Related papers: Anomalous spectral lines and relic quantum nonequi…
We discuss the possibility to find an upper bound on the seesaw scale using the cosmological bound on the cold dark matter relic density. We investigate a simple relation between the origin of neutrino masses and the properties of a dark…
We review the effect of the formation of nonlinear structures on the expansion rate, spatial curvature and light propagation in the universe, focusing on the possibility that it could explain cosmological observations without the…
Gamma-ray line observations provide a versatile tool for studies of nucleosynthesis processes and supernova physics. In particular, the observation of radioactive species in the interstellar medium probes recent nucleosynthesis activity on…
We consider the possibility that the cosmological dark matter consists of particles very close in mass to new colored particles below the TeV scale. While such a scenario is inherently difficult to directly confirm at colliders, we find…
Quantum inequalities are bounds on negative time-averages of the energy density of a quantum field. They can be used to rule out exotic spacetimes in general relativity. We study quantum inequalities for a scalar field with a background…
We discuss the relic density of asymmetric dark matter with long-range interactions in non-standard cosmological scenarios where the extra cosmic energy is introduced. The Hubble expansion rate is modified in non-standard cosmological…
Frequency dependencies of optical characteristics (reflection, transmission and absorption of light) of a quantum well are investigated in a vicinity of interband resonant transitions in a case of two closely located excited energy levels.…
Superstring theory predicts the existence of relic metastable particles whose average lifetime is longer than the age of the universe and which could, in principle, be good dark matter candidates. At the same time, these states would be…
The hypothesis of a discrete fabric of the universe--the "Planck scale"--is always on stage, since it solves mathematical and conceptual problems in the infinitely small. However, it clashes with special relativity, which is designed for…
The detection of X-ray narrow spectral features in the 5-7 keV band is becoming increasingly more common in AGN observations, thanks to the capabilities of current X-ray satellites. Such lines, both in emission and in absorption, are mostly…
In some models of thermal relic dark matter, the relic abundance may be set by inelastic scattering processes (rather than annihilations) becoming inefficient as the universe cools down. This effect has been called coscattering. We present…
We speculate on some novel consequences possibly associated with a change of elementary particle constants with time. These concern the question as to whether particles reaching the earth from distant parts of the universe reflect their…
Despite our present-day inability to predict the topology of the universe it is expected that we should be able to detect it in the near future. A nontrivial detectable topology of the space section of the universe can be probed for all…
We give a pedagogical review of a covariant and fully non-perturbative approach to study nonlinear perturbations in cosmology. In the first part, devoted to cosmological fluids, we define a nonlinear extension of the uniform-density…
One aim of cosmic ray measurements is the search for possible signatures of annihilating or decaying dark matter. The so-called positron excess has attracted a lot of attention in this context. On the other hand it has been proposed that…
Spectral lines of heavy atomic elements in the ejecta of supernovae and neutron star mergers can have important contribution to the opacity of the ejecta matter even when the abundance of the elements is very small. Under favorable…
We introduce a new type of gamma-ray spectral feature, which we denominate gamma-ray triangle. This spectral feature arises in scenarios where dark matter self-annihilates via a chiral interaction into two Dirac fermions, which subsequently…
We consider nonlinear spectroscopic effects - interaction-enhanced double resonance and spectrum instability - that appear in ultracold quantum gases owing to collisional frequency shift of atomic transitions and, consequently, due to the…
Light thermal relics of the hot big bang, often quantified by the parameter $N_\mathrm{eff}$, are one of the primary targets of cosmological measurements. At present, the energy density in such relics is constrained to be less than ten…
Weak-scale supersymmetry is one of the most favoured theories beyond the Standard Model of particle physics that elegantly solves various theoretical and observational problems in both particle physics and cosmology. In this thesis, I…