2,492 research outputs found
Chiral Lagrangian Parameters for Scalar and Pseudoscalar Mesons
The results of a high-statistics study of scalar and pseudoscalar meson
propagators in quenched lattice QCD are presented. For two values of lattice
spacing, ( fm) and 5.9 ( fm), we
probe the light quark mass region using clover improved Wilson fermions with
the MQA pole-shifting ansatz to treat the exceptional configuration problem.
The quenched chiral loop parameters and are determined
from a study of the pseudoscalar hairpin correlator. From a global fit to the
meson correlators, estimates are obtained for the relevant chiral Lagrangian
parameters, including the Leutwyler parameters and . Using the
parameters obtained from the singlet and nonsinglet pseudoscalar correlators,
the quenched chiral loop effect in the nonsinglet scalar meson correlator is
studied. By removing this QCL effect from the lattice correlator, we obtain the
mass and decay constant of the ground state scalar, isovector meson .Comment: 36 pages, 12 figures, LaTe
Quenched Chiral Artifacts for Wilson-Dirac Fermions
We examine artifacts associated with the chiral symmetry breaking induced
through the use of Wilson-Dirac fermions in lattice Monte Carlo computations.
For light quark masses, the conventional quenched theory can not be defined
using direct Monte Carlo methods due to the existence of nonintegrable poles in
physical quantities. These poles are associated with the real eigenvalue
spectrum of the Wilson-Dirac operator. We show how this singularity structure
can be observed in the analysis of both QED in two dimensions and QCD in four
dimensions.Comment: 32 pages (Latex) including 13 figures (EPS
General relativistic gravitational field of a rigidly rotating disk of dust: Solution in terms of ultraelliptic functions
In a recent paper we presented analytic expressions for the axis potential,
the disk metric, and the surface mass density of the global solution to
Einstein's field equations describing a rigidly rotating disk of dust. Here we
add the complete solution in terms of ultraelliptic functions and quadratures.Comment: 5 pages, published in 1995 [Phys. Rev. Lett. 75 (1995) 3046
Glueball calculations in large-N_c gauge theory
We use the light-front Hamiltonian of transverse lattice gauge theory to
compute from first principles the glueball spectrum and light-front
wavefunctions in the leading order of the 1/N_c colour expansion. We find
0^{++}, 2^{++}, and 1^{+-} glueballs having masses consistent with N_c=3 data
available from Euclidean lattice path integral methods. The wavefunctions
exhibit a light-front constituent gluon structure.Comment: 4 pages, 2 figures, uses macro boxedeps.tex, minor corrections in
revised versio
Quenched divergences in the deconfined phase of SU(2) gauge theory
The spectrum of the overlap Dirac operator in the deconfined phase of
quenched gauge theory is known to have three parts: exact zeros arising from
topology, small nonzero eigenvalues that result in a non-zero chiral
condensate, and the dense bulk of the spectrum, which is separated from the
small eigenvalues by a gap. In this paper, we focus on the small nonzero
eigenvalues in an SU(2) gauge field background at and . This
low-lying spectrum is computed on four different spatial lattices (,
, , and ). As the volume increases, the small eigenvalues
become increasingly concentrated near zero in such a way as to strongly suggest
that the infinite volume condensate diverges.Comment: 12 pages, 3 figures, version to appear in Physical Review
Light Hadron Spectrum in Quenched Lattice QCD with Staggered Quarks
Without chiral extrapolation, we achieved a realistic nucleon to (\rho)-meson
mass ratio of (m_N/m_\rho = 1.23 \pm 0.04 ({\rm statistical}) \pm 0.02 ({\rm
systematic})) in our quenched lattice QCD numerical calculation with staggered
quarks. The systematic error is mostly from finite-volume effect and the
finite-spacing effect is negligible. The flavor symmetry breaking in the pion
and (\rho) meson is no longer visible. The lattice cutoff is set at 3.63 (\pm)
0.06 GeV, the spatial lattice volume is (2.59 (\pm) 0.05 fm)(^3), and bare
quarks mass as low as 4.5 MeV are used. Possible quenched chiral effects in
hadron mass are discussed.Comment: 5 pages and 5 figures, use revtex
Boundary value problems for the stationary axisymmetric Einstein equations: a disk rotating around a black hole
We solve a class of boundary value problems for the stationary axisymmetric
Einstein equations corresponding to a disk of dust rotating uniformly around a
central black hole. The solutions are given explicitly in terms of theta
functions on a family of hyperelliptic Riemann surfaces of genus 4. In the
absence of a disk, they reduce to the Kerr black hole. In the absence of a
black hole, they reduce to the Neugebauer-Meinel disk.Comment: 46 page
The Post-Newtonian Approximation of the Rigidly Rotating Disc of Dust to Arbitrary Order
Using the analytic, global solution for the rigidly rotating disc of dust as
a starting point, an iteration scheme is presented for the calculation of an
arbitrary coefficient in the post-Newtonian (PN) approximation of this
solution. The coefficients were explicitly calculated up to the 12th PN level
and are listed in this paper up to the 4th PN level. The convergence of the
series is discussed and the approximation is found to be reliable even in
highly relativistic cases. Finally, the ergospheres are calculated at
increasing orders of the approximation and for increasingly relativistic
situations.Comment: 19 pages, 2 tables, 4 figures Accepted for publication in Phys. Rev.
The Extreme Kerr Throat Geometry: A Vacuum Analog of AdS_2 x S^2
We study the near horizon limit of a four dimensional extreme rotating black
hole. The limiting metric is a completely nonsingular vacuum solution, with an
enhanced symmetry group SL(2,R) x U(1). We show that many of the properties of
this solution are similar to the AdS_2 x S^2 geometry arising in the near
horizon limit of extreme charged black holes. In particular, the boundary at
infinity is a timelike surface. This suggests the possibility of a dual quantum
mechanical description. A five dimensional generalization is also discussed.Comment: 21 page
Bounds on Bess Model Parameters from Vector-Boson Production in e+e- Collisions
The BESS model is the Higgs-less alternative to the standard model of
electroweak interaction, based on nonlinearly realized spontaneous symmetry
breaking. Since it is nonrenormalizable, new couplings (not existing in the SM)
are induced at each loop order. On the basis of the one loop induced
vector-boson self-couplings we study the two- and three-vector-boson-production
processes in collisions at , the expected energy of
the next linear collider (NLC). Assuming that NLC results will agree
with the SM predictions within given accuracy we identify the bounds for the
free parameters of the BESS model.Comment: December 1992, 8 pages LaTeX, 6 figures (not included but available
on request), BI-TP 92/59, LMU-92/1
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