75 research outputs found

### On the Possibility of Super-luminal Propagation in a Gravitational Background

We argue that superluminal propagation in a gravitational field discovered by
Drummond and Hathrell in the lowest order of perturbation theory remains intact
in higher orders. The criticism of this result based on an exact calculation of
the one loop correction to the photon polarization operator in the Penrose
plane wave approximation is not tenable. The statement that quantum causality
is automatically imposed by classical causality is possibly invalid due to the
infrared nature of the same triangle diagram which also contributes to the
quantum trace anomaly.Comment: 11 page

### Conversion of relic gravitational waves into photons in cosmological magnetic fields

Conversion of gravitational waves into electromagnetic radiation is
discussed. The probability of transformations of gravitons into photons in
presence of cosmological background magnetic field is calculated at the
recombination epoch and during subsequent cosmological stages. The produced
electromagnetic radiation is concentrated in the X-ray part of the spectrum. It
is shown that if the early Universe was dominated by primordial black holes
(PBHs) prior to Big Bang Nucleosynthesis (BBN), the relic gravitons emitted by
PBHs would transform to an almost isotropic background of electromagnetic
radiation due to conversion of gravitons into photons in cosmological magnetic
fields. Such extragalactic radiation could be noticeable or even dominant
component of Cosmic X-ray Background.Comment: 24 pages, 8 figures and 1 table; minor changes and more references
have been adde

### Electrodynamics at non-zero temperature, chemical potential, and Bose condensate

Electrodynamics of charged scalar bosons and spin 1/2 fermions is studied at
non-zero temperature, chemical potentials, and possible Bose condensate of the
charged scalars. Debye screening length, plasma frequency, and the photon
dispersion relation are calculated. It is found that in presence of the
condensate the time-time component of the photon polarization operator in the
first order in electric charge squared acquires infrared singular parts
proportional to inverse powers of the spatial photon momentum k.Comment: Two references and explanatory comments are added according to the
referee's suggestions. The paper is accepted for publication in JCA

### Cosmic ray production in modified gravity

This paper is a reply to the criticism of our work on particle production in
modified gravity by D. Gorbunov and A. Tokareva. We show that their arguments
against efficient particle production are invalid. $F(R)$ theories can lead to
an efficient generation of high energy cosmic rays in contracting systems.Comment: In response to criticism by referees several clarifying comments are
added. The results of the paper remain largely unchanged. Version to appear
on EPJ

### Affleck-Dine Baryogenesis and heavy elements production from Inhomogeneous Big Bang Nucleosynthesis

We study the impact of possible high density baryonic bubbles on the early
formed QSO, IGM, and metal poor stars. Such bubbles could be created, under
certain conditions, in Affleck-Dine model of baryogenesis and may occupy a
relatively small fraction of space, while the dominant part of the cosmological
volume has the normal observed baryon-to-photon ratio $\eta = 6\cdot 10^{-10}$.
The value of $\eta$ in the bubbles, could be much larger than the usually
accepted one (it might be even close to unity) without contradicting the
existing data on light element abundances and the observed angular spectrum of
CMBR. We find upper bounds on $\eta$ by comparing heavy elements' abundances
produced in BBN and those of metal poor stars. We conclude that $\eta$ should
be smaller than $10^{-5}$ in some metal poor star regions.Comment: 11 pages, 4 figures, PTPTeX ; added references, changed introduction,
acknowledgments and figure

### The teaching profession in Europe : historical and sociological analysis

A possible effect of direct CP violation in D -> K-S(0)pi(+)pi(-) decay on the gamma measurement from B-+/- -> DK +/-, D -> K-S(0)pi(+)pi(-) Dalitz plot analysis is considered. Systematic uncertainty of gamma coming from the current limits on direct CP violation in D -> K-S(0)pi(+)pi(-) is estimated, and a modified model-independent procedure of B-+/- -> DK +/-, D -> K-S(0)pi(+)pi(-) Dalitz plot analysis is proposed that gives an unbiased gamma measurement even in presence of direct CP violation in charm decays. The technique is applicable to other threebody D decays such as D-0 -> (KSK+K-)-K-0, D-0 -> pi(+)pi(-)pi(0), etc

### Relic Backgrounds of Gravitational Waves from Cosmic Turbulence

Turbulence may have been produced in the early universe during several kind
of non-equilibrium processes. Periods of cosmic turbulence may have left a
detectable relic in the form of stochastic backgrounds of gravitational waves.
In this paper we derive general expressions for the power spectrum of the
expected signal. Extending previous works on the subject, we take into account
the effects of a continuous energy injection power and of magnetic fields. Both
effects lead to considerable deviations from the Kolmogorov turbulence
spectrum. We applied our results to determine the spectrum of gravity waves
which may have been produced by neutrino inhomogeneous diffusion and by a first
order phase transition. We show that in both cases the expected signal may be
in the sensitivity range of LISA.Comment: 25 pages, 1 figur

### Synthetic Light Curves of Shocked Dense Circumstellar Shells

We numerically investigate light curves (LCs) of shocked circumstellar shells
which are suggested to reproduce the observed LC of superluminous SN 2006gy
analytically. In the previous analytical model, the effects of the
recombination and the bolometric correction on LCs are not taken into account.
To see the effects, we perform numerical radiation hydrodynamic calculations of
shocked shells by using STELLA, which can numerically treat multigroup
radiation transfer with realistic opacities. We show that the effects of the
recombination and the bolometric correction are significant and the analytical
model should be compare to the bolometric LC instead of a single band LC. We
find that shocked circumstellar shells have a rapid LC decline initially
because of the adiabatic expansion rather than the luminosity increase and the
shocked shells fail to explain the LC properties of SN 2006gy. However, our
synthetic LCs are qualitatively similar to those of superluminous SN 2003ma and
SN 1988Z and they may be related to shocked circumstellar shells.Comment: 7 pages, 7 figures, 1 table, accepted by Monthly Notices of the Royal
Astronomical Societ

### Ferromagnetic properties of charged vector boson condensate

Bose-Einstein condensation of W bosons in the early universe is studied. It
is shown that, in the broken phase of the standard electroweak theory,
condensed W bosons form a ferromagnetic state with aligned spins. In this case
the primeval plasma may be spontaneously magnetized inside macroscopically
large domains and form magnetic fields which may be seeds for the observed
today galactic and intergalactic fields. However, in a modified theory, e.g. in
a theory without quartic self interactions of gauge bosons or for a smaller
value of the weak mixing angle, antiferromagnetic condensation is possible. In
the latter case W bosons form scalar condensate with macroscopically large
electric charge density i.e. with a large average value of the bilinear product
of W-vector fields but with microscopically small average value of the field
itself.Comment: Some numerical estimates and discussions are added according to the
referee's suggestions. This version is accepted for publication in JCA

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