1,399 research outputs found
Simplicial vs. Continuum String Theory and Loop Equations
We derive loop equations in a scalar matrix field theory. We discuss their
solutions in terms of simplicial string theory -- the theory describing
embeddings of two--dimensional simplicial complexes into the space--time of the
matrix field theory. This relation between the loop equations and the
simplicial string theory gives further arguments that favor one of the
statements of the paper hep-th/0407018. The statement is that there is an
equivalence between the partition function of the simplicial string theory and
the functional integral in a continuum string theory -- the theory describing
embeddings of smooth two--dimensional world--sheets into the space--time of the
matrix field theory in question.Comment: 6 page
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
Implications of Gallium Solar Neutrino Data for the Resonant Spin-Flavor Precession Scenario
We consider the implications of the recent results of SAGE and GALLEX
experiments for the solution of the solar neutrino problem in the framework of
the resonant neutrino spin-flavor precession scenario. It is shown that this
scenario is consistent with all the existing solar neutrino data including the
gallium results. The quality of the fit of the data depends crucially on the
magnetic field profile used which makes it possible to get information about
the magnetic field in the solar interior. In particular, the magnetic field in
the core of the sun must not be too strong ( G). The detection
rate in the gallium detectors turns out to be especially sensitive to the
magnitude of . Predictions for forthcoming solar-neutrino
experiments are made.Comment: LaTeX, 16 pages, 5 figures (not included by available upon request by
fax or ordinary mail
Expansion in Feynman Graphs as Simplicial String Theory
We show that the series expansion of quantum field theory in the Feynman
diagrams can be explicitly mapped on the partition function of the simplicial
string theory -- the theory describing embeddings of the two--dimensional
simplicial complexes into the space--time of the field theory. The summation
over two--dimensional geometries in this theory is obtained from the summation
over the Feynman diagrams and the integration over the Schwinger parameters of
the propagators. We discuss the meaning of the obtained relation and derive the
one--dimensional analog of the simplicial theory on the example of the free
relativistic particle.Comment: Latex, 11pp, Minor mintakes are correcte
Oscillations of high energy neutrinos in matter: Precise formalism and parametric resonance
We present a formalism for precise description of oscillation phenomena in
matter at high energies or high densities, V > \Delta m^2/2E, where V is the
matter-induced potential of neutrinos. The accuracy of the approximation is
determined by the quantity \sin^2 2\theta_m \Delta V/2\pi V, where \theta_m is
the mixing angle in matter and \Delta V is a typical change of the potential
over the oscillation length (l \sim 2\pi/V). We derive simple and physically
transparent formulas for the oscillation probabilities, which are valid for
arbitrary matter density profiles. They can be applied to oscillations of high
energy (E > 10 GeV) accelerator, atmospheric and cosmic neutrinos in the matter
of the Earth, substantially simplifying numerical calculations and providing an
insight into the physics of neutrino oscillations in matter. The effect of
parametric enhancement of the oscillations of high energy neutrinos is
considered. Future high statistics experiments can provide an unambiguous
evidence for this effect.Comment: LaTeX, 5 pages, 1 figure. Linestyles in the figure corrected to match
their description in the caption; improved discussion of the accuracy of the
results; references added. Results and conclusions unchange
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
Classical radiation by free-falling charges in de Sitter spacetime
We study the classical radiation emitted by free-falling charges in de Sitter
spacetime coupled to different kinds of fields. Specifically we consider the
cases of the electromagnetic field, linearized gravity and scalar fields with
arbitrary mass and curvature coupling. Given an arbitrary set of such charges,
there is a generic result for sufficiently late times which corresponds to each
charge being surrounded by a field zone with negligible influence from the
other charges. Furthermore, we explicitly find a static solution in the static
patch adapted to a charge (implying no energy loss by the charge) which can be
regularly extended beyond the horizon to the full de Sitter spacetime, and show
that any other solution decays at late times to this one. On the other hand,
for non-conformal scalar fields the inertial observers naturally associated
with spatially flat coordinates will see a non-vanishing flux far from the
horizon, which will fall off more slowly than the inverse square of the
distance for sufficiently light fields (m^2 + \xi R < 5H^2/4) and give rise to
a total integrated flux that grows unboundedly with the radius. This can be
qualitatively interpreted as a consequence of a classical parametric
amplification of the field generated by the charge due to the time-dependent
background spacetime. Most of these results do not hold for massless minimally
coupled scalar fields, whose special behavior is analyzed separately.Comment: 31 pages, REVTeX4, minor changes, one reference added, version to
appear in Phys. Rev.
Solar Neutrino Data, Neutrino Magnetic Moments and Flavor Mixing
The results of all currently operating solar neutrino experiments are
analyzed in the framework of the resonant neutrino spin--flavor precession
scenario including the effects of neutrino mixing. Nine different profiles of
the solar magnetic field are used in the calculations. It is shown that the
available experimental data can be accounted for within the considered
scenario. The Ga--Ge data lead to an upper limit on the neutrino mixing angle:
\sin 2\theta_0 \aprle 0.25. One can discriminate between small mixing angle
(\sin 2\theta_0 \aprle 0.1) and moderate mixing angle solutions by studying
the solar flux which is predicted to be sizeable for moderate
mixing angles. The expected signals due to in the SNO,
Super--Kamiokande and Borexino experiments are calculated and found to be
detectable for \sin 2\theta_0 \aprge 0.1.Comment: 16 pages, latex, 5 figures available upon request from Author
Neutrino production coherence and oscillation experiments
Neutrino oscillations are only observable when the neutrino production,
propagation and detection coherence conditions are satisfied. In this paper we
consider in detail neutrino production coherence, taking \pi\to \mu \nu \ decay
as an example. We compare the oscillation probabilities obtained in two
different ways: (1) coherent summation of the amplitudes of neutrino production
at different points along the trajectory of the parent pion; (2) averaging of
the standard oscillation probability over the neutrino production coordinate in
the source. We demonstrate that the results of these two different approaches
exactly coincide, provided that the parent pion is considered as pointlike and
the detection process is perfectly localized. In this case the standard
averaging of the oscillation probability over the finite spatial extensions of
the neutrino source (and detector) properly takes possible decoherence effects
into account. We analyze the reason for this equivalence of the two approaches
and demonstrate that for pion wave packets of finite width \sigma_{x\pi} the
equivalence is broken. The leading order correction to the oscillation
probability due to \sigma_{x\pi}\ne 0 is shown to be \sim
[v_g/(v_g-v_\pi)]\sigma_{x\pi}/l_{osc}, where v_g and v_\pi \ are the group
velocities of the neutrino and pion wave packets, and l_{osc} is the neutrino
oscillation length.Comment: LaTeX, 40 pages, 4 figures. v2: minor typos correcte
Exotic smooth structures on 4-manifolds with zero signature
For every integer , we construct infinite families of mutually
nondiffeomorphic irreducible smooth structures on the topological -manifolds
and (2k-1)(\CP#\CPb), the connected sums of
copies of and \CP#\CPb.Comment: 6 page
- âŠ