Vacuum Cherenkov radiation and bremsstrahlung from disformal couplings

van de Bruck, Carsten; Burrage, Clare; Morrice, Jack

Abstract

The simplest way to modify gravity is to extend the gravitational sector to include an additional scalar degree of freedom. The most general metric that can be built in such a theory includes disformal terms, so that standard model fields move on a metric which is the sum of the space time metric and a tensor constructed from first derivatives of the scalar. In such a theory gravitational waves and photons can propagate at different speeds, and these can in turn be different from the maximum speed limit for matter particles. In this work we show that disformal couplings can cause charged particles to emit Cherenkov radiation and bremsstrahlung apparently in vacuum, depending on the background evolution of the scalar field. We discuss the implications of this for observations of cosmic rays, and the constraints that arise for models of dark energy with disformal couplings.

Citation

van de Bruck, C., Burrage, C., & Morrice, J. (2016). Vacuum Cherenkov radiation and bremsstrahlung from disformal couplings. Journal of Cosmology and Astroparticle Physics, 2016(8), Article 003. https://doi.org/10.1088/1475-7516/2016/08/003

• Journal Article Type: Article
• Acceptance Date: Jul 21, 2016
• Publication Date: Aug 2, 2016
• Deposit Date: Apr 21, 2017
• Publicly Available Date: Apr 21, 2017
• Journal: Journal of Cosmology and Astroparticle Physics
• Electronic ISSN: 1475-7516
• Publisher: IOP Publishing
• Peer Reviewed: Peer Reviewed
• Volume: 2016
• Issue: 8
• Article Number: 003
• DOI: https://doi.org/10.1088/1475-7516/2016/08/003
• Public URL: https://nottingham-repository.worktribe.com/output/806976
• Publisher URL: http://iopscience.iop.org/article/10.1088/1475-7516/2016/08/003/meta
• Contract Date: Apr 21, 2017