9,213 research outputs found
Monopole clusters and critical dynamics in four-dimensional U(1)
We investigate monopoles in four-dimensional compact U(1) with Wilson action.
We focus our attention on monopole clusters as they can be identified
unambiguously contrary to monopole loops. We locate the clusters and determine
their properties near the U(1) phase transition. The Coulomb phase is
characterized by several small clusters, whereas in the confined phase the
small clusters coalesce to one large cluster filling up the whole system. We
find that clusters winding around the periodic lattice are absent within both
phases and during the transition. However, within the confined phase, we
observe periodically closed monopole loops if cooling is applied.Comment: 3 pages, Wuppertal preprint WUB 93-3
Monopoles in Compact U(1) -- Anatomy of the Phase Transition
We present evidence that the existence of a first order phase transition in
compact U(1) with Wilson action is not related to monopole loops wrapping
around the toroidal lattice, as has been previously suggested. Our analysis is
based on the suppression of such loops by `soft boundary conditions' that
correspond to an infinitely large chemical potential for the monopoles on the
boundary, during the updating process. It is observed that the double peak
structure characteristic for the first order phase transition reappears at
sufficiently large lattice sizes and separations from the lattice boundary.Comment: 8 pages, (color) ps-figures available via anonymous ftp at
ftp://wpts0.physik.uni-wuppertal.de/pub/monopoles/figures.u
Cosmological Constraints from a Combined Analysis of the Cluster Mass Function and Microwave Background Anisotropies
We present constraints on several cosmological parameters from a combined
analysis of the most recent Cosmic Microwave Background anisotropy data and the
Sloan Digital Sky Survey cluster mass function. We find that the combination of
the two data sets breaks several degeneracies among the parameters and provides
the following constraints: ,
, , ,
.Comment: 7 pages, 1 figur
The three-loop beta-fuction of QCD with the clover action
We calculate, to 3 loops in perturbation theory, the bare -function of
QCD, formulated on the lattice with the clover fermionic action. The dependence
of our result on the number of colors , the number of fermionic flavors
, as well as the clover parameter , is shown explicitly.
A direct outcome of our calculation is the two-loop relation between the bare
coupling constant and the one renormalized in the MS-bar scheme.
Further, we can immediately derive the three-loop correction to the relation
between the lattice -parameter and , which is important in checks
of asymptotic scaling. For typical values of , this correction is found
to be very pronounced.Comment: 14 pages, 2 eps figure
New Record of \u3ci\u3eBrachycercus Maculatus\u3c/i\u3e Berner (Ephemeroptera: Caenidae) From New York and a Key to Larvae of Northeastern Species
Brachycercus maculatus, a member of a rare group of mayflies, is now recorded for the first time from New York State in the upper Hudson River. An illustrated key to the Brachycercus larvae of northeastern North America is provided to spur further study of the genus in the region
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