Found at least 20 result(s)

01.01.1970 (Thursday)

AN' style='color:#f0ad4e'>AN 250' style='color:#f0ad4e'>Exponential inequalities in probability spaces revisited

regular seminar Esther Bou Dagher (Imperial College London)

at:
01:00 - 01:00
KCL, Strand
room: S5.20
abstract:

In this talk, we revisit several results on exponential integrability in probability spaces and derive some new ones. In particular, we give a quantitative form of recent results by Cianchi, Musil, and Pick in the framework of Moser-Trudinger-type inequalities, and recover Ivanisvili-Russellâs inequality for the Gaussian measure. One key ingredient is the use of a dual argument, which is new in this context, that we also implement in the discrete setting of the Poisson measure on integers. This is a joint work with Ali Barki, Sergey Bobkov, and Cyril Roberto.

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 102613' style='color:#f0ad4e'>Wilson Loop Duality and OPE for Form Factors of Half-BPS Operators

Regular Seminar Benjamin Basso (LPENS, Paris)

at:
01:00 - 01:00
KCL Strand
room: S0.12
abstract:

I will explain how to describe form factors of single-trace half-BPS operators in planar N=4 super Yang Mills theory using the T-dual Wilson loop picture. After reviewing earlier results for operators in the stress-tensor multiplet, I will present the dual Wilson loop description for the so-called MHV form factors of half-BPS operators. The general proposal relates these form factors to the matrix elements of a null periodic super Wilson loop with outgoing states composed of zero-momentum scalars. I will present perturbative tests of this description at weak coupling. I will then explain how to obtain exact result at finite coupling in the collinear limit using the Wilson loop Operator Product Expansion. I will conclude with general comments and speculations about form factors of unprotected operators such as the Konishi operator.

Keywords:

01.01.1970 (Thursday)

DS' style='color:#f0ad4e'>DS 242' style='color:#f0ad4e'>Generative AI and Diffusion Models: a Statistical Physics Analysis (Part II)

regular seminar Biroli Giulio (Ãcole Normale Supérieure de Paris)

at:
01:00 - 01:00
KCL, Strand
room: S4.23
abstract:

Part II. A statistical physics analysis using random matrix theory and mean-field methods.

Keywords:

01.01.1970 (Thursday)

GE' style='color:#f0ad4e'>GE 246' style='color:#f0ad4e'>Quiver mutations, Coxeter groups and hyperbolic manifolds

regular seminar Pavel Tumarkin (Durham University)

at:
01:00 - 01:00
KCL, Strand
room: S-2.25
abstract:

Mutations of quivers were introduced by Fomin and Zelevinsky in the context of cluster algebras. Since then, mutations appear (sometimes completely unexpectedly) in various domains of mathematics and physics. Using mutations of quivers, Barot and Marsh constructed a series of presentations of finite Coxeter groups as quotients of infinite Coxeter groups. I will discuss a geometric interpretation of this construction: these presentations give rise to a construction of geometric manifolds with large symmetry groups, in particular to some hyperbolic manifolds of relatively small volume with proper actions of Coxeter groups. If time permits, I will discuss a generalization of the construction of Barot and Marsh leading to a new invariant of bordered marked surfaces, and relation to extended affine Weyl groups. The talk is based on joint works with Anna Felikson, John Lawson and Michael Shapiro.

Keywords:

01.01.1970 (Thursday)

PR' style='color:#f0ad4e'>PR 244' style='color:#f0ad4e'>KCL Probability Seminar: Fastest-Mixing Markov Chain on a Graph

regular seminar Sam Olesker-Taylor (University of Warwick)

at:
01:00 - 01:00
KCL, Strand
room: S4.29
abstract:

Given a graph G = (V,E), consider the set of all discrete-time, reversible Markov chains with equilibrium distribution uniform on V and transitions only across edges E of the graph. We establish a Cheeger-type inequality for the fastest mixing time using the vertex conductance of G. We also consider chains with almost-uniform invariant distribution. Time permitting, we also discuss a construction of a continuous-time chain with exactly-uniform invariant distribution and average jump-rate 1, and mixing time bounded by the d^2 log(n), where d is the graph diameter and n is the number of vertices.

