Title: Overdensities of Ultralight Scalar Fields from Relaxation and Capture
Speaker: Joshua Eby (Stockholm University, OKC, Sweden)
Abstract: Ultralight scalars, with masses m<eV, are highly-motivated extensions of the Standard Model and candidates for dark matter. Their macroscopic wavelengths give rise to unique tendency to 'clump' into large-density, small-scale configurations, including self-gravitating boson stars and gravitational atoms bound to an external gravitational field. Recent work exploring the nature of these bound states has led to significant modifications from the usual assumption of a smooth DM halo with a well-known local density in the vicinity of the Sun, and suggest novel signals in a wide range of experiments. In this talk, I will review the known formation mechanisms for these bound states, from relaxation and capture of scalar waves through gravity and self-interactions, and describe several promising avenues to discover them. I will emphasize how these overdense clumps encode details about the underlying UV physics, making these searches highly complementary to traditional DM search strategies.