Linear analysis of the gravitational beamplasma instability
Abstract
We investigate the wellknown phenomenon of the beamplasma instability in the gravitational sector when a fast population of particles interacts with the massive scalar mode of a Horndeski theory of gravity, resulting in linear growth of the latter amplitude. Following the approach used in the standard electromagnetic case, we start from the dielectric representation of the gravitational plasma, as introduced in a previous analysis of the Landau damping for the scalar Horndeski mode. We then set up the modified VlasovEinstein equation, using a Dirac delta function to describe the fast beam distribution. We thus provide an analytical expression for the dispersion relation, and we demonstrate the existence of a nonzero growth rate for the linear evolution of the Horndeski scalar mode. A numerical investigation is then performed with a trapezoidal beam distribution function, which confirms the analytical results and allows us to demonstrate how the growth rate decreases as the beam spread increases.
 Publication:

European Physical Journal C
 Pub Date:
 June 2023
 DOI:
 10.1140/epjc/s1005202311647z
 arXiv:
 arXiv:2203.16990
 Bibcode:
 2023EPJC...83..486M
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena;
 Physics  Plasma Physics
 EPrint:
 Revised version, two sections added + minor changes