Found at least 20 result(s)

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:

01.01.1970 (Thursday)

GE' style='color:#f0ad4e'>GE 227' style='color:#f0ad4e'>Rational homology spheres and SL(2,C) representations

regular seminar Steven Sivek (Imperial College London )

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

Building on non-vanishing theorems of Kronheimer and Mrowka in instanton Floer homology, Zentner proved that if Y is a homology 3-sphere other than S^3, then its fundamental group admits a homomorphism to SL(2,C) with non-abelian image. In this talk, Iâll explain how to generalize this to any Y whose first homology is 2-torsion or 3-torsion, other than the connect sum of n copies of the three-dimensional real projective space for any n or lens spaces of order 3. This is joint work with Sudipta Ghosh and Raphael Zentner.

Keywords:

01.01.1970 (Thursday)

PR' style='color:#f0ad4e'>PR 217' style='color:#f0ad4e'>KCL Probability Seminar: Directed Spatial Permutations on Asymmetric Tori

regular seminar Tyler Hellmuth (Durham University)

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

Random permutations show up in a variety of areas in mathematics and its applications. In connection with physical applications (e.g., the lambda transition for superfluid helium), there is an interest in random spatial permutations -- that is, laws on permutations that have a 'geometric bias'. There are compelling heuristic arguments that this spatial bias has little effect on the distribution of the largest cycles of a random spatial permutation, provided that large cycles actually exist. I'll discuss a particular model of random spatial permutations (directed permutations on asymmetric tori) where these heuristics can be made precise, and large cycles can be shown to follow the expected (Poisson-Dirichlet) law.

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 102584' 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)

TP' style='color:#f0ad4e'>TP 232' style='color:#f0ad4e'>TBA

journal club Maneerat Chawakorn (KCL)

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

Keywords:

01.01.1970 (Thursday)

ST' style='color:#f0ad4e'>ST 235' style='color:#f0ad4e'>Variational Inference for Cutting Feedback in Misspecified Models

regular seminar Michael Smith (University of Melbourne)

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

Bayesian analyses combine information represented by different terms in a joint Bayesian model. When one or more of the terms is misspecified, it can be helpful to restrict the use of information from suspect model components to modify posterior inference. This is called âœcutting feedbackâ, and both the specification and computation of the posterior for such âœcut modelsâ is challenging. In this paper, we define cut posterior distributions as solutions to constrained optimization problems, and propose variational methods for their computation. These methods are faster than existing Markov chain Monte Carlo (MCMC) approaches by an order of magnitude. It is also shown that variational methods allow for the evaluation of computationally intensive conflict checks that can be used to decide whether or not feedback should be cut. Our methods are illustrated in examples, including an application where recent methodological advances that combine variational inference and MCMC within the variational optimization are used.

Keywords:

01.01.1970 (Thursday)

AN' style='color:#f0ad4e'>AN 237' style='color:#f0ad4e'> Spectral properties of random matrices with heavy-tailed entries

regular seminar Svetlana Malysheva (Queen Mary University of London)

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

The talk will outline the main properties of high-dimensional random matrices whose entries do not have the 4th moment. We will also discuss heavy-tailed random matrices obtained from stock returns.

Keywords:

01.01.1970 (Thursday)

ME' style='color:#f0ad4e'>ME 208' style='color:#f0ad4e'>Maths education seminar: Investigating and Improving Proof Comprehension

regular seminar Lara Alcock (Loughborough University)

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

Undergraduate mathematics students see a lot of written proofs. But how much do they learn from them? Perhaps not as much as we would like, and perhaps we would like to improve their ability to engage with mathematics by reading. This talk will present a sequence of research studies addressing this issue. It will first describe studies on e-Proofs, which attempted to improve comprehension via proof-specific learning resources. It will then describe an eye-tracking study that provided real-time data on both student and expert mathematical reading. Finally, it will describe the effects of generic mathematical self-explanation training, investigated via both experimental and eye-tracking methods. Together, these studies provide insight into what is special about mathematical reading, and how students can be supported in reading more effectively.

Keywords:

01.01.1970 (Thursday)

GE' style='color:#f0ad4e'>GE 236' style='color:#f0ad4e'>Non-archimedean periods for log Calabi-Yau surfaces

regular seminar Soham Karwa (Imperial College London)

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

Period integrals are a fundamental concept in algebraic geometry and number theory. In this talk, we will study the notion of non-archimedean periods as introduced by Kontsevich and Soibelman. We will give an overview of the non-archimedean SYZ program, which is a close analogue of the classical SYZ conjecture in mirror symmetry. Using the non-archimedean SYZ fibration, we will prove that non-archimedean periods recover the analytic periods for log Calabi-Yau surfaces, verifying a conjecture of Kontsevich and Soibelman. This is joint work with Jonathan Lai.

