The possibility of baryogenesis through the evaporation of black holes formed during extended inflation is explored. These black holes are produced due to the collapse of trapped regions of false vacuum during the inflationary phase transition. Immediately after formation, the accretion of mass from the surrounding hot radiation bath in the universe is shown to be an important effect. This causes the lifetime of the black holes to be considerably elongated before they evaporate out through the process of Hawking radiation. It is shown that a sufficient number of black holes last up to well past the electroweak era and hence contribute to the surviving baryon asymmetry in the universe.

Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch ∼ 10 −33 sec to ∼ 5 × 10 −9 sec. In this paper we use Barrow et al's ansatz to model blackhole evaporation in which the modified Hawking temperature goes to zero in the limit of the blackhole attaining a relic state with mass ∼ m pl . Both single mass PBH case as well as the case in which blackhole masses are distributed in the range 8 × 10 2 -3 × 10 5 gm have been considered in our analysis. Blackholes with mass larger than ∼ 10 5 gm appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X −X emissions, averting the baryon number wash-out due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass m is given by ∼ ǫζ(m/1 gm) −1 , where ǫ and ζ are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For ǫ larger than ∼ 10 −4 , the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs. *

Fast radio bursts (FRBs) last for ∼ few milli-seconds and, hence, are likely to arise from the gravitational collapse of supra-massive, spinning neutron stars after they lose the centrifugal support (Falcke & Rezzolla 2014). In this paper, we provide arguments to show that the repeating burst, FRB 121102, can also be modeled in the collapse framework provided the supra-massive object implodes either into a Kerr black hole surrounded by highly magnetized plasma or into a strange quark star. Since the estimated rates of FRBs and SN Ib/c are comparable, we put forward a common progenitor scenario for FRBs and long GRBs in which only those compact remnants entail prompt γ-emission whose kick velocities are almost aligned or anti-aligned with the stellar spin axes. In such a scenario, emission of detectable gravitational radiation and, possibly, of neutrinos are expected to occur during the SN Ib/c explosion as well as, later, at the time of magnetar implosion.

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Discovery of active galactic nuclei at redshifts > ∼ 6 suggests that supermassive black holes (SMBHs) formed early on. Growth of the remnants of Population III stars by accretion of matter, both baryonic as well as collisionless dark matter (DM), leading up to formation of SMBHs is a very slow process. Therefore, such models encounter difficulties in explaining quasars detected at z > ∼ 6. Furthermore, massive particles making up collisionless DM not only have so far eluded experimental detection but they also do not satisfactorily explain gravitational structures on small scales.In recent years, there is a surge in research activities concerning cosmological structure formation that involve coherent, ultra-light bosons in a dark fluid-like or fuzzy cold DM state. In this paper, we study collapse of such ultra-light bosonic halo DM that are in a Bose-Einstein condensate (BEC) phase to give rise to SMBHs on dynamical time scales. Time evolution of such self-gravitating BECs is examined using the Gross-Pitaevskii equation in the framework of time-dependent variational method. Comprised of identical dark bosons of mass m, BECs can collapse to form black holes of mass M ef f on time scales ∼ 10 8 yrs provided m M ef f > ∼ 0.64 m 2 P l . In particular, ultra-light dark bosons of mass ∼ 10 −20 eV can lead to SMBHs with mass > ∼ 10 10 M⊙ at z ≈ 6. Recently observed radio-galaxies in the ELAIS-N1 deep field with aligned jets can also possibly be explained if vortices of a rotating cluster size BEC collapse to form spinning SMBHs with angular momentum J < ∼ 3.6 nW GM 2 c , where nW and M are the winding number and mass of a vortex, respectively.