van de Bruck, C., Burrage, C. and Morrice, J. (2016) Vacuum Cherenkov radiation and bremsstrahlung from disformal couplings. Journal of Cosmology and Astroparticle Physics, 2016 (08). 003.
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.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2016 IOP Publishing Ltd and Sissa Medialab srl. |
Keywords: | dark energy theory; modified gravity |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield) |
Funding Information: | Funder Grant number SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/L000520/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 19 Oct 2017 10:15 |
Last Modified: | 19 Oct 2017 10:15 |
Published Version: | https://doi.org/10.1088/1475-7516/2016/08/003 |
Status: | Published |
Publisher: | IOP Publishing |
Refereed: | Yes |
Identification Number: | 10.1088/1475-7516/2016/08/003 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:122813 |