6,282 research outputs found
The Static Quark-Antiquark Potential: A ``Classical'' Experiment On The Connection Machine CM-2
We describe the Wuppertal university pilot project in applied parallel
computing. We report on a comprehensive high statistics determination of the
static quark-antiquark potential and related quantities from quenched quantum
chromodynamics. New data for the string tension and the plaquette action for
the region 5.5 < beta < 6.8 is presented.Comment: (Talk K. Schilling), 11 pages, postscript (\approx 250K
Weak Decays of Heavy-Light Mesons on the Lattice: Semi-Leptonic Formfactors
We report results (on an intermediate statistics sample) of a study of weak
semi-leptonic formfactors of and decays, addressing the uncertainties
from mass extrapolations to chiral and to heavy quarks. Moreover, we present a
nonperturbative test to the LMK current renormalization scheme for vector
current {\it transition} matrix elements and find remarkable agreement.Comment: 13 pages, uuencoded, updated table
Compact QED under scrutiny: it's first order
We report new results from our finite size scaling analysis of 4d compact
pure U(1) gauge theory with Wilson action. Investigating several cumulants of
the plaquette energy within the Borgs-Kotecky finite size scaling scheme we
find strong evidence for a first-order phase transition and present a high
precision value for the critical coupling in the thermodynamic limit.Comment: Lattice2002(Spin
Colloidal glass transition: Beyond mode-coupling theory
A new theory for dynamics of concentrated colloidal suspensions and the
colloidal glass transition is proposed. The starting point is the memory
function representation of the density correlation function. The memory
function can be expressed in terms of a time-dependent pair-density correlation
function. An exact, formal equation of motion for this function is derived and
a factorization approximation is applied to its evolution operator. In this way
a closed set of equations for the density correlation function and the memory
function is obtained. The theory predicts an ergodicity breaking transition
similar to that predicted by the mode-coupling theory, but at a higher density.Comment: to be published in PR
How to compute Green's Functions for entire Mass Trajectories within Krylov Solvers
The availability of efficient Krylov subspace solvers play a vital role for
the solution of a variety of numerical problems in computational science. Here
we consider lattice field theory. We present a new general numerical method to
compute many Green's functions for complex non-singular matrices within one
iteration process. Our procedure applies to matrices of structure , with
proportional to the unit matrix, and can be integrated within any Krylov
subspace solver. We can compute the derivatives of the solution
vector with respect to the parameter and construct the Taylor expansion
of around . We demonstrate the advantages of our method using a minimal
residual solver. Here the procedure requires intermediate vector for each
Green's function to compute. As real life example, we determine a mass
trajectory of the Wilson fermion matrix for lattice QCD. Here we find that we
can obtain Green's functions at all masses at the price of one
inversion at mass .Comment: 11 pages, 2 eps-figures, needs epsf.st
Frequency domain interferometer simulation with higher-order spatial modes
FINESSE is a software simulation that allows to compute the optical
properties of laser interferometers as they are used by the interferometric
gravitational-wave detectors today. It provides a fast and versatile tool which
has proven to be very useful during the design and the commissioning of
gravitational-wave detectors. The basic algorithm of FINESSE numerically
computes the light amplitudes inside an interferometer using Hermite-Gauss
modes in the frequency domain. In addition, FINESSE provides a number of
commands to easily generate and plot the most common signals like, for example,
power enhancement, error or control signals, transfer functions and
shot-noise-limited sensitivities.
Among the various simulation tools available to the gravitational wave
community today, FINESSE is the most advanced general optical simulation that
uses the frequency domain. It has been designed to allow general analysis of
user defined optical setups while being easy to install and easy to use.Comment: Added an example for the application of the simulation during the
commisioning of the GEO 600 gravitational-wave detecto
Semileptonic Decays of D and B Mesons
We report results of our ongoing investigation concerning semileptonic decays
of heavy pseudoscalar mesons into pseudoscalar and vector mesons. Particular
attention is paid to uncertainties in the and the heavy quark mass
dependence of formfactors. Moreover we present a non-perturbative test to the
LMK current renormalization scheme for vector current transition matrix
elements and find remarkable agreement.Comment: 3 pages, uuencoded, contribution to Lat 9
Multicanonical hybrid Monte Carlo for compact QED
We demonstrate that substantial progress can be achieved in the study of the phase structure of 4-dimensional compact QED by a joint use of hybrid Monte Carlo and multicanonical algorithms, through an efficient parallel implementation. This is borne out by the observation of considerable speedup of tunnelling between the metastable states, close to the phase transition, on the Wilson line. Our approach leads to a general parallelization scheme for the efficient stochastic sampling of systems where (a part of) the Hamiltonian involves the total action or energy in each update step
Semileptonic Decays of Heavy Mesons: A Status Report
We present intermediate results on our ongoing investigation concerning
semileptonic decays of heavy pseudoscalar mesons into pseudoscalar and vector
mesons. The corresponding formfactors are evaluated at several momenta and
appropriate combinations of four light and four heavy quarks, which are chosen
to allow for an extrapolation into the B Meson region. In order to obtain clear
groundstate signals we apply gauge invariant ``Wuppertal'' smearing to the
quarks. The analysis is based on 32 quenched gauge configurations of size at , with Wilson fermions.Comment: 3 pages, uuencoded, contribution to Lat 9
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