November 22nd
when: Thursday 22/11/2018, 10:30
where: KE E-541 (møterom)
speaker: Joe Davighi (University of Cambridge)
title: Topological Terms in Sigma Models on Homogeneous Spaces
abstract:
We present a classification of topological terms appearing sigma models based on maps from an arbitrary worldvolume manifold to a homogeneous space G/H. In three or more dimensions, such sigma models describe Goldstone bosons associated with spontaneously broken symmetries, and thus occur ubiquitously in particle physics, condensed matter physics, and even cosomology. Our classification is based on replacing the sigma model maps with singular homology cycles in G/H, and thus applies for worldvolume manifolds of arbitrary topology. The topological terms that result, which require only the structure of an orientation on the worldvolume, can all be obtained by integrating (possibly only locally-defined) differential forms. In the second part of the talk, we apply this classification to a selection of Composite Higgs models, identifying a slew of previously unnoticed topological terms. These terms can have important phenomenological consequences, including the violation of discrete symmetries. Perhaps most importantly, measuring the coefficient of such a term can allow one to probe the gauge group of the underlying microscopic theory that gives rise to the Composite Higgs.
Slides: can be downloaded here.