Seminars

The superconformal indeces of 4d SCFTs count their BPS states and, holographically, give information on the microstates of the dual black holes. A possible approach to the exact computation of the index requires solving the so-called Bethe Ansatz equations (BAE). In this talk, I will introduce a rewriting of the BAE in terms of elliptic functions, focusing on the case with 16 supercharges. Such a rewriting permits 1) to quantitatively capture the conjectural relation of BAE with the Calogero-Moser integrable system (and the related continuous solutions) and 2) to rephrase the BAE in terms of configurations of lines on a plane intersecting an elliptic curve.

We revisit the anyon gas in a solvable large-charge limit, where the particle number N and the statistical coupling parameter k are taken to infinity with N/k held fixed. In this near-bosonic regime, the statistical interaction 1/k is weak, while its collective effects remain finite. We find a crystalline ground state with O(N/k) lattice sites, in which the long-range statistical interactions are completely screened, yielding a conventional crystal without superfluidity. Our results suggest a quantum phase transition from a crystal at k > k_c to a superfluid at k < k_c, with k_c ≃ 2–5, challenging the expectation that statistical interactions alone necessarily produce superfluidity.
We also discuss how the large-charge expansion captures qualitative and quantitative features beyond its regime of strict validity.

I will present recent results on perturbative correlation functions and operator mixing in ABJM theory, with particular emphasis on a new formulation of the mixing problem as dynamics on the Young lattice and its connections with representation theory, stochastic processes and orthogonal polynomials.

The cobordism conjecture states that the cobordism charge of any consistent quantum gravity theory must be trivial. This implies the existence of a rich set of dynamical spacetime configurations, connecting different theories through domain walls or interpolating between a given theory and the "nothing" via End of The World branes. In this talk, I will present a new class of configurations, which we call junctions, predicted by the conjecture. These configurations connect multiple string theories in their maximal spacetime dimensions. I will provide a microscopic worldsheet description of these junctions as a generalization of the "going up and down the RG flow" interpolations. The interpolations involve, on each branch of the junction, additional degrees of freedom that are gapped along the branch except at the branch point, where the gap closes and triggers the branching transition. These extra degrees of freedom admit an interpretation in terms of additional dimensions in a supercritical string theory, which reduces to the 10d junction configuration via closed tachyon condensation. I will construct explicit examples of junctions involving 10d heterotic, type 0, and type II string theories, as well as their orientifolds. This includes junctions involving 10d chiral theories, in which chiral fields flow between different branches. Finally, I will use these basic junctions as building blocks to construct networks connecting multiple 10d string theories, and I will formulate the rules for their construction in terms of graph theory.

Gauged supergravity theories are a fundamental ingredient for studying string theory compactifications and exploring the landscape of lower-dimensional vacuum solutions. In this context, I will discuss the possibility of introducing open string degrees of freedom (scalars and fluxes) associated with spacetime-filling branes/orientifold planes in dimensional reductions of massive type IIA supergravity. The corresponding lower-dimensional supergravity description requires additional vector multiplets coupled to the gravity multiplet, as well as new embedding tensor components parametrizing the possible gaugings. In particular, I will focus on the four-dimensional setup of https://arxiv.org/abs/2406.15310 and the warped compactification considered in https://arxiv.org/abs/2603.05470. In both cases, the scalar potential of the resulting half-maximal supergravity theory exhibits novel AdS vacuum solutions, both supersymmetric and non-supersymmetric. The analysis of interpolating domain wall solutions provides further insights into their stability and possible non-perturbative transitions between vacua, as illustrated by the seven-dimensional case.

I will present a novel formalism for semiclassical time evolution in quantum mechanics. By identifying complex saddle points of the path integral in real time, real saddles in complex time, and complex saddles in complex time, we reproduce the known answers to classic problems to one loop.
For the decay of a metastable state, there are finite-time and finite-energy analogs of the Euclidean "bounce" which, notably, do not possess strict zero or negative modes.
The motivation of this work is to learn how to compute decay rates in quantum field theory in situations with non-trivial time dependence, by first taking a humble step back into the fascinating world of quantum mechanics.
Based on arXiv:2603.06575, in collaboration with Oliver Janssen, Joel Karlsson and Flavio Riccardi

In this talk, we investigate the possible couplings of a massive spin-2 field to (undeformed) D=4, N=1 supergravity. We do so by constructing the general stress-energy tensor multiplet for the N=1 massive spin-2 supermultiplet. We show that, at leading order in the Planck mass, this coupling is unique: it is characterized by a specific non-minimal coupling to the Riemann tensor, and its spin-2 sector reproduces the one of an oscillator mode in open string theory. The massive spin-1 sector, on the other hand, includes a higher-derivative term that may lead to violations of causality, which can be resolved by introducing infinitely many higher-spin fields, similar to the Regge trajectories in string theory. Moreover, we argue that this coupling is genuinely different from the one arising from Kaluza-Klein reductions of higher-dimensional supergravities, which we show leads instead to a deformation of the massless supersymmetry transformations.

In this journal club we are going to discuss the paper (2601.17122) “Fortuitous Chaos, BPS Black Holes, and Random Matrices”. The paper’s aim is to strengthen the already existing relations between the BPS sector of gauge theories, JT gravity, and matrix models. In particular we will focus on the relationship that is the least explored in the literature: the connection between fortuitous BPS states and random matrix theory. Indeed the connection between fortuitous BPS states and BPS black holes has been known for some years using holography and the Jackiw-Teiltelboim/Random Matrix Model (JT/RMM) correspondence has been sharpened in recent years. The aim of the paper is to show that there exists a simple random matrix model that encodes many of the essential universal features of BPS chaos. We will dive into this topic after a brief review on fortuity,monotone, and fortuitous BPS states.