We study Bose-Einstein condensation and the formation of Bose stars in virialized dark matter halos and miniclusters by universal gravitational interactions. We prove that this phenomenon does occur ...and it is described by a kinetic equation. We give an expression for the condensation time. Our results suggest that Bose stars may form kinetically in mainstream dark matter models such as invisible QCD axions and fuzzy dark matter.
The substructures of light bosonic (axionlike) dark matter may condense into compact Bose stars. We study the collapse of critical-mass stars caused by attractive self-interaction of the axionlike ...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.
Radio-emission of axion stars Levkov, D. G.; Panin, A. G.; Tkachev, I. I.
Physical review. D,
07/2020, Volume:
102, Issue:
2
Journal Article
Peer reviewed
Open access
We study parametric instability of compact axion dark matter structures decaying to radiophotons. Corresponding objects-Bose (axion) stars, their clusters, and clouds of diffuse axions-form ...abundantly in the postinflationary Peccei-Quinn scenario. We develop general description of parametric resonance incorporating finite-volume effects, backreaction, axion velocities, and their (in)coherence. With additional coarse graining, our formalism reproduces kinetic equation for virialized axions interacting with photons. We derive conditions for the parametric instability in each of the above objects, as well as in collapsing axion stars, evaluate photon resonance modes and their growth exponents. As a by-product, we calculate stimulated emission of Bose stars and diffuse axions, arguing that the former can give larger contribution into the radio background. In the case of QCD axions, the Bose stars glow and collapsing stars radioburst if the axion-photon coupling exceeds the original Kim-Shifman-Vainshtein-Zakharov value by 2 orders of magnitude. The latter constraint is alleviated for several nearby axion stars in resonance and absent for axionlike particles. Our results show that the parametric effect may reveal itself in observations, from fast radio bursts to excess radio background.
Instability of rotating Bose stars Dmitriev, A. S.; Levkov, D. G.; Panin, A. G. ...
Physical review. D,
07/2021, Volume:
104, Issue:
2
Journal Article
Peer reviewed
Open access
Light bosonic (axionlike) dark matter may form Bose stars-clumps of nonrelativistic Bose-Einstein condensate supported by self-gravity. We study rotating Bose stars composed of condensed particles ...with nonzero angular momentum l . We analytically prove that these objects are unstable at arbitrary l ≠ 0 if particle self-interactions are attractive or negligibly small. They decay by shedding off the particles and transporting the angular momentum to the periphery of the system until a Saturn-like configuration appears: One (or several) spin-zero Bose stars and clouds of diffuse particles orbit around the mutual center. In the case of no self-interactions, we calculate the profiles and dominant instability modes of the rotating stars: numerically at 1 ≤ l ≤ 15 and analytically at l ≫ 1 . Notably, their lifetimes are always comparable to the inverse binding energies; hence, these objects cannot be considered long-living. Finally, we numerically show that in models with sufficiently strong repulsive self-interactions the Bose star with l = 1 is stable.
It has been recently suggested 1 that a subdominant fraction of dark matter decaying after recombination may alleviate tension between high-redshift (CMB anisotropy) and low-redshift (Hubble ...constant, cluster counts) measurements. In this report, we continue our previous study 2 of the decaying dark matter (DDM) model adding all available recent baryon acoustic oscillation (BAO) and redshift space distortions (RSD) measurements. We find that the BAO/RSD measurements generically prefer the standard ΛCDM and combined with other cosmological measurements impose an upper limit on the DDM fraction at the level of ∼5%, strengthening by a factor of 1.5 limits obtained in 2 mostly from CMB data. However, the numbers vary from one analysis to other based on the same Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) galaxy sample. Overall, the model with a few percent DDM fraction provides a better fit to the combined cosmological data as compared to the ΛCDM: the cluster counting and direct measurements of the Hubble parameter are responsible for that. The improvement can be as large as 1.5σ and grows to 3.3σ when the CMB lensing power amplitude AL is introduced as a free fitting parameter.
It has been recently suggested Z. Berezhiani, A.D. Dolgov, and I.I. Tkachev, Phys. Rev. D 92, 061303 (2015) that emerging tension between cosmological parameter values derived in high-redshift (CMB ...anisotropy) and low-redshift (cluster counts, Hubble constant) measurements can be reconciled in a model which contains a subdominant fraction of dark matter decaying after recombination. We check the model against the CMB Planck data. We find that lensing of the CMB anisotropies by the large-scale structure gives strong extra constraints on this model, limiting the fraction as F< 8% at 2sigma confidence level. However, investigating the combined data set of the CMB and conflicting low-z measurements, we obtain that the model with Fapproximate2%-5% exhibits better fit (by 1.5-3sigma depending on the lensing priors) compared to that of the concordance LambdaCDM cosmological model.
We study GRB 221009A, the brightest gamma-ray burst in the history of observations, using Fermi data. To calibrate them for large inclination angles, we use the Vela X gamma-ray source. Light curves ...in different spectral ranges demonstrate a 300 s overlap of afterglow and delayed episodes of soft prompt emission. We demonstrate that a relatively weak burst precursor that occurs 3 min before the main episode has its own afterglow, i.e., presumably, its own external shock. This is the first observation of such phenomenon which rules out some theoretical models of GRB precursors. The main afterglow is the brightest one, includes a photon with an energy of 400 GeV 9 h after the burst, we show that it is visible in the LAT data for up to two days.
Destruction of axion miniclusters in the Galaxy Dokuchaev, V. I.; Eroshenko, Yu. N.; Tkachev, I. I.
Journal of experimental and theoretical physics,
09/2017, Volume:
125, Issue:
3
Journal Article
Peer reviewed
Open access
Previously, it has been established that axion dark matter (DM) is clustered to form clumps (axion miniclusters) with masses M ≈ 10
–12
M
⊙
. The passages of such clumps through the Earth are very ...rare events occurring once in 10
5
years. It has also been shown that the Earth’s passage through DM streams, which are the remnants of clumps destroyed by tidal gravitational forces from Galactic stars, is a much more probable event occurring once in several years. In this paper, we have performed detailed calculations of the destruction of miniclusters by taking into account their distribution in orbits in the Galactic halo. We have investigated two DM halo models, the Navarro–Frenk–White and isothermal density profiles. Apart from the Galactic disk stars, we have also taken into account the halo and bulge stars. We show that about 2–5% of the axion miniclusters are destroyed when passing near stars and transform into axion streams, while the clump destruction efficiency depends on the DM halo model. The expected detection rate of streams with an overdensity exceeding an order of magnitude is 1–2 in 20 years. The possibility of detecting streams by their tidal gravitational effect on gravitational-wave interferometers is also considered.
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