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The dark dimension scenario, which is motivated from Swampland principles and predicts a single micron scale extra dimension, suggests a consistent framework for the dark sector of the universe. We consider the implications of this scenario…
Dark matter substructure has the potential to discriminate between broad classes of dark matter models. With this in mind, we construct novel solutions to the equations of motion governing condensate dark matter candidates, namely axion…
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…
The baryon asymmetry of the universe may be explained by rotations of the QCD axion in field space and baryon number violating processes. We consider the minimal extension of the Standard Model by a non-Abelian gauge interaction, $SU(2)_R$,…
String and M-theory compactifications generically have compact moduli which can potentially act as the QCD axion. However, as demonstrated here, such a compact modulus can not play the role of a QCD axion and solve the strong CP problem if…
The mass of ultralight axions is determined in order to get the explicit U(1)$_A$ symmetry breaking scale $ \Lambda $ at a Peccei-Quinn scale of the magnitude of the Planck mass. It is assumed that the dominant contribution to the mass of a…
The problem of a condensate of a relativistic neutral vector boson gas constituted of particles bearing a magnetic moment is discussed. Such a vector boson system is expected to be formed either by parallel spin-pairing of neutrons in a…
Nonlinear gravitational condensation theory and quasar-microlensing observations lead to the conclusion that the baryonic mass of most galaxies is dominated by dense clumps of hydrogenous planetoids. Star microlensing collaborations fail to…
Growing amount of data show evidence for statistical and apparent physical association between low-redshift galaxies and high-redshift quasi-stellar objects, suggesting noncosmological origin of their redshift and failure of classical…
Recently there has been interest in the physical properties of dark matter axion condensates. Due to gravitational attraction and self-interactions, they can organize into spatial localized clumps, whose properties were examined by us in…
Lensing flux-ratio anomalies have been frequently observed and taken as evidence for the presence of abundant dark matter substructures in lensing galaxies, as predicted by the cold dark matter (CDM) model of cosmogony. In previous work, we…
A hypothetical particle known as the axion holds the potential to resolve both the cosmic dark matter riddle and particle physics' long-standing, strong CP dilemma. An unusually strong 21-cm absorption feature associated with the initial…
We discuss a QCD-scale composite axion model arising from dark QCD coupled to QCD. The presently proposed scenario not only solves the strong CP problem, but also is compatible with the preheating setup for the QCD baryogenesis. The…
Quantum Chromodynamics (QCD) is the theory of the strong interactions within the Standard Model of particle physics, which explains more than 99% of the mass of the visible Universe. However, there is evidence that a substantial portion of…
If there are a plethora of axions in nature, they may have a complicated potential and create an axion landscape. We study a possibility that one of the axions is so light that it is cosmologically stable, explaining the observed dark…
Searches for dark matter (DM) constituents are presently mainly focused on axions and WIMPs despite the fact that far higher mass constituents are viable. We discuss and dispute whether axions exist and those arguments for WIMPs which arise…
The QCD axion may offer a unified origin for the baryon asymmetry and dark matter through axiogenesis. However, in the minimal QCD axion scenario, axiogenesis either underproduces baryons or overproduces dark matter, and the required…
We propose that the abundance anomalies of proton-capture elements in globular clusters, such as the C-N, Na-O, Mg-Al and Na-F anti-correlations, were produced by super-massive stars with M ~ 10,000 Msun. Such stars could form in the…
Observations of the Sgr A* region in the galactic center confirm the presence of a large amount of matter in a small volume, leading to the consensus that a black hole exists there. However, dynamical observations cannot rule out the…
The recently reported X-ray line signal at $E_\gamma \simeq 3.5\, {\rm keV}$ from a stacked spectrum of various galaxy clusters and the Andromeda galaxy may be originating from a decaying dark matter particle of the mass $2 E_\gamma$. A…