Long-lived Light Mediator to Dark Matter and Primordial Small Scale Spectrum

We calculate the early universe evolution of perturbations in the dark matter energy density in the context of simple dark sector models containing a GeV scale light mediator. We consider the case that the mediator is long lived, with lifetime up to a second, and before decaying it temporarily dominates the energy density of the universe. We show that for primordial perturbations that enter the horizon around this period, the interplay between linear growth during matter domination and collisional damping can generically lead to a sharp peak in the spectrum of dark matter density perturbation. As a result, the population of the smallest DM halos gets enhanced. Possible implications of this scenario are discussed.Comment: 8 pages, 5 figure

Supernova Cooling in a Dark Matter Smog

A light hidden gauge boson with kinetic mixing with the usual photon is a popular setup in theories of dark matter. The supernova cooling via radiating the hidden boson is known to put an important constraint on the mixing. I consider the possible role dark matter, which under reasonable assumptions naturally exists inside supernova, can play in the cooling picture. Because the interaction between the hidden gauge boson and DM is likely unsuppressed, even a small number of dark matter compared to protons inside the supernova could dramatically shorten the free streaming length of the hidden boson. A picture of a dark matter "smog" inside the supernova, which substantially relaxes the cooling constraint, is discussed in detail.Comment: 5 pages, 3 figure

Hyperband wireless

Research at Oxford University is currently exploring the feasibility of this concept with a focus on examining the fundamental aspects such as signal propagation and waveform design. The objective of research proposed here is to compliment the work at Oxford University through addressing ways of managing interference from other spectrum users. This PhD will have collaborative aspects with the Oxford University