Found at least 20 result(s)
Regular Seminar Ana-Maria Raclariu (King's College London)
at: 01:00 - 01:00 KCL Strand room: LIMS abstract: | These lectures will review recent developments surrounding the infrared sector of gravity in (3+1)-dimensional asymptotically flat spacetimes (AFS). In the first part of the course we will introduce soft theorems which govern the low-energy scattering of massless particles such as photons and gravitons. We will explain how these are related to classical observables known as memory effects and discuss their application to computing infrared-finite collider observables and gravitational waveforms. In the second part, we will introduce the notion of asymptotic or large-gauge symmetries and use it to derive the infinite-dimensional asymptotic symmetry algebra of (3+1)-dimensional AFS, also known as the BMS algebra. We will show that the conservation laws associated with these symmetries are equivalent to the Weinberg soft graviton theorem. Time-permitting, we will discuss some implications of these ideas for non-AdS holography. Keywords: |
journal club Maneerat Chawakorn (KCL)
at: 01:00 - 01:00 KCL, Strand room: Norfolk Building 342N abstract: | Keywords: |
regular seminar Alex Shestopaloff (Queen Mary )
at: 01:00 - 01:00 KCL, Strand room: Strand 4.29 abstract: | Keywords: |
Regular Seminar Andrea Guerrieri (CERN)
at: 01:00 - 01:00 KCL Strand room: K3.11 abstract: | The numerical S-matrix Bootstrap aims at establishing non-perturbative universal bounds on physical observables that can be extracted from scattering amplitudes in any dimension. In the first part of the talk, I will review our past explorations of the space of supergravity amplitudes and their connection to String/M theory. I will discuss the universal bounds on the first non-universal correction to sugra amplitudes, and how the extremal solution is compatible with clustering in the Born regime, and with the Quantum Regge growth hypothesis. In the second part of the talk I will report on a first Bootstrap exploration of multi-particle scattering. I will focus on the simplest non-integrable S-matrix describing the scattering of branons on the world-sheet of confining strings in three dimensions.
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regular seminar Roland Bouffanais (University of Geneva)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | For a multi-agent system to respond effectively to evolving environmental conditions, proper information exchange among its units is paramount. This information transfer can either take the form of a simple contagion—stemming from pairwise interactions—or a complex contagion—involving social influence and reinforcement.
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regular seminar Laura Wakelin (KCL)
at: 01:00 - 01:00 KCL, Strand room: S4.29 abstract: | A slope p/q is characterising for a knot K if the oriented homeomorphism type of the 3-manifold obtained by performing Dehn surgery of slope p/q on K uniquely determines the knot K. For any knot K, there exists a bound C(K) such that any slope p/q with |q|≥C(K) is characterising for K. This bound has previously been constructed for certain classes of knots, including torus knots, hyperbolic knots and composite knots. In this talk, I will give an overview of joint work with Patricia Sorya in which we complete this realisation problem for all remaining knots. Keywords: |
regular seminar Bruno Schapira (Institut de Mathématique de Marseille)
at: 01:00 - 01:00 KCL, Strand room: S3.32 abstract: | We will discuss recent results obtained with Amine Asselah and partly with Perla Sousi, concerning the intersection of tree-like random graphs, which includes critical percolation clusters and critical branching random walks ranges in high dimension. One important ingredient of the proofs is a new bound on the n-th point function in percolation and the moments of local times for branching random walks, which may be of independent interest. Keywords: |
regular seminar Serguei Nechaev (CNRS - Universite Paris-Saclay)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | We provide an "optimal fluctuation" approach which allows us to examine the statistics of stretched 2D fractal polymer chains near an impermeable disc. We find that the span of the polymer away from the surface scales with the Kardar-Parisi-Zhang (KPZ) growth exponent 1/3, for any fractal dimension of the polymer. We pay attention to the mathematical analogy of the model under consideration with 1D Balagurov-Vaks trapping problem related to 1D Anderson localization. In parallel we consider statistics of nonuniform 1D random walks  as a "mean-field" approximation of Edelman-Dimitriu approach to RMT and derive the KPZ scaling for the mean-square random walk displacement. We discuss possible applications of obtained results for transport properties in laminar flows of liquids in corrugated channels. Keywords: |
Regular Seminar Ana-Maria Raclariu (King's College London)
at: 01:00 - 01:00 KCL Strand room: LIMS abstract: | These lectures will review recent developments surrounding the infrared sector of gravity in (3+1)-dimensional asymptotically flat spacetimes (AFS). In the first part of the course we will introduce soft theorems which govern the low-energy scattering of massless particles such as photons and gravitons. We will explain how these are related to classical observables known as memory effects and discuss their application to computing infrared-finite collider observables and gravitational waveforms. In the second part, we will introduce the notion of asymptotic or large-gauge symmetries and use it to derive the infinite-dimensional asymptotic symmetry algebra of (3+1)-dimensional AFS, also known as the BMS algebra. We will show that the conservation laws associated with these symmetries are equivalent to the Weinberg soft graviton theorem. Time-permitting, we will discuss some implications of these ideas for non-AdS holography. Keywords: |
journal club Svesko Andy (KCL)
at: 01:00 - 01:00 KCL, Strand room: Norfolk Building 342N abstract: | Keywords: |
regular seminar Chia-Chun Lo (KCL)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | By introducing progressively finer perturbations to a spectral problem in a controlled manner — an example of a procedure known as homogenisation — one hopes to uncover properties of the problem by exhibiting it as the limit of a family of other ones. In this work, we employ this strategy to show that the spectrum of a Schrödinger eigenvalue problem posed on a Riemannian manifold M can be approached by that of a family of Robin eigenvalue problems posed on domains in M with many small perforations.
