Mon, 26 Oct 2009

12:00 - 13:00
L3

Gauge Threshold Corrections for Local String Models

Joe Conlon
(Oxford)
Abstract
Local string models are those where Standard Model degrees of freedom arise on a small region inside a large bulk volume. I study threshold effects on gauge coupling running for such models. The Kaplunovsky-Louis formula for locally supersymmetric gauge theories predicts the unification scale should be the bulk winding mode scale, parametrically large than the string scale where divergences are naively cut off. Analysis of explicit string models on orbifold/orientifold geometries confirms this; the winding mode scale arises from the presence of tadpoles uncancelled in the local model. I briefly discuss phenomenological applications to supersymmetry breaking and gauge coupling unification.
Mon, 19 Oct 2009

12:00 - 13:00
L3

A CY Manifold with 3 Generations and Small Hodge Numbers

Philip Candelas
(Oxford)
Abstract
I will discuss a Calabi-Yau manifold which admits free actions by Abelian and non-Abelian groups of order 12. The quotient manifolds have Euler number -6 and Hodge numbers (h^{11}, h^{21}) = (1,4). Apart from the various presentations of the Yau Manifold, that have Hodge numbers (6,9), this is the only other complete intersection CY manifold to admit a free quotient with Euler number -6 and hence three generations of particles with the standard embedding. I will discuss the spectrum of light particles and the possibility of a transgression to a heterotic vacuum on a manifold with Hodge numbers (2,2).
Mon, 12 Oct 2009

12:00 - 13:00
L3

CANCELLED

Marni Sheppeard
(Oxford)
Tue, 20 Oct 2009
12:00
L3

Relations between Gowdy and Bianchi spacetimes

Alan Rendall
(AEI Golm)
Abstract

Two classes of solutions of the Einstein equations with symmetry which

are frequently studied are the Bianchi and Gowdy models. The aim of this

talk is to explain certain relations between these two classes of

spacetimes which can provide insights into the dynamics of both. In

particular it is explained that the special case of the Gowdy models known as circular loop spacetimes are Bianchi models in disguise. Generalizations of Gowdy spacetimes which can be thought of as inhomogeneous perturbations of some of the Bianchi models are introduced.

Results concerning their dynamics are presented.

Mon, 23 Nov 2009
14:15
L3

Monopoles, Periods and Problems

Harry Braden
(Edinburgh)
Abstract

The modern approach to integrability proceeds via a Riemann surface, the spectral curve.

In many applications this curve is specified by transcendental constraints in terms of periods. I will highlight some of the problems this leads to in the context of monopoles, problems including integer solutions to systems of quadratic forms, questions of real algebraic geometry and conjectures for elliptic functions. Several new results will be presented including the uniqueness of the tetrahedrally symmetric monopole.

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