150,698 research outputs found
Correlation Functions of Hadron Currents in the QCD Vacuum Calculated in Lattice QCD
Point-to-point vacuum correlation functions for spatially separated hadron
currents are calculated in quenched lattice QCD on a lattice
with . The lattice data are analyzed in terms of dispersion
relations, which enable us to extract physical information from small distances
where asymptotic freedom is apparent to large distances where the hadronic
resonances dominate. In the pseudoscalar, vector, and axial vector channels
where experimental data or phenomenological information are available,
semi-quantitative agreement is obtained. In the nucleon and delta channels,
where no experimental data exist, our lattice data complement experiments.
Comparison with approximations based on sum rules and interacting instantons
are made, and technical details of the lattice calculation are described.Comment: 31 pages in REVTeX (with 10 figures to be added using figures
command), MIT CTP #214
The static potential: lattice versus perturbation theory in a renormalon-based approach
We compare, for the static potential and at short distances, perturbation
theory with the results of lattice simulations. We show that a
renormalon-dominance picture explains why in the literature sometimes
agreement, and another disagreement, is found between lattice simulations and
perturbation theory depending on the different implementations of the latter.
We also show that, within a renormalon-based scheme, perturbation theory agrees
with lattice simulations.Comment: 18 pages, 11 figures, lattice data of Necco and Sommer introduced,
references added, some lengthier explanations given, physical results
unchange
The Geometry of Niggli Reduction II: BGAOL -- Embedding Niggli Reduction
Niggli reduction can be viewed as a series of operations in a six-dimensional
space derived from the metric tensor. An implicit embedding of the space of
Niggli-reduced cells in a higher dimensional space to facilitate calculation of
distances between cells is described. This distance metric is used to create a
program, BGAOL, for Bravais lattice determination. Results from BGAOL are
compared to the results from other metric-based Bravais lattice determination
algorithms
An new order parameter with renormalized Polyakov loops
It is well established that physical quantities like the heavy quark
potentials get temperature independent at sufficiently short distances. As a
first application of this feature we suggest a new order parameter for the
confinement/deconfinement phase transition. Our investigations are based on
recent lattice studies.Comment: 2 pages, 2 figures, contribution to 'Statistical QCD', Bielefeld,
August 26-30, 200
Matrix Theory for Baryons: An Overview of Holographic QCD for Nuclear Physics
We provide, for non-experts, a brief overview of holographic QCD and a review
of a recent proposal of matrix-description of multi-baryon systems in
holographic QCD. Based on the matrix model, we derive the baryon interaction at
short distances in multi-flavor holographic QCD. We show that there is a very
universal repulsive core of inter-baryon forces for generic number of flavors.
This is consistent with a recent lattice QCD analysis for N_f = 2, 3 where
repulsive core looks universal. We also provide a comparison of our results
with the lattice QCD and the operator product expansion (OPE) analysis.Comment: 31 pages, 13 figure
The Negativity of the Overlap-Based Topological Charge Density Correlator in Pure-Glue QCD and the Non-Integrable Nature of its Contact Part
We calculate the lattice two-point function of topological charge density in
pure-glue QCD using the discretization of the operator based on the overlap
Dirac matrix. Utilizing data at three lattice spacings it is shown that the
continuum limit of the correlator complies with the requirement of
non-positivity at non-zero distances. For our choice of the overlap operator
and the Iwasaki gauge action we find that the size of the positive core is ~2a
(with a being the lattice spacing) sufficiently close to the continuum limit.
This result confirms that the overlap-based topological charge density is a
valid local operator over realistic backgrounds contributing to the QCD path
integral, and is important for the consistency of recent results indicating the
existence of a low-dimensional global brane-like topological structure in the
QCD vacuum. We also confirm the divergent short-distance behavior of the
correlator, and the non-integrable nature of the associated contact part.Comment: 13 pages, 5 figure
Dynamical Abelian Projection of Gluodynamics
Assuming the monopole dominance, that has been proved in the lattice
gluodynamics, to hold in the continuum limit, we develop an effective scalar
field theory for QCD at large distances to describe confinement. The approach
is based on a gauge (or projection) independent formulation of the monopole
dominance and manifestly Lorentz invariant.Comment: A talk given at QCD96, Montpellier, France, July, 1996 (to appear in
the Proceedings); plain Latex, 6 page
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