744 research outputs found
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
Conserved structural and functional properties of D-domain containing redox-active and -inactive protein disulfide isomerase-related protein chaperones
Light Spectrum and Decay Constants in Full QCD with Wilson Fermions
We present results from an analysis of the light spectrum and the decay
constants f_{\pi} and f_V^{-1} in Full QCD with n_f=2 Wilson fermions at a
coupling of beta=5.6 on a 16^3x32 lattice.Comment: 3 pages, LaTeX with 4 eps figures, Talk presented at
LATTICE96(spectrum
Hyper-systolic processing on APE100\/Quadrics: n-loop computations
We investigate the performance gains from hyper-systolic implementations of n^2-loop problems on the massively parallel computer Quadrics, exploiting its 3-dimensional interprocessor connectivity. For illustration we study the communication aspects of an exact molecular dynamics simulation of n particles with Coulomb (or gravitational) interactions. We compare the interprocessor communication costs of the standard-systolic and the hyper-systolic approaches for various granularities. We predict gain factors as large as 3 on the Q4 and 8 on the QH4 and measure actual performances on these machine configurations. We conclude that it appears feasile to investigate the thermodynamics of a full gravitating n-body problem with O(10000) particles using the new method on a QH4 system
Scanning the Topological Sectors of the QCD Vacuum with Hybrid Monte Carlo
We address a long standing issue and determine the decorrelation efficiency
of the Hybrid Monte Carlo algorithm (HMC), for full QCD with Wilson fermions,
with respect to vacuum topology. On the basis of five state-of-the art QCD
vacuum field ensembles (with 3000 to 5000 trajectories each and
m_pi/m_rho-ratios in the regime >0.56, for two sea quark flavours) we are able
to establish, for the first time, that HMC provides sufficient tunneling
between the different topological sectors of QCD. This will have an important
bearing on the prospect to determine, by lattice techniques, the topological
susceptibility of the vacuum, and topology sensitive quantities like the spin
content of the proton, or the eta' mass.Comment: 5 pages, 4 eps-figure
Towards the glueball spectrum of full QCD
We present first results on masses of the scalar and tensor glueballs as well
as of the torelon from simulations of QCD with two light flavours of Wilson
fermions. The gauge configurations of extent 16^3*32 at beta = 5.6 and kappa =
0.156, 0.157 and 0.1575 have been generated as part of the SESAM collaboration
programme. The present lattice resolutions correspond to 1/a = 2.0-2.3 GeV and
ratios m(pi)/m(rho) = 0.83, 0.76 and 0.71, respectively. Studies on larger
lattice volumes and closer to the chiral limit are in progress.Comment: 4 pages, LaTeX, espcrc2 and epsf styles required, 4 epsf figures,
poster presented by G. Bali at Lattice '9
Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: comparison of different models
Differential spectra of coherent photon bremsstrahlung in relativistic heavy
ion collisions are calculated within various schematic models of the
projectile-target stopping. Two versions of the degradation length model, based
on a phenomenological deceleration law, are considered. The simple shock wave
model is studied analytically. The predictions of these models agree in the
soft photon limit, where the spectrum is determined only by the final velocity
distribution of charged particles. The results of these models in the case of
central Au+Au collisions at various bombarding energies are compared with the
predictions of the microscopic transport model UrQMD. It is shown that at the
AGS energy the coherent photon bremsstrahlung exceeds the photon yield from
-decays at photon energies \omega\loo 50 MeV.Comment: 23 pages RevTeX, 9 eps Figure
- âŠ