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hep-lat/9210006
|
Basis States for Hamiltonian QCD with Dynamical Quarks
|
We discuss the construction of basis states for Hamiltonian QCD on the
lattice, in particular states with dynamical quark pairs. We calculate the
matrix elements of the operators in the QCD Hamiltonian between these states.
Along with the ``harmonic oscillator'' states introduced in previous pure SU(3)
work, these states form a working basis for calculations in full QCD.
| 1992-10-02
| 2007-05-23
|
[
"hep-lat"
] |
Timothy E. Vaughan
|
hep-lat/9210005
|
Fermion Doubling and Gauge Invariance on Random Lattices
|
Random-lattice fermions have been shown to be free of the doubling problem if
there are no interactions or interactions of a non-gauge nature. On the other
hand, gauge interactions impose stringent constraints as expressed by the
Ward-Takahashi identities which could revive the free-field suppressed doubler
modes in loop diagrams. Comparing random lattice, naive and Wilson fermions in
two dimensional abelian background gauge theory, we show that indeed the
doublers are revived for random lattices in the continuum limit. Some
implications of the persistent doubling phenomenon on random lattices are also
discussed.
| 1992-10-02
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
C J Griffin and T D Kieu
|
hep-lat/9210004
|
Multicritical Points in a Lattice Yukawa Model with the Wilson-Yukawa
Coupling
|
For a lattice regularized chiral-invariant $SU(2)_L\times~SU(2)_R$
fermion-scalar model with a Yukawa coupling $y$ and a Wilson-Yukawa coupling
$w$, we investigate the phase structure and in particular show the existence of
the multicritical line, in the strong Yukawa and/or Wilson Yukawa coupling
region, at which four phases meet.
The result is in good agreement with the Monte Carlo simulation.
This analytical result is derived from the effective scalar model obtained by
integrating out the fermion field where the action is explicitly obtained from
the hopping parameter expansion up to next-to-leading order.
For estimates on the correlation function of the scalar field we apply the
mean-field method.
| 1992-10-02
| 2009-10-22
|
[
"hep-lat"
] |
T. Ebihara and K.-I. Kondo
|
hep-lat/9210001
|
Non-uniform measure in 4d simplicial quantum gravity
|
Four-dimensional euclidean quantum gravity has been studied as a discrete
model based on dynamical triangulations by Ambjorn and Jurkiewicz and by
Agishtein and Migdal. We discuss a particular implementation of a Monte Carlo
simulation of simplicial quantum gravity. As an application we introduce a
non-uniform measure and examine its effect on simple aspects of the
mathematical geometry. We find that the transition region from the hot to the
cold phase is shifted and that the criticality of the transition changes.
| 1992-10-01
| 2008-11-26
|
[
"hep-lat"
] |
Bernd Bruegmann
|
hep-lat/9210002
|
4d Simplicial Quantum Gravity with a Non-Trivial Measure
|
We study 4d simplicial quantum gravity in the dynamical triangulation
approach with a non-trivial class of measures. We find that the measure
contribution plays an important role, influencing the phase diagram and the
nature of the (possible) critical theory. We discuss how the lattice theory
could be used to fix the quantum measure in a non-ambiguous way.
| 1992-10-01
| 2008-11-26
|
[
"hep-lat",
"gr-qc",
"hep-th"
] |
Bernd Bruegmann and E. Marinari
|
hep-lat/9210003
|
The Running Coupling from SU(3) Gauge Theory
|
We present high precision results on the static quark-antiquark-potential on
32^4 and smaller lattices, using the standard Wilson action at BETA = 6.0, 6.2,
6.4, and 6.8 on the Connection Machine CM-2. Within our statistical errors (1%)
we did not observe any finite size effects affecting the potential values, on
varying the spatial lattice extent from 0.9 fm up to 3.3 fm. We find violations
of asymptotic scaling in the bare coupling up to BETA = 6.8. We demonstrate
that scaling violations on the string tension can be considerably reduced by
introducing effective coupling schemes, which allow for a safer extrapolation
of LAMBDA_Lattice to its continuum value. We are also able to see and to
quantify the running of the coupling from the interquark force. From this we
extract the ratio \sqrt{SIGMA}/LAMBDA_L. Both methods yield consistent values
for the LAMBDA-parameter: LAMBDA_MSbar = 0.558(-0.007+0.017)\sqrt{SIGMA}
= 246(-3+7) MeV.
| 1992-10-01
| 2009-10-22
|
[
"hep-lat"
] |
G.S. Bali and K. Schilling
|
hep-lat/9209027
|
Chern-Simons term in the 4-dimensional SU(2) Higgs Model
|
Using Seiberg's definition for the geometric charge in SU(2) lattice gauge
theory, we have managed to apply it also to the Chern-Simons term. We checked
the periodic structure and determined the Chern-Simons density on small
lattices $L^4$ and $L^3 \times 2,\, 4$ with $L=4,\, 6,\mbox{ and }8$ near the
critical region in the SU(2) Higgs model. The data indicate that tunneling is
increased at high temperature.
| 1992-09-30
| 2009-10-22
|
[
"hep-lat"
] |
F. Karsch, M. L. Laursen, T. Neuhaus and B. Plache
|
hep-lat/9209026
|
Bose Condensation and $Z_N$ Symmetry Breaking in the Mixed Model of
Induced QCD
|
The mixed model of the large $ N $ induced QCD, with $ N_f \ll N $ flavors of
heavy fermions in fundamental representation, is solved in the local limit. The
$ Z_N$ symmetry is broken spontaneously in the large $ N $ limit, evading the
Elitzur "no-go" theorem. As a result of this symmetry breaking, there is the
Bose condensate of the eigenvalues of the scalar field, proportional to $
\frac{N_f}{N} $. This condensate leads to the mass unit, which goes to zero as
fractional power of $ \frac{N_f}{N} $, thus defining the new kind of the local
limit of this lattice theory. There is a strong coupling region below this mass
scale, which revives the hopes of induction of realistic QCD.
| 1992-09-29
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
A.A. Migdal
|
hep-lat/9209025
|
Monte Carlo simulation of lattice ${\rm CP}^{N-1}$ models at large N
|
In order to check the validity and the range of applicability of the 1/N
expansion, we performed numerical simulations of the two-dimensional lattice
CP(N-1) models at large N, in particular we considered the CP(20) and the
CP(40) models. Quantitative agreement with the large-N predictions is found for
the correlation length defined by the second moment of the correlation
function, the topological susceptibility and the string tension. On the other
hand, quantities involving the mass gap are still far from the large-$N$
results showing a very slow approach to the asymptotic regime. To overcome the
problems coming from the severe form of critical slowing down observed at large
N in the measurement of the topological susceptibility by using standard local
algorithms, we performed our simulations implementing the Simulated Tempering
method.
| 1992-09-28
| 2009-10-22
|
[
"hep-lat"
] |
Ettore Vicari (Dipartimento di Fisica dell'Universita`, I-56126 Pisa,
Italy)
|
hep-lat/9209024
|
Multicanonical Cluster Algorithm and the 2-D 7-State Potts Model
|
I present a hybrid-like two-step algorithm, which combines a microcanonical
update of a spin system using demons, with a multicanonical demon refresh. The
algorithm is free from the supercritical slowing down that burdens the
canonical methods: the exponential increase of the tunnelling time between the
metastable states in the first-order phase transitions, when the volume of the
system is increased. The demons act as a buffer between the multicanonical heat
bath and the spin system, allowing the spin system to be updated with any
microcanonical demon procedure, including cluster methods. The cluster
algorithm is demonstrated with the 2-dimensional 7-state Potts model, using
volumes up to $128^2$. The tunnelling time is found to increase as $L^{1.82}$,
where $L$ is the linear dimension of the system.
