536 research outputs found
Potentials between heavy-light mesons from lattice and inverse scattering theory
We extend our investigation of heavy-light meson-meson interactions to a
system consisting of a heavy-light meson and the corresponding antiparticle. An
effective potential is obtained from meson-antimeson Green-functions computed
in a quenched simulation with staggered fermions. Comparisons with a simulation
using an tree-level and tadpole improved gauge action and a full QCD
simulation show that lattice discretization errors and dynamical quarks have no
drastic influence. Calculations from inverse scattering theory propose a
similar shape for potentials.Comment: 3 pages, 5 EPS figures, Poster presented at "Lattice'97", to appear
in the proceeding
Analytic solutions of the Madelung equation
We present analytic self-similar solutions for the one, two and three
dimensional Madelung hydrodynamical equation for a free particle. There is a
direct connection between the zeros of the Madelung fluid density and the
magnitude of the quantum potential.Comment: 10 pages, 3 figure
Two-body spectra of pseudoscalar mesons with an --improved lattice action using Wilson fermions
We extend our calculations with the second-order tree-level and tadpole
improved next-nearest-neighbor action to meson-meson systems. Correlation
matrices built from interpolating fields representing two pseudoscalar mesons
(pion-pion) with relative momenta p are diagonalized, and the mass spectrum is
extracted. Link variable fuzzing and operator smearing at both sinks and
sources is employed. Calculations are presented for two values of the hopping
parameter. The spectrum is used to discuss the residual interaction in the
meson-meson system.Comment: 3 pages, 4 EPS figures, Poster presented at "Lattice'97", to appear
in the proceeding
Spectral properties of a two-orbital Anderson impurity model across a non-Fermi liquid fixed point
We study by NRG the spectral properties of a two-orbital Anderson impurity
model in the presence of an exchange splitting which follows either regular or
inverted Hund's rules. The phase diagram contains a non-Fermi liquid fixed
point separating a screened phase, where conventional Kondo effect occurs, from
an unscreened one, where the exchange-splitting takes care of quenching the
impurity degrees of freedom. On the Kondo screened side close to this fixed
point the impurity density of states shows a narrow Kondo-peak on top of a
broader resonance. This narrow peak transforms in the unscreened phase into a
narrow pseudo-gap inside the broad resonance. Right at the fixed point only the
latter survives. The fixed point is therefore identified by a jump of the
density of states at the chemical potential. We also show that particle-hole
perturbations which simply shift the orbital energies do not wash out the fixed
point, unlike those perturbations which hybridize the two orbitals.
Consequently the density-of-state jump at the chemical potential remains finite
even away from particle-hole symmetry, and the pseudo-gap stays pinned at the
chemical potential, although it is partially filled in. We also discuss the
relevance of these results for lattice models which map onto this Anderson
impurity model in the limit of large lattice-coordination. Upon approaching the
Mott metal-insulator transition, these lattice models necessarily enter a
region with a local criticality which reflects the impurity non-Fermi liquid
fixed point. However, unlike the impurity, the lattice can get rid of the
single-impurity fixed-point instability by spontaneously developing
bulk-coherent symmetry-broken phases, which we identify for different lattice
models.Comment: 43 pages, 11 figures. Minor corrections in the Appendi
Coupled-Cluster Theory Revisited. Part II: Analysis of the single-reference Coupled-Cluster equations
In a series of two articles, we propose a comprehensive mathematical
framework for Coupled-Cluster-type methods. In this second part, we analyze the
nonlinear equations of the single-reference Coupled-Cluster method using
topological degree theory. We establish existence results and qualitative
information about the solutions of these equations that also sheds light on the
numerically observed behavior. In particular, we compute the topological index
of the zeros of the single-reference Coupled-Cluster mapping. For the truncated
Coupled-Cluster method, we derive an energy error bound for approximate
eigenstates of the Schrodinger equation.Comment: Published in: ESAIM: M2AN Volume 57, Number 2, March-April 2023,
Pages 545-58
Selectivity of metal alloy catalysts in the hydrogenolysis of 2-methyloxacycloalkanes under pressure
Meson-meson interactions -- from static to dynamic valence quarks
A method for the extraction of an effective meson-meson potential from Green
functions, which can be obtained from a lattice simulation, is presented.
Simulations are carried out for compact QED and QCD in four dimensions using
the quenched approximation and the hopping parameter expansion. In a further
study, a heavy-light meson is considered employing a conjugate gradient
algorithm for the light propagators. Due to the Pauli exclusion principle, the
results for QED indicate the existence of a hard core, but for QCD there is
strong attraction at small meson distances.Comment: 4 pages, uuencoded gziped postscript file, contribution to
LATTICE'95, Melbourne, Australia (list of authors completed
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