A. D. Dolgov

Neutron-antineutron oscillations: Theoretical status and experimental prospects

This paper summarizes the relevant theoretical developments, outlines some ideas to improve experimental searches for free neutron-antineutron oscillations, and suggests avenues for future improvement in the experimental sensitivity.

Cosmology and neutrino properties

A brief review for particle physicists on the cosmological impact of neutrinos and on restrictions on neutrino properties from cosmology is given. The paper includes a discussion of upper bounds on neutrino mass and possible ways to relax them, methods to observe the cosmic-neutrino background, bounds on the cosmological lepton asymmetry which are strongly improved by neutrino oscillations, cosmological effects of breaking of the spin-statistics theorem for neutrinos, bounds on mixing parameters of active and possible sterile neutrinos with account of active-neutrino oscillations, bounds on right-handed currents and neutrino magnetic moments, and some more.

Matter and antimatter in the universe

Different scenarios of baryogenesis are briefly reviewed from the point of view of possibility of generation of cosmologically interesting amount of antimatter. It is argued that creation of antimatter is possible and natural in many models. In some models not only anti-helium may be produced but also a heavier anti-elements and future observations of the latter would be critical for discovery or establishing stronger upper limits on existence of antimatter. Incidentally a recent observation of iron-rich quasar may present a support to one special model of antimatter creation.

Beasts in Lambda-CDM Zoo

Recent astronomical discoveries of supermassive black holes (quasars), gamma-bursters, super-novae, and dust at high redshifts, z = (5−10), are reviewed. Such a dense population of the early universe is at odds with the conventional mechanisms of its possible origin. Similar data from the contemporary universe, which are also in conflict with natural expectations, are considered too. Two possible mechanisms are suggested, at least one of which can potentially solve all these problems. As a by-product of the last model, an abundant cosmological antimatter may be created.

Big Bang Nucleosynthesis

Abstract 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 given.

Neutrino Oscillations and Cosmology

Phenomenology of neutrino oscillations in vacuum and in cosmological plasma is considered. Neutrino oscillations in vacuum are usually described in plane wave approximation. In this formalism there is an ambiguity if one should assume σp=0 and correspondingly σE∈0 or vice versa σE=0 and σp∈0, or some other condition. We will use the standard set of quantum field theory rules and show that the theoretical description is unambiguous and that the state of oscillating neutrinos is determined by the conditions of their registration. The wave packet formalism is a natural result of such an approach. Oscillating neutrinos in cosmological plasma cannot be described in terms of wave function because of a fast loss of coherence due to elastic or inelastic scattering, so that one should use the density matrix formalism. Kinetic equations for the density matrix of oscillating neutrinos are derived. Numerical and semi-analytical solutions of the equations are examined. In particular a possibility of amplification of cosmological lepton asymmetry in the sector of active neutrinos mixed to sterile ones is critically discussed.

Matter-antimatter domains in the universe

Abstract A possible existence of cosmologically large domains of antimatter or astronomical “anti-objects” is discussed. A brief review of different scenarios of baryogenesis predicting a noticeable amount of antimatter is given. Though both theory and observations indicate that the universe is most possibly uniformly charge asymmetric without any noticeable amount of antimatter, several natural scenarios are possible that allow for cosmologically (astronomically) interesting objects in close vicinity to us. The latter may be discovered by observation of cosmic ray antinuclei.

How to see an antistar

Polarization of photons emitted in weak decays occurring at distant star makes it possible to determine whether this star is made from antimatter. The observation of neutrinos (antineutrinos) produced at neutronization (antineutronization) reactions at the beginning of SN

Dark matter in the universe

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