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After few minutes the Universe evolved through conditions of temperature and density which permitted the first synthesis of astrophysically interesting abundances of D, 3He, 4He and 7Li. The relic abundances are sensitive probes of the…
Using state-of-the-art ab initio interaction-induced dipole and potential-energy surfaces for hydrogen-helium (H2-He) pairs, we compute the rototranslational collision-induced absorption coefficient at 40-400 K for frequencies covering…
Here we report new ${\it ab initio}$ calculations of the effective recombination coefficients for the \ion{N}{ii} recombination spectrum. We have taken into account the density dependence of the coefficients arising from the relative…
Observational measures of the primordial helium mass fraction, $Y_{\rm P}$, are of interest for cosmology and fundamental particle physics. Current measures obtained from H II regions agree with the Standard Model prediction to…
We solved the radiative transfer and statistical equilibrium equations in a two-dimensional cross-section of a cylindrical structure oriented horizontally and lying above the solar surface. The cylinder is filled with a mixture of hydrogen…
The double detonation is a widely discussed mechanism to explain Type Ia supernovae from explosions of sub-Chandrasekhar mass white dwarfs. In this scenario, a helium detonation is ignited in a surface helium shell on a carbon/oxygen white…
We perform a study of electromagnetic radiation in heavy-ion collisions at Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) and SPS energies using the iEBE-MUSIC framework, which includes 3D dynamical Monte Carlo Glauber…
The dispersion coefficients $C_6$, $C_8$, and $C_{10}$ for the interactions between H, He, and Li are calculated using variational wave functions in Hylleraas basis sets with multiple exponential scale factors. With these highly correlated…
The nebular spectra of Type Ia supernovae ($\gtrapprox$ 100 days after explosion) consist mainly of emission lines from singly- and doubly-ionised Fe-group nuclei. However, theoretical models for many scenarios predict that non-thermal…
The primordial helium abundance Y_p is commonly inferred from abundance determinations in low-metallicity extragalactic HII-regions. Such determinations may be subject to systematic uncertainties that are investigated here. Particular…
The standard model of cosmic ray propagation has been very successful in explaining all kinds of the Galactic cosmic ray spectra. However, high precision measurement recently revealed the appreciable discrepancy between data and model…
Multiplicity fluctuations in heavy ion collisions obtain comparable contributions both from initial stage of the collisions, and from final stage interaction. We calculate the former component, using the ``wounded nucleon'' model and…
A semi-phenomenological model of a many-particle system of 4He atoms is proposed, in which a helium atom is considered as a complex consisting of a nucleus and a bound pair of electrons in the singlet state. At zero temperature, there are…
We examine cosmic microwave background constraints on variations in the recombination history of the universe. We use a very general extension to the standard model of recombination characterized by two parameters, a and b, which multiply…
The radiation at collision of high-energy particles is formed over a rather long distances and therefore is sensitive to an environment. In particular the smallness of the transverse dimensions of the colliding beams leads to suppression of…
Multiplicities in e+e- annihilation and relativistic heavy ion collisions show remarkable similarities at high energies. A thermal-statistical model is proposed to explain the differences which occur mainly at low beam energies. Two…
I give an overview of experimental and theoretical results for antiproton and antihydrogen scattering with atoms and molecules (in particular H, He). At low energies ($\lesssim1$~keV) there are practically no experimental data available.…
A recently generated theoretical line list of C II dielectronic recombination lines together with observational data gathered from the literature is used to investigate the electron temperature in a range of astronomical objects, mainly…
VHE (Very High Energy, E>100 GeV) radiation emitted at cosmological distances will pair produce on low-energy diffuse extragalactic background radiation before ever reaching us. This prevents us from directly seeing most of the VHE emission…
Accurately determining the elemental abundances of a low metallicity nebula strongly depends on measuring the density (n$_e$) and temperature (T$_e$) of the gas. Because these two parameters are inherently degenerate when derived solely…