47,663 research outputs found
Recent results using all-point quark propagators
Pseudofermion methods for extracting all-point quark propagators are
reviewed, with special emphasis on techniques for reducing or eliminating
autocorrelations induced by low eigenmodes of the quark Dirac operator. Recent
applications, including high statistics evaluations of hadronic current
correlators and the pion form factor, are also described.Comment: LateX, 3 pages, 6 eps figures, Lattice2002(algor), corrected some
typo
Unquenched Studies Using the Truncated Determinant Algorithm
A truncated determinant algorithm is used to study the physical effects of
the quark eigenmodes associated with eigenvalues below 420 MeV. This initial
high statistics study focuses on coarse () lattices (with O()
improved gauge action), light internal quark masses and large physical volumes.
Three features of full QCD are examined: topological charge distributions,
string breaking as observed in the static energy and the eta prime mass.Comment: Lattice2001(confinement); 3pgs(Latex), 4figs.(ps
Physical Effects of Infrared Quark Eigenmodes in LQCD
A truncated determinant algorithm is used to study the physical effects of
the quark eigenmodes associated with eigenvalues below 400 MeV. This initial
study focuses on coarse lattices (with O(a^2) improved gauge action), light
internal quark masses and large physical volumes. Four bellwether full QCD
processes are discussed: topological charge distributions, the eta prime
propagator, string breaking as observed in the static energy and the rho decay
into two pions.Comment: LATTICE99(Confinement); 3pgs(Latex), 4figs.(eps
Optical signatures of molecular particles via mass-selected cluster spectroscopy
A new molecular beam apparatus was developed to study optical absorption in cold (less than 100 K) atomic clusters and complexes produced by their condensation with simple molecular gases. In this instrument, ionized clusters produced in a laser vaporization nozzle source are mass selected and studied with photodissociation spectroscopy at visible and ultraviolet wavelengths. This new approach can be applied to synthesize and characterize numerous particulates and weakly bound complexes expected in planetary atmospheres and in comets
Globular Cluster Luminosity Functions and the Hubble Constant from WFPC2 Imaging: Galaxies in the Coma I Cloud
The membership of some galaxies in the nearby (d ~ 12 Mpc) Coma I cloud is
uncertain. Here we present globular cluster luminosity functions (GCLFs) from
the HST for two bright ellipticals which may belong to this group. After
fitting the GCLF, we find a turnover magnitude of m_V^0 = 23.23 +/- 0.11 for
NGC 4278 and m_V^0 = 23.07 +/- 0.13 for NGC 4494. Our limiting magnitude is
about two magnitudes fainter than these values, making this data among the most
complete GCLFs published to date. The fitted GCLF dispersions (~ 1.1 mag.) are
somewhat smaller than typical values for other ellipticals. Assuming an
absolute turnover magnitude of M_V^0 = -7.62, and after applying a small
metallicity correction, we derive distance modulii of (m -- M) = 30.61 +/- 0.14
for NGC 4278 and 30.50 +/- 0.15 for NGC 4494. These distance estimates are
compared to other methods, and lie within the published range of values. We
conclude that both galaxies lie at the same distance and are both members of
the Coma I cloud.Comment: 13 pages, Latex. Full paper also available at
http://www.ucolick.org/~forbes/home.htm
Hadronic Correlators from All-point Quark Propagators
A method for computing all-point quark propagators is applied to a variety of
processes of physical interest in lattice QCD. The method allows, for example,
efficient calculation of disconnected parts and full momentum-space 2 and 3
point functions. Examples discussed include: extraction of chiral Lagrangian
parameters from current correlators, the pion form factor, and the unquenched
eta-prime.Comment: LATTICE01(Algorithms and Machines
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