Related papers: Galaxy Phase-Space Density Data Preclude that Bose…
Axions differ from the other cold dark matter candidates in that they form a degenerate Bose gas. It is shown that their huge quantum degeneracy and large correlation length cause cold dark matter axions to thermalize through gravitational…
We present a new mechanism to deplete the energy density of the QCD axion, making decay constants as high as $f_a \simeq 10^{17}\,\rm{GeV}$ viable for generic initial conditions. In our setup, the axion couples to a massless dark photon…
In all supersymmetric theories, gravitinos, with mass suppressed by the Planck scale, are an obvious candidate for dark matter; but if gravitinos ever reached thermal equilibrium, such dark matter is apparently either too abundant or too…
We show that if dark matter in a typical galaxy is a degenerate Fermi gas, particles should have a mass of $\sim$ 1eV for the galaxy to be stable. While this is the mass range of the active neutrinos, they are not a dark matter candidate in…
The Bose-Einstein (BE) condensates of weakly interacting bosons in a strong gravity field, such as AGN (Active Galactic Nuclei), BHs (black holes) and neutron stars, are discussed. Being bound systems in gravity fields, these are stable…
Potential small-scale discrepancies in the picture of galaxy formation painted by the $\Lambda$CDM paradigm have led to considerations of modified dark matter models. One such dark matter model that has recently attracted much attention is…
The QCD axion and axion-like particles, as leading dark matter candidates, can also have interesting implications for dark matter substructures if the Peccei-Quinn symmetry is broken after inflation. In such a scenario, axion perturbations…
The Hawking evaporation of small black holes formed by the collapse of dark matter at the center of neutron stars plays a key role in loosing the constraint on the mass of asymmetric bosonic non-interacting dark matter particles. Different…
Recent studies suggest that dark matter could take the form of a Bose-Einstein condensate (BEC), a possibility motivated by anomalies in galactic rotation curves and the missing mass problem in galaxy clusters. We investigate the…
Evolution of inhomogeneities in the axion field around the QCD epoch is studied numerically, including for the first time important non-linear effects. It is found that perturbations on scales corresponding to causally disconnected regions…
In this paper, we search for correlations between the intrinsic properties of galaxies and the Bose-Einstein condensate (BEC) under a scalar field dark matter (SFDM) at temperature of condensation greater than zero. According to this…
Axions are some of the best motivated particles beyond the Standard Model. We show how the attractive self-interactions of dark matter (DM) axions over a broad range of masses, from $10^{-22}$ eV to $10^7$ GeV, can lead to nongravitational…
The cosmological scenario where the Peccei-Quinn symmetry is broken after inflation is investigated. In this scenario, topological defects such as strings and domain walls produce a large number of axions, which contribute to the cold dark…
Axion is a popular candidate for dark matter particles. Axionic dark matter may form Bose-Einstein condensate and may be gravitationally bound to form axion clumps. Under the presence of electromagnetic waves with frequency…
This work continues the construction of a recently proposed model of dark matter stars. In this model, dark matter quanta are sterile massless particles that are emitted from the central regions of the galaxy in the radial direction. As a…
One intriguing BSM particle is the QCD axion, which could simultaneously provide a solution to the Strong CP problem and account for some, if not all, of the dark matter density in the universe. This particle is a pNGB of the conjectured…
Cold and hot dark matter (CDM, HDM) imprint distinctive effects on the cosmological observables, naturally, they are often thought to be made of different kinds of particles. However, we point out that CDM and HDM could share a common…
The naturalness problem of PQ symmetry motivates study of the heavy QCD axion, with masses $m_a >$ 1 MeV generated at scales above the QCD scale, and low values of the PQ symmetry breaking scale, $f_a$. We compute the abundance of such…
We consider the effects of an uncorrelated random potential on the properties of Bose-Einstein Condensate (BEC) dark matter halos, which acts as a source of disorder, and which is added as a new term in the Gross-Pitaevskii equation,…
We observe that photon cooling after big bang nucleosynthesis (BBN) but before recombination can remove the conflict between the observed and theoretically predicted value of the primordial abundance of $^7$Li. Such cooling is ordinarily…