47,288 research outputs found
Confinement: Understanding the Relation Between the Wilson Loop and Dual Theories of Long Distance Yang Mills Theory
In this paper we express the velocity dependent, spin dependent heavy quark
potential in QCD in terms of a Wilson Loop determined
by pure Yang Mills theory. We use an effective dual theory of long-distance
Yang Mills theory to calculate for large loops; i.e. for loops of
size . ( is the flux tube radius, fixed by the value of the
Higgs (monopole) mass of the dual theory, which is a concrete realization of
the Mandelstam 't Hooft dual superconductor mechanism of confinement).
We replace by , given by a functional integral
over the dual variables, which for can be evaluated by a
semiclassical expansion, since the dual theory is weakly coupled at these
distances. The classical approximation gives the leading contribution to
and yields a velocity dependent heavy quark potential which
for large becomes linear in , and which for small approaches lowest
order perturbative QCD. This latter fact means that these results should remain
applicable down to distances where radiative corrections giving rise to a
running coupling constant become important. The spin dependence of the
potential reflects the vector coupling of the quarks at long range as well as
at short range. The methods developed here should be applicable to any
realization of the dual superconductor mechanism. They give an expression
determining independent of the classical approximation, but
semi classical corrections due to fluctuations of the flux tube are not worked
out in this paper. Taking these into account should lead to an effective string
theory free from the conformal anomaly.Comment: 39 pages, latex2e, 1 figure(fig.eps
Excerpts from selected LANDSAT 1 final reports in geology
The standard formats for the summaries of selected LANDSAT geological data are presented as checklists. These include: (1) value of LANDSAT data to geology, (2) geologic benefits, (3) follow up studies, (4) cost benefits, (5) optimistic working scales, (6) statistical analysis, and (7) enhancement effects
Collision of Viscoelastic Spheres: Compact Expressions for the Coefficient of Normal Restitution
The coefficient of restitution of colliding viscoelastic spheres is
analytically known as a complete series expansion in terms of the impact
velocity where all (infinitely many) coefficients are known. While beeing
analytically exact, this result is not suitable for applications in efficient
event-driven Molecular Dynamics (eMD) or Monte Carlo (MC) simulations. Based on
the analytic result, here we derive expressions for the coefficient of
restitution which allow for an application in efficient eMD and MC simulations
of granular Systems.Comment: 4 pages, 4 figure
Structures of K0.05Na0.95NbO3 (50–300 K) and K0.30Na0.70NbO3 (100–200 K)
Rietveld refinement using neutron powder diffraction data is reported for the potential lead-free piezoelectric material KxNa1 - xNbO3 (x = 0.05, x = 0.3) at low temperatures. The structures were determined to be of rhombohedral symmetry, space group R3c, with the tilt system a-a-a- for both compositions. It was found that some of the structural parameters differ significantly in the two structures, and particularly the NbO6 octahedral strains as a function of temperature. The 300 K profile for K0.05Na0.95NbO3 shows the coexistence of rhombohedral and monoclinic phases, which indicates that the phase boundary is close to room temperature; the phase boundary for K0.30Na0.70NbO3 is found to be at approximately 180 K
The relativistic interaction in the Wilson loop approach
We study the relativistic interaction starting from the
Feynman-Schwinger representation of the gauge-invariant quark-antiquark Green
function. We focus on the one-body limit and discuss the obtained
non-perturbative interaction kernel of the Dirac equation.Comment: 5 pages, Latex (espcrc2.sty) To be published in the proceedings of
High-Energy Physics International Euroconference on Quantum
Chromodynamics:QCD97; 25th Anniversary of QCD, Montpellier, France, 3-9 July
199
Interparticle Potential up to Next-to-leading Order for Gravitational, Electrical, and Dilatonic Forces
Long-range forces up to next-to-leading order are computed in the framework
of the Einstein-Maxwell-dilaton system by means of a semiclassical approach to
gravity. As has been recently shown, this approach is effective if one of the
masses under consideration is significantly greater than all the energies
involved in the system. Further, we obtain the condition for the equilibrium of
charged masses in the system.Comment: 19 pages, 19 figures, RevTeX4.1. Revised version, Title change
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