21,618 research outputs found
On Multiple Zeta Values of Even Arguments
For k <= n, let E(2n,k) be the sum of all multiple zeta values with even
arguments whose weight is 2n and whose depth is k. Of course E(2n,1) is the
value of the Riemann zeta function at 2n, and it is well known that E(2n,2) =
(3/4)E(2n,1). Recently Z. Shen and T. Cai gave formulas for E(2n,3) and
E(2n,4). We give two formulas form E(2n,k), both valid for arbitrary k <=n, one
of which generalizes the Shen-Cai results; by comparing the two we obtain a
Bernoulli-number identity. We also give explicit generating functions for the
numbers E(2n,k) and for the analogous numbers E*(2n,k) defined using multiple
zeta-star values of even arguments.Comment: DESY number added; misprints fixed; reference added. Second revision
(2016): New result on multiple zeta-star values adde
A new code for parameter estimation in searches for gravitational waves from known pulsars
We describe the consistency testing of a new code for gravitational wave
signal parameter estimation in known pulsar searches. The code uses an
implementation of nested sampling to explore the likelihood volume. Using fake
signals and simulated noise we compare this to a previous code that calculated
the signal parameter posterior distributions on both a grid and using a crude
Markov chain Monte Carlo (MCMC) method. We define a new parameterisation of two
orientation angles of neutron stars used in the signal model (the initial phase
and polarisation angle), which breaks a degeneracy between them and allows more
efficient exploration of those parameters. Finally, we briefly describe
potential areas for further study and the uses of this code in the future.Comment: Accepted for proceedings of Amaldi 9 meetin
Nanoscale electron-beam-driven metamaterial light sources
Free-standing and fiber-coupled photonic metamaterials act as nanoscale, free-electron-driven, tuneable light sources: emission occurs at wavelengths determined by structural geometry in response to electron-beam excitation of metamaterial resonant plasmonic modes
Valley-Hall Kink and Edge States in Multilayer Graphene
We report on a theoretical study of one-dimensional (1D) states localized at
few-layer graphene system ribbon edges, and at interfaces between few-layer
graphene systems with different valley Hall conductivities. These 1D states are
topologically protected when valley mixing is neglected. We address the
influence on their properties of stacking arrangement, interface structure, and
external electric field perpendicular to the layers. We find that 1D states are
generally absent at multilayer ribbon armchair direction edges, but present
irrespective of crystallographic orientation at any internal valley-Hall
interface of an ABC stacked multilayer.Comment: 5 pages, 3 figure
Comparison of methods for estimating continuous distributions of relaxation times
The nonparametric estimation of the distribution of relaxation times approach
is not as frequently used in the analysis of dispersed response of dielectric
or conductive materials as are other immittance data analysis methods based on
parametric curve fitting techniques. Nevertheless, such distributions can yield
important information about the physical processes present in measured
material. In this letter, we apply two quite different numerical inversion
methods to estimate the distribution of relaxation times for glassy \lila\
dielectric frequency-response data at 225 \kelvin. Both methods yield unique
distributions that agree very closely with the actual exact one accurately
calculated from the corrected bulk-dispersion Kohlrausch model established
independently by means of parametric data fit using the corrected modulus
formalism method. The obtained distributions are also greatly superior to those
estimated using approximate functions equations given in the literature.Comment: 4 pages and 4 figure
Chiral boundary conditions for Quantum Hall systems
A quantum mesoscopic billiard can be viewed as a bounded electronic system
due to some external confining potential. Since, in general, we do not have
access to the exact expression of this potential, it is usually replaced by a
set of boundary conditions. We discuss, in addition to the standard Dirichlet
choice, the other possibilities of boundary conditions which might correspond
to more complicated physical situations including the effects of many body
interactions or of a strong magnetic field. The latter case is examined more in
details using a new kind of chiral boundary conditions for which it is shown
that in the Quantum Hall regime, bulk and edge characteristics can be described
in a unified way.Comment: 16 pages, LaTeX, 2 figures, to be published in the Proceedings of the
Minerva workshop on Mesoscopics, Fractals and Neural Networks, Phil. Mag.
(1997
A Note on the Pfaffian Integration Theorem
Two alternative, fairly compact proofs are presented of the Pfaffian
integration theorem that is surfaced in the recent studies of spectral
properties of Ginibre's Orthogonal Ensemble. The first proof is based on a
concept of the Fredholm Pfaffian; the second proof is purely linear-algebraic.Comment: 8 pages; published versio
The Influence of Formulation, Buffering, pH and Divalent Cations on the Activity of Endothall on Hydrilla.
Endothall has been used as an aquatic herbicide for more
than 40 years and provides very effective weed control of
many weeds. Early research regarding the mechanism-of-action
of endothall contradicts the symptomology normally associated
with the product. Recent studies suggest endothall
is a respiratory toxin but the mechanism-of-action remains
unknown. To further elucidate the activity of endothall, several
endothall formulations were evaluated for their effects
on ion leakage, oxygen consumption and photosynthetic oxygen
evolution from hydrilla shoot tips. The influence of pH,
buffering and divalent cations was also evaluated. (PDF contains 6 pages.
Buffalo National River Ecosystems - Part II
The priorities were established for the Buffalo National River Ecosystem Studies through meetings and correspondence with Mr. Roland Wauer and other personnel of the Office of Natural Sciences, Southwest Region of the National Park Service. These priorities were set forth in the appendix of contract no. CX 700050443 dated May 21, 1975
Mechanical Evidence of the Orbital Angular Momentum to Energy Ratio of Vortex Beams
We measure, in a single experiment, both the radiation pressure and the torque due to a wide variety of
propagating acoustic vortex beams. The results validate, for the first time directly, the theoretically
predicted ratio of the orbital angular momentum to linear momentum in a propagating beam. We
experimentally determine this ratio using simultaneous measurements of both the levitation force and
the torque on an acoustic absorber exerted by a broad range of helical ultrasonic beams produced by a
1000-element matrix transducer array. In general, beams with helical phase fronts have been shown to
contain orbital angular momentum as the result of the azimuthal component of the Poynting vector around
the propagation axis. Theory predicts that for both optical and acoustic helical beams the ratio of the
angular momentum current of the beam to the power should be given by the ratio of the beam’s
topological charge to its angular frequency. This direct experimental observation that the ratio of the
torque to power does convincingly match the expected value (given by the topological charge to angular
frequency ratio of the beam) is a fundamental result
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