8,954 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
The fraction of Bose-Einstein condensed triplons in TlCuCl3 from magnetization M(T,H)-data
In this study we calculate the fraction of condensed magnetic quasiparticles
of TlCuCl3 from magnetization M(T,H)-data. It is independent of the direction
of the magnetic field and slightly decreases with increasing magnetic field.Comment: 8 pages, 10 figure
Finite-Size Effects in Lattice QCD with Dynamical Wilson Fermions
As computing resources are limited, choosing the parameters for a full
Lattice QCD simulation always amounts to a compromise between the competing
objectives of a lattice spacing as small, quarks as light, and a volume as
large as possible. Aiming to push unquenched simulations with the Wilson action
towards the computationally expensive regime of small quark masses we address
the question whether one can possibly save computing time by extrapolating
results from small lattices to the infinite volume, prior to the usual chiral
and continuum extrapolations. In the present work the systematic volume
dependence of simulated pion and nucleon masses is investigated and compared
with a long-standing analytic formula by Luescher and with results from Chiral
Perturbation Theory. We analyze data from Hybrid Monte Carlo simulations with
the standard (unimproved) two-flavor Wilson action at two different lattice
spacings of a=0.08fm and 0.13fm. The quark masses considered correspond to
approximately 85 and 50% (at the smaller a) and 36% (at the larger a) of the
strange quark mass. At each quark mass we study at least three different
lattices with L/a=10 to 24 sites in the spatial directions (L=0.85-2.08fm).Comment: 21 pages, 20 figures, REVTeX 4; v2: caption of Fig.7 corrected, one
reference adde
Pressure-induced Superconductivity in CaLi2
A search for superconductivity has been carried out on the hexagonal
polymorph of Laves-phase CaLi2, a compound for which Feng, Ashcroft, and
Hoffmann predict highly anomalous behavior under pressure. No superconductivity
is observed above 1.10 K at ambient pressure. However, high-pressure ac
susceptibility and electrical resistivity studies to 81 GPa reveal bulk
superconductivity in CaLi2 at temperatures as high as 13 K. The normal-state
resistivity shows a dramatic increase with pressure.Comment: bulk superconductivity in CaLi2 now confirme
String breaking with dynamical Wilson fermions
We present results of our ongoing determination of string breaking in full
QCD with N_f=2 Wilson fermions. Our investigation of the fission of the static
quark-antiquark string into a static-light meson-antimeson system is based on
dynamical configurations of size 24^3 x 40 produced by the TxL collaboration.
Combining various optimization methods we determine the matrix elements of the
two-by-two system with so far unprecedented accuracy. The all-to-all light
quark propagators occurring in the transition element are computed from
eigenmodes of the Hermitian Wilson-Dirac matrix complemented by stochastic
estimates in the orthogonal subspace. We observe a clear signature for
level-splitting between ground state and excited potential. Thus, for the first
time, string breaking induced by sea quarks is observed in a simulation of
4-dimensional lattice-QCD.Comment: 3 pages, 3 figures, contribution to Lattice 200
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
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