Triangle Seminars

Abstract:
Compact binaries with asymmetric mass ratios are key expected sources for next-generation gravitational-wave detectors. Gravitational self-force theory has been successful in producing post-adiabatic waveforms that describe the quasicircular inspiral around a nonspinning black hole with sub-radian accuracy, in remarkable agreement with numerical relativity simulations. Current self-force models, however, break down at the innermost stable circular orbit (ISCO), missing the final merger and ringdown stages. In this talk, I will show how the self-force waveforms can be extended beyond the ISCO, building first-principles inspiral-merger-ringdown waveforms. I will then dissect the final merger-ringdown waveforms and compare them with a self-consistently calculated sum over quasinormal modes and a stationary-phase approximation. Finally, I will briefly discuss how beyond-GR effects can be modularly added in this framework.

Abstract:
Symmetries of a quantum field theory are implemented by topological operators. These are special extended operators whose correlation functions are insensitive to continuous deformations of their support. The classification of generalized symmetries thus reduces to understanding the spectrum of such topological operators across different codimensions. While a generic QFT may admit infinitely many topological operators, their topological nature imposes strong consistency conditions on their structure. In this talk, I will present a set of such constraints in 2+1 and 3+1 dimensions and highlight how they severely restrict the spectrum of topological operators in higher dimensions, in contrast to 1+1 dimensions. Using these constraints, I will argue that the action of non-invertible symmetries on local operators in higher dimensions is highly restricted. In particular, this action is either invertible or, when non-invertible, admits a description in terms of gauging a finite symmetry.

Abstract:
Integrated four point functions in SCFTs are interesting observables, for instance providing non-trivial constraints to the stringy corrections strong coupling supergravity effective action in holographic models. More recently the attention has shifted towards understanding integrated correlators involving heavy operators in N=4 SYM, such as those describing giant gravitons in the bulk. A remarkable feature of this class of HHLL integrated correlators is that their strong ‘t Hooft coupling expansions have a universal perturbative expansion in 1/ \lambda which is independent of the precise details of the heavy operators. I will discuss the origin of this universality of giant correlators, show that it persists to all orders in the 1/N expansion, and explain its breakdown for operators dual to backreacted geometries. On a more technical level I will introduce a family of Ginibre ensembles which efficiently compute the perturbative expansion of HHLL integrated correlators at finite N. As a result I will propose an exact formula for all integrated correlators of giant graviton operators.

Abstract:
High-energy scattering poses very intriguing challenges in theoretical physics, with implications ranging from the structure of the proton to trans-Planckian gravitational scattering. In this regime, quantum chromodynamics (QCD) exhibits a remarkably rich and intricate structure, where expectations based on naive factorisation break down. New dynamical phenomena emerge, playing a crucial role in ensuring the unitarity of the theory.
In this talk, I will briefly review the high-energy dynamics of QCD and discuss how recent advances in the study of scattering amplitudes provide new tools to investigate this regime in a controlled and systematic way. I will highlight some of the resulting insights, along with their implications and possible directions for future work.