Keywords: Markov chain, mixing time, Cheeger inequality

n/a

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 102612' style='color:#f0ad4e'>Krylov perspective on Modular Hamiltonians and QCD.

Exceptional Seminar Pawel Caputa (U. Warsaw)

at:
01:00 - 01:00
KCL Strand
room: BH NE -1.01
abstract:

I will discuss some of the recent developments in the Krylov complexity. In particular, I will focus on the applications of the Krylov basis techniques to the modular Hamiltonian evolution and I will discuss a new angle on entanglement entropy in QCD at high energies. Based on arXiv:2306.14732 [hep-th] and work in progress.

Keywords:

01.01.1970 (Thursday)

DS' style='color:#f0ad4e'>DS 241' style='color:#f0ad4e'>Generative AI and Diffusion Models: a Statistical Physics Analysis (Part I)

regular seminar Biroli Giulio (Ãcole Normale Supérieure de Paris)

at:
01:00 - 01:00
KCL, Strand
room: S4.23
abstract:

Part I, Introduction and theoretical basis: how time-reversing Langevin dynamics one can create images from white noise.

Keywords:

Distinguished Visitor Series at KCL. First part of a mini-course.

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 247' style='color:#f0ad4e'>TBA

journal club William Pannell (KCL)

at:
01:00 - 01:00
KCL, Strand
room: Norfolk 342 N
abstract:

Keywords:

01.01.1970 (Thursday)

NT' style='color:#f0ad4e'>NT 213' style='color:#f0ad4e'>Internal number theory seminar: Explicit local solubility in families of varieties

regular seminar Chris Keyes (KCL)

at:
01:00 - 01:00
KCL, Strand
room: K0.50
abstract:

How often does a randomly chosen variety have a point? Answering this question depends on the family of varieties in question, how we decide to order them, and what kinds of points we are looking for. Motivated by rational points, we endeavor to explicitly describe how often a randomly chosen variety is everywhere locally soluble. When our family is described by the fibers of a suitable morphism, this likelihood is equal to the product of local probabilities at each place and in some cases may be computed exactly. In particular, in joint work with Lea Beneish we find that for almost 97% of integral binary sextic forms f(x,z), the superelliptic curve y^3 = f(x,z) is everywhere locally soluble, with the local factors described explicitly by rational functions. Time permitting, we will discuss ongoing work on determining how often a cubic hypersurface has a rational point.

Keywords:

01.01.1970 (Thursday)

ST' style='color:#f0ad4e'>ST 239' style='color:#f0ad4e'>Annealed Sequential Monte Carlo Samplers

regular seminar Saifuddin Syed (University of Oxford)

at:
01:00 - 01:00
KCL, Strand
room: S5.20
abstract:

Sequential Monte Carlo Samplers (SMCS) constitute a widely used class of SMC algorithms that calculate normalizing constants and simulate complex multi-modal target distributions. Typically, SMCS utilizes a process known as annealing, which propagates solutions from a tractable reference distribution to the intractable target through a continuous path of increasingly complex distributions. SMCS delivers state-of-the-art performance when adequately tuned, although this can pose a challenge for current tuning methods, yielding a random run-time and compromising the normalizing constant's unbiasedness.

In this talk, we intend to describe all the components of an SMCS algorithm and their influence on the variance of the normalizing constant. Specifically, we will demonstrate that SMCS exhibits fundamentally different behaviour in large particle and dense schedule limits. The dense schedule limit reveals the natural geometry induced by annealing, which can pinpoint optimal performance and tune the number of particles, number of annealing distributions, annealing schedules, the resampling schedule, and the path. Lastly, we propose an efficient, black-box algorithm for tuning SMCS that delivers optimal performance within a fixed, user-specified computation budget, all while preserving the unbiasedness of the normalizing constant.

