6,670 research outputs found
Simulation of a Hybrid Optical/Radio/Acoustic Extension to IceCube for EeV Neutrino Detection
Astrophysical neutrinos at EeV energies promise to be an interesting
source for astrophysics and particle physics. Detecting the predicted
cosmogenic (``GZK'') neutrinos at 10 - 10 eV would test models of
cosmic ray production at these energies and probe particle physics at 100
TeV center-of-mass energy. While IceCube could detect 1 GZK event per
year, it is necessary to detect 10 or more events per year in order to study
temporal, angular, and spectral distributions. The IceCube observatory may be
able to achieve such event rates with an extension including optical, radio,
and acoustic receivers. We present results from simulating such a hybrid
detector.Comment: 4 pages, 2 figures; to appear in the Proceedings of the 29th ICRC,
Pune, Indi
Let's face the music: A behavioral and electrophysiological exploration of score reading
This experiment was carried out to determine whether reading diatonic violations in a musical score elicits similar endogenous ERP components when hearing such violations in the auditory modality. In the behavioral study, musicians were visually presented with 120 scores of familiar musical pieces, half of which contained a diatonic violation. The score was presented in a measure-by-measure manner. Self-paced reading was significantly delayed for measures containing a violation, indicating that sight reading a violation requires additional effort. In the ERP study, the musical phrases were presented in a “RSVP”-like manner. We predicted that diatonic violations would elicit a late positive component. However, the ERP associated with the measure where a violation was presented showed a negativity instead. The negativity started around 100 ms and lasted for the entire recording period. This long-lasting negativity encompassed at least three distinct effects that were possibly related to violation detection, working memory processing, and a further integration/interpretation process
Relativistic Magnetic Monopole Flux Constraints from RICE
We report an upper limit on the flux of relativistic monopoles based on the
non-observation of in-ice showers by the Radio Ice Cherenkov Experiment (RICE)
at the South Pole. We obtain a 95% C.L. limit of order 10^{-18}/(cm^2-s-sr) for
intermediate mass monopoles of 10^7<gamma<10^{12} at the anticipated energy
E=10^{16} GeV. This bound is over an order of magnitude stronger than all
previously published experimental limits for this range of boost parameters
gamma, and exceeds two orders of magnitude improvement over most of the range.
We review the physics of radio detection, describe a Monte Carlo simulation
including continuous and stochastic energy losses, and compare to previous
experimental limits.Comment: 16 pages, 6 figures. Accepted for publication in Phys. Rev. D. Minor
revisions, including expanded discussion of monopole energy uncertaint
Charm meson resonances in decays
Motivated by recent experimental results we reconsider semileptonic decays within a model which combines heavy quark symmetry and
properties of the chiral Lagrangian. We include excited charm meson states,
some of them recently observed, in our Lagrangian and determine their impact on
the charm meson semileptonic form factors. We find that the inclusion of
excited charm meson states in the model leads to a rather good agreement with
the experimental results on the shape of the form factor. We
also calculate branching ratios for all decays.Comment: 9 pages, 4 figures; minor corrections, added some discussion, version
as publishe
Superlattice Patterns in Surface Waves
We report novel superlattice wave patterns at the interface of a fluid layer
driven vertically. These patterns are described most naturally in terms of two
interacting hexagonal sublattices. Two frequency forcing at very large aspect
ratio is utilized in this work. A superlattice pattern ("superlattice-I")
consisting of two hexagonal lattices oriented at a relative angle of 22^o is
obtained with a 6:7 ratio of forcing frequencies. Several theoretical
approaches that may be useful in understanding this pattern have been proposed.
In another example, the waves are fully described by two superimposed hexagonal
lattices with a wavelength ratio of sqrt(3), oriented at a relative angle of
30^o. The time dependence of this "superlattice-II" wave pattern is unusual.
