HEP Theory Journal Club

Phantom fluid cosmology: constraints and direct detection

Jim Cline

McGill

Phantom fields have been widely invoked as a source of dark energy in  cosmology, but rarely taken seriously as quantum theories. The vacuum is  automatically unstable to production of negative-energy ghost particles  plus normal particles, requiring such theories to be effective only, below  some UV cutoff. I will present recent cosmological constraints arising  from the vacuum instability, both at the level of the homogeneous  background, and the density perturbations.  We find that the fluid of  particles produced from vacuum decay can ameliorate but not solve the  notorious Hubble tension problem, and cannot fully replace the  cosmological constant as a source of dark energy.  The vacuum decay can be  a source of boosted dark radiation, which might be detectable if it  interacts with ordinary matter. I will show that this could fit recent  excess events reported by the DAMIC experiment at SNOLAB.