Bootstrapping (A)dS exchanges
Gravitational observables are inherently holographic in nature. When
the asymptotic boundary of space time admits a canonical definition of
time this allows to use standard principles of Quantum Mechanics to
describe such observables. On the other hand the situation is not
clear otherwise. This is the case in dS space where the boundary is
space-like. Nonetheless bulk causality must be imprinted at the
boundary in some way.
In this talk I will discuss how to bootstrap tree level amplitudes
both in AdS and dS. I will fix from first principles the form of such
holographic observables discussing their singularities. In AdS I will
also discuss how the knowledge of exchange amplitudes alone allows to
derive non-perturbative constraints on CFT correlators writing down
extremal functionals for the CFT bootstrap in arbitrary dimensions
Thursday, 26th of March 2020, 14:30
Revisiting the epsilon expansion
There are many interacting CFTs with scalar degrees of freedom, like the O(N) fixed point in 2 < d < 4 dimensions. Surprisingly, little is known about the classification of such fixed points, even in perturbation theory. In this talk I will explore this well-known problem in the framework of the epsilon expansion. I will argue that consistent CFTs can only live in a small region of the high-dimensional space of all possible theories, and I'll discuss bounds on spectra of anomalous dimensions. Finally I’ll address the same question in the case of N gauged complex scalars, which leads to qualitatively different answers.
Tuesday, 18th of February 2019, 14:30, sala Wataghin
Resurgence and non-perturbative physics: from string theory to superconductors
It is often said that perturbation theory is insufficient to understand many physical problems, and that non-perturbative effects are needed. It turns out that making this statement precise requires the mathematical framework of resurgence theory, in which perturbative series are extended to so-called trans-series, and non-perturbative effects can be detected by looking at perturbation theory at large orders.
In this talk I will first review the basics of the theory of resurgence, and then present some of its recent applications to problems ranging from string theory to superconductivity.
Tuesday, 11th of February 2019, 14:30, aula D
We introduce bi-fermion fishnet theories, a class of models describing integrable sectors of four-dimensional gauge theories with non-maximal supersymmetry. Bi-fermion theories are characterized by a single complex scalar field and two Weyl fermions interacting only via chiral Yukawa couplings. The latter generate oriented Feynman diagrams forming hexagonal lattices, whose fishnet structure signals an underlying integrability that we exploit to compute anomalous dimensions of BMN-vacuum operators. Furthermore, we investigate Lunin-Maldacena deformations of N=2 superconformal field theories with deformation parameter γ and prove that bi-fermion models emerge in the limit of large imaginary γ and vanishing 't Hooft coupling g , with $ge^{−iγ/2}$ fixed. We explicitly find non-trivial conformal fixed points and compute the scaling dimensions of operators for any γ and in presence of double-trace deformations. Finally we also compute the exact spectrum of the shortest BMN operator.
Tuesday, 28th of January 2019, 15:30, sala Wataghin
Open Closed Superstring Field Theory
The open closed superstring field theory is necessary to study the field theory of an interacting system of open and closed strings in the presence of D branes. We construct the 1PI effective action and the BV master action for the open closed superstring field theory and generalize the result to the case of unoriented strings.
Tuesday, 21st of January 2020, 14:30, sala Wataghin
We consider gravitational perturbations of 2D dilaton gravity systems and show that these can be recast into $T\bar{T}$-deformations (at least) under certain conditions, where $T$ means the energy-momentum tensor of the matter field coupled to a dilaton gravity.
In particular, the class of theories under this condition includes a Jackiw-Teitelboim (JT) theory with a negative cosmological constant including conformal matter fields.
This is a generalization of the preceding work on the flat-space JT gravity by S.Dubovsky, V.Gorbenko and M.Mirbabayi [arXiv:1706.06604
].
Thursday, 19th of December 2019, 14:30, sala Wataghin
The cosmological constant in supergravity and in string theory
I will discuss the cosmological constant as parameter in supergravity and in string theory. In particular, I will present examples of four-dimensional de Sitter vacua as a result of moduli stabilisation in string compactifications consistent with weak coupling and large volume and in view of the swampland conjectures.
Tuesday, 19th of November 2019, 14:30, sala Wataghin
Generalized ADHM equations from open superstring field theory
Using the framework of marginal deformations in the WZW-like open superstring field theory, we will review the derivation of flatness conditions for D-brane configurations whose worldsheet description admits a global N=2 superconformal symmetry. We will see that evaluation of these conditions localizes on the boundary of worldsheet moduli space, thus providing very simple algebraic constraints on the moduli. Adding the so-called Ellwood invariant to the open SFT action, we will also exhibit modifications of this procedure which are necessary when we turn on an infinitesimal NSNS background. We will demonstrate the utility this method for dealing with a number of concrete superstring backgrounds. In the cases with enough spacetime supersymmetry, we will recover the known structure of F-, D- and Fayet-Iliopoulos terms.
Tuesday, 5th of November 2019, 14:30, sala Wataghin
This talk is based on my work [arXiv:1907.03759
]. I recently studied the classical integrability of O(d,d) transformations including not only O(d,d;Z) duality but also global O(d,d;R) deformation. The latter is known in the traditional literature to generate so-called current-current (\(J \bar J\)) deformations of 2D CFTs. I start from some reviews of Yang-Baxter (YB) deformations of string backgrounds as well as the doubled sigma model. Then I will present how to easily construct the Lax connections in the O(d,d) deformed models via O(d,d) map. Finally I will briefly comment on small questions/ideas on local O(d,d;R), YB, and JJbar in order to consider what we could do more on YB deformations in relation to Moyal product and TTbar deformation.
Tuesday, 29th of October 2019, 14:30, sala Wataghin
Non-Abelian gauge theories invariant under diffeomorphisms
Motivated by the fact that some interesting non-Abelian models invariant under general coordinate transformations do not have a suitable action description yet, we present a canonical construction of this type of actions in three spacetime dimensions. As a result, we obtain a class of theories possessing a finite number of propagating degrees of freedom, and analyze three particular cases.
Tuesday, 15th of October 2019, 14:30, sala Watachin