796 research outputs found
Neutrino oscillations: deriving the plane-wave approximation in the wave-packet approach
The plane-wave approximation is widely used in the practical calculations
concerning neutrino oscillations. A simple derivation of this approximation
starting from the neutrino wave-packet framework is presented.Comment: Presented at the 36th ITEP Winter School of Physics, session
"Particle Physics", February 8-16, 2008, Otradnoe, Russi
Dark matter and generation of galactic magnetic fields
A new scenario for creation of galactic magnetic fields is proposed which is
operative at the cosmological epoch of the galaxy formation, and which relies
on unconventional properties of dark matter. Namely, it requires existence of
feeble but long range interaction between the dark matter particles and
electrons. In particular, millicharged dark matter particles or mirror
particles with the photon kinetic mixing to the usual photon can be considered.
We show that in rotating protogalaxies circular electric currents can be
generated by the interactions of free electrons with dark matter particles in
the halo, while the impact of such interactions on galactic protons is
considerably weaker. The induced currents may be strong enough to create the
observed magnetic fields on the galaxy scales with the help of moderate dynamo
amplification. In addition, the angular momentum transfer from the rotating gas
to dark matter component could change the dark matter profile and formation of
cusps at galactic centers would be inhibited. The global motion of the ionized
gas could produce sufficiently large magnetic fields also in filaments and
galaxy clusters.Comment: 8 pages, refined version published in Eur. Phys. J. C73, 2620 (2013
Condensation of charged bosons in plasma physics and cosmology
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.Comment: 9 pages, invited talk at the International Seminar "Quarks 2010",
Kolomna, Russia, June, 6-12, 201
Difference between radiative transition rates in atoms and antiatoms
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.Comment: 5 pages, 5 figure
Evolution of thick domain walls in inflationary and universe
We study the evolution of thick domain walls in the different models of
cosmological inflation, in the matter-dominated and radiation-dominated
universe, or more generally in the universe with the equation of state
. We have found that the domain wall evolution crucially depends on
the time-dependent parameter , where is the
Hubble parameter and is the thickness of the wall in flat
space-time. For the physical thickness of the wall, ,
tends with time to , which is microscopically small. Otherwise, when
, the wall steadily expands and can grow up to a cosmologically
large size.Comment: 15 pages, 9 figure
Baryogenesis from Gravitational Decay of TeV-Particles in Theories with Low Scale Gravity
In models with the fundamental gravity scale in the TeV range, early
cosmology is quite different from the standard picture, because the universe
must have arisen at a much lower temperature and the electroweak symmetry was
probably never restored. In this context, baryogenesis appears to be
problematic: if the involved physics is essentially that of the Standard Model,
``conventional'' non-conserving baryon number processes are completely
negligible at such low temperatures. In this paper we show that the observed
matter-antimatter asymmetry of the universe may be generated by gravitational
decay of TeV-mass particles: such objects can be out of equilibrium after
inflation and, if their mass is of the same order of magnitude as the true
quantum gravity scale, they can quickly decay through a black hole intermediate
state, violating global symmetries, in particular, baryon number. In this
context, we take advantage of the fact that the ``Sakharov conditions'' for
baryogenesis can be more easily satisfied with a low fundamental scale of
gravity.Comment: 18 pages, added reference
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