE) for Conformal Field Theories in odd dimensions, dual to Einstein gravity with negative cosmological constant in one dimension higher. We make explicit the equivalence between renormalized entropy and the renormalized area of the entangling surface. In particular, for constant-curvature surfaces, HEE is fully determined in terms of a single topological number (Euler characteristic).

Tuesday, 9 October 2018, 14:30, Aula Fubini

A Quantum Universe before the Big Bang(s)

The fundamental role of quantum physics in modern cosmology entails a deep revision of our traditional ideas about the Big Bang and the beginning of time.

Friday, 5 October 2018, ore 14:30 — Aula C (theory colloquium)

Carrollian Fluids and Ricci-flat Holography

In this talk I will firstly show how, starting from a general covariant relativistic fluid, a sensible limit where the speed of light vanishes can be taken. This limit affects also the geometry and symmetries of the theory, which will be intensively discussed. Secondly, I will point out that this limit is the behavior of the boundary theory in AdS fluid-gravity duality as the bulk cosmological constant goes to zero. Eventually, after reviewing some important facts in AdS holography, we will be able to establish a holographic correspondence between Carrollian fluids living on null infinity and asymptotically flat solutions of Einstein equations.

Tuesday, 2 October 2018, ore 14:30 — Aula Wataghin

Singular OPEs and open string background independence

In this talk I will discuss a new solution in open bosonic string field theory which can describe a completely general open string background. In particular, the solution can be constructed from boundary condition changing operators with generic and singular operator products. This is work in progress with C. Maccaferri.

Tuesday, 26 June 2018, 14:30, Aula Wataghin

Line defects and emitted radiation

In the context of (super)conformal field theories extended probes may preserve enough symmetry to put strong constraints on physical observables. We discuss such constraints for a BPS line defect in four-dimensional N=2 superconformal field theories, with a particular focus on supersymmetric Wilson lines. For the latter case our techniques allow to prove a simple non-trivial relation between the energy emitted by a moving particle and the insertion of a stress tensor operator in the defect background. We discuss the existence of such a relation for other defects and we outline its powerful role for exact computations via localization.

Tuesday, 12 June 2018, 14:30, Aula Wataghin

The Importance of Being Disconnected, A Principal Extension for Serious Groups

We introduce gauge theories based on a class of disconnected gauge groups, called principal extensions. These groups implement in a consistent way the discrete gauging of charge conjugation, for arbitrary rank. Focusing on the principal extension of SU(N), we explain how many of the exact methods for theories with 8 supercharges can be put into practice in that context. We then explore the physical consequences of having a disconnected gauge group: we find that the Coulomb branch is generically non-freely generated, and the global symmetry of the Higgs branch is modified in a non-trivial way.

Tuesday, 5 June 2018, 15:30, Aula Wataghin

On singularities of Super-conformal field theories

Carefully studying the singularity structure of the moduli space of vacua of super conformal field theories, provides an incredibly powerful tool to extract information about such theories. In particular I will outline a concrete, yet technically challenging, strategy to go about carrying out a classification for SCFTs with extended supersymmetry in 4d.

I will explain in details how this classification has been worked out successfully for N=2 SCFTs in rank-1 and it is very promising in higher ranks and even more with higher Supersymmetry (N≥​​3). Carrying out this systematic study, we have already learned many new features about SCFTs which I will discuss throughout my talk.

Tuesday, 5 June 2018, 14:00, Aula Wataghin

AdS/CFT and F-theory

I will discuss supersymmetric $AdS_3$ solutions in F-theory, that is Type IIB supergravity with non-trivial varying axio-dilaton, which are holographically dual to 2d superconformal field theories preserving at least (0,2) supersymmetries. The aim of this work is to set up holography in the context of F-theory, which are traditionally two distinct areas of string theory. The talk will be based on the arXiv papers arXiv:1705.04679 and arXiv:1712.07631 .

Tuesday, 29 May 2018, 14:30, Aula Wataghin

Non-Projected Supermanifolds through Simple Examples

Recently Donagi and Witten have shown how some major issues in superstring perturbation theory arise in connection with the so-called “non-projected” supermanifolds, a special class of supermanifolds whose geometry cannot be reconstructed starting from ordinary geometric data. In this talk I will review the foundations of supergeometry with special attention to non-projected supermanifolds. In particular, I will explain how to deal with them through some examples and by classifying non-projected supermanifolds over projective spaces. General embedding spaces such as super Grassmannians are also considered.

Tuesday, 15 May 2018, 11:30, Aula Fubini

Aspects of 4d/2d reductions

The talk is focused on the twisted compactification of 4d toric quiver gauge theories on compact constant curvature Riemann surfaces. The 2d theories obtained by this procedure have, in general, N=(0,2) supersymmetry and, for opportune choices of the fluxes, they are conjectured to be conformal. We derive a general holographic formula for their 2d central charge and we match it with the field theory result. The latter is obtained from the geometry of the 4d moduli space, encoded in the toric diagram.

Tuesday, 24 April 2018, 14:30, Aula Wataghin