arXiv subjects
Publications and source records attributed to A. D. Dolgov.
Since the Standard Model most probably cannot explain the large value of CP asymmetries recently observed in D-meson decays we propose the fourth quark-lepton generation explanation of it. As a byproduct weakly mixed leptons of the fourth generation make it possible to save the baryon number of the Universe from erasure by sphalerons. An impact of the 4th generation on BBN is briefly discussed.
We demonstrate that CP violation results in a difference of the partial decay rates of atoms and antiatoms. The magnitude of this difference is estimated.
Possibility of gravitational repulsion in General Relativity is discussed and astronomical data in favor of cosmological acceleration are described. The problem of vacuum energy is emphasized and possible ways of its solution are indicated. The main attention is payed to adjustment mechanism which in principle could compensate originally huge vacuum energy down to cosmologically acceptable value and to solve the coincidence problem of a close magnitudes of the non-compensated remnants of vacuum energy and the energy density of the universe at the present time. Finally possible modifications of gravity at large scales which could induce accelerated cosmological expansion are considered.
Pierre Auger collaboration have recently put forward the hypothesis that the arrival directions of the highest energy cosmic rays correlate with the subset of local active galactic nuclei (AGN). We perform a blind test of AGN hypothesis using publicly available event sets collected by Yakutsk, AGASA and HiRes experiments. The consistency of the procedure requires the event energies to be normalized towards the common energy scale. The number of correlating events in resulting data-set is 3 of 21 which is consistent with expected random background.
A non-local field theory which breaks discrete symmetries, including C, P, CP, and CPT, but preserves Lorentz symmetry, is presented. We demonstrate that at one-loop level the masses for particle and antiparticle remain equal due to Lorentz symmetry only. An inequality of masses implies breaking of the Lorentz invariance and non-conservation of the usually conserved charges.
The Universe evolution during the radiation-dominated epoch in the R^2-extended gravity theory is considered. The equations of motion for R and H are solved analytically and numerically. The particle production rate by the oscillating curvature is calculated in one-loop approximation and the back reaction of particle production on the evolution of R is taken into account. Possible implications of the model for cosmological creation of non-thermal dark matter is discussed.
Observational manifestations of some models of modified gravity, which have been suggested to explain the accelerated cosmological expansion, are analyzed for gravitating systems with time dependent mass density. It is shown that if the mass density rises with time, the system evolves to the singular state with infinite curvature scalar. The corresponding characteristic time is typically much shorter than the cosmological time.
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.
The screening of impurities in plasma with Bose-Einstein condensate of electrically charged bosons is considered. It is shown that the screened potential is drastically different from the usual Debye one. The polarization operator of photons in plasma acquires infrared singular terms at small photon momentum and the screened potential drops down as a power of distance and even has an oscillating behavior, similar to the Friedel oscillations in plasma with degenerate fermions. The magnetic properties of the cosmological plasma with condensed W-bosons are also discussed. It is shown that W-bosons condense in the ferromagnetic state. It could lead to spontaneous magnetization of the primeval plasma. The created magnetic fields may seed galactic and intergalactic magnetic fields observed in the present-day universe.
The possibility of creation of cosmologically significant antimatter are analyzed in different scenarios of baryogenesis. It is argued that there may exist plenty of antimatter even in our Galaxy. Possible forms of antimatter objects and their observational signatures are discussed.
An introductory lectures on cosmology at ITEP Winter School for students specializing in particle physics are presented. Many important subjects are not covered because of lack of time and space but hopefully the lectures may serve as a starting point for further studies.
General features of generation of the cosmological charge asymmetry in CPT non-invariant world are discussed. If the effects of CPT violation manifest themselves only in mass differences of particles and antiparticles, the baryon asymmetry of the universe hardly can be explained solely by breaking of CPT invariance. However, CPT non-invariant theories may lead to a new effect of distorting the usual equilibrium distributions. If this takes place, CPT violation may explain the baryon asymmetry of the universe.
Possible mechanisms of baryogenesis are reviewed. Special attention is payed to those which allow for creation of astronomically significant domains or objects consisting of antimatter. Observational manifestations of cosmological antimatter are discussed.
A model which leads to abundant antimatter objects in the Galaxy (anti-clouds, anti-stars, etc) is presented. Observational manifestations are analyzed. In particular, the model allows for all cosmological dark matter to be made out of compact baryonic and antibaryonic objects.
A model of inhomogeneous baryogenesis based on the Affleck and Dine mechanism is described. A simple coupling of the scalar baryon field to the inflaton allows for formation of astronomically significant bubbles with a large baryon (or antibaryon) asymmetry. During the farther evolution these domains form compact stellar-like objects, or lower density clouds, or primordial black holes of different size. According to the scenario, such high baryonic number objects occupy relatively small fraction of space but despite that they may significantly contribute to the cosmological mass density. For some values of parameters the model allows the possibility the whole dark matter in the universe to be baryonic. Furthermore, the model allows the existence of the antibaryonic B-bubbles, i.e. a significant fraction of the mass density in the universe can be in the form of the compact antimatter objects (e.g. anti-stars).
This is a brief review for particle physicists on cosmological impact of neutrinos and on restrictions on neutrino properties from cosmology. The paper includes 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 spin-statistics theorem for neutrinos, bounds on mixing parameters of active and possible sterile neutrinos with the account of active neutrino oscillations, bounds on right-handed currents and neutrino magnetic moments, and some more.
A new mechanism of adjustment of vacuum energy down to the observed value from an initially huge one is considered. The mechanism is based on a very strong variation of the gravitational coupling constant in very early universe. The model predicts that the non--compensated remnant of vacuum energy changes very slowly at late stages of the cosmological evolution and is naturally close to the observed one. Asymptotically the effective vacuum energy tends to a negative value, so the cosmological expansion should stop and turn into contraction. There remains the problem of introduction of the usual matter into the model and therefore realising realistic cosmology.
Two scenarios of low temperature baryogenesis in theories with TeV scale gravity are discussed. It is argued that strong gravity at TeV energies is very favorable for baryogenesis. In both scenarios the proton decay is either absent or suppressed far below existing bounds. On the other hand, neutron-antineutron oscillations are at the verge of discovery. Some other rare decays with non-conservation of lepton or baryon numbers are predicted.