| 1992-09-25
| 2009-10-22
|
[
"hep-lat"
] |
K. Rummukainen
|
hep-lat/9209023
|
Modified $U(1)$ lattice gauge theory: towards realistic lattice QED
|
We study properties of the compact $~4D~$ $U(1)$ lattice gauge theory with
monopoles {\it removed}. Employing Monte Carlo simulations we calculate
correlators of scalar, vector and tensor operators at zero and nonzero momenta
$~\vec{p}~$. We confirm that the theory without monopoles has no phase
transition, at least, in the interval $~0 < \beta \leq 2~$. There the photon
becomes massless and fits the lattice free field theory dispersion relation
very well. The energies of the $~0^{++}~$, $~1^{+-}~$ and $~2^{++}~$ states
show a rather weak dependence on the coupling in the interval of $~\beta~$
investigated, and their ratios are practically constant. We show also a further
modification of the theory suppressing the negative plaquettes to improve
drastically the overlap with the lowest states (at least, for $~J=1$).
| 1992-09-23
| 2007-05-23
|
[
"hep-lat"
] |
V.G. Bornyakov, V.K. Mitrjushkin and M. M\"uller-Preussker
|
hep-lat/9209022
|
On the Viability of Lattice Perturbation Theory
|
In this paper we show that the apparent failure of QCD lattice perturbation
theory to account for Monte Carlo measurements of perturbative quantities
results from choosing the bare lattice coupling constant as the expansion
parameter. Using instead ``renormalized'' coupling constants defined in terms
of physical quantities, like the heavy-quark potential, greatly enhances the
predictive power of lattice perturbation theory. The quality of these
predictions is further enhanced by a method for automatically determining the
coupling-constant scale most appropriate to a particular quantity. We present a
mean-field analysis that explains the large renormalizations relating lattice
quantities, like the coupling constant, to their continuum analogues. This
suggests a new prescription for designing lattice operators that are more
continuum-like than conventional operators. Finally, we provide evidence that
the scaling of physical quantities is asymptotic or perturbative already at
$\beta$'s as low as 5.7, provided the evolution from scale to scale is analyzed
using renormalized perturbation theory. This result indicates that reliable
simulations of (quenched) QCD are possible at these same low $\beta$'s.
| 1992-09-22
| 2009-10-22
|
[
"hep-lat"
] |
G.P.Lepage and P.B.Mackenzie
|
hep-lat/9209021
|
Neural multigrid for gauge theories and other disordered systems
|
We present evidence that multigrid works for wave equations in disordered
systems, e.g. in the presence of gauge fields, no matter how strong the
disorder, but one needs to introduce a "neural computations" point of view into
large scale simulations: First, the system must learn how to do the simulations
efficiently, then do the simulation (fast).
The method can also be used to provide smooth interpolation kernels which are
needed in multigrid Monte Carlo updates.
| 1992-09-21
| 2011-04-20
|
[
"hep-lat"
] |
M. Baeker, T. Kalkreuter, G. Mack and M. Speh
|
hep-lat/9209020
|
The Phase Diagram of Fluid Random Surfaces with Extrinsic Curvature
|
We present the results of a large-scale simulation of a Dynamically
Triangulated Random Surface with extrinsic curvature embedded in
three-dimensional flat space. We measure a variety of local observables and use
a finite size scaling analysis to characterize as much as possible the regime
of crossover from crumpled to smooth surfaces.
| 1992-09-18
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
Mark Bowick, Paul Coddington, Leping Han, Geoffrey Harris and Enzo
Marinari
|
hep-lat/9209019
|
Multi-quark energies in QCD
|
Four-quark potentials for $SU(2)$ are evaluated in the static limit with the
quenched approximation -- using a lattice of $16^3\times 32$ and $\beta=2.4$.
The four quarks are restricted to the corners of rectangles with sides upto
seven lattice spacings long. The results are analysed in terms of a strategy
based on interquark two-body potentials -- as advocated earlier by the authors.
This shows that a standard two-body approach overestimates the four-quark
binding energy by upto a factor of about three for the largest rectangles.
| 1992-09-15
| 2008-11-26
|
[
"hep-lat"
] |
A.M.Green, C.Michael and J.E.Paton
|
hep-lat/9209018
|
Lyapunov Exponent of SU(3) Gauge Theory
|
The classical SU(3) gauge theory is shown to be deterministic chaotic. Its
largest Lyapunov exponent is dertermined, from which a short time scale of
thermalization of a pure gluon system is estimated. The connection to gluon
damping rate is discussed.
| 1992-09-14
| 2010-11-01
|
[
"hep-lat"
] |
C. Gong
|
hep-lat/9209017
|
Finite-Size Scaling Study of the Three-Dimensional Classical Heisenberg
Model
|
We use the single-cluster Monte Carlo update algorithm to simulate the
three-dimensional classical Heisenberg model in the critical region on simple
cubic lattices of size $L^3$ with $L=12, 16, 20, 24, 32, 40$, and $48$. By
means of finite-size scaling analyses we compute high-precision estimates of
the critical temperature and the critical exponents, using extensively
histogram reweighting and optimization techniques. Measurements of the
autocorrelation time show the expected reduction of critical slowing down at
the phase transition. This allows simulations on significantly larger lattices
than in previous studies and consequently a better control over systematic
errors in finite-size scaling analyses.
| 1992-09-11
| 2009-10-22
|
[
"hep-lat"
] |
Christian Holm and Wolfhard Janke
|
hep-lat/9209016
|
Direct Monte Carlo Measurement of the Surface Tension in Ising Models
|
I present a cluster Monte Carlo algorithm that gives direct access to the
interface free energy of Ising models. The basic idea is to simulate an
ensemble that consists of both configurations with periodic and with
antiperiodic boundary conditions. A cluster algorithm is provided that
efficently updates this joint ensemble. The interface tension is obtained from
the ratio of configurations with periodic and antiperiodic boundary conditions,
respectively. The method is tested for the 3-dimensional Ising model.
| 1992-09-10
| 2009-10-22
|
[
"hep-lat"
] |
Martin Hasenbusch
|
hep-lat/9209015
|
Chern-Simons term and Topological Charge on the Lattice
|
In a somewhat overlooked work by Seiberg, a definition of the topological
charge for SU(N) lattice fields was given. Here, it is shown that Seibergs and
L\"{u}schers charge definition are related up to the section of the bundle.
With the continued interest in baryon number violating processes, Seibergs
paper is useful since it allows for a Chern-Simons number also.
| 1992-09-09
| 2007-05-23
|
[
"hep-lat"
] |
M.L.Laursen
|
hep-lat/9209014
|
Glueballs and Hybrid Mesons
|
We discuss states in the meson spectrum which have explicit gluonic
components. Glueballs (with no valence quarks) and hybrid mesons (with valence
quarks) are both reviewed. We present in some detail lattice simulation
results. ( to appear in proceedings of QCD-20 years, Aachen Workshop)
| 1992-09-08
| 2007-05-23
|
[
"hep-lat",
"hep-ph"
] |
Chris Michael
|
hep-lat/9209013
|
Surface Tension, Surface Stiffness, and Surface Width of the
3-dimensional Ising Model on a Cubic Lattice
|
We compute properties of the interface of the 3-dimensional Ising model for a
wide range of temperatures, covering the whole region from the low temperature
domain through the roughening transition to the bulk critical point. The
interface tension sigma is obtained by integrating the surface energy density
over the inverse temperature beta. We use lattices of size L x L x T, with L up
to 64, and T up to 27. The simulations with antiperiodic boundary conditions in
T-direction are done with the Hasenbusch-Meyer interface cluster algorithm that
turns out to be very efficient. We demonstrate that in the rough phase the
large distance behavior of the interface is well described by a massless
Gaussian dynamics. The surface stiffness coefficient kappa is determined. We
also attempt to determine the correlation length xi and study universal
quantities like xi^2 * sigma and xi^2 * kappa. Results for the interfacial
width on lattices up to 512 x 512 x 27 are also presented.
| 1992-09-07
| 2009-10-22
|
[
"hep-lat",
"cond-mat"
] |
Martin Hasenbusch and Klaus Pinn
|
hep-lat/9209012
|
Rotational Symmetry and Regularization Dependence in the
$\Phi^4_4$-Model
|
We study the one component $\Phi^4$ model for four different lattice actions
in the Gaussian limit and for the Ising model in the broken phase. Emphasis is
put on the euclidean invariance properties of the boson propagator. A measure
of the violation of rotational symmetry serves as a tool to compare the
regularization dependence of the triviality bound.
