# All Upcoming Events

On Thursday at 12:45 in L2, a seminar in
the Strings Junior series:

Johan Henriksson

Higgs bundles

On Thursday at 13:00 in Dalitz Institute, a seminar in
the Dalitz Seminar in Fundamental Physics series:

None (Oxford)

Cancelled

On Thursday at 16:00 in L6, a seminar in
the Number Theory series:

Anna Cadoret (Université Paris 6 (IMJ-PRG))

The fundamental theorem of Weil II (for curves) with ultra product coefficients

*l-adic cohomology was built to provide an etale cohomology with coefficients in a field of characteristic 0. This, via the Grothendieck trace formula, gives a cohomological interpretation of L-functions - a fundamental tool in Deligne's theory of weights developed in Weil II. Instead of l-adic coefficients one can consider coefficients in ultra products of finite fields. I will state the fundamental theorem of Weil II for curves in this setting and explain briefly what are the difficulties to overcome to adjust Deligne's proof. I will then discuss how this ultra product variant of Weil II allows to extend to arbitrary coefficients previous results of Gabber and Hui, Tamagawa and myself for constant $\mathbb{Z}_\ell$-coefficients. For instance, it implies that, in an $E$-rational compatible system of smooth $\overline{\mathbb{Q}}_\ell$-sheaves all what is true for $\overline{\mathbb{Q}}_\ell$-coefficients (semi simplicity, irreducibility, invariant dimensions etc) is true for $\overline{\mathbb{F}}_\ell$-coefficients provided $\ell$ is large enough or that the $\overline{\mathbb{Z}}_\ell$-models are unique with torsion-free cohomology provided $\ell$ is large enough.*

**Further information:**
On Thursday at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

Christophe Grojean (DESY Hamburg)

Assessing the Higgs (self-)couplings

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

Thordur Jonsson (Iceland)

The dynamical triangulation approach to quantum gravity

On Monday at 12:45 in L3, a seminar in
the String Theory series:

Albrecht Klemm (Bonn)

TBA

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

Matthias Wink (Oxford University)

Constructions of cohomogeneity one Ricci solitons

On Tuesday at 12:00 in L4, a seminar in
the Relativity series:

Dhritiman Nandan (Edinburgh University)

Amplitude relations in Einstein-Yang-Mills theory

**I will discuss recent developments in the study of scattering amplitudes in Einstein-Yang-Mills theory. At tree level we find new structures at higher order collinear limits and novel connections with amplitudes in Yang-Mills theory using the CHY formalism. Finally I will comment on unitarity based observations regarding one-loop amplitudes in the theory. **

**Further information:**
On Tuesday at 15:45 in L4, a seminar in
the Algebraic Geometry series:

Evgeny Shinder (Sheffield)

Specialization of (stable) rationality

*The specialization question for rationality is the following one: assume that very general fibers of a flat proper morphism are rational, does it imply that all fibers are rational? I will talk about recent solution of this question in characteristic zero due to myself and Nicaise, and Kontsevich-Tschinkel. The method relies on a construction of various specialization morphisms for the Grothendieck ring of varieties (stable rationality) and the Burnside ring of varieties (rationality), which in turn rely on the Weak Factorization and Semi-stable Reduction Theorems.*

**Further information:**
On Thursday, November 30, at 12:45 in L2, a seminar in
the Strings Junior series:

Hadleigh Frost

Analytic continuation of path integrals

On Thursday, November 30, at 13:00 in Dalitz Institute, a seminar in
the Dalitz Seminar in Fundamental Physics series:

Hendrik Vogel (SLAC)

TBA

On Thursday, November 30, at 16:00 in L6, a seminar in
the Number Theory series:

Sam Chow (York)

A Galois counting problem

*We count monic quartic polynomials with prescribed Galois group, by box height. Among other things, we obtain the order of magnitude for quartics, and show that non-quartics are dominated by reducibles. Tools include the geometry of numbers, diophantine approximation, the invariant theory of binary forms, and the determinant method. Joint with Rainer Dietmann.*

**Further information:**
On Thursday, November 30, at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

Ana Achucarro (Universiteit Leiden)

Multifield inflation

On Thursday, November 30, at 17:00 in L3, a seminar in
the String Theory series:

Benjamin Assel (Cern)

RG flows in 3d N=4 gauge theories

*I will present a new approach to study the RG flow in 3d N=4 gauge theories, based on an analysis of the Coulomb branch of vacua. The Coulomb branch is described as a complex algebraic variety and important information about the strongly coupled fixed points of the theory can be extracted from the study of its singularities. I will use this framework to study the fixed points of U(N) and Sp(N) gauge theories with fundamental matter, revealing some surprising scenarios at low amount of matter.*

**Further information:**
On Friday, December 1, at 15:30 in Martin Wood Lecture Theatre, a seminar in
the Colloquia Series Seminars series:

Prof Frederick K. Lamb (University of Illinois)

The Iran Nuclear Deal

On Friday, December 1, at 16:00 in L1, a seminar in
the Math Colloquium series:

Luigi Ambrosio (Scuola Normale Superiore di Pisa)

New developments in the synthetic theory of metric measure spaces with Ricci curvature bounded from below

*The theory of metric measure spaces with Ricci curvature from below is growing very quickly, both in the 'Riemannian' class RCD and the general CD one. I will review some of the most recent results, by illustrating the key identification results and technical tools (at the level of calculus in metric measure spaces) underlying these results.*

**Further information:**
On Monday, December 4, at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Nathan Dunfield (Illinois at Urbana-Champaign)

Floer homology, group orders, and taut foliations of hyperbolic 3-manifolds

*A bold conjecture of Boyer-Gorden-Watson and others posit that for any irreducible rational homology 3-sphere M the following three conditions are equivalent: (1) the fundamental group of M is left-orderable, (2) M has non-minimal Heegaard Floer homology, and (3) M admits a co-orientable taut foliation. Very recently, this conjecture was established for all graph manifolds by the combined work of Boyer-Clay and Hanselman-Rasmussen-Rasmussen-Watson. I will discuss a computational survey of these properties involving half a million hyperbolic 3-manifolds, including new or at least improved techniques for computing each of these properties.*

**Further information:**
On Tuesday, December 5, at 12:00 in L4, a seminar in
the Relativity series:

Kasper Larsen (Southampton University)

Azurite: A new algorithm for finding bases of loop integrals

*Scattering amplitudes computed at a fixed loop order, along with any other object computed in perturbative QFT, can be expressed as a linear combination of a finite basis of loop integrals. To compute loop amplitudes in practise, such a basis of integrals must be determined. In this talk I introduce a new algorithm for finding bases of loop integrals and discuss its implementation in the publically available package Azurite.*

**Further information:**