Academic Year 2021/2022

Unless otherwise stated, seminars will take place in Seminar Room of the ICMS at the University of Edinburgh.
Please contact the organisers Praxitelis Ntokos (UoE) or Bart Vlaar (HW) with any questions regarding the seminars.
We are piloting a hybrid seminar format. Speakers and attendees can opt to join in-person or remotely using Zoom. Unless otherwise stated below, the bi-seminars will be held fortnightly on Wednesdays at 14:30-15:30 and 16:00-17:00, room 5.10 in the ICMS of the Bayes Centre. Instructions for Zoom attendees will be shared before each seminar.
Wednesday, 29 September 2021
Gabriel Larios (IFT Madrid and University of Michigan)
Infinite towers of massive modes arise for every compactification of higher dimensional theories. Understanding the properties of these Kaluza-Klein towers on non-trivial solutions with an AdS factor has been a longstanding issue with clear holographic interest, as they describe the spectrum of single-trace operators of the dual CFTs at strong coupling and large N. In this talk, I will focus on two classes of solutions of such kind. The first class consists of AdS4 solutions of D=11 and Type II supergravity that can be obtained from maximal gauged supergravities in D=4. For the later part, I will describe new families of solutions in N=(1,1) supergravity in D=6 which uplift from half-maximal supergravity in D=3. In both cases, the spectra can be computed using recent techniques from Exceptional Field Theory, and the information thus obtained leads to several unexpected conclusions.
Wednesday, 6 October 2021
Andrea Cristofoli (University of Edinburgh)
A particle physics approach to describing black hole interactions is opening new avenues for understanding gravitational-wave observations. In this talk, we will review this paradigm change showing how general relativity naturally emerges from scattering amplitudes. Applications for deriving solutions to Einstein field equations, the bending of light and waveforms - directly from quantum field theory - are explained.
Chiara Toldo (University of Amsterdam)
While multicenter black holes in asymptotically flat space have long been object of study, the construction of multi black holes geometries in Anti-de Sitter spacetimes remains so far elusive. In this talk I will discuss recent progress on the search for these solutions. Working in the probe approximation, I will show that there exist stable ad metastable black hole bound states in compactifications of M-theory on 7-dimensional Sasaki-Einstein manifolds with Betti multiplets and AdS4 vacua. I will map out their thermodynamic landscape and discuss the relevance of these setups for describing glassy systems via holography. I will finally discuss their supersymmetric limits, in light of recent developments regarding the entropy matching for stationary AdS4 black holes via localization in the dual 3d CFT.
Wednesday, 20 October 2021
PhD Student talks (University of Edinburgh and Heriot-Watt University)
Justin Vines (Albert Einstein Institute, MPI)
Classical gravitational interactions of spinning black holes (BHs) can be usefully described by certain limits of certain quantum scattering amplitudes, for massive higher-spin fields "minimally coupled" to gravity. Tree-level interactions between two BHs are determined by 3-point amplitudes (BH in, BH out, meeting one graviton) which are arguably well understood -- on the quantum side, for arbitrary-spin massive particles; classically, to all orders in the BH spin. Two-BH (conservative) interactions at the classical 1-loop level (and other processes) are argued to be determined by the additional 4-point "Compton" amplitude (BH in, BH out, meeting two gravitons), which is more poorly understood -- on the quantum side, up to spin-2 (or 5/2?); classically, up to 4th (or 5th?) order in the BH spin. In this talk, we'll discuss efforts to better understand the BH-graviton Compton amplitude for higher spins, and its applications, including directly interpreting its classical limit as the o utgoing amplitude for an incoming gravitational plane wave scattering off a Kerr BH.
Wednesday, 3 November 2021
Chris Heunen (University of Edinburgh)
We provide axioms that guarantee a category is equivalent to that of continuous linear functions between Hilbert spaces. The axioms are purely categorical and do not presuppose any analytical structure such as probabilities, convexity, complex numbers, continuity, or dimension. We'll discuss the axioms, sketch the proof of the theorem, and survey open questions, further directions, and context. (Based on joint work with Andre Kornell arxiv:2109.07418.)
