36,858 research outputs found
Search for neutrino charged current coherent pion production at SciBooNE
SciBooNE is a neutrino experiment measuring the neutrino cross sections on
carbon in the one GeV region. We have performed a search for charged current
coherent pion production from muon neutrinos scattering on carbon, \nu_\mu 12^C
\to \mu 12^C \pi^+. No evidence for coherent pion production is observed. We
set 90% confidence level upper limits on the cross section ratio of charged
current coherent pion production to the total charged current cross section at
0.67\times 10^{-2} at mean neutrino energy 1.1 GeV and 1.36 \times 10^{-2} at
mean neutrino energy 2.2 GeV. The kinematic distributions of the final data
sample are also presented.Comment: 6 pages, 6 figures, Proceedings of the 6th International Workshop on
Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt09
Trace anomalies and the string-inspired definition of quantum-mechanical path integrals in curved space
We consider quantum-mechanical path integrals for non-linear sigma models on
a circle defined by the string-inspired method of Strassler, where one
considers periodic quantum fluctuations about a center-of-mass coordinate. In
this approach one finds incorrect answers for the local trace anomalies of the
corresponding -dimensional field theories in curved space. The quantum field
theory approach to the quantum-mechanical path-integral, where quantum
fluctuations are not periodic but vanish at the endpoints, yields the correct
answers. We explain these results by a detailed analysis of general coordinate
invariance in both methods. Both approaches can be derived from the same
operator expression and the integrated trace anomalies in both schemes agree.
In the string-inspired method the integrands are not invariant under general
coordinate transformations and one is therefore not permitted to use Riemann
normal coordinates.Comment: LaTeX, 12 pages, 17 figure
Poisson-Lie T-Duality and Supersymmetry
We review aspects of Poisson-Lie T-duality which we explicitly formulate as a
canonical transformation on the world-sheet. Extensions of previous work on
T-duality in relation to supersymmetry are also discussed. (Contribution to the
proceedings of the 30th International Symposium Ahrenshoop on the Theory of
Elementary Particles, Buckow, Germany, 26-31 August 1996)Comment: 12 pages, late
Quantum Wire-on-Well (WoW) Cell With Long Carrier Lifetime for Efficient Carrier Transport
A quantum wire-on-well (WoW) structure, taking advantage of the layer undulation of an In- GaAs/GaAs/GaAsP superlattice grown on a vicinal substrate, was demonstrated to enhance the carrier collection from the confinement levels and extend the carrier lifetime (220 ns) by approximately 4 times as compared with a planar reference superlattice. Strained InGaAs/GaAs/GaAsP superlattices were grown on GaAs substrates under exactly the same condition except for the substrate misorientation (0o- and 6o- off). The growth on a 6o-off substrate induced significant layer undulation as a result of step bunching and non-uniform precursor incorporation between steps and terraces whereas the growth on a substrate without miscut resulted in planar layers. The undulation was the most significant for InGaAs layers, forming periodically aligned InGaAs nanowires on planar wells, a wire-on-well structure. As for the photocurrent corresponding to the sub-bandgap range of GaAs, the light absorption by the WoW was extended to longer wavelengths and weakened as compared with the planar superlattice, and almost the same photocurrent was obtained for both the WoW and the planar superlattice. Open-circuit voltage for the WoW was not affected by the longer-wavelength absorption edge and the same value was obtained for the two structures. Furthermore, the superior carrier collection in the WoW, especially under forward biases, improved fill factor compared with the planer superlattice
Random global coupling induces synchronization and nontrivial collective behavior in networks of chaotic maps
The phenomena of synchronization and nontrivial collective behavior are
studied in a model of coupled chaotic maps with random global coupling. The
mean field of the system is coupled to a fraction of elements randomly chosen
at any given time. It is shown that the reinjection of the mean field to a
fraction of randomly selected elements can induce synchronization and
nontrivial collective behavior in the system. The regions where these
collective states emerge on the space of parameters of the system are
calculated.Comment: 2 pages, 2 figs, accepted in The European Physical Journa
Reduction of Dilute Ising Spin Glasses
The recently proposed reduction method for diluted spin glasses is
investigated in depth. In particular, the Edwards-Anderson model with \pm J and
Gaussian bond disorder on hyper-cubic lattices in d=2, 3, and 4 is studied for
a range of bond dilutions. The results demonstrate the effectiveness of using
bond dilution to elucidate low-temperature properties of Ising spin glasses,
and provide a starting point to enhance the methods used in reduction. Based on
that, a greedy heuristic call ``Dominant Bond Reduction'' is introduced and
explored.Comment: 10 pages, revtex, final version, find related material at
http://www.physics.emory.edu/faculty/boettcher
Duality in Non-Trivially Compactified Heterotic Strings
We study the implications of duality symmetry on the analyticity properties
of the partition function as it depends upon the compactification length. In
order to obtain non-trivial compactifications, we give a physical prescription
to get the Helmholtz free energy for any heterotic string supersymmetric or
not. After proving that the free energy is always invariant under the duality
transformation and getting the zero temperature
theory whose partition function corresponds to the Helmholtz potential, we show
that the self-dual point is a generic singularity
as the Hagedorn one. The main difference between these two critical
compactification radii is that the term producing the singularity at the
self-dual point is finite for any . We see that this behavior at
actually implies a loss of degrees of freedom below that point.Comment: (Preprint No. FTUAM-92/12) 17 page
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