| 1992-09-07
| 2010-11-19
|
[
"hep-lat"
] |
C.B. Lang and U. Winkler
|
hep-lat/9209011
|
A quantitative study of the Kosterlitz-Thouless phase transition in a
system of two-dimensional plane rotators ( XY model ) by high temperature
expansions through $\beta^{20}$
|
High temperature series expansions of the spin-spin correlation function for
the plane rotator (or XY) model on the square lattice are extended by three
terms through order $\beta^{20}$. Tables of the expansion coefficients are
reported for the correlation function spherical moments of order $l=0,1,2$. The
expansion coefficients through $\beta^{15}$ for the vorticity are also
tabulated. Our analysis of the series supports the Kosterlitz-Thouless
predictions on the structure of the critical singularities and leads to fairly
accurate estimates of the critical parameters.
| 1992-09-04
| 2009-10-22
|
[
"hep-lat",
"cond-mat"
] |
P. Butera and M. Comi (Istituto Nazionale di Fisica Nucleare
Dipartimento di Fisica, Universit\`a di Milano Via Celoria 16, 20133 Milano,
Italy)
|
hep-lat/9209009
|
Monopole Percolation and The Universality Class of the Chiral Transition
in Four Flavor Noncompact Lattice QED
|
We simulate four flavor noncompact lattice QED using the Hybrid Monte Carlo
algorithm on $10^4$ and $16^4$ lattices. Measurements of the monopole
susceptibility and the percolation order parameter indicate a transition at
$\beta = {1/e^2} = .205(5)$ with critical behavior in the universality class of
four dimensional percolation. We present accurate chiral condensate
measurements and monitor finite size effects carefully. The chiral condensate
data supports the existence of a power-law transition at $\beta = .205$ in the
same universality class as the chiral transition in the two flavor model. The
resulting equation of state predicts the mass ratio $m_\pi^2/m_\sigma^2$ in
good agreement with spectrum calculations while the hypothesis of a
logarithmically improved mean field theory fails qualitatively.
| 1992-09-04
| 2009-10-22
|
[
"hep-lat"
] |
A. Kocic, J.B. Kogut and K.C. Wang
|
hep-lat/9209010
|
Universal Properties of Chiral Simmetry Breaking
|
We discuss chiral symmetry breaking critical points from the perspective of
PCAC, correlation length scaling and the chiral equation of state. A scaling
theory for the ratio $R_\pi$ of the pion to sigma masses is presented. The
Goldstone character of the pion and properties of the longitudinal and
transverse chiral susceptibilities determine the ratio $R_\pi$ which can be
used to locate critical points and measure critical indices such as $\delta$.
We show how PCAC and correlation length scaling determine the pion mass'
dependence on the chiral condensate and lead to a practical method to measure
the anomalous dimension $\eta$. These tools are proving useful in studies of
the chiral transition in lattice QED and the quark-gluon plasma transition in
lattice QCD.
| 1992-09-04
| 2009-10-22
|
[
"hep-lat"
] |
A. Kocic, J.B. Kogut and M.-P. Lombardo
|
hep-lat/9209007
|
SU(2) Potentials from Large Lattices
|
We measure accurate values of the inter-quark potentials on a $48^{3}56$
lattice with SU(2) pure gauge theory at $ \beta =2.85$. The scale is set by
extracting the string tension - we obtain ${\sqrt K}a=0.063(3)$ at $\beta
=2.85.$ From a careful study of the small-$R$ potentials in the region 2 GeV $<
R^{-1} < 5$ GeV, we extract a running coupling constant and estimate the scale
$\Lambda _{\msbar} = 272(24)$ MeV.
| 1992-09-03
| 2011-02-19
|
[
"hep-lat"
] |
The UKQCD Collaboration: S.P. Booth, A. Hulsebos, A.C. Irving, A.
McKerrell, C. Michael, P.S. Spencer, P.W. Stephenson
|
hep-lat/9209008
|
The Running Coupling from SU(3) Lattice Gauge Theory
|
{}From an accurate determination of the inter-quark potential, one can study
the running coupling constant for a range of $R$-values and hence estimate the
scale $\Lambda_{\msbar} $. Detailed results are presented for $SU(3)$ pure
gauge theory.
| 1992-09-03
| 2011-02-19
|
[
"hep-lat"
] |
The UKQCD Collaboration: S.P. Booth, D.S. Henty, A. Hulsebos, A.C.
Irving, C. Michael, P.W. Stephenson
|
hep-lat/9209006
|
Capillary Waves in Binder's Approach to the Interface Tension
|
In Binder's approach the reduced interface tension sigma of the Ising model
in the broken phase is determined from the finite volume effects of the
partition function Z(M) at fixed total magnetization M. For small |M| the
partition function of a system of size L^d with periodic boundary conditions is
dominated by configurations with two interfaces, such that Z(M) ~ exp(- 2 sigma
L^{d-1}). Capillary wave fluctuations of the interfaces correct this result to
Z(M) ~ exp(- 2 sigma L^{d-1}) with x = -1. The knowledge of the pre-exponential
behavior allows an improved fit of numerical data, and a determination of the
interface stiffness.
| 1992-09-03
| 2007-05-23
|
[
"hep-lat",
"cond-mat"
] |
U.-J. Wiese
|
hep-lat/9209005
|
High Precision Simulation Techniques for Lattice Field Theory
|
An overview is given over the recently developed and now widely used Monte
Carlo algorithms with reduced or eliminated critical slowing down. The basic
techniques are overrelaxation, cluster algorithms and multigrid methods. With
these tools one is able to probe much closer than before the universal
continuum behavior of field theories on the lattice.
| 1992-09-02
| 2011-04-15
|
[
"hep-lat"
] |
Ulli Wolff (CERN)
|
hep-lat/9209003
|
Chern-Simons Currents and Chiral Fermions on the Lattice
|
We compute the Chern-Simons current induced by Wilson fermions on a $d=2n+1$
dimensional lattice, making use of a topological interpretation of the momentum
space fermion propagator as a map from the torus to the sphere, $T^{d}\to
S^{d}$. These mappings are shown to fall in different homotopy classes
depending on the value of $m/r$, where $m$ is the fermion mass and $r$ is the
Wilson coupling. As a result, the induced Chern-Simons term changes
discontinuously at $d+1$ different values for $m$, unlike in the continuum.
This behavior is exactly what is required by the peculiar spectrum found for a
recently proposed model of chiral lattice fermions as zeromodes bound to a
domain wall.
| 1992-09-01
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
Maarten Golterman, Karl Jansen and David Kaplan
|
hep-lat/9209004
|
The Finite Temperature Phase Diagram of a U(1) Higgs-Yukawa Model
|
The finite temperature phase diagram of a U(1) Higgs-Yukawa model at a finite
value of the scalar self coupling $\lambda$ is investigated by means of a
large-$N_f$ calculation and numerical simulations. The phase diagram is similar
to the one at zero temperature and shows a ferromagnetic, two symmetric and an
antiferromagnetic phase. However, the phase transition lines are shifted to
larger values of the Yukawa coupling demonstrating the occurence of the finite
temperature symmetry restoration.
| 1992-09-01
| 2009-10-22
|
[
"hep-lat"
] |
Karl Jansen
|
hep-lat/9209001
|
Asymptotic Freedom and Euclidean Quantum Gravity
|
Pure SU(2) gauge theory is the simplest asymptotically free theory in four
dimensions. To investigate Euclidean quantum gravity effects in a fundamental
length scenario, we simulate 4$d$ SU(2) lattice gauge theory on a dynamically
coupled Regge skeleton. The fluctuations of the skeleton are governed by the
standard Regge-Einstein action. From a small $2\cdot 4^3$ lattice we report
exploratory numerical results, limited to a region of strong gravity where the
Planck mass and hadronic masses take similar orders of magnitude. We find a
range of the Planck mass where stable bulk expectation values are obtained
which vary smoothly with the gauge coupling, and a remnant of the QCD
deconfining phase transition is located. Note: The full ps file of this
preprint is also available via anonymous ftp to ftp.scri.fsu.edu. To get the ps
file, ftp to this address and use for username "anonymous" and for password
your name. The file is in the directory pub/krishnan (to go to that directory
type: cd pub/krishnan) and is called gravity.ps (to get it type: get
gravity.ps). If you have any problems send mail to krishnan@ds1.scri.fsu.edu.
