Seminar of the institute

Screened fifth forces and discrete symmetry breaking

by Peter Millington (University of Nottingham)

Europe/Berlin
Abbeanum/Ground floor-HS 2 - Hörsaal 2 (TPI, FSU Jena)

Abbeanum/Ground floor-HS 2 - Hörsaal 2

TPI, FSU Jena

50
Description

Modifications of general relativity often involve coupling additional scalar fields to the Ricci curvature, leading to scalar-tensor theories of Brans-Dicke type.  If the additional scalar fields are light, they can give rise to long-range fifth forces, which are subject to stringent constraints from local tests of gravity.  These constraints can be evaded by appealing to so-called screening mechanisms, wherein non-linearities and environmental dependence suppress the fifth force in regions of local matter density.  After reviewing the known classes of screening mechanism, we show that fifth forces only arise for the Standard Model (SM) due to mass mixing with the Higgs field, and we emphasise the pivotal role played by discrete and continuous symmetry breaking.  Quite remarkably, if one assumes that such light, non-minimally coupled scalar fields do exist in nature, the non-observation of fifth forces has the potential to tell us about the structure of the SM Higgs sector and the origin of its symmetry breaking.  Moreover, with these observations, we argue that certain classes of scalar-tensor theories (as studied in cosmology and astro-particle physics) are entirely equivalent to Higgs-portal theories (as studied in high-energy physics) at the level of their dimension-four operators, suggesting that Higgs portals may yield a much wider phenomenology than has previously been realised.