Mathematical Physics Group

The seminars begin at 2.30pm if not stated otherwise.

Oct 3rd: Lorenzo Ruggeri (Tsinghua U.) - Aula Lagrange

Title: Exact Results for SQFTs on Spaces with Conical Singularities (slides)

Abstract: I will discuss exact results for SQFTs on spaces with conical singularities, both orbifolds with deficit angles and branched covers with surplus angles. To compute these results, I will show how, in both cases, the behaviour of SQFTs near the singularity is reproduced by the insertion of Gukov-Witten defects on a smooth space. This approach allows the computation of perturbative and, in dimensions four and above, instantonic contributions for a large class of spaces and for different ways to preserve supersymmetry. Moreover, contributions from fluxes are obtained from perturbative ones dimensionally reducing along a non-trivial fiber. Interestingly, spaces with the same parameters controlling the surplus or deficit angles have matching partition functions. I will conclude by highlighting possible directions for future research, including non-trivial checks of AdS/CFT and exact results on spaces with orbifold singularities C^2/G, where G is a finite subgroup of SU(2).

Oct 17th: Michele Correggi (PoliMi) - Aula Lagrange 

Title: Quantum Point Charges Interacting with Quasi-classical Electromagnetic Fields (slides)

Abstract: We study effective models describing systems of quantum particles interacting with quantized (electromagnetic) fields in the quasi-classical regime, e.g., when the field's state shows a large average number of excitations. Once the field's degrees of freedom are traced out on factorized states, the reduced dynamics of the particles' system is described by an effective Schrödinger operator keeping track of the field's state. We prove that, under suitable assumptions on the latter, such effective models are well-posed even if the particles are point-like, that is no ultraviolet cut-off is imposed on the interaction with quantum fields.

Nov 7th: Rodolfo Panerai (Cologne U.) - Aula Monod

Title: Localization and Resummation in 2d Yang-Mills Theory (slides)

Abstract: In this talk, I will present the all-orders perturbative expansion of the partition function of 2d Yang-Mills on arbitrary closed surfaces around unstable instantons, i.e. higher critical points of the classical action. I will describe two approaches to this result: through resummation of the lattice partition function, and through non-standard supersymmetric localization. The result of localization is a novel effective action that is itself a distribution rather than a function of the supersymmetric moduli.

Nov 14th: Veronica Fantini (IHES) - Aula Monod 

Title: Summability for State Integrals of Hyperbolic Knots

Abstract: Given an hyperbolic knot K, state integrals are convergent integrals of products of Faddeev’s quantum dilogarithm associated to certain triangulations of S^3\K. Their asymptotic expansions are divergent power series that were conjectured to be resurgent and Borel summable by Garoufalidis, Gu and Mariño. In this talk, I will prove the conjecture for the knots 4_1 and 5_2.

Nov 21st: Alejandro Cabo Bizet (UniSa) - Aula 2

Title: The Schwarzian from Gauge Theories

Abstract: I will explain how the Schwarzian emerges from the partition function of N=4 Super-Yang-Mills and how the mass gap of the former, computed in the field theory side, kinematically matches the answer in supergravity once the holographic dictionary is imposed.

Nov 28th: Pieter Bomans (Oxford) - Aula 1

Title: Spindles from Disorder Defects (slides)

Abstract: Spindle and disc solutions have recently attracted substantial interest, though their physical interpretation remained somewhat elusive. In this talk, I present a compelling interpretation of these solutions as arising from co-dimension two disorder defects positioned at the sphere’s poles. To support this perspective, I construct explicit supergravity solutions and calculate corresponding holographic observables, offering robust evidence for our interpretation. Additionally, I introduce a bulk-to-defect inflow formalism, facilitating the extraction of diverse defect data.

Dec 5th: Davide Usseglio (UniNa) - Aula Monod

Title: Analytical Self Force for Scattering of Black Holes

Abstract: In this talk, I will review the Self-Force approach to perturbations in black hole geometries and present our formalism for analytically computing corrections to unbound motion using a combined Post-Minkowskian (PM) and Post-Newtonian (PN) expansion. Our method generalizes the computation of gravitational and non-gravitational Self-Force for any equatorial-plane orbit. Testing this approach, we analyzed the scattering of a scalar charge around a Schwarzschild black hole, reproducing known results and extending them to the 5PM order. I will conclude with a discussion of the challenges in advancing to higher orders and share preliminary results on the gravitational case.