| 1992-09-01
| 2009-10-22
|
[
"hep-lat"
] |
Bernd A. Berg, Balasubramanian Krishnan and Mohammad Katoot
|
hep-lat/9209002
|
Critical Momenta of Lattice Chiral Fermions
|
We determine the critical momenta for chiral fermions in the domain wall
model recently suggested by Kaplan. For a wide range of domain wall masses $m$
and Wilson couplings $r$ we explicitly exhibit the regions in momentum space
where the fermions are chiral. We compare the critical momenta for the
infinitely large system with those obtained on a finite lattice.
| 1992-09-01
| 2009-10-22
|
[
"hep-lat"
] |
Karl Jansen and Martin Schmaltz
|
hep-lat/9208030
|
Lattice Calculation of QCD Vacuum Correlation Functions
|
The first exploratory calculations of QCD vacuum correlation functions on a
lattice are reported. Qualitative agreement with phenomenological results is
obtained in channels for which experimental data are available, and these
correlation functions are shown to be useful in exploring approximations based
on sum rules and interacting instantons.
| 1992-08-28
| 2007-05-23
|
[
"hep-lat"
] |
M.-C. Chu, J. M. Grandy, S. Huang and J. W. Negele
|
hep-lat/9208029
|
A Study of the $N=2$ Kazakov-Migdal Model
|
We study numerically the SU(2) Kazakov-Migdal model of `induced QCD'. In
contrast to our earlier work on the subject we have chosen here {\it not} to
integrate out the gauge fields but to keep them in the Monte Carlo simulation.
This allows us to measure observables associated with the gauge fields and
thereby address the problem of the local $Z_2$ symmetry present in the model.
We confirm our previous result that the model has a line of first order phase
transitions terminating in a critical point. The adjoint plaquette has a clear
discontinuity across the phase transition, whereas the plaquette in the
fundamental representation is always zero in accordance with Elitzur's theorem.
The density of small $Z_2$ monopoles shows very little variation and is always
large. We also find that the model has extra local U(1) symmetries which do not
exist in the case of the standard adjoint theory. As a result, we are able to
show that two of the angles parameterizing the gauge field completely decouple
from the theory and the continuum limit defined around the critical point can
therefore not be `QCD'.
| 1992-08-27
| 2009-10-22
|
[
"hep-lat"
] |
Sinya Aoki, Andreas Gocksch and Yue Shen
|
hep-lat/9208027
|
Non-perturbative analysis, Gribov horizons and the boundary of the
fundamental domain
|
In this contribution to the proceedings we will describe some of the details
for constructing the Gribov horizon and the boundary of the fundamental modular
domain, when restricting to some low energy modes of pure SU(2) gauge theory in
a spherical spatial geometry. The fundamental domain is a one-to-one
representation of the set of gauge invariant degrees of freedom, in terms of
transverse gauge fields. Boundary identifications are the only remnants of the
Gribov copies.
| 1992-08-27
| 2007-05-23
|
[
"hep-lat",
"hep-th"
] |
Pierre van Baal and R.E. Cutkosky
|
hep-lat/9208026
|
Numerical Study of Finite Size Scaling for First Order Phase Transitions
|
I present results of simulations of the q=10 and q=20 2-d Potts models in the
transition region. The asymptotic finite size behavior sets in only for
extremely large lattices. We learn from this simulation that finite size
scaling cannot be used to decide that a transition is first order.
| 1992-08-27
| 2016-04-26
|
[
"hep-lat",
"cond-mat"
] |
Alain Billoire
|
hep-lat/9208028
|
Running Coupling and the Lambda-Parameter from SU(3) Lattice Simulations
|
We present new results on the static qq-potential from high statistics
simulations on 32^4 and smaller lattices, using the standard Wilson beta = 6.0,
6.4, and 6.8. Within our statistical errors we do not observe any finite size
effects affecting the potential values, on varying the spatial lattice extent
from 0.9fm up to 3.3fm. We are able to see and quantify the running of the
coupling from the Coulomb behaviour of the interquark force. From this we
extract the ratio \sqrt{sigma}/Lambda_L. We demonstrate that scaling violations
on the string tension can be considerably reduced by introducing effective
coupling schemes, which allow for a safe extrapolation of \Lambda_L to its
continuum value. Both methods yield consistent values for Lambda: Lambda_MSbar
= 0.558_{-0.007}^{+0.017}\sqrt{sigma} = 246_{-3}^{+7}MeV. At the highest energy
scale attainable to us we find alpha(5 GeV) = 0.150(3)
| 1992-08-27
| 2016-08-31
|
[
"hep-lat"
] |
Gunnar S. Bali and Klaus Schilling
|
hep-lat/9208025
|
Decuplet Baryon Structure from Lattice QCD
|
The electromagnetic properties of the SU(3)-flavor baryon decuplet are
examined within a lattice simulation of quenched QCD. Electric charge radii,
magnetic moments, and magnetic radii are extracted from the E0 and M1 form
factors. Preliminary results for the E2 and M3 moments are presented giving the
first model independent insight to the shape of the quark distribution in the
baryon ground state. As in our octet baryon analysis, the lattice results give
evidence of spin-dependent forces and mass effects in the electromagnetic
properties. The quark charge distribution radii indicate these effects act in
opposing directions. Some baryon dependence of the effective quark magnetic
moments is seen. However, this dependence in decuplet baryons is more subtle
than that for octet baryons. Of particular interest are the lattice predictions
for the magnetic moments of $\Omega^-$ and $\Delta^{++}$ for which new recent
experimental measurements are available. The lattice prediction of the
$\Delta^{++}/p$ ratio appears larger than the experimental ratio, while the
lattice prediction for the $\Omega^-/p$ magnetic moment ratio is in good
agreement with the experimental ratio.
| 1992-08-26
| 2008-11-26
|
[
"hep-lat",
"hep-ph"
] |
Derek B. Leinweber, Terrence Draper, and R.M. Woloshyn
|
hep-lat/9208023
|
Mixed Model of Induced QCD
|
The problems with the $Z_N$ symmetry breaking in the induced QCD are
analyzed. We compute the Wilson loops in the strong coupling phase, but we do
not find the $Z_N$ symmetry breaking, for arbitrary potential. We suggest to
bypass this problem by adding to the model a heavy fermion field in a
fundamental representation of $ SU(N) $. Remarkably, the model still can be
solved exactly by the Rieman-Hilbert method, for arbitrary number $N_f$ of
flavors. At $ N_f \ll N \rightarrow \infty $ there is a new regime, with two
vacuum densities. The $Z_N$ symmetry breaking density satisfies the linear
integral equation, with the kernel, depending upon the old density. The
symmetry breaking requires certain eigenvalue condition, which takes some extra
parameter adjustment of the scalar potential.
| 1992-08-22
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
A.A. Migdal
|
hep-lat/9208024
|
Finite-Size Scaling on the Ising Coexistence Line
|
We report tests of finite-size scaling ansatzes in the low temperature phase
of the two-dimensional Ising model. For moments of the magnetisation density,
we find good agreement with the new ansatz of Borgs and Koteck\'y, and clear
evi consequences of the convexity of the free energy are not adequately treated
in either of these approaches.\lb {\it Keywords}\/: Finite-size scaling, 2-d
Ising, pure-phase susceptibility.
| 1992-08-22
| 2011-04-15
|
[
"hep-lat",
"cond-mat"
] |
S.Gupta and A.Irbaeck
|
hep-lat/9208020
|
The confined-deconfined Interface Tension and the Spectrum of the
Transfer Matrix
|
The reduced tension $\sigma_{cd}$ of the interface between the confined and
the deconfined phase of $SU(3)$ pure gauge theory is related to the finite size
effects of the first transfer matrix eigenvalues. A lattice simulation of the
transfer matrix spectrum at the critical temperature $T_c = 1/L_t$ yields
$\sigma_{cd} = 0.139(4) T_c^2$ for $L_t = 2$. We found numerical evidence that
the deconfined-deconfined domain walls are completely wet by the confined
phase, and that the confined-deconfined interfaces are rough.
