Dispersive gravitational waves in gases and plasmas

Abstract

Recent detection of electromagnetic (EM) waves along with gravitational waves (GWs) has ushered in the era of multimessenger astronomy. On one hand, it has the potential to yield precious information about the environment of the corresponding astrophysical compact objects, and on the other hand, it can greatly complement the “standard siren” technique of using GWs in cosmology, and benefit our understanding about the early Universe physics. However, to fully leverage all the possible information from the correlation of GWs with EM waves, their coupling outside the vacuum modes must be considered as well, requiring a careful thorough study of the coupling of self-consistent GWs with EM plasma modes. This thesis concerns developing such a formalism to study the collective effects of GWs interacting with gases and plasmas. The standard approach to study GW--matter coupling is to solve Einstein--Vlasov equations, but it has proven to be prohibitively cumbersome and typically involves oversimplifications, unable to account for the collective effects. We use an alternative, variational formulation to derive the gauge-invariant wave equation for collective oscillations of the self-consistent metric, EM fields and plasma. This forms a foundation for studying GW--plasma interactions rigorously.