Keywords:

01.01.1970 (Thursday)

AN' style='color:#f0ad4e'>AN 248' style='color:#f0ad4e'>Fokas Diagonalization

regular seminar Dave Smith ( Yale-NUS College)

at:
01:00 - 01:00
KCL, Strand
room: S5.20
abstract:

We describe a new form of diagonalization for linear two point constant coefficient differential operators with arbitrary linear boundary conditions. Although the diagonalization is in a weaker sense than that usually employed to solve initial boundary value problems (IBVP), we show that it is sufficient to solve IBVP whose spatial parts are described by such operators. We argue that the method described may be viewed as a reimplementation of the Fokas transform method for linear evolution equations on the finite interval. The results are extended to multipoint and interface operators, including operators defined on networks of finite intervals, in which the coefficients of the differential operator may vary between subintervals, and arbitrary interface and boundary conditions may be imposed\DSEMIC differential operators with piecewise constant coefficients are thus included.

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 102611' style='color:#f0ad4e'>Harmonic analysis and the conformal bootstrap reloaded

Regular Seminar Dalimil Mazac (IPhT, Saclay)

at:
01:00 - 01:00
KCL Strand
room: S0.12
abstract:

I will discuss a connection between harmonic analysis on hyperbolic n-manifolds and conformal field theory in n-1 dimensions. Used in one direction, this connection leads to new spectral bounds on hyperbolic manifolds. Used in the other direction, it offers a new viewpoint on the spectra data of conformal field theories.

Keywords:

01.01.1970 (Thursday)

ME' style='color:#f0ad4e'>ME 218' style='color:#f0ad4e'>Maths education seminar: Effective practice in mathematical outreach

regular seminar Peter Rowlett (Sheffield Hallam University)

at:
01:00 - 01:00
KCL, Strand
room: K0.50
abstract:

There are many ways to engage with mathematics, and therefore many different forms of maths engagement aimed at different audiences. A brief survey will present a range of different practices and encourage thought about target audience. We'll consider how to design effective outreach, and how informal engagement with maths before university can influence the decision to study maths at university. From a practical point of view, I will describe a programme of maths engagement for secondary school students implemented in local schools and on campus.

Keywords:

01.01.1970 (Thursday)

GE' style='color:#f0ad4e'>GE 243' style='color:#f0ad4e'>Knots, minimal surfaces and J-holomorphic curves

regular seminar Joel Fine (Université Libre de Bruxelles)

at:
01:00 - 01:00
KCL, Strand
room: S4.29
abstract:

Let $K$ be a knot or link in the 3-sphere, thought of as the ideal boundary of hyperbolic 4-space $\mathbb{H}^4$. I will describe a programme to count minimal surfaces in $\mathbb{H}^4$ which have $K$ as their asymptotic boundary. This should give an isotopy invariant of the knot. I will explain what has been proved and what remains to be done. Minimal surfaces correspond to $J$-holomorphic curves in the twistor space $Z\to\mathbb{H}^4$, and so this invariant can be seen as a Gromov-Witten type invariant of $Z$. The big difference with the âœstandardâ situation is that the almost complex structure on $Z$ (equivalently, the metric on $\mathbb{H}^4$) blows up at the boundary. This means the $J$-holomorphic equation, or minimal surface equation, becomes degenerate at the boundary of the domain. As a consequence, both the Fredholm and compactness parts of the story need to be reworked by hand. If there is time I will explain how this can be done, relying on results of Mazzeo-Melrose from the 0-calculus, and also some results from the theory of minimal surfaces.

Keywords:

01.01.1970 (Thursday)

PR' style='color:#f0ad4e'>PR 219' style='color:#f0ad4e'>KCL Probability Seminar: Convergence in law in metric and submetric spaces

regular seminar Adam Jakubowski (Nicolaus Copernicus University in Torun)

at:
01:00 - 01:00
KCL, Strand
room: S4.29
abstract:

In 1953 Yu. Prohorov published a paper on weak convergence of
probability measures on metric spaces, bringing a new, extended context to the Invariance Principle proved by Donsker two years earlier.
Prohorovâs formalism, publicised in books by K.R. Parthasarathy and
P. Billingsley, established the equivalence of the notion of convergence
in law of stochastic processes and the weak convergence of their distributions. This point of view is completely justified in metric spaces,
especially in Polish spaces.