| 1992-08-21
| 2009-10-22
|
[
"hep-lat"
] |
B. Grossmann, M.L. Laursen, T. Trappenberg and U.-J. Wiese
|
hep-lat/9208022
|
Four - Fermi Theories in Fewer Than Four Dimensions
|
Four-fermi models in dimensionality $2<d<4$ exhibit an ultra-violet stable
renormalization group fixed point at a strong value of the coupling constant
where chiral symmetry is spontaneously broken. The resulting field theory
describes relativistic fermions interacting non-trivially via exchange of
scalar bound states. We calculate the $O(1/N_f)$ corrections to this picture,
where $N_f$ is the number of fermion species, for a variety of models and
confirm their renormalizability to this order. A connection between
renormalizability and the hyperscaling relations between the theory's critical
exponents is made explicit. We present results of extensive numerical
simulations of the simplest model for $d=3$, performed using the hybrid Monte
Carlo algorithm on lattice sizes ranging from $8^3$ to $24^3$. For $N_f=12$
species of massless fermions we confirm the existence of a second order phase
transition where chiral symmetry is spontaneously broken. Using both direct
measurement and finite size scaling arguments we estimate the critical
exponents $\beta$, $\gamma$, $\nu$ and $\delta$. We also investigate symmetry
restoration at non-zero temperature, and the scalar two-point correlation
function in the vicinity of the bulk transition. All our results are in
excellent agreement with analytic predictions, and support the contention that
the $1/N_f$ expansion is accurate for this class of models.
| 1992-08-21
| 2016-08-31
|
[
"hep-lat"
] |
Simon Hands, Aleksandar Kocic and John B. Kogut
|
hep-lat/9208021
|
Spectroscopy, Equation Of State And Monopole Percolation In Lattice QED
With Two Flavors
|
Non-compact lattice QED with two flavors of light dynamical quarks is
simulated on $16^4$ lattices, and the chiral condensate, monopole density and
susceptibility and the meson masses are measured. Data from relatively high
statistics runs at relatively small bare fermion masses of 0.005, 0.01, 0.02
and 0.03 (lattice units) are presented. Three independent methods of data
analysis indicate that the critical point occurs at $\beta =0.225(5)$ and that
the monopole condensation and chiral symmetry breaking transitions are
coincident. The monopole condensation data satisfies finite size scaling
hypotheses with critical indices compatible with four dimensional percolation.
The best chiral equation of state fit produces critical exponents
($\delta=2.31$, $\beta_{mag}=0.763$) which deviate significantly from mean
field expectations. Data for the ratio of the sigma to pion masses produces an
estimate of the critical index $\delta$ in good agreement with chiral
condensate measurements. In the strong coupling phase the ratio of the meson
masses are $M_\sigma^2/M_\rho^2\approx 0.35$, $M_{A_1}^2/M_\rho^2\approx 1.4$
and $M_\pi^2/M_\rho^2\approx 0.0$, while on the weak coupling side of the
transition $M_\pi^2/M_\rho^2\approx 1.0$, $M_{A_1}^2/M_\rho^2\approx 1.0$,
indicating the restoration of chiral symmetry.\footnote{$\,^{}$}{August 1992}
| 1992-08-21
| 2009-10-22
|
[
"hep-lat"
] |
S.J. Hands, A. Kocic, J.B. Kogut, R.L. Renken, D.K. Sinclair and K.C.
Wang
|
hep-lat/9208019
|
Fast vectorized algorithm for the Monte Carlo Simulation of the Random
Field Ising Model
|
An algoritm for the simulation of the 3--dimensional random field Ising model
with a binary distribution of the random fields is presented. It uses
multi-spin coding and simulates 64 physically different systems simultaneously.
On one processor of a Cray YMP it reaches a speed of 184 Million spin updates
per second. For smaller field strength we present a version of the algorithm
that can perform 242 Million spin updates per second on the same machine.
| 1992-08-21
| 2009-10-22
|
[
"hep-lat"
] |
H. Rieger
|
hep-lat/9208018
|
The Hyperfine Splitting in Charmonium: Lattice Computations Using the
Wilson and Clover Fermion Actions
|
We compute the hyperfine splitting $m_{J/\psi}-m_{\eta_c}$ on the lattice,
using both the Wilson and $O(a)$-improved (clover) actions for quenched quarks.
The computations are performed on a $24^3\times48$ lattice at $\beta = 6.2$,
using the same set of 18 gluon configurations for both fermion actions. We find
that the splitting is 1.83\err{13}{15} times larger with the clover action than
with the Wilson action, demonstrating the sensitivity of the spin-splitting to
the magnetic moment term which is present in the clover action. However, even
with the clover action the result is less than half of the physical
mass-splitting. We also compute the decay constants $f_{\eta_c}$ and
$f^{-1}_{J/\psi}$, both of which are considerably larger when computed using
the clover action than with the Wilson action. For example for the ratio
$f^{-1}_{J/\psi}/f^{-1}_{\rho}$ we find 0.32\err{1}{2} with the Wilson action
and $0.48\pm 3$ with the clover action (the physical value is 0.44(2)).
| 1992-08-21
| 2011-02-19
|
[
"hep-lat"
] |
UKQCD Collaboration: C.R. Allton, C.T. Sachrajda, S.P. Booth, K.C.
Bowler, D.S. Henty, R.D. Kenway, B.J. Pendleton, D.G. Richards, J.N. Simone,
A.D. Simpson, C. Michael and P.W. Stephenson
|
hep-lat/9208015
|
Duality in Long-Range Ising Ferromagnets
|
It is proved that for a system of spins $\sigma _i = \pm 1$ having an
interaction energy $-\sum K_{ij} \sigma _i \sigma _j $ with all the $K_{ij}$
strictly positive,one can construct a dual formulation by associating a dual
spin $S_{ijk} = \pm 1$ to each triplet of distinct sites $i,j$ and $k$. The
dual interaction energy reads $-\sum _{(ij)} D_{ij} \prod _{k \neq i,j}
S_{ijk}$ with $tanh(K_{ij})\ = \ exp(-2D_{ij})$, and it is invariant under
local symmetries. We discuss the gauge-fixing procedure, identities relating
averages of order and disorder variables and representations of various
quantities as integrals over Grassmann variables. The relevance of these
results for Polyakov's approach of the 3D Ising model is briefly discussed.
| 1992-08-20
| 2008-11-26
|
[
"hep-lat",
"hep-th"
] |
Yannick Meurice
|
hep-lat/9208017
|
The triviality bound on the Higgs mass; its value and what it means
|
Older lattice work exploring the Higgs mass triviality bound is briefly
reviewed. It indicates that a strongly interacting scalar sector in the minimal
standard model cannot exist; on the other hand low energy QCD phenomenology
might be interpreted as an indication that it could. We attack this puzzle
using the $1/N$ expansion and discover a simple criterion for selecting a
lattice action that is more likely to produce a heavy Higgs particle. Depending
on the precise form of the limitation put on the cutoff effects, our large $N$
calculations, when combined with old numerical data, suggest that the Higgs
mass bound might be around 750 $GeV$, which is higher than the $\sim 650~GeV$
previously obtained. Preliminary numerical work indicates that an increase of
at least 19\% takes place at $N=4$ on the $F_4$ lattice when the old simple
action is replaced with a new action (still containing only nearest neighbor
interactions) if one uses the lattice spacing as the physical cutoff for both
actions. It appears that, while a QCD like theory could produce $M_H / F ~ \sim
6$, a meaningful ``minimal elementary Higgs'' theory cannot have $M_H/ F~
\gtapprox 3$. Still, even at 750 $GeV$, the Higgs particle is so wide ($\sim
290~$GeV), that one cannot argue any more that the scalar sector is weakly
coupled.
| 1992-08-20
| 2009-10-22
|
[
"hep-lat",
"hep-ph"
] |
H. Neuberger, U. M. Heller, M. Klomfass, P. Vranas
|
hep-lat/9208016
|
Embedding Z(3) in SU(3)
|
We consider the design of a non-local MonteCarlo algorithm for $SU(3)$
lattice systems according to the idea of {\em embedding} the degrees of freedom
corresponding to the center of the group $Z(3)$. As a crucial ingredient to
reach this goal, we present a practical implementation of a cluster algorithm
for $Z(3)$ systems with general random pair interaction.
| 1992-08-20
| 2007-05-23
|
[
"hep-lat"
] |
Enrico Onofri
|
hep-lat/9208014
|
Noncomputability Arising In Dynamical Triangulation Model Of
Four-Dimensional Quantum Gravity
|
Computations in Dynamical Triangulation Models of Four-Dimensional Quantum
Gravity involve weighted averaging over sets of all distinct triangulations of
compact four-dimensional manifolds. In order to be able to perform such
computations one needs an algorithm which for any given $N$ and a given compact
four-dimensional manifold $M$ constructs all possible triangulations of $M$
with $\leq N$ simplices. Our first result is that such algorithm does not
exist. Then we discuss recursion-theoretic limitations of any algorithm
designed to perform approximate calculations of sums over all possible
triangulations of a compact four-dimensional manifold.
| 1992-08-18
| 2009-10-22
|
[
"hep-lat"
] |
A. Nabutovsky, R. Ben-Av
|
hep-lat/9208013
|
Gauge invariant extremization on the lattice
|
Recently, a method was proposed and tested to find saddle points of the
action in simulations of non-abelian lattice gauge theory. The idea, called
`extremization', is to minimize $\int(\dl S/\dl A_\mu)^2$. The method was
implemented in an explicitly gauge variant way, however, and gauge dependence
showed up in the results.
