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
Machine learning for lattice QFT and string theory
Machine learning has revolutionized most fields it has penetrated, and
the range of its applications is growing rapidly. The last years has
seen efforts towards bringing the tools of machine learning to lattice
QFT and, more recently, to string theory. After reviewing the general
ideas behind machine learning, I will discuss several applications: 1)
predicting the critical temperature of the confinement phase transition
in 2+1 QED, 2) computing the Casimir energy for a 3d QFT, 3) predicting
the Hodge numbers of Calabi-Yau 3-folds. I will conclude by giving some
general thoughts on the use of ML for mapping effective QFT and building
a string field theory.
Tuesday, 1st of October 2019, 14:30, sala Fubini
Canonical quantization of the Szekeres spacetime
In this talk, I will discuss the canonical quantisation of an inhomogeneous spacetime by the use of the symmetries on the configuration space. I focus on the Szekeres spacetime with or without a cosmological constant. The physical interest on this system is that it can describe early inhomogeneous discrepancies from the homogeneous spacetime in the early universe. I will explain the general procedure, usually performed in the context of the minisuperspace approximation. Then, I will discuss the solution of the quantum equations, which is a wave functional to be interpreted. We derive a probability density and discuss the transition to the classical limit and the implications for the current state of the universe.
Thursday, 26th September 2019, 14:30, sala Watachin
Holographic RG flows, on flat and curved manifolds and F-theorems
We carefully analyze the structure of holographic RG Flows dual to QFTs on Minkowski spacetime, and find several exotic possibilities beyond the known vanilla cases. We then proceed and study the holographic RG flows dual to QFTs on curved manifolds (spheres , de Sitter and AdS).
We analyze the general structure, and control fully the UV and IR asymptotic expansions. We also analyze the exotic flows found in flat space.
The de Sitter case provides an interesting interpretation of the on-shell action as a finite temperature free energy of the QFT.
We also study F-functions in the context of field theories on $S^3$, with the radius of $S^3$ playing the role of RG scale. We show that the on-shell action, evaluated over a set of holographic RG flow solutions, can be used to define good F-functions, which decrease monotonically along the RG flow from the UV to the IR for a wide range of examples. We check that these observations hold beyond holography for the case of a free fermion on $S^3$ ($\Delta=2$) and the free boson on $S^3$ ($\Delta=1$), resolving a long-standing problem regarding the non-monotonicity of the free energy for the free massive scalar. We also show that for a particular choice of entangling surface, we can define good F-functions from an entanglement entropy, which coincide with certain F-functions obtained from the on-shell action.
Tuesday, 11th of June 2019, 14:30, sala Castagnoli
N=2 to N=1 with one hypermultiplet
A clear picture, and a classification, of N=2 theories with a single hypermultiplet
and a ground state breaking only one supersymmetry has only recently emerged.
I will discuss these results in global supersymmetry and (Minkowski) supergravity
theories. Establishing them required to lift some controversies and
escape some strong statements in mathematical papers.
Tuesday, 21st of May 2019, 14:00, sala Wataghin
The large charge expansion
The large-charge approach consists in studying conformal field theories in sectors of fixed and large global charge. This allows performing a perturbative expansion of a generically strongly-coupled theory with the inverse charge acting as a controlling parameter. In this talk, I will present the basic idea of the large quantum number expansion using the simplest example of the 3D O(2) model at the Wilson-Fisher fixed point at large global charge and then extend its treatment to the O(2N) vector model. New lattice results confirm our predictions to high accuracy.
I will further show that the large-charge expansion can also be successfully applied to non-relativistic CFTs.
Tuesday, 7th of May 2019, 14:30, sala Wataghin