Gravitational Rainbows: LIGO and Dark Energy at its Cutoff

de Rham, Claudia (Theoretical Physics, Blackett Laboratory, Imperial College, London, SW7 2AZ, United Kingdom) (CERCA, Department of Physics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, Ohio 44106, USA) ; Melville, Scott (Theoretical Physics, Blackett Laboratory, Imperial College, London, SW7 2AZ, United Kingdom)

27 November 2018

Abstract: The recent direct detection of gravitational waves from a neutron star merger with optical counterpart has been used to severely constrain models of dark energy that typically predict a modification of the gravitational wave speed. However, the energy scales observed at LIGO, and the particular frequency of the neutron star event, lie very close to the strong coupling scale or cutoff associated with many dark energy models. While it is true that at very low energies one expects gravitational waves to travel at a speed different than light in these models, the same is no longer necessarily true as one reaches energy scales close to the cutoff. We show explicitly how this occurs in a simple model with a known partial UV completion. Within the context of Horndeski, we show how the operators that naturally lie at the cutoff scale can affect the speed of propagation of gravitational waves and bring it back to unity at LIGO scales. We discuss how further missions including LISA and PTAs could play an essential role in testing such models.


Published in: Physical Review Letters 121 (2018)
Published by: APS
DOI: 10.1103/PhysRevLett.121.221101
arXiv: 1806.09417
License: CC-BY-4.0



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