593 research outputs found
Secularly growing loop corrections in strong electric fields
We calculate one--loop corrections to the vertexes and propagators of photons
and charged particles in the strong electric field backgrounds. We use the
Schwinger--Keldysh diagrammatic technique. We observe that photon's Keldysh
propagator receives growing with time infrared contribution. As the result,
loop corrections are not suppressed in comparison with tree--level
contribution. This effect substantially changes the standard picture of the
pair production. To sum up leading IR corrections from all loops we consider
the infrared limit of the Dyson--Schwinger equations and reduce them to a
single kinetic equation.Comment: 16 pages, no figures; Minor correction
Neutrinos with Mixing in Twisting Magnetic Fields
Transitions in a system of neutrinos with vacuum mixing and magnetic moments,
propagating in matter and transverse magnetic field, are considered. It is
shown that in the realistic case of magnetic field direction varying along the
neutrino path qualitatively new phenomena become possible: permutation of
neutrino conversion resonances, appearance of resonances in the
neutrino-antineutrino () transition
channels, neutrino-antineutrino resonant conversion, large amplitude
oscillations, merging of different
resonances (triple resonances). Possible phenomenological implications of these
effects are briefly discussed.Comment: LaTeX, 35 pages, 4 figures (not included but available upon request).
In memoriam of Ya.A. Smorodinsky. SISSA-170/92/E
Chizhov and Petcov Reply
We have found in [1] new conditions for a total neutrino conversion in the
case of neutrino oscillations taking place in a medium, consisting of n = 2 (or
3) alternating layers with constant densities and . It is claimed in
[4] that our results are particular case of enhancement of neutrino
oscillations, which was suggested earlier by other authors and was widely
discussed in the literature. We refute these claims, confirming the novelty of
our results.Comment: 2 pages, LATEX; concise (essentially 1 page) and somewhat modified
version of Ref. SISSA 5/2000/EP (hep-ph/0003110); reply on the ``Comment on
New Conditions for a Total Neutrino Conversion in a Medium'', Phys. Rev.
Lett. 85 (2000) 3978; published as ``Chizhov and Petcov Reply'' in Phys. Rev.
Lett. 85 (2000) 397
Supernova prompt neutronization neutrinos and neutrino magnetic moments
It is shown that the combined action of spin-flavor conversions of supernova
neutrinos due to the interactions of their Majorana-type transition magnetic
moments with the supernova magnetic fields and flavor conversions due to the
mass mixing can lead to the transformation of \nu_e born in the neutronization
process into their antiparticles \bar{\nu}_e. Such an effect would have a clear
experimental signature and its observation would be a smoking gun evidence for
the neutrino transition magnetic moments. It would also signify the leptonic
mixing parameter |U_{e3}| in excess of 10^{-2}.Comment: LaTex, 25 pages, 3 figures. v4: Discussion section expanded,
references added. Matches the published versio
On the backreaction issue for the black hole in de Sitter space-time
We consider quantum real massive scalar field in the de Sitter-Schwarzschild
space-time backround. To have an analytic head way we study in detail the
two-dimensional case, assuming that the situation in four dimensions will not
be much different conceptually. It is assumed, that quantum field is in a
thermal state i.e. described by the planckian distribution for the exact modes
in the geometry under consideration. We calculate approximately the expectation
value of stress-energy tensor near the cosmological and black hole horizons. It
is shown that for a generic temperature backreaction from quantum fields on the
geometry cannot be neglected. Thus, de Sitter-Schwarzschild space-time geometry
inevitably is strongly modified by the quantum fluctuations of the matter
fields.Comment: 10 pages, references, comments and calculation details adde
Triplet Leptogenesis in Left-Right Symmetric Seesaw Models
We discuss scalar triplet leptogenesis in a specific left-right symmetric
seesaw model. We show that the Majorana phases that are present in the model
can be effectively used to saturate the existing upper limit on the
CP-asymmetry of the triplets. We solve the relevant Boltzmann equations and
analyze the viability of triplet leptogenesis. It is known for this kind of
scenario that the efficiency of leptogenesis is maximal if there exists a
hierarchy between the branching ratios of the triplet decays into leptons and
Higgs particles. We show that triplet leptogenesis typically favors branching
ratios with not too strong hierarchies, since maximal efficiency can only be
obtained at the expense of suppressed CP-asymmetries.Comment: 16 pages, 5 figures, published versio
- …