153 research outputs found
The electromagnetic vertex of neutrinos in an electron background and a magnetic field
We study the electromagnetic vertex function of a neutrino that propagates in
an electron background in the presence of a static magnetic field. The
structure of the vertex function under the stated conditions is determined and
it is written down in terms of a minimal and complete set of tensors. The
one-loop expressions for all the form factors is given, up to terms that are
linear in the magnetic field, and the approximate integral formulas that hold
in the long wavelength limit are obtained. We discuss the physical
interpretation of some of the form factors and their relation with the concept
of the neutrino induced charge. The neutrino acquires a longitudinal and a
transverse charge, due to the fact that the form factors depend on the
transverse and longitudinal components of the photon momentum independently. We
compute those form factors explicitly in various limiting cases and find that
the longitudinal and transverse charge are the same for the case of a
non-relativistic electron gas, but not otherwise.Comment: 18 pages. Revtex4, axodra
Gravitational coupling of neutrinos in a medium
In a medium that contains electrons but not the other charged leptons, such
as normal matter, the gravitational interactions of neutrinos are not the same
for all the neutrino flavors. We calculate the leading order matter-induced
corrections to the neutrino gravitational interactions in such a medium and
consider some of their physical implications.Comment: 21 pages, Latex, uses axodraw.sty (typos corrected; two references
added. To appear in Phys. Rev. D
Nucleon contribution to the neutrino electromagnetic vertex in matter
We calculate the nucleon contribution to the electromagnetic vertex of a
neutrino in a background of particles, including the effect of the anomalous
magnetic moment of the nucleons. Explicit formulas for the form factors are
given in various physical limits of practical interest. Several applications of
the results are mentioned, including the effect of an external magnetic field
on the dispersion relation of a neutrino in matter.Comment: LaTeX, 18 pages; to appear in PR
Electromagnetic properties of a neutrino stream
In a medium that contains a neutrino background in addition to the matter
particles, the neutrinos contribute to the photon self-energy as a result of
the effective electromagnetic vertex that they acquire in the presence of
matter. We calculate the contribution to the photon self-energy in a dense
plasma, due to the presence of a gas of charged particles, or neutrinos, that
moves as a whole relative to the plasma. General formulas for the transverse
and longitudinal components of the photon polarization tensor are obtained in
terms of the momentum distribution functions of the particles in the medium,
and explicit results are given for various limiting cases of practical
interest. The formulas are used to study the electromagnetic properties of a
plasma that contains a beam of neutrinos. The transverse and longitudinal
photon dispersion relations are studied in some detail. Our results do not
support the idea that neutrino streaming instabilities can develop in such a
system. We also indicate how the phenomenon of optical activity of the neutrino
gas is modified due to the velocity of the neutrino background relative to the
plasma. The general approach and results can be adapted to similar problems
involving relativistic plasmas and high-temperature gauge theories in other
environments.Comment: Revtex, 19 pages and 3 included ps file
Gauge Independence of Limiting Cases of One-Loop Electron Dispersion Relation in High-Temperature QED
Assuming high temperature and taking subleading temperature dependence into
account, gauge dependence of one-loop electron dispersion relation is
investigated in massless QED at zero chemical potential. The analysis is
carried out using a general linear covariant gauge. The equation governing the
gauge dependence of the dispersion relation is obtained and used to prove that
the dispersion relation is gauge independent in the limiting case of momenta
much larger than . It is also shown that the effective mass is not
influenced by the leading temperature dependence of the gauge dependent part of
the effective self-energy. As a result the effective mass, which is of order
, does not receive a correction of order from one loop, independent
of the gauge parameter.Comment: Revised and enlarged version, 14 pages, Revte
Axial vector current in an electromagnetic field and low-energy neutrino-photon interactions
An expression for the axial vector current in a strong, slowly varying
electromagnetic field is obtained. We apply this expression to the construction
of the effective action for low-energy neutrino-photon interactions.Comment: 6 pages, references updated, final version to appear in Phys. Rev.
Neutrino damping rate at finite temperature and density
A first principle derivation is given of the neutrino damping rate in
real-time thermal field theory. Starting from the discontinuity of the neutrino
self energy at the two loop level, the damping rate can be expressed as
integrals over space phase of amplitudes squared, weighted with statistical
factors that account for the possibility of particle absorption or emission
from the medium. Specific results for a background composed of neutrinos,
leptons, protons and neutrons are given. Additionally, for the real part of the
dispersion relation we discuss the relation between the results obtained from
the thermal field theory, and those obtained by the thermal average of the
forward scattering amplitude.Comment: LaTex Document, 19 pages, 3 figure
Radiative Neutrino Decay in Media
In this letter we introduce a new method to determine the radiative neutrino
decay rate in the presence of a medium. Our approach is based on the
generalisation of the optical theorem at finite temperature and density.
Differently from previous works on this subject, our method allows to account
for dispersive and dissipative electromagnetic properties of the medium. Some
inconsistencies that are present in the literature are pointed-out and
corrected here. We shortly discuss the relevance of our results for neutrino
evolution in the early universe.Comment: 11 pages, 3 encapsulated figure
Neutrino self-energy and dispersion in a medium with magnetic field
We calculate the one-loop thermal self-energy of a neutrino in a constant and
homogeneous magnetic field to all orders in the magnetic field strength using
Schwinger's proper time method. We obtain the dispersion relation under various
conditions.Comment: 17 pp, RevTeX, one figur
Neutrino magnetic moment in a magnetized plasma
The contribution of a magnetized plasma to the neutrino magnetic moment is
calculated. It is shown that only part of the additional neutrino energy in
magnetized plasma connecting with its spin and magnetic field strength defines
the neutrino magnetic moment. It is found that the presence of magnetized
plasma does not lead to the considerable increase of the neutrino magnetic
moment in contrast to the results presented in literature previously.Comment: 7 page, 1 figures, based on the talk presented by E.N.Narynskaya at
the XVI International Seminar Quarks'2010, Kolomna, Moscow Region, June 6-12,
2010, to appear in the Proceeding
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