Programma 6-8 Aprile

Campi, gravità e stringhe (L. Bonora)

Roberto Balbinot

"Density correlations as signal of Hawking radiation in BEC acoustic black holes "

In this talk I shall discuss the evidence of Hawking emission of Bogoliubov phonons from a sonic horizon in a flowing one-dimensional atomic Bose-Einstein condensate. The presence of Hawking radiation is revealed from peculiar long-range patterns in the density-density correlation function of the gas. Quantitative agreement between the fully microscopic calculations and the prediction of analog models is obtained in the hydrodynamic limit. New features are predicted and the robustness of the Hawking signal against a finite temperature discussed.

Mariano Cadoni

"Black hole entropy and low-dimensional gravity"

We review the use of  gravity in two- and three-dimensional AdS spacetime for understanding from a miscroscopic point of view  both thermodynamical and entaglement entropy of black holes. In particular, we focus on the different realizations of AdS_2 quantum gravity and their use to explain black hole entropy.

Mauro Carfora

"Renormalization group and ancient solutions of the Ricci flow"

"Ricci flow has been the point of departure and the motivating example for important developments in geometric analysis, most spectacularly for G. Perelman~Rs proof of Thurston~Rs geometrization program for three-manifolds and of the famous Poincar\uffff conjecture. As it is well known, the Ricci flow also appears naturally in Quantum Field Theory (QFT), as the weak coupling limit of the renormalization group analysis of non-linear sigma models. Such an observation suggested that methods of quantum field theory may have useful applications in geometric flow theory, and that the properties of geometric flows  may shed light on the nature of significant models of QFT. We briefly discuss such issues."

Jarah Evslin

"Contrasting confinement in superconductors and superQCD"

Type II superconductors and softly broken N=2 gauge theories are the two most popular toy models for QCD.  I will argue that the vortices responsible for confinement in the two theories behave radically differently, for example the former repel and the latter attract.  As a result the vacuum structures are quite different, only the latter is translation-invariant. Therefore at most one theory resembles QCD, I present evidence that it is the former.

Dario Francia

"On unconstrained higher spins of any symmetry"

I will introduce the subject of Higher-Spin Field Theory, reviewing its basic motivations together with some of its classical difficulties. Established results due to Fronsdal and Labastida describe free  higher-spin gauge fields in terms of tensors subject to certain algebraic constraints. Such constraints, on the other hand, are not suggested by String Theory and conflict with the linear `geometry' available for these fields. I will thus describe Lagrangian formulations of the same systems, devoid of constraints, and applicable to (spinor-) tensors of any symmetry type, commenting on their geometrical meaning.

Gianluca Grignani

"Quantizing strings on AdS_4 x C P^3: pp-waves, giant magnons and beyond"

I will examine the sigma model of type IIA string theory on AdS_4 x CP^3 which is the string dual of the N = 6 superconformal Chern-Simons theory of Aharony, Bergman, Jafferis and Maldacena (ABJM theory). In particular I will discuss its integrability. I will derive the full magnon dispersion relation and compare it to results for the ABJM theory at weak coupling. Then I will consider finite-size corrections to the energy of string states and  compare them to solutions of the all loop Bethe equations.

Camillo Imbimbo

"The coupling of Chern-Simons gauge theory of 3-dimensional topological gravity."

We describe the coupling and the anomalies of Chern-Simons 3-dimensional gauge theory, and of certain higher-ghost generalizations of it, to topological gravity. The analysis sheds some new light on the so-called rigid vector supersymmetry of Chern-Simons gauge-fixed theory.

Alberto Lerda

"Stringy instanton effects in supersymmetric gauge theories"

Motivated by possible implications on the problem of moduli stabilization and other phenomenological aspects, we study stringy instanton effects in supersimmetric models with D-branes at orbifold singularities and background fluxes. We find a rich variety of instanton-generated interactions, ranging from superpotentials and Beasley-Witten like multi-fermion terms to non-supersymmetric flux-induced instanton interactions.