Here we show how extremization can be formulated in a way that preserves
gauge invariance on the lattice. The method applies to any gauge group and any
lattice action. The procedure is worked out in detail for the standard
plaquette action with gauge groups U(1) and SU(N).
| 1992-08-16
| 2009-10-22
|
[
"hep-lat"
] |
A.J. van der Sijs
|
hep-lat/9208012
|
Scaling and Asymptotic Scaling in the SU(2) Gauge Theory
|
We determine the critical couplings for the deconfinement phase transition in
$SU(2)$ gauge theory on $N_\tau \times N_\sigma^3$ lattices with $N_\tau = 8$
and 16 and $N_\sigma$ varying between 16 and 48. A comparison with string
tension data shows scaling of the ratio $T_c / \sqrt{\sigma}$ in the entire
coupling regime $\beta =2.30-2.75$, while the individual quantities still
exhibit large scaling violations. We find $T_c / \sqrt{\sigma}=0.69(2)$. We
also discuss in detail the extrapolation of $T_c / Lambda_{\rm{\bar{M}
\bar{S}}}$ and $\sqrt{\sigma} / Lambda_{\rm{\bar{M}\bar{S}}}$ to the continuum
limit. Our result, which is consistent with the above ratio, is $T_c /
Lambda_{\rm{\bar{M}\bar{S}}} = 1.23(11)$ and $\sqrt{\sigma} /
Lambda_{\rm{\bar{M}\bar{S}}} = 1.79(12)$. We also comment upon corresponding
results for $SU(3)$ gauge theory and four flavour QCD.
| 1992-08-14
| 2009-10-22
|
[
"hep-lat"
] |
J. Fingberg, U. M. Heller and F. Karsch
|
hep-lat/9208011
|
An Improved Acceptance Procedure for the Hybrid Monte Carlo Algorithm
|
The probability of accepting a candidate move in the hybrid Monte Carlo
algorithm can be increased by considering a transition to be between windows of
several states at the beginning and end of the trajectory, with a state within
the selected window being chosen according to the Boltzmann probabilities. The
detailed balance condition used to justify the algorithm still holds with this
procedure, provided the start state is randomly positioned within its window.
The new procedure is shown empirically to significantly improve performance for
a test system of uncoupled oscillators.
| 1992-08-12
| 2008-02-03
|
[
"hep-lat"
] |
R. M. Neal
|
hep-lat/9208007
|
Introduction to Lattice Gaugefixing and Effective Quark and Gluon Masses
|
This talk was presented to a non-lattice audience at the June, 1992 Paris
Workshop on QCD Vacuum Structure. We report on the status of quark and gluon
propagators in quenched, gaugefixed lattice QCD. In Landau gauge we find that
the effective quark mass in the chiral limit is $M_q \sim 350(40)MeV$. Quark
and gluon propagators, the slope of the quark dispersion relation, and
effective masses all appear to depend on gauge. A link-chain picture of lattice
gaugefixing in the color $N\to\infty$ and strong coupling limit, where the
system becomes almost solvable, supports the gauge variance of these numerical
results. Subscribers will be given one Postscript file, the Figure included.
Latex and Axis versions available from KY at kyee@rouge.phys.lsu.edu on
request.
| 1992-08-12
| 2007-05-23
|
[
"hep-lat",
"cond-mat",
"hep-ph"
] |
Claude Bernard, Amarjit Soni, Ken Yee
|
hep-lat/9208006
|
Continuum Gauge Fields from Lattice Gauge Fields
|
On the lattice some of the salient features of pure gauge theories and of
gauge theories with fermions in complex representations of the gauge group seem
to be lost. These features can be recovered by considering part of the theory
in the continuum. The prerequisite for that is the construction of continuum
gauge fields from lattice gauge fields. Such a construction, which is gauge
covariant and complies with geometrical constructions of the topological charge
on the lattice, is given in this paper. The procedure is explicitly carried out
in the $U(1)$ theory in two dimensions, where it leads to simple results.
| 1992-08-12
| 2009-10-22
|
[
"hep-lat"
] |
M. Goeckeler, A. S. Kronfeld, G. Schierholz and U.-J. Wiese
|
hep-lat/9208009
|
A New Technique for Measuring the Strangemess Content of the Proton on
the Lattice
|
A new technique for computing the strangeness content of the proton on the
lattice is described. It is applied to the calculation of the strange quark
contribution to the proton's spin, specifically to the evaluation of the proton
matrix element of the strange quark axial current. Preliminary results are not
in disagreement with the EMC experiment. NOTE: This paper is available only in
postscript form.
| 1992-08-12
| 2009-10-22
|
[
"hep-lat",
"hep-ph"
] |
Jeffrey E. Mandula and Michael C. Ogilvie
|
hep-lat/9208008
|
Phase Transitions in Induced QCD
|
The variety of the phase transitions in Induced QCD are studied. Depending
upon the parameters in the scalar field potential, there could be infinite
number of fixed points, with different critical behavior. The integral equation
for the density of the eigenvalues of the scalar field are generalized to the
weak coupling phases, with the gap at the origin. We find a wide class of the
massive solutions of these integral equations in the strong coupling phases,
and derive an explicit eigenvalue equation for the scalar branch of the mass
spectrum.
| 1992-08-12
| 2015-06-25
|
[
"hep-lat",
"hep-th"
] |
A.A.Migdal
|
hep-lat/9208010
|
Gribov Copies and Smeared Correlation Functions in Lattice QCD
|
We study the influence of Gribov copies in the Coulomb gauge on the smeared
hadronic correlation functions that are involved in the determination of the B
meson decay constant. We find that the residual gauge freedom associated to
Gribov copies induces observable noise effects, though at the level of
numerical accuracy of our simulation these effects are not relevant to the
final determination of f_B. Our results indicate that such effects may become
important on bigger lattices.
| 1992-08-12
| 2009-10-22
|
[
"hep-lat"
] |
M.L. Paciello, C. Parrinello, S. Petrarca, B. Taglienti, A. Vladikas
|
hep-lat/9208005
|
Comparison of Lattice Coulomb Gauge Wave Functions in Quenched
Approximation and with Dynamical Fermions
|
We present a comparison of Coulomb gauge wave functions from $6/{g^2}=6.0$
quenched simulations with two simulations which include the effects of
dynamical fermions: simulations with two flavors of dynamical staggered quarks
and valence Wilson quarks at $6/{g^2}=5.6$ and simulations with two flavors of
dynamical Wilson quarks and Wilson valence quarks, at $6/{g^2}=5.3$. The
spectroscopy of these systems is essentially identical. Parameterizations of
the wave functions are presented which can be used as interpolating fields for
spectroscopy calculations. The sizes of particles are calculated using these
parameterized wave functions. The resulting sizes are small, approximately half
the sizes of the physical states. The charge radius of the neutron, which
provides an indication of the asymmetries between the wave functions of up and
down quarks, is calculated. Although the size of the nucleon in these
simulations is small, the ratio of the charge radius of the neutron to that of
the proton is consistent with the physical value. We find no significant
differences between the quenched and dynamical simulations.
| 1992-08-07
| 2009-10-22
|
[
"hep-lat"
] |
M. Hecht, et al. (High Energy Monte Carlo Grand Challenge)
|
hep-lat/9208004
|
A Rigourous Treatment of the Lattice Renormalization Problem of F_B
|
The $B$-meson decay constant can be measured on the lattice using a $1/m_b$
expansion. To relate the physical quantity to Monte Carlo data one has to know
the renormalization coefficient, $Z$, between the lattice operators and their
continuum counterparts. We come back to this computation to resolve
discrepancies found in previous calculations. We define and discuss in detail
the renormalization procedure that allows the (perturbative) computation of
$Z$. Comparing the one-loop calculations in the effective Lagrangian approach
with the direct two-loop calculation of the two-point $B$-meson correlator in
the limit of large $b$-quark mass, we prove that the two schemes give
consistent results to order $\alpha_s$. We show that there is, however, a
renormalization prescription ambiguity that can have sizeable numerical
consequences. This ambiguity can be resolved in the framework of an $O(a)$
improved calculation, and we describe the correct prescription in that case.
