Tue, 06 May 2025
16:00
L6

Random matrix insights into discrete moments

Christopher Hughes
(University of York)
Abstract

One curious little fact about the Riemann zeta function is that if you evaluate its derivatives at the zeros of zeta, then on average this is real and positive (even though the function is complex). This has been proven for some time now, but the aim of this talk is to generalise the question further (higher derivatives, complex moments) and gain insight using random matrix theory. The takeaway message will be that there are a multitude of different proof techniques in RMT, each with their own advantages

Approximate solutions of a general stochastic velocity-jump model subject to discrete-time noisy observations
Ceccarelli, A Browning, A Baker, R Bulletin of Mathematical Biology volume 87 issue 5 (25 Mar 2025)

On Friday 14th March, we'll celebrate Pi Day with delicious Banoffee Pi.

Banoffee is a dessert with a buttery biscuit base, rich toffee, and fresh bananas. Apparently it is a fairly recent addition to menus, British in origin, dating as far back as, er, 1971.

Time-harmonic waves in Korteweg and nematic-Korteweg fluids
Farrell, P Zerbinati, U Physical Review E volume 111 issue 3 (28 Mar 2025)

We're looking for an Undergraduate Studies Administrator here in Maths. Please pass on to anyone you think might be interested in working with you all.

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Image: Kathleen Hyndman (1928-2022), Radiate/Glow, 1975, acrylic on canvas, 122 x 114 cm. Currently in the South Mezzanine, Andrew Wiles Building

Thu, 13 Mar 2025
16:00
L5

A Forward-Backward Approach to Endogenous Distress Contagion

Philipp Jettkant
(Imperial College )
Further Information

Please join us for refreshments outside the lecture room from 15:30.

Abstract

In this talk, I will introduce a dynamic model of a banking network in which the value of interbank obligations is continuously adjusted to reflect counterparty default risk. An interesting feature of the model is that the credit value adjustments increase volatility during downturns, leading to endogenous distress contagion. The counterparty default risk can be computed backwards in time from the obligations' maturity date, leading to a specification of the model in terms of a forward-backward stochastic differential equation (FBSDE), coupled through the banks' default times. The singular nature of this coupling, makes a probabilistic analysis of the FBSDE challenging. So, instead, we derive a characterisation of the default probabilities through a cascade of partial differential equations (PDE). Each PDE represents a configuration with a different number of defaulted banks and has a free boundary that coincides with the banks' default thresholds. We establish classical well-posedness of this PDE cascade, from which we derive existence and uniqueness of the FBSDE.

This week's short video with some invaluable advice at the end for those of you who sit through committees.

Reducing transmission in multiple settings is required to eliminate the risk of major Ebola outbreaks: a mathematical modelling study
Evans, A Hart, W Longobardi, S Desikan, R Sher, A Thompson, R Journal of the Royal Society Interface volume 22 issue 224 (19 Mar 2025)
The motion of a bubble in a non-uniform Hele-Shaw flow
Booth, D Griffiths, I Howell, P Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences volume 481 issue 2311 (02 Apr 2025)
J. M. F. Wright and Newton's method of first and last ratios
Hollings, C Research in History and Philosophy of Mathematics: The CSHPM 2024 Volume
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