Weyl anomaly cancellation in string theories on generalized supergravity backgrounds
Recently, there has been a fundamental and significant development
in the Green-Schwarz (GS) formulation of superstring theory.
In this formulation, the kappa-symmetry plays a central role
to ensure the consistency of the theory. In 2016, Tseytlin and Wulff
showed that the kappa-symmetry constraints of the GS superstring defined
on an arbitrary background lead to a "generalized" supergravity,
which contains an additional (non-dynamical) vector field, rather than
the standard supergravity. This result indicates that we might have
overlooked a potentially important ingredient in the low-energy
effective theory of string theory for long time, and may open up new
directions including phenomenology and cosmology.
In this talk, I will give an overview on the progress on Yang-Baxter
deformations of the $AdS_5 \times S^5$ superstring and the generalized
supergravity. Finally, I would like to discuss the cancellation of
Weyl anomaly in string theories on generalized supergravity
backgrounds.
Tuesday, 12th of February 2019, 14:30, sala Wataghin
A-infinity algebra from supermanifolds.
Inspired by the analogy between different types of differential forms on
supermanifolds and string fields in superstring theory, we construct new
multilinear non-associative products of forms which yield an
$A_\infty$-algebra.
Tuesday, 29th of January 2019, 14:30, sala Franzinetti
Living on the walls of Super-QCD
Super-QCD, the supersymmetric version of ordinary QCD, admits isolated vacua and dynamical domain walls between them. I will present a class of three-dimensional Chern-Simons theories to describe the effective dynamics on these walls. Our proposal passes several non-trivial checks, which I will discuss in detail. The domain wall dynamics is very rich and enjoys interesting phenomena, as for example a second order phase transition where multiple vacua coalesce into a single one and where supersymmetry gets enhanced, in some cases. Our proposal includes and extends previous results in the literature, solving also some old puzzles, and provides a complete picture of Super-QCD domain walls.
Tuesday, 22th of January 2019, 14:30, sala Wataghin
4d SCFTs via discrete gauging
I will introduce the notion of discrete gauging in the context of 4d SCFTs and I will show how, using this procedure, we can obtain new SCFTs starting from 4d SCFTs mother theories. At the beginning of the talk I will review the mathematical tools that will be employed, that is to say the Superconformal index and the Higgs branch Hilbert series. I will then apply the discrete gauging in two different contexts. In the first case I will show how starting from $\mathcal{N}=4$ SYM, and discretely gauging a $\mathbb{Z}_n$ subgroup of the global symmetry group, we can obtain new $\mathcal{N}=4$ or $\mathcal{N}=3$ SCFTs (depending on the value of $n$). I will give a prescription for how to perform the discrete gauging at the level of the superconfomal index and Higgs branch Hilbert series. Finally I will give an overview of the results that we got in this context, in particular we will see that the Coulomb branches of the daughter theories generically are not-freely generated. Then I will focus on 4d SCFTs with $\mathcal{N}=2$ supersymmetry. In this context the mother theory will be always provided by a theory with SU(N), gauge group and the daughter theory will be obtained gauging the automorphism group of the Dynkin diagram. I will then analyse the consequences of this gauging. We will see that the global symmetry of the Higgs branch is modified in a non-trivial way and that, also for this class of theories, the corresponding Coulomb branch is generically not-freely generated.
The talk will be mainly based on the following two articles:
Tuesday, 12th of December 2018, 14:30, sala Wataghin
Black hole entropy from 5D twisted indices
I will describe the calculation of twisted indices of five
dimensional gauge theories with minimal supersymmetry at large N, and
show how this quantity is related to black hole entropy through the
AdS/CFT correspondence. The indices I consider count BPS states on
toric Kahler four manifolds with an R-symmetry twist, and are closely
related to generalizations of Donaldson-Witten theory. I will show that
the entropy of the corresponding charged BPS black holes can be
calculated in terms of the effective prepotential using a novel set of
Bethe ansatz equations.
Tuesday, 4 December 2018, 14:30, Aula Wataghin
T-duality and Double Sigma Models
After discussing some proposals for a manifestly T-dual invariant string world-sheet, the notion of Poisson-Lie T-duality will be introduced together with the one of Drinfeld double that constitutes the algebraic structure necessary for the existence of such duality . As an illustrating example, a simple mechanical system, the three-dimensional isotropic rigid rotator, will be investigated as a 0+1 field theory, aiming at understanding how such duality works and how it is related to Generalized Geometry. The model is defined over the group manifold of SU(2) and its dual is introduced having the Poisson-Lie dual of SU(2) as configuration space. A “double" generalized action with configuration space SL(2,C), i.e. the Drinfeld double of SU(2), is then defined containing twice as many variables as the original. It reduces to the original action or to its dual, once constraints are suitably implemented. Furthermore, the geometric structures of this double action can be understood in terms of Generalized Geometry. The case of Principal Chiral Model will be also briefly illustrated.
Tuesday, 27 November 2018, 14:30, Aula Wataghin
Towards the 1-loop effective action of type IIB orientifolds
I will review the status of 1-loop corrections to the effective action of certain string orientifolds. Concretely, I will mainly focus on the moduli sector of 4-dimensional toroidal type IIB orientifolds with N=1 supersymmetry. Emphasis will be put on recent results concerning field redefinitions of the moduli fields which are enforced at string 1-loop level in order to comply with supersymmetry.
Tuesday, 20 November 2018, 14:30, Aula Wataghin
The superfluid universality class of large charge operators
Large charge operators in a conformal field theory can be studied using superfluids. We review this connection and analyze the effect of adding vortices to the superfluid. We also verify a nontrivial numerical prediction using a large N model. We end with some comments on the holographic interpretation of large charge operators.
Tuesday, 13 November 2018, 14:30, Aula Castagnoli
Surface defects of class $S_k$ theories as transfer matrices of integrable lattice models
We compute the index of class $S_k$ theories with surface defects labeled by symmetric representations of SU(N). The index of the theory deformed by surface defects is related to the index of the undeformed theory by an action of a family of difference operators (=defect operators). These defect operators can be shown to correspond to transfer matrices constructed from L-operators obtained by reduction of the most general known solution to the rank one Yang--Baxter equation (i.e. the BSDS R-matrix). For rank one theories it is possible to extract directly the L-operator, which corresponds to a fundamental building block of the class $S_k$ quiver (reduced by an appropriate Higgsing leading to the surface defect in the IR). This result is based on properly interpreting the work arXiv:1412.3383
from the gauge theory perspective.
Tuesday, 6 November 2018, 14:30, Aula Wataghin
Holographic RG flows from 7D gauged Supergravity
After reviewing properties and examples of holographic renormalization-group (RG) flows, I will present explicit solutions interpolating between AdS vacua of 7-dimensional gauged Supergravity. These vacua are characterized by two nilpotent elements, and are naturally interpreted as type IIA AdS7 solutions. I will show how they allow to test the conjecture that the hierarchy of the RG flow among a class of 6D SCFTs is determined by a partial ordering of nilpotent elements of the gauge group G that defines the theory.
Tuesday, 30 October 2018, 14:30, Aula Wataghin