Speaker
Description
A strong first-order phase transition offers the intriguing possibility of explaining
the stochastic gravitational wave background at nHz frequencies. In order to avoid
cosmological constraints, such a phase transition must have occurred in a dark sector
with non-negligible couplings to the standard model -- opening promising avenues of
connecting the gravitational wave signal to the cosmological dark matter abundance.
In order to illustrate this, I will consider a classically conformal dark sector
with a U(1) gauge symmetry. The spontaneous breaking of this symmetry generates
both gravitational waves and sources the mass of a fermionic sub-GeV dark matter
candidate. Contact with the standard model is established through kinetic
mixing of the U(1) gauge bosons with ordinary photons, a possibility that is
actively being searched for at various collider experiments. I will discuss the
rich phenomenology of such a scenario, demonstrating that it can successfully
generate both the observed nHz gravitational wave background and the cosmological
dark matter abundance, while at the same time avoiding all current constraints.
If time allows, I will further contemplate about what a future gravitational wave
signal observed by LISA may tell us about dark matter production in the early
universe.
| Research Area | Dark Matter |
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