# All Upcoming Events

On Monday at 12:00 in Fisher Room, a seminar in
the String Theory series:

Tudor Dimofte (IAS, Princeton)

The Coulomb branch of 3d N=4 theories

**Further information:**While the Higgs branch of a 3d N=4 gauge theory is protected from quantum corrections and its metric is easily computable, the Coulomb branch suffers both perturbative and nonperturbative corrections, and has long remained mysterious. I will present a construction of the Coulomb branch as a complex manifold, and (in principle) as a hyperkahler manifold. In particular, holomorphic functions on the Coulomb branch come from vevs of monopole operators in a chiral ring, and it turns out that this ring has a simple, quasi-abelian description. Applying the construction to linear quiver gauge theories, one finds new descriptions of singular monopole moduli spaces. I may also touch upon relations to equivariant vortex counting, geometric representation theory, and symplectic duality.

On Monday at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Gergely Berczi (Oxford)

Invariants for parametrised subgroups of GL(n)

On Tuesday at 12:00 in L5, a seminar in
the Relativity series:

Piotr Tourkine (University of Cambridge (DAMTP))

Tropical Amplitudes

**Further information:**A systematic understanding of the low energy limit of string theory scattering amplitudes is essential for conceptual and practical reasons. In this talk, I shall report on a work where this limit has been analyzed using tropical geometry. Our result is that the field theory amplitudes arising in the low energy limit of string theory are written in a very compact form as integrals over a single object, the tropical moduli space. This picture provides a general framework where the different aspects of the low energy limit of string theory scattering amplitudes are systematically encompassed; the Feynman graph structure and the ultraviolet regulation mechanism. I shall then give examples of application of the formalism, in particular at genus two, and discuss open issues. No knowledge of tropical geometry will be assumed and the topic shall be introduced during the talk.

On Tuesday at 14:00 in Fisher Room, DWB, a seminar in
the Holography series:

Jerome Gauntlett (Imperial College, London)

tba

On Wednesday at 12:00 in L5, a seminar in
the Strings Junior series:

Andreas Braun (University of Oxford)

F-theory: string dualities and geometry - Part II

On Thursday at 13:00 in Dalitz Institute, DWB, a seminar in
the Particle Phenomenology Forum series:

Jim Talbert (University of Oxford)

Soft collinear effective theory

On Thursday at 16:15 in Sciama Lecture Theatre, a seminar in
the Particles and fields series:

Ernest Ma (University of California, Riverside)

Radiative type II seesaw mechanism for neutrino mass with dark matter

On Friday at 16:30 in L1, a seminar in
the Math Colloquium series:

Professor Jorge Nocedal (Northwestern University)

Recent Advances in Optimization Methods for Machine Learning

**Further information:**Optimization methods for large-scale machine learning must confront a number of challenges that are unique to this discipline. In addition to being scalable, parallelizable and capable of handling nonlinearity (even non-convexity), they must also be good learning algorithms. These challenges have spurred a great amount of research that I will review, paying particular attention to variance reduction methods. I will propose a new algorithm of this kind and illustrate its performance on text and image classification problems.

On Friday, May 1, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Physics Colloquia series:

Andre Lukas (Oxford)

tba

On Friday, May 1, at 16:30 in L1, a seminar in
the Math Colloquium series:

Martin Hairer (University of Warwick)

Taming infinities

**Further information:**Some physical and mathematical theories have the unfortunate feature that if one takes them at face value, many quantities of interest appear to be infinite! Various techniques, usually going under the common name of “renormalisation” have been developed over the years to address this, allowing mathematicians and physicists to tame these infinities. We will tip our toes into some of the mathematical aspects of these techniques and we will see how they have recently been used to make precise analytical statements about the solutions of some equations whose meaning was not even clear until recently.

On Tuesday, May 5, at 14:00 in Fisher Room, DWB, a seminar in
the Holography series:

Mario Flory (Max Planck Institute Munich)

Entanglement Entropy in a Holographic Model of the Kondo Effect

On Tuesday, May 12, at 12:00 in L4, a seminar in
the Quantum Field Theory series:

Krzysztof Meissner (Warsaw)

to be announced

On Friday, May 15, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Physics Colloquia series:

Pasquale Blasi (Acietri)

tba

On Tuesday, May 26, at 14:00 in Seminar Room 501, DWB, a seminar in
the Holography series:

Javier Mas (U.Santiago de Compostela)

tba

On Friday, May 29, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Physics Colloquia series:

Marc Mezard (ENS, Paris)

tba

On Tuesday, June 2, at 12:00 in L4, a seminar in
the Quantum Field Theory series:

Sylvie Paycha (Potsdam)

Renormalisation and the Euler-Maclaurin formula on cones

**Further information:**[based on joint work with Li Guo and Bin Zhang] We apply to the study of exponential sums on lattice points in convex rational polyhedral cones, the generalised algebraic approach of Connes and Kreimer to perturbative quantum field theory. For this purpose we equip the space of cones with a connected coalgebra structure. The algebraic Birkhoff factorisation of Connes and Kreimer adapted and generalised to this context then gives rise to a convolution factorisation of exponential sums on lattice points in cones. We show that this factorisation coincides with the classical Euler-Maclaurin formula generalised to convex rational polyhedral cones by Berline and Vergne by means of an interpolating holomorphic function. We define renormalised conical zeta values at non-positive integers as the Taylor coefficients at zero of the interpolating holomorphic function. When restricted to Chen cones, this yields yet another way to renormalise multiple zeta values at non-positive integers.

On Tuesday, June 9, at 14:00 in Seminar Room 501, DWB, a seminar in
the Holography series:

Ayan Mukhopadhyay (TBA)

tba

On Friday, June 19, at 16:30 in L3, a seminar in
the Math Colloquium series:

Gunnar Carlsson (Stanford University)

The Shape of Data

**Further information:**There has been a great deal of attention paid to 'Big Data' over the last few years. However, often as not, the problem with the analysis of data is not as much the size as the complexity of the data. Even very small data sets can exhibit substantial complexity. There is therefore a need for methods for representing complex data sets, beyond the usual linear or even polynomial models. The mathematical notion of shape, encoded in a metric, provides a very useful way to represent complex data sets. On the other hand, Topology is the mathematical sub discipline which concerns itself with studying shape, in all dimensions. In recent years, methods from topology have been adapted to the study of data sets, i.e. finite metric spaces. In this talk, we will discuss what has been done in this direction and what the future might hold, with numerous examples.