It is, however, much less satisfactory in non-metric spaces, as was
shown by examples due to X. Fernique, given long time ago.
We show that in a large class of submetric spaces there exists a
stronger mode of convergence, coinciding with the weak convergence
on metric spaces, and much more suitable for needs of contemporary
theory of stochastic partial differential equations.

A submetric space is a topological space (X,tau) admitting a continuous metrics d that in turn determines a metric topology $\tau_d \subset \tau$ (where this inclusion is in general strict). As a standard (and the simplest)
example may serve a separable Hilbert space equipped with the weak
topology.

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 234' style='color:#f0ad4e'>Log corrections to Kerr

journal club Andrew Svesko (KCL)

at:
01:00 - 01:00
KCL, Strand
room: Norfolk Building 342N
abstract:

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 102585' style='color:#f0ad4e'>Lonti: The initial (boundary) value problem in numerical general relativity

Regular Seminar Pau Figueras (QMUL)

at:
01:00 - 01:00
KCL Strand
room: LIMS
abstract:

In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinââ¬â¢s theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.

Keywords:

01.01.1970 (Thursday)

AN' style='color:#f0ad4e'>AN 238' style='color:#f0ad4e'>New methods and results in two old problems

regular seminar Michael Levitin (University of Reading)

at:
01:00 - 01:00
KCL, Strand
room: S5.20
abstract:

I will discuss a recent progress on two classical problems. The first one comes mostly from applied mathematics and numerical analysis: find tight universal and preferably simple enclosures for zeros of Bessel functions, of their derivatives, and possibly of other special functions. The second one comes primarily from number theory: find bounds for the number of lattice points under the graph of a given function (with some restrictions on the class of functions). As an application of these results, Iâll show the validity of inequalities à la Pólya for the magnetic Aharonov--Bohm Laplacian in the disk, discuss possible generalisations, and open problems. The talk covers some joint works, mostly in progress, with N. Filonov, I. Polterovich, and D. A. Sher.

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 102610' style='color:#f0ad4e'>Conformal boundary conditions, Cardy's variational ansatz and phase structure of 2D QFTs

Regular Seminar Anatoly Konechny (Heriot-Watt)

at:
01:00 - 01:00
KCL Strand
room: S0.12
abstract:

We will consider perturbations of 2D CFTs by multiple relevant operators. The massive phases of such perturbations can be labeled by conformal boundary conditions. Cardy's variational ansatz approximates the vacuum state of the perturbed theory by a smeared conformal boundary state. In this talk we will discuss the limitations and propose generalisations of this ansatz using both analytic and numerical insights based on TCSA.

In particular we analyse the stability of Cardy's ansatz states with respect to boundary relevant perturbations using bulk-boundary OPE coefficients. We show that certain transitions between the massive phases arise from a pair of boundary RG flows. The RG flows start from the conformal boundary on the transition surface and end on those that lie on the two sides of it. As an example we work out the details of the phase diagram for the Ising field theory and for the tricritical Ising model perturbed by the leading thermal and magnetic fields. Based on arXiv:2306.13719.

Keywords:

01.01.1970 (Thursday)

ME' style='color:#f0ad4e'>ME 209' style='color:#f0ad4e'>Maths education seminar: What can universities learn from the learning and teaching of mathematics at King's Maths School?

regular seminar Dan Abramson (King's College London)

at:
01:00 - 01:00
KCL, Strand
room: K0.50
abstract:

King's College London Mathematics School is for students aged 16-18 with an enthusiasm and aptitude for mathematics, and aims to widen participation in high-quality degrees and careers in the mathematical sciences.

The school opened in 2014 and for nearly 10 years has been evolving a pedagogy and curriculum tuned to generating confident, skilled and articulate mathematical thinkers.

In this talk I will explore those aspects of pedagogy and culture at KCLMS that universities might use to improve their teaching and learning.

Keywords: