21,462 research outputs found
Multichannel operation of an integrated acousto-optic wavelength routing switch for WDM systems
Polarization independent acousto-optic tunable filters (PIAOTF's) can operate as transparent wavelength-selective crossconnects to route signals in wavelength division multiplexed optical networks. In this paper, a new low power PIAOTF is characterized as a switch in multiwavelength operation, using four equally spaced lightwave signals with wavelengths between 1546 nm and 1558 nm. Interchannel interference due to sidelobe excitation is lower than -11 dB for single wavelength switching and is equal to -6 dB in the extreme case of simultaneous switching of all wavelength channels. Sources of interport and interchannel crosstalk for single and multiple wavelength switching are identified
Constructing Krall-Hahn orthogonal polynomials
Given a sequence of polynomials , an algebra of operators acting in the linear space of polynomials and an operator with , where is any arbitrary eigenvalue,
we construct a new sequence of polynomials by considering a linear
combination of consecutive :
. Using the concept of
-operator, we determine the structure of the sequences
in order that the polynomials are
eigenfunctions of an operator in the algebra . As an application,
from the classical discrete family of Hahn polynomials we construct orthogonal
polynomials which are also eigenfunctions of higher-order difference
operators.Comment: 26 pages. arXiv admin note: text overlap with arXiv:1307.1326,
arXiv:1407.697
Large-scale anisotropy in scalar turbulence
The effect of anisotropy on the statistics of a passive tracer transported by
a turbulent flow is investigated. We show that under broad conditions an
arbitrarily small amount of anisotropy propagates to the large scales where it
eventually dominates the structure of the concentration field. This result is
obtained analytically in the framework of an exactly solvable model and
confirmed by numerical simulations of scalar transport in two-dimensional
turbulence
Localization and chiral symmetry in 2+1 flavor domain wall QCD
We present results for the dependence of the residual mass of domain wall
fermions (DWF) on the size of the fifth dimension and its relation to the
density and localization properties of low-lying eigenvectors of the
corresponding hermitian Wilson Dirac operator relevant to simulations of 2+1
flavor domain wall QCD. Using the DBW2 and Iwasaki gauge actions, we generate
ensembles of configurations with a space-time volume and an
extent of 8 in the fifth dimension for the sea quarks. We demonstrate the
existence of a regime where the degree of locality, the size of chiral symmetry
breaking and the rate of topology change can be acceptable for inverse lattice
spacings GeV.Comment: 59 Pages, 23 figures, 1 MPG linke
Thermodynamics of nano-spheres encapsulated in virus capsids
We investigate the thermodynamics of complexation of functionalized charged
nano-spheres with viral proteins. The physics of this problem is governed by
electrostatic interaction between the proteins and the nano-sphere cores
(screened by salt ions), but also by configurational degrees of freedom of the
charged protein N-tails. We approach the problem by constructing an appropriate
complexation free energy functional. On the basis of both numerical and
analytical studies of this functional we construct the phase diagram for the
assembly which contains the information on the assembled structures that appear
in the thermodynamical equilibrium, depending on the size and surface charge
density of the nano-sphere cores. We show that both the nano-sphere core charge
as well as its radius determine the size of the capsid that forms around the
core.Comment: Submitte
Vector form factor in K_l3 semileptonic decay with two flavors of dynamical domain-wall quarks
We calculate the vector form factor in K \to \pi l \nu semileptonic decays at
zero momentum transfer f_+(0) from numerical simulations of two-flavor QCD on
the lattice. Our simulations are carried out on 16^3 \times 32 at a lattice
spacing of a \simeq 0.12 fm using a combination of the DBW2 gauge and the
domain-wall quark actions, which possesses excellent chiral symmetry even at
finite lattice spacings. The size of fifth dimension is set to L_s=12, which
leads to a residual quark mass of a few MeV. Through a set of double ratios of
correlation functions, the form factor calculated on the lattice is accurately
interpolated to zero momentum transfer, and then is extrapolated to the
physical quark mass. We obtain f_+(0)=0.968(9)(6), where the first error is
statistical and the second is the systematic error due to the chiral
extrapolation. Previous estimates based on a phenomenological model and chiral
perturbation theory are consistent with our result. Combining with an average
of the decay rate from recent experiments, our estimate of f_+(0) leads to the
Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V_{us}|=0.2245(27), which is
consistent with CKM unitarity. These estimates of f_+(0) and |V_{us}| are
subject to systematic uncertainties due to the finite lattice spacing and
quenching of strange quarks, though nice consistency in f_+(0) with previous
lattice calculations suggests that these errors are not large.Comment: 23 pages, 11 figures, 7 tables, RevTeX4; v3: one table added, results
and conclusions unchanged, final version to appear in Phys.Rev.
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