Speaker
Description
Ultralight scalar boson of particle mass 10-22 ~ 10-21 eV/c2, motivated by Axion-Like Particle (ALP), is one of the dark matter candidates, so called UltraLight Dark Matter (ULDM). Its de'Brogile wavelength of ~O(1kpc) gives rise to the wave nature in our universe, governed by Schrodinger-Poisson Equation (SPE) in the nonrelativistic limit.
We focus on two properties of ULDM dynamics. First, the dynamical friction is waked by the quantum pressure of ULDM fluid, which suppresses the small-scale structure formation against gravitational collapse. This contributes to the Bose-Einstein condensation, leads to the formation of soliton core, which we regard as the core of ULDM halo. Second, an unstable ULDM system stabilizes while expelling probability density to infinity, which called "Gravitational Cooling". We performed numerical simulations of 1) Head-on collision of two ULDM halos comparing with CDM case, and 2) Binary Black Holes inside single ULDM halo. Through these, we suggest the Gravitational Cooling as the dominant effect for ULDM halo dynamics rather than Dynamical Friction.
