We study Bose-Einstein condensation and formation of Bose stars in the virialized dark matter halos/miniclusters by universal gravitational interactions. We prove that this phenomenon does occur and it is described by kinetic equation. We give expression for the condensation time. Our results suggest that Bose stars may form kinetically in the mainstream dark matter models such as invisible QCD axions and Fuzzy Dark Matter.1. Introduction. Bose stars are lumps of Bose -Einstein condensate bounded by self-gravity [1,2]. They can be made of condensed dark matter (DM) bosonssay, invisible QCD axions [3] or Fuzzy DM [4]. That is why their physics, phenomenology and observational signatures remain in the focus of cosmological research for decades [5], see recent papers [6,7]. Unfortunately, formation of Bose stars is still poorly understood and many recent works have to assume their existence.In this Letter we study Bose-Einstein condensation in the virialized DM halos/miniclusters caused by universal gravitational interactions. We work at large occupation numbers which is correct if the DM bosons are light. Notably, we consider kinetic regime where the initial coherence length and period of the DM particles are close to the de Broglie values (mv) −1 and (mv 2 ) −1 and much smaller than the halo size R and condensation time τ gr ,

The substructures of light bosonic (axion-like) dark matter may condense into compact Bose stars. We study collapses of the critical-mass stars caused by attractive self-interaction of the axion-like particles and find that these processes proceed in an unexpected universal way. First, nonlinear self-similar evolution (called "wave collapse" in condensed matter physics) forces the particles to fall into the star center. Second, interactions in the dense center create an outgoing stream of mildly relativistic particles which carries away an essential part of the star mass. The collapse stops when the star remnant is no longer able to support the self-similar infall feeding the collisions. We shortly discuss possible astrophysical and cosmological implications of these phenomena.1. Introduction. Increasingly stringent experimental constraints [1] on low-energy supersymmetry reignited discussion of non-supersymmetric dark matter candidates such as the QCD axion [2] and axion-like particles (ALP) [3]. The interest is heated up by fast progress [4] in ALP searches and peculiar properties of the axion-like dark matter related, in particular, to the misalignment mechanism of its generation [5], see also [6,7].A very special possibility opening up due to tiny velocities and large occupation numbers of the ALP dark matter is formation of Bose stars [8-10] -gravitationally bound puddles of the ALP Bose condensate. These objects were observed as "solitonic galaxy cores" in numerical simulations [11] of structure formation by ultralight (m ∼ 10 −22 eV) ALP dark matter. At larger ALP masses and, notably, in the case of the QCD axion, the Bose stars were conjectured [6,12] to appear in the centers of the axion miniclusters [13,14] which populate the Universe if the Peccei-Quinn symmetry is broken after inflation, cf. [15]. Although the last mechanism is not yet confirmed by numerical modeling, it is safe to say that the axion Bose stars constitute a part of the dark mass at least in some ALP dark matter models.Rich phenomenology of the Bose stars is related to the peculiar self-interaction potentials [2,3] of the ALP and QCD axion fields a(x),

We make use of a semiclassical method for calculating the suppression exponent for topology changing transitions in high-energy electroweak collisions. In the Standard Model these processes are accompanied by violation of baryon and lepton number. By using a suitable computational technique we obtain results for s-wave scattering in a large region of initial data. Our results show that baryon and lepton number violation remains exponentially suppressed up to very high energies of at least 30 sphaleron masses (250 TeV). We also conclude that the known analytic approaches inferred from low energy expansion provide reasonably good approximations up to the sphaleron energy (8 TeV) only.