Dec 12th: Jacopo Papalini (Gent U.) - Aula Monod

Title: Gravity Hologram of Double-Scaled SYK (slides)

Abstract: In this talk, I will propose the bulk gravitational dual of double-scaled SYK. Remarkably, the low energy dynamics of SYK model are captured by the Schwarzian quantum mechanics, which is holographically dual to JT gravity at the disk level. This duality has taught us various lessons about quantum black holes in recent years. Consequently, the bulk dual of DSSYK would provide an all-energy version of JT gravity, potentially offering a version of UV completeness for a theory of quantum gravity. After a brief introduction to the SYK model in the double-scaling limit and drawing on semiclassical analysis, I will construct the relevant holographic dictionary and perform a canonical quantization of the bulk gravity theory, precisely reproducing all amplitudes of DSSYK. This proposed bulk dual will exhibit several fascinating features, such as a deviation from the standard Hawking entropy formula and the discretization of space at the quantum level.

Jan 16th: Leonardo Santilli (Tsinghua) - Monod

Title: Holograms and Mirrors - A Long (Quiver) Story (slides)

Abstract:  I will discuss the large N limit of linear quiver SCFTs. Special emphasis is put on 5d SCFTs, and their holographic dual. I will begin with a review of 5d SCFTs and their engineering in M-theory and Type IIB string theory. I will then introduce mass deformation and describe the associated RG flow. The large N limit of linear quivers is solved next. I will also study codimenson-2 defects on both sides of the holographic duality and highlight their relevance in geometric engineering.

Feb 13th: Paolo Lorenzoni (Milano B.) - Aula 4

Title: The Generalised Hodograph Method for Non-Diagonalisable Integrable Systems of Hydrodynamic Type (slides)

Abstract: The generalised hodograph method is the  main tool to solve integrable systems  of hydrodynamic  type admitting Riemann invariants. In this talk, based  in a joint work with Sara Perletti  and Karoline van Gemst, I will explain how to extend the method to regular non-diagonalisable integrable systems of hydrodynamic type exploiting the relation between such systems and F-manifolds with compatible connections.

Feb 18th: Rishi Mouland (Imperial College) - Aula Monod

Title: Giant Gravitons and Volume Minimisation (slides)

Abstract: The partition function of a large N gauge theory with string theory dual can be understood, at least formally, as a sum over bulk closed string states, supplemented non-perturbatively by open strings extended between D-branes. Conversely, in a regime of large charges, it is recovered by the free energy of a suitable black hole geometry. We study the relationship between these two pictures in the context of the superconformal index of 4d N=2 theories dual to AdS5 x SE5. We identify the contribution of a given giant graviton configuration with the volume of a specific metric deformation of SE5, corresponding to the near-horizon geometry of the full back-reacted solution. We recover the black hole free energy by extremising over such geometries, thus uncovering a map between giant graviton states and black hole microstates.

Mar 20th: Marcelo Oyarzo (PoliTo) - Aula S

Title: Equation of State and Stability of Black Holes in the D=4 Gauged STU Model

Abstract: The N=8 SO(8) gauged SUGRA in D=4 corresponds to the low-energy dynamics of M-theory when it is compactified on S7. A great effort has been put into the construction of solutions of consistent truncations of the maximal theory, such as the STU model. In this talk, I will review both supersymmetric and non-supersymmetric black hole solutions known in the literature, with particular emphasis on the static planar black hole configurations with four charges. For this family, I will present a new thermodynamic stability analysis, due to the fact that the equation of state can be found analytically.

April 30th: Nicolò Petri (INFN) - Aula Professori 

Title: Metric Positivity in AdS Vacua (slides)

Abstract: The formulation of abstract notions about physical theories to study their universal features is a typical strategy of modern high-energy physics. In this regard, a widely accepted belief is that geometrical notions, like metrics and distances between vacua configurations of physical theories, should always exist. However, defining a consistent metric and distance between vacua in gravitational theories is an important open problem. In my talk, I will examine this issue in relation to the 'AdS conjecture', a key development within the Swampland program. The main goal is to introduce a consistent procedure for defining and computing metrics on the space of gravity vacua, providing a clear way to measure distance. Starting with very simple vacua in string theory, like Freund-Rubin ones, I will demonstrate how these new concepts can be constructed explicitly. The key idea underlying the procedure involves considering the off-shell quadratic variation of the string theory action and evaluating it over the space of on-shell solutions. During the talk, I will also explore how this framework sheds light on the ongoing debate regarding the consistency of scale-separated vacua in string theory.

May 22nd: Valter Moretti (UniTn) - Aula S

Title: On the Localisation of Quantum Relativistic Particles: Recent Results and Open Problems (slides) 

Abstract: I will review the long standing issue of the quantum relativistic localization, discussing some recent result I obtained in collaboration with other authors. Depending of time, the introduction will cover:

(1) the structure of quantum theories in Hilbert spaces;

(2) the use of projection-valued measures PVM;

(3) the use of positive operator-valued measures POVM;

(4) the problematic notion of state after measurement;

(5) the probalmatics of the measurement process with the demands of causality, when relativity turns on.

June 12th: Fabio Apruzzi (UniPd) - TBA

Title: TBA

Abstract: TBA

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