Related papers: The Big Bang Was Not That Bright
It is discussed how the ideas of entropy and the second law of thermodynamics, conceived long ago during the nineteenth century, underly why cosmological dark matter exists and originated in the first three years of the universe in the form…
Observations of quasars reveal that many supermassive black holes (BHs) were in place less than 700 million years after the Big Bang. However, the origin of the first BHs remains a mystery. Seeds of the first BHs are postulated to be either…
Some few hundred million years after the big bang the Universe was illuminated by the first stars and galaxies thereby bringing an end to the cosmological dark ages. Since the installation of WFC3 on the Hubble Space Telescope our ability…
We describe how cosmology has converged towards a beautiful model of the Universe: the Big Bang Universe. We praise this model, but show there is a dark side to it. This dark side is usually called ``the cosmological problems'': a set of…
If even a relatively small number of black holes were created in the early universe, they will constitute an increasingly large fraction of the total energy density as space expands. It is thus well-motivated to consider scenarios in which…
Black holes formed in the early universe, prior to the formation of stars, can exist as dark matter and also contribute to the black hole merger events observed in gravitational waves. We set a new limit on the abundance of primordial black…
Paramount among the processes that ended the cosmic `dark ages' must have been the formation of the first generation of stars (the so-called Population III). We summarize recent progress in constraining its nature, and we discuss the basic…
Although most proposed dark matter candidates are stable, in order for dark matter to be present today, the only requirement is that its lifetime is longer than the age of the Universe, t_U ~ 4 10^17 s. Moreover, the dark matter particle…
We prove that the primordial black holes in the early universe did not decay until the gravity decoupled from the other interactions. Rabinowitz' two objections to the formation of Holeums are shown to be inapplicable. We show that…
The standard theoretical estimation of the thermal dark matter abundance may be significantly altered if properties of dark matter particles in the early universe and at the present cosmological epoch differ. This may happen if, e.g., a…
The origin of dark matter as a thermal relic offers a compelling way in which the early universe was initially populated by dark matter. Alternative explanations typically appear exotic compared to the simplicity of thermal production.…
Currently the asteroid mass window (mass $\sim 10^{17}- 10^{21}$ grams) remains unconstrained for Primordial Black Holes (PBHs) to make up all of the dark matter content of the universe. Given these PBHs have very small masses, their…
By adding a matter-coupled dark energy field to Einstein's General Relativity (GR), this paper proves that the dynamical dark energy field can change the frequency of photons from distant galaxies as well as from background radiation of…
The nature of dark matter remains unknown, but upcoming measurements probing the high-redshift Universe may provide invaluable insight. In the presence of dark matter-baryon scattering, the suppression in the matter power spectrum and the…
Quasars, powered by supermassive black holes (SMBH), are among the brightest objects in the universe. In the vicinity of an SMBH, X-ray photons from an active galactic nucleus (AGN) can heat the surrounding gas to several hundred kelvin.…
This year marks half a century since Stephen Hawking made his greatest scientific discovery by theoretically proving that black holes aint so black, as they behave like hot bodies with an absolute temperature that depends inversely on their…
We investigate the dust properties and star-formation signature of galaxies in the early universe by stacking 111227 objects in the recently released COSMOS catalogue on maps at wavelengths bracketing the peak of warmed dust emission. We…
Recent cosmological data favour additional relativistic degrees of freedom beyond the three active neutrinos and photons, often referred to as 'dark' radiation. Light sterile neutrinos is one of the prime candidates for such additional…
Mechanisms for the generation of the matter-antimatter asymmetry and dark matter strongly depend on the reheating temperature T_R, the maximal temperature reached in the early universe. Forthcoming results from the LHC, low energy…
We consider the production of axion dark matter through the misalignment mechanism in the context of a nonstandard cosmological history involving early matter domination by a scalar field with a time-dependent decay rate. In cases where the…