Astrophysical Probes of Exotic Particles

Abstract

Dark matter has been one of the most elusive puzzles in our understanding of the cosmos for over seventy years now. In this document, we explore the effects of the pair production of certain exotic particle states called millimagnetically charged particles (mmCPs) on the gravitational waves generated by a magnetar. We explicitly calculate the di erence in the time evolution of the gravitational wave (GW) amplitude which, when the waves are detected in the future, could serve as a signature of the presence of said mmCPs. In this enterprise, we fi rst present the necessary background on gravitational waves and then look at the existing literature on the gravitational waves in the context of isolated neutron stars. Due to the presence of multiple ideas on neutron star magnetic fields, we choose the ideas which we believe are the closest to reality and proceed to calculate the deformation to the star which generates a non-zero quadrupolar ellipticity and thus, gravitational waves. The amplitude of the gravitational waves is directly affected by the strength of the magnetic eld. We compare the GW amplitude by evolving the magnetic eld with and without the presence of mmCPs and nd that there is a difference. In the last chapter, we explore the application of an interesting idea regarding worldline instantons that recently appeared in the literature. We wish to see the potential arenas this new idea may open up in this sub eld. We also apply the technique to two different situations and find that the solution matches the known solution.