17,788 research outputs found
RURAL ECONOMIC DEVELOPMENT: NEW OPPORTUNITIES AND CHALLENGES FOR COMMERCIAL BANKERS
The report discusses commercial banks' role in supporting economic development in rural America. It details demographic and economic trends in rural America. It discusses a number of economic development programs available to commercial bankers and to private sector/public sector partnerships. Finally, the report proposes a set of new tools for commercial bankers to further strengthen their participation in rural community economic development. Note: Figures are not included in the machine readable copy--contact the authors for more information.demographic trends, economic trends, rural America, role of commercial banks, economic development programs, new tools for bankers, Community/Rural/Urban Development, Financial Economics,
Dependence on the spin structure of the eta and rokhlin invariants
We study the dependence of the eta invariant on the spin structure,
where is a twisted Dirac operator on a (4k+3)-dimensional spin manifold.
The difference between the eta invariants for two spin structures related by a
cohomolgy class which is the reduction of a H^1(M,\Za)-class is shown to be a
half integer. As an application of the technique of proof the generalized
Rokhlin invariant is shown to be equal modulo 8 for two spin structures related
in this way.Comment: 10 page
Large volume behavior of Yang-Mills propagators
We summarize results on finite-volume effects in the propagators of Landau
gauge Yang-Mills theory using Dyson-Schwinger equations on a 4-dimensional
torus. We demonstrate explicitly how the solutions for the gluon and the ghost
propagator tend towards their respective infinite volume forms in the
corresponding limit. We discuss the relation of our solutions with results from
lattice Monte-Carlo simulations.Comment: 7 pages, 2 figures, Presented by CF at the XXV International
Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg,
German
Vertex functions and infrared fixed point in Landau gauge SU(N) Yang-Mills theory
The infrared behaviour of vertex functions in an SU(N) Yang-Mills theory in
Landau gauge is investigated employing a skeleton expansion of the
Dyson-Schwinger equations. The three- and four-gluon vertices become singular
if and only if all external momenta vanish while the dressing of the
ghost-gluon vertex remains finite in this limit. The running coupling as
extracted from either of these vertex functions possesses an infrared fixed
point. In general, diagrams including ghost-loops dominate in the infrared over
purely gluonic ones.Comment: 14 pages, 8 figures, v2: typos corrected, version to be published in
PL
An Introduction to Conformal Ricci Flow
We introduce a variation of the classical Ricci flow equation that modifies
the unit volume constraint of that equation to a scalar curvature constraint.
The resulting equations are named the Conformal Ricci Flow Equations because of
the role that conformal geometry plays in constraining the scalar curvature.
These equations are analogous to the incompressible Navier-Stokes equations of
fluid mechanics inasmuch as a conformal pressure arises as a Lagrange
multiplier to conformally deform the metric flow so as to maintain the scalar
curvature constraint. The equilibrium points are Einstein metrics with a
negative Einstein constant and the conformal pressue is shown to be zero at an
equilibrium point and strictly positive otherwise. The geometry of the
conformal Ricci flow is discussed as well as the remarkable analytic fact that
the constraint force does not lose derivatives and thus analytically the
conformal Ricci equation is a bounded perturbation of the classical
unnormalized Ricci equation. That the constraint force does not lose
derivatives is exactly analogous to the fact that the real physical pressure
force that occurs in the Navier-Stokes equations is a bounded function of the
velocity. Using a nonlinear Trotter product formula, existence and uniqueness
of solutions to the conformal Ricci flow equations is proven. Lastly, we
discuss potential applications to Perelman's proposed implementation of
Hamilton's program to prove Thurston's 3-manifold geometrization conjectures.Comment: 52 pages, 1 figur
Temperature Dependence of Gluon and Ghost Propagators in Landau-Gauge Yang-Mills Theory below the Phase Transition
The Dyson-Schwinger equations of Landau-gauge Yang-Mills theory for the gluon
and ghost propagators are investigated. Numerical results are obtained within a
truncation scheme which has proven to be successful at vanishing temperature.
For temperatures up to 250 MeV we find only minor quantitative changes in the
infrared behaviour of the gluon and ghost propagators. The effective action
calculated from these propagators is temperature-independent within the
numerical uncertainty.Comment: 9 pages, 14 figures, submitted to EPJ C, typos corrected, reference
and 2 minor clarifications added, in v3: one paragraph extended, some
references added, version to appear in EPJ
Solving the Ghost-Gluon System of Yang-Mills Theory on GPUs
We solve the ghost-gluon system of Yang-Mills theory using Graphics
Processing Units (GPUs). Working in Landau gauge, we use the Dyson-Schwinger
formalism for the mathematical description as this approach is well-suited to
directly benefit from the computing power of the GPUs. With the help of a
Chebyshev expansion for the dressing functions and a subsequent appliance of a
Newton-Raphson method, the non-linear system of coupled integral equations is
linearized. The resulting Newton matrix is generated in parallel using OpenMPI
and CUDA(TM). Our results show, that it is possible to cut down the run time by
two orders of magnitude as compared to a sequential version of the code. This
makes the proposed techniques well-suited for Dyson-Schwinger calculations on
more complicated systems where the Yang-Mills sector of QCD serves as a
starting point. In addition, the computation of Schwinger functions using GPU
devices is studied.Comment: 19 pages, 7 figures, additional figure added, dependence on
block-size is investigated in more detail, version accepted by CP
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