Dark compact objects in a first order phase transition

Jan Tristram Acuña^1*, Po-Yan Tseng¹

¹Department of Physics, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Jan Tristram Acuña, email:jtacuna@gapp.nthu.edu.tw

The study of first order phase transitions (FOPT) in the context of early Universe cosmology has recently been motivated by the discovery of stochastic gravitational waves by NANOGrav. Such dynamics may only be realized by extending the Standard Model, which may provide a basic framework to construct a dark sector model. Here I will introduce a mechanism to form compact objects, such as Fermi balls and primordial black holes (PBH), through an FOPT in the dark sector. We found that an SKA-like pulsar timing facility can be used to probe the signals from this FOPT scenario, namely the stochastic GW signal and Doppler shift of the timing signal due to the passage of compact objects near a pulsar. Viable FOPT scenarios correspond to critical temperatures within the 0.1-10 keV range, and those which lead to the formation of PBHs of mass 10^-8 to 10 solar masses. Furthermore, motivated by the result that black holes are characterized by their mass and spin, I will present some preliminary results on the spins of false vacuum bubbles, induced by cosmological perturbations during the FOPT. This may serve as a first step in determining the initial spins of PBHs produced through this mechanism.

Keywords: primordial black holes, first order phase transition, pulsar timing, stochastic gravitational waves, dark sector