Finally we give the numerical values of $Z$ that correspond to the different
types of lattice approximations discussed in the paper.
| 1992-08-05
| 2010-03-19
|
[
"hep-lat"
] |
Ph.Boucaud, J-P Leroy, J. Micheli, O. P\`ene and G.C Rossi
|
hep-lat/9208003
|
A Parallel Cluster Labeling Method for Monte Carlo Dynamics
|
We present an algorithm for cluster dynamics to efficiently simulate large
systems on MIMD parallel computers with large numbers of processors. The method
divides physical space into rectangular cells which are assigned to processors
and combines a serial local procedure with a nearest neighbor relaxation
process. By controlling overhead and reducing inter-processor communication
this method attains good performance and speed-up. The complexity and scaling
properties of the algorithm are analyzed.
The algorithm has been used to simulate large 2d Ising systems (up to 27808 X
27808 sites) with Swendsen-Wang dynamics. Typical updating times on the order
of 82 nanosecs/site and efficiencies larger than 90% have been obtained using
256 processors on the CM-5 supercomputer.
| 1992-08-03
| 2009-10-22
|
[
"hep-lat"
] |
Mike Flanigan and Pablo Tamayo
|
hep-lat/9208002
|
Chern-Simons term in the 4-dimensional SU(2) Higgs model
|
Using a variation of Lueschers geometric charge definition for SU(2) lattice
gauge theory, we have managed to give a geometric expression for it's
Chern-Simons ter. From this definition we have checked the periodic structure.
we determined the Chern-Simons density for symmetric and asymmetric lattices
near the critical region in the SU(2) Higgs model. The data indicate that
tunneling is increased at high temperature.
| 1992-08-03
| 2011-04-20
|
[
"hep-lat"
] |
F.Karsch, M.L.Laursen, T.Neuhaus, B.Plache and U.-J.Wiese
|
hep-lat/9208001
|
Non-Exponential Relaxation Time Scales in Disordered Systems: an
Application to Protein Dynamics
|
We study the dynamics of an heteropolymeric chain relaxing toward a new
equilibrium configuration after the action of an external perturbation. We
compare the results from Monte Carlo simulations with the results of a Langevin
normal mode decomposition. We discuss, for sake of comparison, the case of an
ordered homopolymeric chain.
| 1992-08-02
| 2008-02-03
|
[
"hep-lat",
"cond-mat",
"q-bio.QM"
] |
G. Iori, E. Marinari and G. Parisi
|
hep-lat/9207033
|
A Lower Bound on $T_{SR}/{m_{\rm H}}$ in the O(4) Model on Anisotropic
Lattices
|
Results of an investigation of the $O(4)$ spin model at finite temperature
using anisotropic lattices are presented. In both the large $N$ approximation
and numerical simulations using the Wolff cluster algorithm we find that the
ratio of the symmetry restoration temperature $T_{\rm SR}$ to the Higgs mass
$m_{\rm H}$ is independent of the anisotropy $\xi$. From the numerical
simulations we obtain a lower bound of $T_{\rm SR} / m_{\rm H} \simeq 0.58 \pm
0.02$ at a value for the Higgs mass $m_{\rm H}a_s \simeq 0.5$, which is lowered
further by about $10\%$ at $m_{\rm H}a_s \simeq 1$. Requiring certain timelike
correlation functions to coincide with their spacelike counterparts, quantum
and scaling corrections to the anisotropy are determined and are found to be
small, i.e., the anisotropy is found to be close to the ratio of spacelike and
timelike lattice spacings.
| 1992-07-31
| 2009-10-22
|
[
"hep-lat"
] |
R.V. Gavai, U. M. Heller, F. Karsch, T. Neuhaus and B. Plache
|
hep-lat/9207034
|
Chiral Yukawa models in the planar limit
|
We consider the most general renormalizable chiral Yukawa model with
$SU(3)_{\rm color}$ replaced by $SU(N_c)$, $SU(2)_{\rm L}$ replaced by $SU(N_w
)$ and $U(1)_{Y}$ replaced by $U(1)^{N_w -1}$ in the limit $N_c
\rightarrow\infty$, $N_w \rightarrow\infty$ with the ratio
$\rho=\sqrt{{N_w}\over{N_c}} \ne 0,\infty$ held fixed. Since for $N_w \ge 3$
only one renormalizable Yukawa coupling per family exists and there is no
mixing between families the limit is appropriate for the description of the
effects of a heavy top quark when all the other fermions are taken to be
massless. A rough estimate of the triviality bound on the Yukawa coupling is
equivalent to $m_t \le 1~TeV$.
| 1992-07-31
| 2009-10-22
|
[
"hep-lat",
"hep-ph"
] |
G. Bathas and H. Neuberger
|
hep-lat/9207035
|
The Phase Diagram of the $N=2$ Kazakov-Migdal Model
|
We have determined the phase diagram of the simplest version of a lattice
model introduced in the recent work of Kazakov and Migdal. If $m_0$ and
$\lambda$ are the bare mass and self coupling of the scalar field in the model
respectively, we find a line of first order phase transitions in the ($m_0,
\lambda$) plane ending in a critical point where $\lambda$ is nonzero. Kazakov
and Migdal speculate that their model of scalar field theory could induce QCD.
Our work indicates that for $N=2$ there is no continuum limit for the
Kazakov-Migdal model except at the critical end point. Whether or not a
nontrivial continuum limit exists in the vicinity of the critical point
requires careful study of the renormalization group properties of the model.
| 1992-07-31
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
Andreas Gocksch and Yue Shen
|
hep-lat/9207032
|
Topological susceptibility and string tension in the lattice CP(N)
models
|
In the lattice CP(N) models we studied the problems related to the measure of
the topological susceptibility and the string tension . We perfomed numerical
simulations at N=4 and N=10. In order to test the universality, we adopted two
different lattice formulations. Scaling and universality tests led to the
conclusion that at N=10 the geometrical approach gives a good definition of
lattice topological susceptibility. On the other hand, N=4 proved not to be
large enough to suppress the unphysical configurations, called dislocations,
contributing to the topological susceptibility. We obtained other
determinations of the topological susceptibility by the field theoretical
method, wich relies on a local definition of the lattice topological charge
density, and the cooling method. They gave quite consistent results, showing
scaling and universality. The large-N expansion predicts an exponential area
law behavior for sufficiently large Wilson loops, which implies confinement,
due to the dynamical matter fields and absence of the screening phenomenon. We
determined the string tension, without finding evidence of screening effects.
| 1992-07-31
| 2016-08-31
|
[
"hep-lat"
] |
M. Campostrini, P. Rossi, and E. Vicari
|
hep-lat/9207031
|
Finite Size Scaling of Probability Distributions in SU(2) Lattice Gauge
Theory and Phi^4 Field Theory
|
For a system near a second order phase transition, the probability
distribution for the order parameter can be given a finite size scaling form.
This fact is used to compare the finite temperature phase transition for the
Wilson lines in d=3+1 SU(2) lattice gauge theory with the phase transition in
d=3 phi^4 field theory. I exhibit the finite size scaled probability
distributions in the form of a function of two variables (the reduced
`temperature' and the magnetization) for both models. The two surfaces look
identical, and an analysis of the errors also suggests that they are the same.
