Seminars

Abstract:TBA

Abstract: I will discuss our recent proposal for the Symmetry Topological Field Theory (SymTFT) for global, continuous spacetime symmetries (https://arxiv.org/abs/2509.07965 ). For a d-dimensional theory, it is given by a (d + 1)-dimensional BF-theory for the spacetime symmetry group, and whenever d is even, it includes also Chern-Simons couplings, that encode conformal and gravitational anomalies. This proposal is supported by the similarity to two-dimensional Jackiw-Teitelboim gravity in the d = 1 case and the topological limit of four-dimensional gravity in the d = 3 case. I will discuss how topological defects constructed from this SymTFT act by applying the associated spacetime symmetry transformation. Finally, I will discuss the relation to gravity and holography.

Abstract: TBA

Abstract: In this talk, I will discuss some interesting features of heavy–heavy–light–light correlators in N=4 supersymmetric Yang–Mills theory, where the light operators belong to the stress-tensor multiplet and the heavy ones correspond to giant gravitons, realised holographically as D3-branes. I will focus in particular on the associated Integrated Correlators, for which exact expressions can be obtained despite few results are known for the correlators themselves. I will highlight several interesting properties of these integrated correlators, especially the emergence of universal structures in the strong-coupling regime.

Abstract: We study gravitational form factors for baryons using the holographic description of QCD based on a D4-D8 brane system in type IIA string theory.  In holographic QCD, the baryons are represented as solitons in a 5-dimensional gauge theory. We obtain the soliton solution by solving the equations of motion numerically. Using this result, the gravitational form factors and related quantities are calculated.

Abstract: We argue that collider observables such as hadron number flux can be matched onto a linear combination of detectors/light-ray operators in perturbative QCD. The spectrum of detectors in QCD is subtle, due to recombination between the DGLAP and BFKL trajectories. We explain how to define and renormalize these trajectories at one-loop, systematically incorporating their recombination. The leading and subleading soft gluon theorems play an important role, and our analysis suggests the presence of an infinite series of further subleading soft theorems for squared-amplitudes/form factors. Combined with our light-ray matching hypothesis, the anomalous dimensions of recombined DGLAP/BFKL detectors yield a prediction for the energy dependence of the number of particles in a jet, as well as other predictions for more general energy-weighted hadron measurements. Time permitting, we will also discuss applications to energy correlators.

Abstract: Almost 30 years ago Dima Kharzeev argued that, contrary to naive intuition, the flow of baryon number in highly inelastic high energy processes is not traced by the valence quarks but by a gluonic structure, the string junction, postulated many years earlier by Giancarlo Rossi and myself and, independently from QCD, by Xavier Artru. I will discuss recent experimental evidence in favour of this claim by using the 50+ year old Feynman-Wilson analog model adapted to the topological expansion of QCD.

Abstract: We consider planar codimension-one defects and interfaces in N = 4 super-symmetric Yang–Mills (SYM) theory, realized by the D3/D5-brane intersection. Working in the probe limit, where the number of D5-branes is small compared to the number of D3-branes, we obtain analytic results for the holographic entanglement entropy of a ball-shaped region centered on the defect. A defect renormalization group flow is triggered by giving the defect hypermultiplets a mass, which corresponds to separating the D3- and D5-branes. Along this flow the entanglement C-function decreases monotonically. We also allow the D5-branes to carry worldvolume flux corresponding to dissolved D3-branes, in which case the setup describes an interface between two copies of N = 4 SYM theory with different gauge groups, where an RG flow is triggered by a mass term for vector multiplets. Here we again find monotonic behavior of the entanglement C-function, although its interpretation as a measure of effective degrees of freedom is problematic. We investigate possible alternative measures of degrees of freedom.

Abstract: Many string compactifications have moduli fields that can take different possible values at infinity. We address the question: given two compactifications that differ by the asymptotic values of the moduli, should we regard them as different theories or different states of the same theory? We fix a precise criterion that distinguishes between these two possibilities and show that the answer depends on whether the non-compact part of the space-time is asymptotically flat or asymptotically AdS. In the former case different values of asymptotic moduli give different states of the same theory while in the latter case they correspond to different theories.

Abstract: Numerical investigation of the non-linear fate of the Aretakis instability has pointed towards the existence of a dynamical black hole solution which remains extremal and features a persistent instability and associated horizon hair forever. I will discuss how one can realize this solution analytically within JT gravity.