Theory Colloquium

# Spin of Primordial Black Holes

## by Mehrdad Mirbabayi (ICTP Trieste)

Wednesday, July 10, 2019 from to (Europe/Berlin)
at DESY Hamburg ( build. 2a, SR2 )
 Description Primordial black holes, formed from rare peaks in the primordial fluctuations $\zeta$, are non-rotating at zeroth order in $\zeta_rms$. We show that the spin also vanishes at first order in $\zeta_rms$, suggesting the dimensionless spin parameter $a_rms \sim \zeta_rms^2$. We identify one quadratic contribution to the spin by calculating (and extrapolating to the formation time) the torque on a black hole due to ambient acoustic waves. For a reasonable density of primordial black holes this implies a percent level spin parameter.