Gravitational particle production in braneworld cosmology

Gravitational particle production in time variable metric of an expanding universe is efficient only when the Hubble parameter $H$ is not too small in comparison with the particle mass. In standard cosmology, the huge value of the Planck mass $M_{Pl}$ makes the mechanism phenomenologically irrelevant. On the other hand, in braneworld cosmology the expansion rate of the early universe can be much faster and many weakly interacting particles can be abundantly created. Cosmological implications are discussed.Comment: 4 pages, 1 figure, v3 with new definition of $\Lambda$ and minor text modification

Light millicharged particles and large scale cosmic magnetic fields

After a brief review of different types of scenarios suggested for the solution of the problem of galactic and intergalactic magnetic field generation, the mechanism based on the electric current induction by hypothetical millicharged particles interacting with electrons in cosmic medium is discussed. The proposed model successfully describes observational data. The new light millicharged particles can contribute from a small fraction up to 100% to the cosmological dark matter.Comment: 6 pages, no figures; talk presented at Sixteenth Lomonosov Conference On Elementary Particle Physics, Moscow State University, Moscow, 22-28 August, 201

BARYOGENESIS. byvited talk at TAUP 93, LNGS, Italy, September 1993

A review of the present state of the baryogenesis is given with an emphasis on electroweak baryogenesis. Technical details of the numerous models cosidered in the literature are not elaborated but unresolved problems of the issue are considered. Different logically possible alternatives of the electroweak scenarios are presented. A possible impact of bariogenesis on the universe structure formation is discussed.Comment: 25 pages, UM-AC-93-31 Latex fil

Baryogenesis, 30 Years after

A review of the basic principles of baryogenesis is given. Baryogenesis in heavy particle decays as well as electroweak, SUSY-condensate, and spontaneous baryogenesis are discussed. The models of abundant creation of antimatter in the universe are briefly reviewed.Comment: 30 pages, latex twic

Cosmology at the Turn of Centuries

A brief review of the present-day development of cosmology is presented for mixed physical audience. The universe history is briefly described. Unsolved problems are discussed, in particular, the mystery of the cosmological constant and dark energy, the problems of dark matter, and baryogenesis. A brief discussion of the cosmological role of neutrinos is also given.Comment: 20 pages, Invited talk presented at the International Conference I.Ya. Pomeranchuk and Physics at the Turn of Centuries, January 24-28, 2003, Moscow, Russia. A comment on spectral index of inflationary perturbations and one reference are adde

Contemporary gravitational waves from primordial black holes

Stochastic background of gravitational waves (GW) generated by the interactions between primordial black holes (PBH) in the early universe and by PBH evaporation is considered. If PBHs dominated in the cosmological energy density prior to their evaporation, GWs from the earlier stages (e.g. inflation) would be noticeably diluted. On the other hand, at the PBH dominance period they could form dense clusters where PBH binary formation might be significant. These binaries would be efficient sources of the gravitational waves.Comment: 8 pages, presented at Les Rencontres de Physique de la Vall\'ee d'Aoste. La Thuile 2011, to be published in Il Nuovo Cimento Results and Perspectives in Particle Physic

Neutrino Degeneracy and Chemically Inhomogeneous Universe

A possibility that the universe may be strongly inhomogeneous chemically, while very smooth energetically, is considered. A possible mechanism which could lead to such a picture is a large and inhomogeneous lepton asymmetry. The model may explain possibly observed variation of primordial deuterium by an order of magnitude and predicts helium-rich and possibly helium-poor regions where the helium mass fraction differs from the observed 25% by a factor of 2 in either direction. Helium variation can be observed by a different dumping rate of CMB angular spectrum at small angles at different patches of the sky.Comment: 7 pages, latex twice; presented at COSMO-98, Monterey, USA, November, 199

Particle Production in Cosmology and Imaginary Time Method

After brief personal recollections of the author's long-time friendship with Misha Marinov the problem of particle production by classical time- varying scalar field is discussed. In the quasiclassical limit the calculations are done by imaginary time method developed, in particular, in Marinov's works. The method permits to obtain simple analytical expressions which well agree with the later found numerical solutions. The results are compared with perturbative calculations and it is argued that perturbation theory gives an upper limit for the rate of production.Comment: 24 pages, latex; to appear in the Michael Marinov Memorial Volume, "Multiple facets of quantization and supersymmetry", edited by M. Olshanetsky and A. Vainshtein (World Scientific) (a few references added