Disformally coupled scalar fields and inspiralling trajectories
Abstract
We show how a nearly massless scalar field conformally and disformally coupled to matter can affect the dynamics of two bodies in their inspiralling phase before merging. We discuss both the conservative dynamics, e.g., how the energy of the bound system is corrected by the conformal and disformal interactions, and the dissipative part where scalars and gravitons are emitted. The first disformal correction to the EinsteinInfeldHoffmann Lagrangian is obtained using both the Fokker method relying on the equations of motion and an Effective Field Theory approach using Feynman diagrams. This leads to a correction to the energy functional at the 2 postNewotnian level for eccentric orbits, which vanishes for circular orbits up to the 7 postNewtonian order. The dissipative power from the disformal interaction gives a correction to the monopole and quadrupole terms in the presence of a conformal coupling. Although this correction vanishes for circular orbits at leading order, this is not the case for elliptical orbits allowing us to derive a bound on the disformal coupling from the time drift of the period for the HulseTaylor binary pulsar, which is slightly stronger than the one from fifth force tests. We conclude that the prospect of observing disformal effects for inspiraling systems lies in the accurate monitoring of eccentric trajectories as expected for the LISA experiment.
 Publication:

Physical Review D
 Pub Date:
 June 2019
 DOI:
 10.1103/PhysRevD.99.124034
 arXiv:
 arXiv:1903.03842
 Bibcode:
 2019PhRvD..99l4034B
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology
 EPrint:
 24 pages, 3 figures