Fedele Lizzi

"Overview of Recent Progresses in Noncommutative Geometry in Physics"

I will give a short review, for nonspecialists, of some results in noncommutative geometry relevant to physical applications. The emphasis will be in work of the last few years and I will touch upon field theories on noncommutative spaces, fuzzy spaces, and Connes' approach to the standard model

Luca Martucci

"On moduli and effective theory of N=1 warped compactifications"

I will discuss the moduli space of N=1 type II warped compactions to flat space with generic internal fluxes. Using the underlying integrable generalized complex structure that characterizes these vacua, the different closed string deformations will be naturally classified by H-twisted cohomologies and identified with chiral and linear multiplets of the effective four-dimensional theory. The Kaehler potential for the chiral fields will be also discussed and, as an example, type IIB warped Calabi-Yau compactifications will be considered in more detail.

Wolfgang Mueck

"Holographic Renormalization and Fake Supergravity"

Fake SUGRA systems provide the bulk setup for holographic renormalization group flows, which are of interest in AdS/CFT and non-AdS/non-CFT. Studying fluctuations around holographic renormalization group flow backgrounds, one calculates the correlation functions in the dual QFTs. In the talk, the use of gauge-invariant variables for such calculations is advertized. Various applications to AdS/CFT and non-AdS/non-CFT are presented.

Matteo Siccardi

"Matrix model and beta-deformed N=4 SYM"

In this talk I will review my collaboration with prof. Yoshida, presenting two different approaches to the study of the low-energy dynamics of supersymmetric gauge field theories. First, I'll consider a method inspired by the Exact Renormalization Group techniques for the calculation of the celebrated N=1 Veneziano-Yankielowicz superpotential. Second, I will discuss the Dijkgraaf-Vafa correspondence in its application to the determination of the holomorphic part of the beta-deformation of N=4 SYM.

Dmitri Sorokin

"Type IIA string in AdS4 x CP3 superspace"

Recent progress in understanding AdS4/CFT3 correspondence has  requested the knowledge of an explicit form of the superstring  action in type IIA superbackground whose bosonic subspace is AdS4xCP3. We show how the required AdS4xCP3 superspace with 32 fermionic directions can be obtained by the dimensional reduction of the D=11 AdS4 x S7 superspace. We also show that the previously constructed OSp(6|4)/U(3)xSO(1,3) supercoset string action with 24 fermions describes only a subsector of the complete Green-Schwarz superstring. It is still to be determined whether the Green-Schwarz superstring in the complete AdS4 x CP3 superbackground is classically integrable.

Yassen Stanev

"Finite massless supersymmetric ladder diagrams without regularization"

We show that in the massless N=1 supersymmetric Wess-Zumino theory it is possible to devise a computational strategy by which the x-space calculation of the ladder 4-point correlators can be carried out without introducing any regularization. We derive a representation valid at all loop orders in terms of conformal invariant integrals. We discuss also some applications to N=1 SYM theories.

Alberto Zaffaroni

"N=2 Chern-Simons Theories and M2 branes"

We investigate the properties of N=2 Chern-Simons theories in three dimensions and their relation to the AdS4/CFT3 correspondence. We study a large class of theories arising on the world-volume of membranes in M theory.

Roberto Zucchini

"Gauging the Poisson sigma model"

We review briefly the Poisson and the Weil sigma models. We show how to carry out the gauging of the Poisson model in an AKSZ inspired formulation by coupling it to a generalization of the Weil model. We call the resulting gauged field theory, Poisson-Weil sigma model. As an application, we carry out a  gauge fixing of the pure Weil model and of the Poisson-Weil model. In the first case, we obtain the 2-dimensional version of Donaldson-Witten topological gauge theory. In the second case, we recover Baptista's gauged A topological sigma model, describing the moduli space of solutions of the so-called vortex equations.