Related papers: Axion Cloud Decay due to the Axion-photon Conversi…
A recent revision of black hole scaling relations (Kormendy & Ho 2013), indicates that the local mass density in black holes should be increased by up to a factor of five with respect to previously determined values. The local black hole…
Light feebly-coupled bosonic particles can efficiently extract the rotational energy of rapidly spinning black holes on sub-astrophysical timescales via a phenomenon known as black hole superradiance. In the case of light axions, the feeble…
Axion dark matter or any ultralight bosonic dark matter can go through Bose-Einstein condensation due to the large phase density, leading to the formation of axion stars or solitons in dark matter halo centers. The formation rate is…
We present a solution of the Schr\"odinger-Poisson system based on the WKB ansatz for the wave function. In this way we obtain a description of a gravitationally bound clump of axion dark matter by a superposition of energy eigenstates with…
We propose a model for the QCD axion which is realized through a coupling of the Peccei-Quinn scalar field to magnetically charged fermions at high energies. We show that the axion of this model solves the strong CP problem and then…
Accretion disks around supermassive black holes have regions where the Rosseland mean opacity can be much larger than the electron scattering opacity primarily due to the large number of bound-bound transitions in iron. We study the effects…
Axions seem ubiquitous in string theories and some of them may be produced non-thermally by heavy scalar decays, contributing to dark radiation. We study various cosmological effects of photons produced from the axionic dark radiation…
Polarization measurements of thermal radiation from magnetic white dwarf (MWD) stars have been proposed as a probe of axion-photon mixing. The radiation leaving the surface of the MWD is unpolarized, but if low-mass axions exist then…
We examine the effects of photon bubble instability in radiation-dominated accretion disks such as those found around black holes in active galactic nuclei and X-ray binary star systems. Two- and 3-D numerical radiation MHD calculations of…
In axion electrodynamics, magnetic fields enable axion-photon mixing. Recent proposals suggest that rotating, conductive plasmas in neutron star magnetospheres could trigger axion superradiant instabilities -- an intriguing idea, given that…
It has long been known that matter charged under a broken U(1) gauge symmetry collapsing to form a black hole will radiate away the associated external (massive) gauge field. We show that the timescale for the radiation of the monopole…
We show that the coherent axion field spontaneously decays by emitting axion particles via quantum tunneling if axion potential has more than one minimum. By employing the $\hbar$-expansion and mean field approximation, we develop a…
We estimated the magnetic field strength at the horizon radius of black holes, that is derived by the magnetic coupling process and depended on the black hole mass $M_{BH}$ and the accretion rate $\dot{M}$. Our estimation is based on the…
The axion decay into charged fermion-antifermion pair $a ~\to f ~\tilde f$ is studied in external crossed and magnetic fields. The result we have obtained can be of use to re-examine the lower limit on the axion mass in case of possible…
Axion clumps in an external magnetic field can emit electromagnetic radiation which causes them to decay. In the presence of a plasma, such radiation can become resonant if the clump frequency matches the plasma frequency. Typically, the…
Axion-like particles (ALPs) and photons can quantum mechanically interconvert when propagating through magnetic fields, and ALP-photon conversion may induce oscillatory features in the spectra of astrophysical sources. We use deep (370 ks),…
We present a search for axion-like particles, $a$, produced in photon-proton collisions at a center-of-mass energy of approximately 4 GeV, focusing on the scenario where the $a$-gluon coupling is dominant. The search uses $a\to\gamma\gamma$…
We discuss some striking properties of photons propagating in a cold axion condensate oscillating coherently in time with a frequency $1/m_a$. Three effects are discussed in this contribution: (a) due to the time dependence of the…
The amplitude of the pseudoscalar (axion) or scalar field fluctuates on a time scale of order of million field oscillation periods which is a typical coherence time in the virialized axion galactic dark matter halo model. This causes…
In particle physics, axions and axion-like particles are ubiquitous. Remarkably, ultra-light axions could constitute dark matter or dark energy. Therefore, it is important to detect axions experimentally. In the presence of a magnetic…