Academia Sinica Logo

In the context of cosmology, we examine the growth of primordial black holes into stupendously large black holes of $\sim10^{12}\textup{--}10^{18}{\nm,M}_\odot$ by accreting the Bose--Einstein-condensate (BEC) fluid dark matter. The relativistic Bondi accretion is applicable in the Thomas--Fermi regime, where the equation of state of the BEC is radiationlike after the Big Bang Nucleosynthesis in the radiation-dominated era while becomes a condensate mimicking cold dark matter after matter-radiation equality. Under cosmological constraints, the critical mass for runaway growth is $\gtrsim10^{10}{\nm,M}_\odot$.