Mon, 21 Jan 2013

12:00 - 13:00
L3

Umbral Moonshine

Miranda Cheng
(Jussieu)
Abstract
Mock modular forms are generalizations of modular forms first introduced by Ramanujan. Their properties had been mysterious for 80 years until various breakthroughs in the past 10 years. In the last century, the Monstrous Moonshine Conjecture initiated the study of the fascinating relation between modular forms and sporadic groups. In this talk I will report a conjecture on a new type of "umbral moonshine" relating a set of mock modular forms, including many of Ramanujan's original examples, and the representation theory of a set of finite groups. One instance of such a surprising umbral moonshine phenomenon relates the largest Mathieu group to the elliptic genus of K3 surfaces, as was first observed by Euguchi-Ooguri-Tachikawa in 2010. Moreover, there are hints suggesting that all occurrences of umbral moonshine have a close relation to K3-compactifications of string theory. However, despite of these tantalising hints the origin and the explanation of this umbral moonshine is still unclear at the moment. This talk is based on the arXiv pre-print: 1201.4140, 1204.2779 with John Duncan and Jeff Harvey.
Mon, 14 Jan 2013

12:00 - 13:00
L3

Non-commuting closed strings on non-geometric backgrounds

Magdalena Larfors
(Oxford)
Abstract
Strings are extended objects, and this means that they can be compactified not only on Riemannian manifolds, but also on more exotic spaces with generalized transition functions. An example of this is the T-fold, where T-duality is used to glue the Neveu-Schwarz fields of the background. Collectively, these exotic set-ups are known as non-geometric string compactifications, and in this talk I will discuss two of their aspects. First, I will present a field redefinition in the Neveu-Schwarz sector that allows a ten-dimensional, effective description of certain non-geometric backgrounds. This redefinition is inspired by Generalized Geometry and Double Field Theory. Second, I will show that closed strings become non-commuting when non-geometric fluxes are turned on. This will be done through the analysis of a three-torus with H-flux and its T-dual configurations.
Tue, 15 Jan 2013

12:00 - 13:00
L3

Supersymmetric loop space

Mir Faizal
Abstract

We will first review the construction of N =1

supersymmetric Yang-Mills theory in three dimensions. Then we will

construct a superloop space formulation for this super-Yang-Mills

theory in three dimensions.Thus, we will obtain expressions for loop

connection and loop curvature in this superloop space. We will also

show that curvature will vanish, unless there is a monopole in the

spacetime. We will also construct a quantity which will give the

monopole charge in this formalism. Finally, we will show how these

results hold even in case of deformed superspace.

Thu, 24 Jan 2013

14:00 - 15:00
L3

Cocycle twists of tensor categories and of rational Cherednik algebras

Yuri Bazlov
(Manchester University)
Abstract

Central extensions of a finite group G correspond to 2-cocycles on G, which give rise to an abelian cohomology group known as the Schur

multiplier of G. Recently, the Schur multiplier was defined in a much more

general setting of a monoidal category. I will explain how to twist algebras by categorical 2-cocycles and will mention the role of

such twists the theory of quantum groups. I will then describe an approach to twisting rational Cherednik algebras by cocycles,

and will discuss possible applications of this new construction to the representation theory of these algebras.

Thu, 07 Mar 2013

17:00 - 18:00
L3

Pure Inductive Logic

Jeff Paris
(Manchester)
Abstract

I shall give a non-technical survey of Pure Inductive Logic, a branch of Carnap's Inductive Logic which was

anticipated early on in that subject but has only recently begun to be developed as an area of Mathematical Logic. My intention

is to cover its origins and aims, and to pick out some of the key concepts which have emerged in the last decade or so.

Thu, 07 Mar 2013

14:00 - 15:00
L3

Borel- Schur algebras and resolutions of Weyl modules

Ana Paula Santana
(University of Coimbra)
Abstract

Using the Borel-Schur algebra, we construct explicit characteristic-free resolutions for Weyl modules for the general linear group. These resolutions provide an answer to the problem, posed in the 80's by A. Akin and D. A. Buchsbaum, of constructing finite explicit and universal resolutions of Weyl modules by direct sums of divided powers. Next we apply the Schur functor to these resolutions and prove a conjecture of Boltje and Hartmann on resolutions of co-Specht modules. This is joint work with I. Yudin.

Thu, 28 Feb 2013

17:00 - 18:00
L3

Rational values of certain analytic functions

Gareth Jones
(Manchester)
Abstract

Masser recently proved a bound on the number of rational points of bounded height on the graph of the zeta function restricted to the interval [2,3]. Masser's bound substantially improves on bounds obtained by Bombieri-Pila-Wilkie. I'll discuss some results obtained in joint work with Gareth Boxall in which we prove bounds only slightly weaker than Masser's for several more natural analytic functions.

Thu, 21 Feb 2013

17:00 - 18:00
L3

Multiplicity in difference geometry

Ivan Tomasic
(QMUL)
Abstract

The study of difference algebraic geometry stems from the efforts of Macintyre and Hrushovski to

count the number of solutions to difference polynomial equations over fields with powers of Frobenius.

We propose a notion of multiplicity in the context of difference algebraic schemes and prove a first principle

of preservation of multiplicity. We shall also discuss how to formulate a suitable intersection theory of difference schemes.

Thu, 07 Feb 2013

17:00 - 18:00
L3

The Outer Model Programme

Peter Holy
(Bristol)
Abstract

The Outer Model Programme investigates L-like forcing  extensions of the universe, where we say that a model of Set Theory  is L-like if it satisfies properties of Goedel's constructible universe of sets L. I will introduce the Outer Model Programme, talk  about its history, motivations, recent results and applications. I  will be presenting joint work with Sy Friedman and Philipp Luecke.

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