Related papers: Dark radiation and small-scale structure problems …
For the minimal QCD axion model it is generally believed that overproduction of dark matter constrains the axion mass to be above a certain threshold, or at least that the initial misalignment angle must be tuned if the mass is below that…
The generic expectation in string/supergravity models is that there are multiple moduli fields with masses of the order of the supersymmetry breaking scale. We study the cosmology that arises as a result of vacuum misalignment of these…
A small breaking of R-parity reconciles thermal leptogenesis, gravitino dark matter and primordial nucleosynthesis. We find that the same breaking relaxes cosmological bounds on the axion multiplet. Naturally expected spectra become allowed…
Light axions ($m_a \lesssim 10^{-10}$ eV) can form dense clouds around rapidly rotating astrophysical black holes via a mechanism known as rotational superradiance. The coupling between axions and photons induces a parametric resonance,…
We propose a model to explain tiny masses of neutrinos with the lepton number conservation, where neither too heavy particles beyond the TeV-scale nor tiny coupling constants are required. Assignments of conserving lepton numbers to new…
Black-hole superradiance has been used to place very strong bounds on a variety of models of ultralight bosons such as axions, new light scalars, and dark photons. It is common lore to believe that superradiance bounds are broadly model…
We present a simple model of dark matter that can address astrophysical and cosmological puzzles across a wide range of scales. The model is an application of the Secretly Asymmetric Dark Matter mechanism, where several flavors of dark…
Axions and dark photons are common in many extensions of the Standard Model. The dark axion portal -- an axion coupling to the dark photon and photon -- can significantly modify their phenomenology. We study the cosmological constraints on…
Warm dark matter (WDM) might more easily account for small scale clustering measurements than the heavier particles typically invoked in Lambda cold dark matter (LCDM) cosmologies. In this paper, we consider a Lambda WDM cosmology in which…
The majoron provides an attractive dark matter candidate, directly associated to the mechanism responsible for spontaneous neutrino mass generation within the standard model framework. Here we update the cosmological and astrophysical…
Axions are a theoretically promising dark matter (DM) candidate. In the presence of radiation from bright astrophysical sources at radio frequencies, nonrelativistic DM axions can undergo stimulated decay to two nearly back-to-back photons,…
Sterile neutrinos can be generated in the early universe through oscillations with active neutrinos and represent a popular and well-studied candidate for our universe's dark matter. Stringent constraints from X-ray and gamma-ray line…
We study the formation of non-linear structures in Warm Dark Matter (WDM) models and in a Long-Lived Charged Massive Particle (CHAMP) model. CHAMPs with a decay lifetime of about 1 yr induce characteristic suppression in the matter power…
The dark energy dominated warm dark matter (WDM) model is a promising alternative cosmological scenario. We explore large-scale structure formation in this paradigm. We do this in two different ways: with the halo model approach and with…
It is entirely possible that our Universe is filled with dark radiation, such as SM neutrinos or new physics states, that are sourced by the decay of dark matter with cosmologically long lifetime. If non-thermal neutrinos produced such way…
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…
The thermal production mechanism of dark matter is attractive and well-motivated by predictivity. A representative of this type of dark matter candidate is the canonical, weakly interacting massive particles. An alternative is…
The lightest supersymmetric particle, most likely the lightest neutralino, is one of the most prominent particle candidates for cold dark matter (CDM). We show that the primordial spectrum of density fluctuations in neutralino CDM has a…
Popular extensions of the standard model of particle physics feature new fields and symmetries which could, for example, dynamically generate neutrino masses from $B-L$ spontaneous symmetry breaking. If a new light scalar that decays into…
We investigate the clumping of cold dark matter (CDM) at small scales. If the CDM particle is the neutralino, we find that collisional damping during its kinetic decoupling from the radiation fluid and free streaming introduce a small-scale…