Keywords:

01.01.1970 (Thursday)

PR' style='color:#f0ad4e'>PR 216' style='color:#f0ad4e'>KCL Probability Seminar: Random walks in dynamic environments.

regular seminar Guillaume Conchon-Kerjan (King's College London)

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

At the boundary of (discrete) probability and statistical physics, random walks in dynamic environments represent a way to model a particle advected by a fluid. Though some models are quite simple to define (usually, the environment is an evolving particle system, such as the exclusion process or a "cloud" of random walks), interest for this topic among probabilists has strongly increased in the past decade. These models feature complex technical challenges, as the time-dependency of the environment totally reshuffles the structure of space-time correlations, compared to the more classical setting of walks in static environment. In this talk, we will present this context and highlight how some key features such as recurrence/transience or the fluctuations of the walker are still the subject of many conjectures.

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 225' style='color:#f0ad4e'>BPS Ensembles of Strings and Fivebranes

regular seminar Zigdon Yoav ()

at:
01:00 - 01:00
KCL, Strand
room: K0.17
abstract:

We study ensembles of 1/2-BPS bound states of fundamental strings and NS-fivebranes (NS5-F1) in the decoupling limit. We revisit a solution corresponding to an ensemble average of these bound states, and find that the appropriate duality frame for describing the near-source structure is the T-dual NS5-P frame.
When members of the ensemble spin with two fixed angular potentials about two orthogonal planes, our main result is that an ensemble average of them gives rise to a smooth horizonless solution characterized by an ellipsoidal structure. This contrasts with ring structures obtained when fixing the angular momenta instead of the angular potentials\DSEMIC we trace this difference of ensembles to large fluctuations of the angular momentum in the ensemble of fixed angular potential.

Keywords:

01.01.1970 (Thursday)

TP' style='color:#f0ad4e'>TP 102583' 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)

TP' style='color:#f0ad4e'>TP 233' style='color:#f0ad4e'>Towards black hole states

journal club Simon Ekhammar (KCL)

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

I will discuss the problem of counting states in superconformal field theories, focusing on 4D N=4 SYM. The main focus will be on reviewing background material before briefly commenting on some recent developments in 2306.04693 and 2209.06728. I also hope to make some comments on the history of the problem.

Keywords:

01.01.1970 (Thursday)

ST' style='color:#f0ad4e'>ST 229' style='color:#f0ad4e'>Unsupervised attack pattern detection in honeypot data using Bayesian topic modelling

regular seminar Francesco Sanna Passino (Imperial College London)

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

Cyber-systems are under near-constant threat from intrusion attempts. Attacks types vary, but each attempt typically has a specific underlying intent, and the perpetrators are typically groups of individuals with similar objectives. Clustering attacks appearing to share a common intent is very valuable to threat-hunting experts. This talk explores topic models for clustering terminal session commands collected from honeypots, which are special network hosts designed to entice malicious attackers. The main practical implications of clustering the sessions are two-fold: finding similar groups of attacks, and identifying outliers. A range of statistical topic models are considered, adapted to the structures of command-line syntax. In particular, concepts of primary and secondary topics, and then session-level and command-level topics, are introduced into the models to improve interpretability. The proposed methods are further extended in a Bayesian nonparametric fashion to allow unboundedness in the vocabulary size and the number of latent intents. The methods are shown to discover an unusual MIRAI variant which attempts to take over existing cryptocurrency coin-mining infrastructure, not detected by traditional topic-modelling approaches. This is joint work with Daniyar Ghani (Imperial College London), Anastasia Mantziou (Alan Turing Institute), Philip Thiede (formerly at Imperial College London, now at Abios), Ross Bevington (Microsoft), Nicholas A. Heard (Imperial College London).

Keywords:

01.01.1970 (Thursday)

AN' style='color:#f0ad4e'>AN 230' style='color:#f0ad4e'>Existence results for the Landau equation

regular seminar Amélie Loher (University of Cambridge)

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

We consider the Landau equation with Coulomb potentials. We discuss a global existence result close to equilibrium and a short time existence result for general data. In both cases we take initial data in unweighted Lp spaces for p > 3/2. We thus work with the weakest class of initial data that has been considered until now. This is joint work with William Golding (UT Austin) and Maria Gualdani (UT Austin).

Keywords: