Univ. of Arizona
Wednesday, November 30, 2016
Light scalar fields such as axions and string moduli can play an important role in early-universe cosmology. However, many factors can significantly impact their late-time cosmological abundances. For example, in cases where the potentials for these fields are generated dynamically — such as during cosmological mass-generating phase transitions — the duration of the time interval required for these potentials to fully develop can have significant repercussions. Likewise, in scenarios with multiple scalars, mixing generated amongst the fields can also give rise to modifications of the resulting late-time abundances. While previous studies have focused on these effects in isolation, surprising new features arise from the interplay between them. These include large suppressions in the late-time scalar abundance --- even by many orders of magnitude --- as well as parametrically-resonant enhancements, and a ``re-overdamping'' phenomenon which causes the energy density to behave in ways that differ from pure dark matter or vacuum energy. In this talk, I shall discuss the origins and implications of these effects, and how they can appear in situations in which our scalar fields form an entire Kaluza-Klein tower.