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Big Bang Nucleosynthesis (BBN) and the Cosmic Background Radiation (CBR) provide complementary probes of the early evolution of the Universe and of its particle content. Neutrinos play important roles in both cases, influencing the…
Cosmology is well suited to study the effects of long range interactions due to the large densities in the early Universe. In this article, we explore how the energy density and equation of state of a fermion system diverge from the…
The self-energy effect on the neutron-proton (np) pairing gap is investigated up to the third order within the framework of the extend Bruecker-Hartree-Fock (BHF) approach combined with the BCS theory. The self-energy up to the second-order…
Leading finite temperature effects on the neutrino decoupling temperature in the early Universe have been studied. We have incorporated modifications of the dispersion relation and the phase space distribution due to the presence of…
During the era of primordial nucleosynthesis the background of non-equilibrium antineutrinos is being formed due to decays of neutrons and nuclei of tritium. The spectra of antineutrinos of this background were calculated taking into…
We study the effect of neutrino degeneracy on primordial nucleosynthesis in a universe in which the cosmological scale factor evolves linearly with time. The degeneracy parameter of electron type neutrinos ($\xi_e$) determines the $n/p$…
A decaying particle that dominates the energy density of the universe and then decays with a lifetime $\sim 10^{-1}$ sec into electromagnetically-interacting particles can heat the background electron neutrinos more than the $\mu$ and…
We consider the decoherence effects in the propagation of active neutrinos due to the non-forward neutrino scattering processes in a matter background composed of electrons and nucleons. We calculate the contribution to the imaginary part…
A procedure for studying low energy neutrinos processes using hadronic physics ideas is proposed. We describe how the neutrino-neutrino interactions can be modelled using massive gauge theories. The mass of the gauge bosons is created by…
The primordial abundances of the light nuclides produced by Big Bang Nucleosynthesis (BBN) during the first 20 minutes in the evolution of the Universe are sensitive to the universal density of baryons and to the expansion rate of the early…
In this chapter, we provide an overview of the physics of colliding black holes and neutron stars and of the impact of neutrinos on these systems. Observations of colliding neutron stars play an important role in nuclear astrophysics today.…
Cosmological scenarios with a non-standard equation of state can involve ultrastiff fluids, understood as primordial fluids for which $p/\rho> 1$. Their energy densities can dominate the Universe energy budget at early times, in the…
Recent determinations of the deuterium abundance, $^2$H/H, in high redshift Lyman limit hydrogen clouds challenge the usual picture of primordial nucleosynthesis based on \lq\lq concordance\rq\rq\ of the calculated light element ($^2$H,…
We discuss novel ways in which neutrino oscillation experiments can probe dark matter. In particular, we focus on interactions between neutrinos and ultra-light ("fuzzy") dark matter particles with masses of order $10^{-22}$ eV. It has been…
Prediction of the primordial abundances of elements in the big-bang nucleosynthesis (BBN) is one of the three strong evidences for the big bang model. Precise knowledge of the baryon-to-photon ratio of the Universe from observations of the…
(abridged) In the presence of a light WIMP (mass m_chi < 30 MeV), there are degeneracies among the WIMP's nature, its couplings to standard model particles, its mass, and the number of equivalent (additional) neutrinos, Delta N_nu. These…
A review of Big Bang Nucleosynthesis (BBN) is presented. Observations of deuterium and helium-4 are discussed. Some BBN restrictions on non-standard physics, especially on neutrino properties and time-variation of fundamental constants are…
The physics of the mysterious and stealthy neutrino is at the heart of many phenomena in the cosmos. These particles interact with matter and with each other through the aptly named weak interaction. At typical astrophysical energies the…
During Big Bang Nucleosynthesis (BBN), in the first 20 minutes of the evolution of the Universe, the light nuclides, D, 3He, 4He, and 7Li were synthesized in astrophysically interesting abundances. The Cosmic Microwave Background Radiation…
It is generally expected that adding light sterile species would increase the effective number of neutrinos, $N_{eff}$. In this paper we discuss a scenario that $N_{eff}$ can actually decrease due to the neutrino oscillation effect if…