Variations on the vev flip-flop: instantaneous freeze-out and decaying dark matter

Abstract

In this work we consider a simple model for dark matter and identify regions of parameter space where the relic abundance is set via kinematic thresholds, which open and close due to thermal effects. We discuss instantaneous freeze-out, where dark matter suddenly freezesout when the channel connecting dark matter to the thermal bath closes, and decaying dark matter, where dark matter freezes-out while relativistic and later decays when a kinematic threshold temporarily opens. These mechanisms can occur in the vicinity of a one-step or a two-step phase transition. In all cases thermal effects provide this dynamic behaviour, while ensuring that dark matter remains stable until the present day. *

Detailed Calculation of Primordial Black Hole Formation During First-Order Cosmological Phase Transitions

“…Similarly, the physics of early Universe phase transitions has become a popular topic in recent years, again driven by the prospect of observing gravitational waves from these phase transitions in upcoming experiments [28][29][30][31][32][33][34]. Besides significant advances in our understanding of the dynamics of these phase transitions [35][36][37][38][39] and in our computational techniques [40][41][42][43][44][45][46], phase transitions have been widely used as phenomenological tools, for instance to explain the baryon asymmetry of the Universe via electroweak baryogenesis [47][48][49][50][51][52][53][54][55][56][57][58][59] and other mechanisms [60][61][62][63][64][65][66], to form DM "nuggets" [67][68][69], or to set the abundance of particle dark matter [70][71][72][73]. Most r...…”

Filtered Dark Matter at a First Order Phase Transition

“…The impact of cosmological phase transitions on DM has been studied in a variety of different contexts [8]: a phase transition may alter the expansion rate of the Universe during freeze-out [9][10][11], inject entropy [10][11][12], alter DM stability [13][14][15], alter DM properties during freezein [16,17] (see also [18]), produce DM nonthermally [19][20][21][22], or produce an excess of DM over antimatter [23][24][25][26][27][28][29]. Conversely, a dark sector may trigger an electroweak FOPT [30][31][32][33][34][35][36][37][38][39][40].…”

Fermi-ball dark matter from a first-order phase transition

“…Recently, there has been a growing number of studies on the DM generated in association with a first-order cosmic phase transition (FOPT). During an FOPT, the discontinuity of the scalar vacuum expectation value (VEV) could be crucial in DM physics, by altering the decay of DM [7][8][9], by generating asymmetric DM [10][11][12][13][14][15][16][17][18], by producing DM nonthermally [19], by filtering DM to the true vacuum [20][21][22], by condensing particles into the false vacuum to form (scalar) Q-ball DMs [23,24] or quark (or quark-like fermion) nuggets [25][26][27][28][29][30][31][32], and by producing the primordial black holes [33,34]. 1 In this paper, we propose a new mechanism in which during an FOPT dark fermions are trapped inside the false vacuum to subsequently form compact macroscopic DM candidates, which we call "Fermi-balls."…”