Neutrinos in cosmology

Abstract

Cosmological implications of neutrinos are reviewed. The following subjects are discussed at a different level of scrutiny: cosmological limits on neutrino mass, neutrinos and primordial nucleosynthesis, cosmological constraints on unstable neutrinos, lepton asymmetry of the universe, impact of neutrinos on cosmic microwave radiation, neutrinos and the large scale structure of the universe, neutrino oscillations in the early universe, baryo/lepto-genesis and neutrinos, neutrinos and high energy cosmic rays, and briefly some more exotic subjects: neutrino balls, mirror neutrinos, and neutrinos from large extra dimensions. Content

Cosmology seeking friendship with sterile neutrinos

“…St, 14.60.Pq, 98.80.Es, 98.80.Cq Introduction.-Big-bang nucleosynthesis (BBN) has for many years provided the best inference of the radiation content of the universe. This inference implies the existence of approximately three neutrino flavors and hence three generations of elementary particles [1,2]. Of course, by the early 1990s, precision measurements of the Z 0 decay width at LEP had superseded this early cosmological evidence.…”

Introduction to Cosmology

“…This analytical estimate was confirmed by precise numerical solution of the integrodifferential kinetic equation; for discussion and the list of references see review [12]. This effect leads to an increase of the effective number of neutrino species:…”

“…This equation is simply the law of covariant energy-momentum conservation (7) in metric (12). Problem 1.…”

“…In what follows we will consider only this case, moreover, the effects of curvature are typically small. To solve this equation one needs first to calculate the Christoffel symbols for metric (12). In 3D flat space they have very simple form:…”

Mass limits for dark clusters of degenerate fermions

“…In this work we will deal with fully degenerate fermionic dark matter. Semidegenerate massive neutrinos, with different degrees of degeneracy, have been extensively addressed; see, for example, Freese et al (1983); Kang & Steigman (1992); Lesgourgues & Pastor (1999); Lesgourgues & Liddle (2001); Dolgov et al (2002b);and Dolgov (2002a).…”