João Melo (DAMTP, University of Cambridge)
For quantum fields in curved spacetimes there isn't a unique notion of vacuum state and the in and out vacua might be different, therefore, to perform calculations with interacting theories we require the use of the Schwinger-Keldysh formulation, very similar to undergraduate quantum mechanics. However, the usual assumption that the theory is free at past infinity isn't necessarily true and there is a need to modify the usual formalism to take this into account, resulting in a 3x3 matrix of propagators instead of the more familiar 2x2. In my talk I will describe this new formalism and test it in flat spacetime with the surprising conclusion that even in Minkowski spacetime it seems like the theory isn't free at past infinity at finite temperature as is commonly assumed.
Wednesday, 17 November 2021
Valentina Forini (City, University of London)
Wilson lines are a prototypical example of defect in QFT. I will consider the defect CFT_1 defined by correlators of operator insertions on a supersymmetric Wilson line in the d=3 superconformal ABJM model, illustrating how superspace techniques, analytic bootstrap and direct Witten diagrammatics can be used, combined with holography, to find its CFT data. I will then present a nonperturbative definition of Mellin amplitude for more general CFT_1 four-point correlators, and describe the use of this formalism to derive new results.
Anthony Ashmore (University of Chicago)
Calabi-Yau metrics and hermitian Yang-Mills connections have played a key role in both mathematics and physics in recent decades, and are particularly important for deriving semi-realistic models of particle physics from string theory. Unfortunately, explicit expressions for these objects are few and far between, leaving us unable, for example, to compute particle masses or couplings in string models. I will review recent progress on using machine learning techniques to compute these quantities numerically, with a particular focus on the example of computing gauge connections on line bundles.
Wednesday, 8 December 2021
Daniel Roggenkamp ( University of Mannheim )
In this talk I will explain, in the example of Rozansky-Witten models with affine target spaces, how to reconstruct an (extended) TQFT from its identity defect. For illustration I will shoot a sparrow with a cannon and use defects to rederive the state spaces of affine RW models for arbitrary surfaces.
Lotte Hollands ( Heriot-Watt University )
In this talk I will re-express the Nekrasov-Shatashvili free energy for a four-dimensional N=2 gauge theory as an integral of a ratio of Wronskians of solutions to the relevant oper equation, with the AD2 theory and the pure SU(2) theory as two main examples. This motivates the definition of a generalized Nekrasov-Shatashvili free energy for any four-dimensional N=2 theory of class S, and makes a connection with abelianization and exact WKB analysis. We will end with some remarks regarding the five-dimensional generalization and the relation to similar mathematical structures underlying the topological string partition function. This talk is based on 2109.14699 and work in progress.
Wednesday, 15 December 2021
Jan Sbierski (University of Edinburgh)
One can paraphrase Penrose’s strong cosmic censorship conjecture as stating that general relativity is generically a deterministic theory. While the full conjecture remains wide open there has long been evidence pointing towards its validity at least for small perturbations of exact rotating Kerr black holes. In this talk I will give a brief historical account of this evidence, discuss the analytic as well as the geometric aspects of this conjecture, and conclude by presenting forthcoming work on the linear instability of the Kerr Cauchy horizon.
Alfredo Guevara (Harvard University)
Scattering amplitudes are very natural in (2,2) signature, where the on-shell three-point functions do not vanish. Motivated by recent progress in celestial holography, we link (2,2) scattering amplitudes to Black Holes in (2,2) Klein space, and study their global structure. The link is very natural from the perspective of twistor theory. These black holes are a simple analytic continuation away from (1,3) solutions, but their (2,2) signature unveils new properties such as a direct diffeomorphism between Kerr Taub-NUT and Taub-NUT spacetimes.
PhD comics take on seminars