Related papers: Dark Radiation and Dark Matter in Large Volume Com…
Dark photons can be resonantly produced in the early universe via their coupling to an oscillating axion field. However, this mechanism typically requires large axion--dark photon couplings or some degree of fine-tuning. In this work, we…
An axion rotating in field space can produce dark photons in the early universe via tachyonic instability. This explosive particle production creates a background of stochastic gravitational waves that may be visible at pulsar timing arrays…
The astronomical dark matter could be made of weakly interacting and massive particles. If so, these species would be abundant inside the Milky Way, where they would continuously annihilate and produce cosmic rays. Those annihilation…
It is conjectured that dark matter (DM) was produced before inflation from neutral particles present after the Big Bang and survived inflation due to a specific coupling with gravitation, while the charged particles existing after the Big…
Dark matter has been recognized as an essential part of matter for over 70 years now, and many suggestions have been made, what it could be. Most of these ideas have centered on Cold Dark Matter, particles that are expected in extensions of…
The detection of dark matter is central to particle physics and cosmology. Current fashionable supersymmetric models provide a dark matter candidate, the lightest supersymmetric particle (LSP). When combined with fairly well understood…
We discuss a novel mechanism for generating dark matter from a fast-rolling scalar field, relevant for both inflation and rotating axion models, and apply it specifically to the (QCD) axion. Dark matter comes from scalar field fluctuations…
Ignorance of the initial condition for the axion dynamics in the early Universe has led us to consider an $O(1)$ valued initial amplitude, and that prefers the decay constant, $F_a$, of the QCD axion to be an intermediate scale such as…
We propose simple scenarios where the observed dark matter abundance arises from decays and scatterings of heavy quarks through freeze-in of an axion-like particle with mass in the $10 {\rm \, keV} - 1 {\rm \, MeV}$ range. These models can…
Explicit string models which can realize inflation and low-energy supersymmetry are notoriously difficult to achieve. Given that sequestering requires very specific configurations, supersymmetric particles are in general expected to be very…
We motivate Higgsino dark matter from a solution to the cosmological moduli/gravitino problem. Cosmological moduli/gravitino should be heavy enough to decay before the onset of Big Bang Nucleosynthesis, and this requirement typically forces…
As-yet undiscovered light bosons may constitute all or part of the dark matter (DM) of our Universe, and are expected to have (weak) self-interactions. We show that the quartic self-interactions generically induce the capture of dark matter…
High energy particles are produced by the annihilation of dark matter particles in our galaxy. These are presently searched for using balloon-borne antiproton and positron detectors and large area, deep underground neutrino telescopes. Dark…
We show that in large-field inflationary scenarios, superheavy (many orders of magnitude larger than the weak scale) dark matter will be produced in cosmologically interesting quantities if superheavy stable particles exist in the mass…
Dark matter could have an electroweak origin, yet communicate with the visible sector exclusively through gravitational interactions. In a set-up addressing the hierarchy problem, we propose a new dark matter scenario where gravitational…
Recent analyses of WMAP9 data show that dark radiation-- parametrized by the apparent number of additional neutrinos \Delta N_{eff} contributing to the cosmic expansion-- is consistent with the Standard Model and bounded from above by about…
In mirage-mediation models there exists a modulus field whose mass is O(1000) TeV and its late-decay may significantly change the standard thermal relic scenario of the dark matter. We study nonthermal production of the dark matter directly…
We discuss a scenario that gravitinos produced non-thermally by an inflaton decay constitute dark matter in the present universe. We find that this scenario is realized for wide ranges of the inflaton mass and the vacuum expectation value.…
One of the greatest mysteries in astrophysics and cosmology is the nature and the origin of cold dark matter, which represents more than 84% of the mass in the universe. Dark matter reacts on and produces gravitational forces and governs…
Recently it has been suggested that dark radiation in the form of axions produced during the decay of string theory moduli fields could be responsible for the soft x-ray excess in galaxy clusters. These soft X-ray photons come about due to…