785 research outputs found
Towards the Theory of Non--Abelian Tensor Fields I
We present a triangulation--independent area--ordering prescription which
naturally generalizes the well known path ordering one. For such a prescription
it is natural that the two--form ``connection'' should carry three ``color''
indices rather than two as it is in the case of the ordinary one--form gauge
connection. To define the prescription in question we have to define how to
{\it exponentiate} a matrix with three indices. The definition uses the fusion
rule structure constants.Comment: 22 pages, 18 figure
Superkamiokande and solar antineutrinos
We propose to exploit the angular distribution of the positrons emitted in
the inverse beta decay to extract a possible antineutrino signal from the
Superkamiokande background. From the statistics collected in just 101.9 days
one obtains a model independent upper bound on the antineutrino flux (for
energy greater than 8.3 MeV) Phi < 9*10^4 cm^-2 s^-1 at the 95% C.L. By
assuming the same energy spectrum as for the 8B neutrinos, the 95% C.L. bound
is Phi < 6*10^4 cm^-2 s^-1. Within three years of data taking, the sensitivity
to neutrino-antineutrino transition probability will reach the 1% level, thus
providing a stringent test of hybrid oscillation models.Comment: 7 pages, 1 figure, Late
Quantum field theoretic approach to neutrino oscillations in matter
We consider neutrino oscillations in non-uniform matter in a quantum field
theoretic (QFT) approach, in which neutrino production, propagation and
detection are considered as a single process. We find the conditions under
which the oscillation probability can be sensibly defined and demonstrate how
the properly normalized oscillation probability can be obtained in the QFT
framework. We derive the evolution equation for the oscillation amplitude and
discuss the conditions under which it reduces to the standard
Schr\"odinger-like evolution equation. It is shown that, contrary to the common
usage, the Schr\"odinger-like evolution equation is not applicable in certain
cases, such as oscillations of neutrinos produced in decays of free pions
provided that sterile neutrinos with eV exist.Comment: LaTeX, 24 pages + 16 pages of appendices, 1 figure. V2: typos
correcte
Reheat temperature in supersymmetric hybrid inflation models
The allowed range of parameters for supersymmetric hybrid inflation and its
extensions are investigated. The lower bound on the reheat temperature T_r in
these models with hierarchical right handed neutrinos is found to be 3*10^7
GeV. (T_r as low as 100 GeV is possible for quasi degenerate right handed
neutrinos.) We also present revised estimates for the scalar spectral index and
the symmetry breaking scale associated with inflation.Comment: 15 pages, 8 figures, revtex4. v2: minor changes, matches published
versio
Stimulated Neutrino Transformation with Sinusoidal Density Profiles
Large amplitude oscillations between the states of a quantum system can be
stimulated by sinusoidal external potentials with frequencies that are similar
to the energy level splitting of the states or a fraction thereof. Situations
when the applied frequency is equal to an integer fraction of the energy level
splittings are known as parametric resonances. We investigate this effect for
neutrinos both analytically and numerically for the case of arbitrary numbers
of neutrino flavors. We look for environments where the effect may be observed
and find that supernova are the one realistic possibility due to the necessity
of both large densities and large amplitude fluctuations. The comparison of
numerical and analytic results of neutrino propagation through a model
supernova reveals it is possible to predict the locations and strengths of the
stimulated transitions that occur.Comment: 14 pages, 6 figure
De Sitter space and perpetuum mobile
We give general arguments that any interacting non--conformal {\it classical}
field theory in de Sitter space leads to the possibility of constructing a
perpetuum mobile. The arguments are based on the observation that massive free
falling particles can radiate other massive particles on the classical level as
seen by the free falling observer. The intensity of the radiation process is
non-zero even for particles with any finite mass, i.e. with a wavelength which
is within the causal domain. Hence, we conclude that either de Sitter space can
not exist eternally or that one can build a perpetuum mobile.Comment: 11 pages revtex, no figures. Added discussion to strengthen
conclusio
Neutrino Physics: Open Theoretical Questions
We know that neutrino mass and mixing provide a window to physics beyond the
Standard Model. Now this window is open, at least partly. And the questions
are: what do we see, which kind of new physics, and how far "beyond"? I
summarize the present knowledge of neutrino mass and mixing, and then formulate
the main open questions. Following the bottom-up approach, properties of the
neutrino mass matrix are considered. Then different possible ways to uncover
the underlying physics are discussed. Some results along the line of: see-saw,
GUT and SUSY GUT are reviewed.Comment: 17 pages, latex, 12 figures. Talk given at the XXI International
Symposium on Lepton and Photon Interactions at High Energies, ``Lepton Photon
2003", August 11-16, 2003 - Fermilab, Batavia, IL US
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
Resonant neutrino spin-flavor precession and supernova shock revival
A new mechanism of supernova shock revival is proposed, which involves
resonant spin--flavor precession of neutrinos with a transition magnetic moment
in the magnetic field of the supernova. The mechanism can be operative in
supernovae for transition magnetic moments as small as provided
the neutrino mass squared difference is in the range . It is shown that this mechanism can increase the
neutrino--induced shock reheating energy by about 60\%.Comment: 16 pages, latex, 2 figures. added few reference
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