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We estimate the sensitivity of various experiments detecting ultra-high-energy cosmic rays to primary photons with energies above 10^19 eV. We demonstrate that the energy of a primary photon may be significantly (up to a factor of ~ 10)…
I selectively review the theoretical properties and observational limits pertaining to dark atoms, as well as composite dark matter candidates bound by a confining gauge interaction: dark glueballs, glueballinos, mesons and baryons.…
Particle physics candidates for cosmological dark matter are usually considered as neutral and weakly interacting. However stable charged leptons and quarks can also exist and, hidden in elusive atoms, play the role of dark matter. The…
Traditional dark matter models, eg. WIMPs, assume dark matter is weakly coupled to the standard model so that elastic scattering between dark matter and baryons can be described perturbatively by Born approximation. Most direct detection…
Common extensions of the Standard Model of particle physics predict the existence of a "hidden" sector that comprises particles with a vanishing or very weak coupling to particles of the Standard Model (visible sector). For very light (m <…
The existence of a new, photon-like, massive particle, the gamma' or dark photon, is postulated in several extensions of the Standard Model. These models are often advocated to explain some recent puzzling astrophysical observations, as…
We extend recently proposed mimetic dark matter (DM) and dust of dark energy (DE) models to a U(1)-charged gauged scalar field. This extension yields a mass to the photon via the Higgs mechanism. The square of this photon mass is…
The possible existence of a new gauge boson U, light and very weakly coupled, allows for Light Dark Matter particles, which could also be at the origin of the 511 keV line from the galactic bulge. Independently of dark matter, and taking…
Starting from the evidence that dark matter indeed exists and permeates the entire cosmos, various bounds on its properties can be estimated. Beginning with the cosmic microwave background and large scale structure, we summarize bounds on…
We investigate cosmological and astrophysical constraints on dark photons with masses $\sim 10^{-1}$-$10^3$ MeV. These dark photons can be copiously produced either in the early universe or during core-collapse supernovae, potentially…
We present a novel search for dark photon dark matter (DM) using terrestrial magnetic field measurements at frequencies below 100 Hz. Coherently oscillating dark photon DM can induce a monochromatic magnetic field via kinetic mixing with…
The scattering of sub-GeV dark matter in direct detection experiments happens at characteristic wavelengths comparable or larger than the interparticle spacing. Collective effects in the target material must therefore be accounted for when…
In unparticle dark matter (unmatter) models the equation of state of the unmatter is given by $p=\rho/(2d_U+1)$, where $d_U$ is the scaling factor. Unmatter with such equations of state would have a significant impact on the expansion…
We propose a novel mechanism with two component dark matter models. The subdominant dark matter can thermalize the dominant one in galaxies, and leads to core density profiles. Using ultralight dark photons and $\mathrm{GeV}$-$\mathrm{TeV}$…
Dark photons are particles invoked in some extensions of the Standard Model which could account for at least part of the dark matter content of the Universe. It has been proposed that the production of dark photons in stellar interiors…
We find that a class of models of MeV-GeV dark matter in which dark matter interacts strongly can be constrained by the observation of gravitational waves from neutron star mergers. Trace amounts of dark matter, either produced during the…
In a model with an extra $U(1)$ gauge to SM gauge group, we have shown the allowed region of masses of extra gauge boson and the dark matter which is the lightest one among other right-handed Majorana fermions present in the model. To…
Sub-GeV dark matter candidates are of increasing interest, because long-favored candidates such as GeV-scale WIMPs have not been detected. For low-mass dark matter, model-independent constraints are weak or nonexistent. We show that for…
We propose to search for scalar dark matter via its effects on the electromagnetic fine-structure constant and particle masses. Scalar dark matter that forms an oscillating classical field produces `slow' linear-in-time drifts and…
We reinterpret the results of the direct searches for dark matter in terms of composite dark matter, i.e. dark matter particles that form neutral bound states, generically called dark atoms, either with ordinary particles, or with other…