Primordial black holes from a cosmic phase transition: The collapse of Fermi-balls

Old Phase Remnants in First Order Phase Transitions

“…Introduction-First order phase transitions (FOPTs) are found across disciplines as diverse as biology [1,2], condensed matter physics [3,4], and cosmology [5]. In the cosmological context, FOPTs are a natural consequence of many Beyond Standard Model theories, and could play a crucial role in generating the matterantimatter asymmetry [6][7][8][9][10], forming dark matter [11][12][13][14][15][16][17][18][19][20][21] and primordial black holes (PBHs) [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], and leave detectable signals in current or near-future gravitational wave detectors [42][43][44][45][46][47].…”

“…As a result, analytic methods were developed to estimate the TV nucleation rate, wall velocity, and bubble distribution [51][52][53][54][55][56][57][58][59][60][61][62][63]. On the other hand, FV remnants are more relevant for the mechanisms involving trapping particles in the FV to realize baryogenesis [64], dark matter [14][15][16][17][18][19][20][21] and PBHs [32][33][34][35][36]. Lacking an equivalent detailed description of the FV remnants, previous studies had to either use naive estimations of the average remnant size and density [15,19], or take those observables as free parameters [32,33].…”

“…Application to Primordial Black Holes-As a concrete example, we apply our method to the Fermiball/PBH formation scenario proposed in Refs. [19,34] and subsequently studied in Refs. [21,35,36].…”

“…As the remnants shrink, the fermions and anti-fermions annihilate, leaving only the asymmetrical portion supported by degeneracy pressure. The total number of χ fermions trapped in a remnant with size R * at the FV percolation time t * is [19,34]…”

“…Lacking methods to compute the R * distribution, Refs. [19,34] estimated the average size to be we are able to derive the R * distribution using Eq. ( 22), and obtain…”