The instantaneous patterns reveal a time-periodic stripe modulation that breaks
the 6-fold symmetry at any instant, but the stripes are absent in the time
average. The instantaneous patterns are not simply amplitude modulations of the
primary standing wave. A transition from the superlattice-II state to a 12-fold
quasi-crystalline pattern is observed by changing the relative phase of the two
forcing frequencies. Phase diagrams of the observed patterns (including
superlattices, quasicrystalline patterns, ordinary hexagons, and squares) are
obtained as a function of the amplitudes and relative phases of the driving
accelerations.Comment: 15 pages, 14 figures (gif), to appear in Physica
Nonlinear Competition Between Small and Large Hexagonal Patterns
Recent experiments by Kudrolli, Pier and Gollub on surface waves,
parametrically excited by two-frequency forcing, show a transition from a small
hexagonal standing wave pattern to a triangular ``superlattice'' pattern. We
show that generically the hexagons and the superlattice wave patterns bifurcate
simultaneously from the flat surface state as the forcing amplitude is
increased, and that the experimentally-observed transition can be described by
considering a low-dimensional bifurcation problem. A number of predictions come
out of this general analysis.Comment: 4 pages, RevTex, revised, to appear in Phys. Rev. Let
Strain gradient crystal plasticity with evolving length scale: Application to voided irradiated materials
International audienceA micromorphic crystal plasticity model is used to simulate slip band localization in single crystalsunder simple shear at finite deformations. Closed form analytical solutions are derived for singleslip in the case of positive, zero and negative strain hardening. Linear negative strain hardening,i.e. linear softening, leads to a constant localization slip band width, while non linear softening andsaturating behaviour results in an increasing band width. An enhanced model is therefore proposed inorder to maintain a bounded localization slip band width when considering an exponential softeningbehaviour. Analytical solutions are used to validate finite element computation of the same boundaryvalue problems. The enhanced micromorphic crystal plasticity model is then applied to predict theinteraction between localized slip bands and voids encountered in voided irradiated materials. For thatpurpose, periodic porous unit cells are loaded in simple shear with a strain gradient crystal plasticitymatrix material. The finite element simulation results show that, for a given void volume fraction, thelarger the voids, the wider the localization band. However, for a given void size, the larger the voidvolume fraction, the narrower the localization band. In addition a satisfactory qualitative agreementof the rotation and elongation of the voids with the experimental observations made in irradiatedmaterials is observed, where small voids are shown to remain ellipsoidal for larger shear strains thanlarge voids which deform into peanut-like shapes
D_s spectrum and leptonic decays with Fermilab heavy quarks and improved staggered light quarks
We present preliminary results for the D_s meson spectrum and decay constants
in unquenched lattice QCD. Simulations are carried out with 2+1 dynamical
quarks using gauge configurations generated by the MILC collaboration. We use
the ``asqtad'' a^2 improved staggered action for the light quarks, and the
clover heavy quark action with the Fermilab interpretation. We compare our
spectrum results with the newly discovered 0+ and 1+ states in the D_s system.Comment: 3pp. Presented at 21st International Symposium on Lattice Field
Theory (LATTICE 2003), Tsukuba, Ibaraki, Japan, 15-19 Jul 200
Puzzles of excited charm meson masses
We attempt a comprehensive analysis of the low lying charm meson states which
present several puzzles, including the poor determination of masses of several
non-strange excited mesons. We use the well-determined masses of the ground
states and the strange first excited states to `predict' the mass of the
non-strange first excited state in the framework of heavy hadron chiral
perturbation theory, an approach that is complementary to the well-known
analysis of Mehen and Springer. This approach points to values for the masses
of these states that are smaller than the experimental determinations. We
provide a critical assessment of these mass measurements and point out the need
for new experimental information.Comment: 9 pages, 1 figure, accepted for publication in Physics Letters
Tactics for Reasoning modulo AC in Coq
We present a set of tools for rewriting modulo associativity and
commutativity (AC) in Coq, solving a long-standing practical problem. We use
two building blocks: first, an extensible reflexive decision procedure for
equality modulo AC; second, an OCaml plug-in for pattern matching modulo AC. We
handle associative only operations, neutral elements, uninterpreted function
symbols, and user-defined equivalence relations. By relying on type-classes for
the reification phase, we can infer these properties automatically, so that
end-users do not need to specify which operation is A or AC, or which constant
is a neutral element.Comment: 16
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