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Triangular Seminar Shiraz Minwalla (TIFR, Mumbai)
at: 01:00 - 01:00 KCL Strand room: S-2.23 abstract: | Black holes in AdS$_d$ ($d \geq 4$) are always unstable at large angular momentum and sometimes unstable at large charge. We present proposals for the end points of these instabilities. Our constructions suggest new entropy formulae for ${\cal N}=4$ Yang Mills theory for a range of charges around extremality, and in particular for those that saturate the BPS bound. Keywords: |
Triangular Seminar Marina David (KU Leuven)
at: 01:00 - 01:00 KCL Strand room: S-2.23 abstract: | In this talk, I will show how one can study gravitational perturbations from the near-horizon region of extremal and near-extremal rotating black holes in a general higher-derivative extension of Einstein gravity. I will explain how the near-horizon Teukolsky equation is modified via a correction to the angular separation constant. The near-horizon region also provides constraints on the form of the full modified Teukolsky radial equation, which serve as a stepping stone towards the study of quasinormal modes of near-extremal black holes. In the second part of the talk, I will present a new family of EFT, motivated by preserving two fundamental properties of GR: gravitational waves are non-birefringent, and black hole quasinormal modes are isospectral. This leads to a novel class of EFT extensions, which remarkably, coincides with predictions from string theory and implies a previously unknown feature of string theory effective actions. Keywords: |
regular seminar Daniele Toniolo (UCL)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | Keywords: |
regular seminar Sophie Morier-Genoud (Université Reims Champagne Ardenne)
at: 01:00 - 01:00 KCL, Strand room: STRAND BLDG S4.29 abstract: | The talk will start from the elementary fact that positive rational numbers can be expanded as finite continued fractions with positive integer coefficients. The positive integer coefficients have combinatorial interpretations in the sense that ‘’they count something’’. I will present combinatorial interpretations based on the Farey graph. Introducing a formal parameter q, I will then make a deformations of the objects and refine the countings. This will bring notions of q-rationals, q-continued fractions, q-SL(2,Z). I will explain the constructions and give the main properties of all these q-analogs. Finally, I will connect this theory to the Burau representation of the braid group B3, and give a partial answer to the question of faithfulness of the complex specialisations of this representation. Keywords: |
regular seminar Spyridon Pougkakiotis (King's College London)
at: 01:00 - 01:00 KCL, Strand room: s5.20 abstract: | In this talk, we will discuss a novel result establishing that risk-constrained functional optimization problems with general integrable nonconvex instantaneous reward/constraint functions exhibit strong duality, regardless of nonconvexity.
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regular seminar Thomas Sauerwald (University of Cambridge)
at: 01:00 - 01:00 KCL, Strand room: S3.32 abstract: | In the balanced allocation problem we wish to allocate m balls (jobs) into n bins (servers) by allowing each ball to choose from some bins sampled uniformly at random. The goal is to maintain a small gap between the maximum load and average load.
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Regular Seminar Ana-Maria Raclariu (King's College London)
at: 01:00 - 01:00 KCL Strand room: LIMS abstract: | These lectures will review recent developments surrounding the infrared sector of gravity in (3+1)-dimensional asymptotically flat spacetimes (AFS). In the first part of the course we will introduce soft theorems which govern the low-energy scattering of massless particles such as photons and gravitons. We will explain how these are related to classical observables known as memory effects and discuss their application to computing infrared-finite collider observables and gravitational waveforms. In the second part, we will introduce the notion of asymptotic or large-gauge symmetries and use it to derive the infinite-dimensional asymptotic symmetry algebra of (3+1)-dimensional AFS, also known as the BMS algebra. We will show that the conservation laws associated with these symmetries are equivalent to the Weinberg soft graviton theorem. Time-permitting, we will discuss some implications of these ideas for non-AdS holography. Keywords: |
regular seminar Andrea Dotto (KCL)
at: 01:00 - 01:00 KCL, Strand room: K2.31 abstract: | The mod p Langlands correspondence for GL_2(Q_p) relates irreducible mod p representations of this group, to mod p representations of the absolute Galois group of Q_p. In contrast with the situation over the complex numbers, all attempts at extending this correspondence to more general p-adic Lie groups have been so far unsuccessful, due to the lack of a classification of irreducible representations. In this talk we will discuss what can be gained by shifting attention from the irreducible objects to the whole category of representations. The results are joint work in progress with Matthew Emerton and Toby Gee, and with Bao V. Le Hung.
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journal club Drukker Nadav (KCL)
at: 01:00 - 01:00 KCL, Strand room: Norfolk Building 342N abstract: | Keywords: |