1,276 research outputs found
Structure of Dusty Plasma under Microgravity
The structure of dust particles in dusty plasmas under microgravity has been analyzed by molecular dynamics simulation. The charge neutrality condition satisfied by the system composed of dust particles and ambient plasma is properly taken into account. It is shown that dust particles form shell structures at low temperatures and the number of shells are obtained as a phase diagram in the plane of two parameters characterizing the system: the number of particles and the strength of screening. It is also shown that these structures are almost independent of the strength of screening
The Yang-Mills gradient flow and SU(3) gauge theory with 12 massless fundamental fermions in a colour-twisted box
We perform the step-scaling investigation of the running coupling constant,
using the gradient-flow scheme, in SU(3) gauge theory with twelve massless
fermions in the fundamental representation. The Wilson plaquette gauge action
and massless unimproved staggered fermions are used in the simulations. Our
lattice data are prepared at high accuracy, such that the statistical error for
the renormalised coupling, g_GF, is at the subpercentage level. To investigate
the reliability of the continuum extrapolation, we employ two different lattice
discretisations to obtain g_GF. For our simulation setting, the corresponding
gauge-field averaging radius in the gradient flow has to be almost half of the
lattice size, in order to have this extrapolation under control. We can
determine the renormalisation group evolution of the coupling up to g^2_GF ~ 6,
before the onset of the bulk phase structure. In this infrared regime, the
running of the coupling is significantly slower than the two-loop perturbative
prediction, although we cannot draw definite conclusion regarding possible
infrared conformality of this theory. Furthermore, we comment on the issue
regarding the continuum extrapolation near an infrared fixed point. In addition
to adopting the fit ansatz a'la Symanzik for performing this task, we discuss a
possible alternative procedure inspired by properties derived from low-energy
scale invariance at strong coupling. Based on this procedure, we propose a
finite-size scaling method for the renormalised coupling as a means to search
for infrared fixed point. Using this method, it can be shown that the behaviour
of the theory around g^2_GF ~ 6 is still not governed by possible infrared
conformality.Comment: 24 pages, 6 figures; Published version; Appendix A added for
tabulating data; One reference included; Typos correcte
Effects of low-lying fermion modes in the epsilon regime
We investigate the effects of low-lying fermion modes on the QCD partition
function in the epsilon-regime. With the overlap Dirac operator we calculate
several tens of low-lying fermion eigenvalues on the quenched lattice. By
partially incorporating the fermion determinant through the truncated
determinant approximation, we calculate the partition function and other
related quantities for Nf = 1 and compare them with the theoretical predictions
obtained by Leutwyler and Smilga.Comment: 3 pages, 5 figures, Talk presented at Lattice2004(chiral), Fermilab,
June 21-26, 200
Lattice study of infrared behaviour in SU(3) gauge theory with twelve massless flavours
We present details of a lattice study of infrared behaviour in SU(3) gauge
theory with twelve massless fermions in the fundamental representation. Using
the step-scaling method, we compute the coupling constant in this theory over a
large range of scale. The renormalisation scheme in this work is defined by the
ratio of Polyakov loops in the directions with different boundary conditions.
We closely examine systematic effects, and find that they are dominated by
errors arising from the continuum extrapolation. Our investigation suggests
that SU(3) gauge theory with twelve flavours contains an infrared fixed point.Comment: 29 pages, 15 figures, 4 tables. Minor revision. Published versio
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