Abstract

We present the coupling between a gravitational wave in a Minkowski spacetime with dark matter modelled by a self-interacting complex scalar field. In flat spacetime, quantum fluctuations in dark matter, as described as a Bose-Einstein condensate (BEC), are stable and display a relativistic Bogoliubov dispersion relation. In the weak gravitational field limit, both relativistic and nonrelativistic models self-gravitating dark matter suggest the formation of structures as the result of a dynamical (Jeans) instability. In this work we show that in the presence of spontaneous symmetry breaking of the dark matter field, the gravitational wave is damped for wave-lengths larger than the Jeans length. Such energy is converted to the Bogoliubov modes of the BEC that in their turn become unstable and grow, leading to the formation of structures even in the absence of expansion. Remarkably, this compensated attenuation/amplification mechanism is the signature of a discrete PT symmetry-breaking of the system.

Keywords

Dark matter, Bose-Einstein condensate, spontaneous symmetry breaking, gravitational wave, Jeans length