This strengthens the idea that the SU(2) effective line theory is in the Ising
universality class. I argue for the wider application of the method used here.
| 1992-07-29
| 2007-05-23
|
[
"hep-lat"
] |
Stuart Staniford-Chen
|
hep-lat/9207030
|
Global Demons in Field Theory : Critical Slowing Down in the Xy Model
|
We investigate the use of global demons, a `canonical dynamics', as an
approach to simulating lattice regularized field theories. This
deterministically chaotic dynamics is non-local and non-Hamiltonian, and
preserves the canonical measure rather than $\delta(H-E)$. We apply this
inexact dynamics to the 2D XY model, comparing to various implementations of
hybrid Monte Carlo, focusing on critical exponents and critical slowing down.
In addition, we discuss a scheme for making energy non-conserving dynamical
algorithms exact without the use of a Metropolis hit.
| 1992-07-27
| 2009-10-22
|
[
"hep-lat"
] |
Dimitri Kusnezov (Yale) and John Sloan (Ohio State)
|
hep-lat/9207029
|
Topology of the Yang-Mills Configuration space
|
It will be described how to uniquely fix the gauge using Coulomb gauge
fixing, avoiding the problem of Gribov copies. The fundamental modular domain,
which represents a one-to-one representation of the set of gauge invariant
degrees of freedom, is a bounded convex subset of the trans- verse gauge
fields. Boundary identifications are the only remnants of the Gribov copies,
and carry all the information about the topology of the Yang-Mills
configuration space. Conversely, the known topology can be shown to imply that
(on a set of measure zero on the boundary) some points of the boundary coincide
with the Gribov horizon. For the low-lying energies, wavefunctionals can be
shown to spread out "across" certain parts of these boundaries. This is how the
topology of Yang-Mills configuration space has an essential influence on the
low-lying spectrum, in a situation where these non- perturbative effects are
not exponentially suppressed.
This write-up is a short summary, with adequate references, where details on
most of the material I have presented can be found. However, not published
before, is a new observation concerning Henyey's gauge copies.
| 1992-07-27
| 2007-05-23
|
[
"hep-lat",
"hep-th"
] |
Pierre van Baal
|
hep-lat/9207028
|
Monte Carlo Calculation of Phase Shift in Four Dimensional O(4) $\phi^4$
Theory
|
The phase shift of the O(4) symmetric $\phi^4$ theory in the symmetric phase
is calculated numerically using the relation between phase shift and energy
levels of two-particle states recently derived by L\"{u}scher. The results
agree with the prediction of perturbation theory. A practical difficulty of the
method for a reliable extraction of the phase shift for large momenta due to
the necessity of a precise determination of excited two-particle energy levels
is pointed out.
| 1992-07-26
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
Jun Nishimura
|
hep-lat/9207027
|
A new approach to noncompact lattice qed with light fermions
|
We discuss detailed simulations of the non compact abelian model coupled to
light fermions, using a method previously developed that includes the effects
of the fermionic interactions in an effective action. The approximations
involved are related to an expansion in the flavour number. We address the
problem of the (non) triviality of the theory through a study of the analytical
properties of the effective action as a function of the pure gauge energy. New
numerical results for the plaquette energy, chiral condensate and a qualitative
analysis of the phase diagram are also presented.
| 1992-07-24
| 2015-06-25
|
[
"hep-lat"
] |
V. Azcoiti, G. Di Carlo and A.F. Grillo
|
hep-lat/9207026
|
A Multicanonical Algorithm and the Surface Free Energy in SU(3) Pure
Gauge Theory
|
We present a multicanonical algorithm for the SU(3) pure gauge theory at the
deconfinement phase transition. We measure the tunneling times for lattices of
size L^3x2 for L=8,10, and 12. In contrast to the canonical algorithm the
tunneling time increases only moderately with L. Finally, we determine the
interfacial free energy applying the multicanonical algorithm.
| 1992-07-23
| 2009-10-22
|
[
"hep-lat",
"astro-ph",
"cond-mat"
] |
B.Grossmann, M.L.Laursen, T.Trappenberg, U.-J.Wiese
|
hep-lat/9207025
|
QCD thermodynamics with two flavors of Wilson quarks at N_t=6
|
We report on a study of hadron thermodynamics with two flavors of Wilson
quarks on 12^3x6 lattices. We have studied the crossover between the high and
low temperature regimes for three values of the hopping parameter, kappa=0.16,
0.17, and 0.18. At each of these values of kappa we have carried out spectrum
calculations on 12^3x24 lattices for two values of the gauge coupling in the
vicinity of the crossover in order to set an energy scale for our
thermodynamics calculations and to determine the critical value of the gauge
coupling for which the pion and quark masses vanish. For kappa=0.17 and 0.18 we
find coexistence between the high and low temperature regimes over 1,000
simulation time units indicating either that the equilibration time is
extremely long or that there is a possibility of a first order phase
transition. The pion mass is large at the crossover values of the gauge
coupling, but the crossover curve has moved closer to the critical curve along
which the pion and quark masses vanish, than it was on lattices with four time
slices. In addition, values of the dimensionless quantity T_c/m_rho are in
closer agreement with those for staggered quarks than was the case at N_t=4. (A
POSTSCRIPT VERSION OF THIS PAPER IS AVAILABLE BY ANONYMOUS FTP FROM
sarek.physics.ucsb.edu (128.111.8.250) IN THE FILE pub/wilson_thermo.ps)
| 1992-07-22
| 2009-10-22
|
[
"hep-lat"
] |
Claude Bernard, Michael C. Ogilvie, Thomas A. DeGrand, Carleton DeTar,
Steven Gottlieb, Alex Krasnitz, R. L. Sugar, and D. Toussaint
|
hep-lat/9207024
|
Large $N$ analysis of the Higgs mass triviality bound
|
We calculate the triviality bound on the Higgs mass in scalar field theory
models whose global symmetry group $SU(2)_L \times SU(2)_{\rm custodial}
\approx O(4)$ has been replaced by $O(N)$ and $N$ has been taken to infinity.
Limits on observable cutoff effects at four percent in several regularized
models with tunable couplings in the bare action yield triviality bounds
displaying a large degree of universality. Extrapolating from $N=\infty$ to
$N=4$ we conservatively estimate that a Higgs particle with mass up to
$0.750~TeV$ and width up to $0.290~TeV$ is realizable without large cutoff
effects, indicating that strong scalar self interactions in the standard model
are not ruled out.
Note: The full ps file of this preprint is also available via anonymous ftp
to ftp.scri.fsu.edu. To get the ps file, ftp to this address and use for
username "anonymous" and for password your name. The file is in the directory
pub/vranas (to go to that directory type: cd pub/vranas) and is called
lrg_n_hig.ps (to get it type: get lrg_n_hig.ps)
| 1992-07-22
| 2009-10-22
|
[
"hep-lat",
"hep-ph"
] |
Urs M. Heller, Herbert Neuberger and Pavlos Vranas
|
hep-lat/9207022
|
Crossover Between Weakly and Strongly Self-avoiding Random Surfaces
|
We investigate the crossover between weak and strong self-avoidance in a
simulation of random surfaces with extrinsic curvature. We consider both
dynamically triangulated and rigid surfaces with the two possible
discretizations of the extrinsic curvature term.
| 1992-07-21
| 2009-10-22
|
[
"hep-lat"
] |
C.F. Baillie and D.A. Johnston
|
hep-lat/9207023
|
Multicanonical Spin Glass Simulations
|
We report a Monte Carlo simulation of the $2D$ Edwards-Anderson spin glass
model within the recently introduced multicanonical ensemble. Replica on
lattices of size $L^2$ up to $L=48$ are investigated. Once a true groundstate
is found, we are able to give a lower bound on the number of statistically
independent groundstates sampled. Temperature dependence of the energy, entropy
and other quantities of interest are easily calculable. In particular we report
the groundstate results. Computations involving the spin glass order parameter
are more tedious. Our data indicate that the large $L$ increase of the
ergodicity time is reduced to an approximately $V^3$ power law. Altogether the
results suggest that the multicanonical ensemble improves the situation of
simulations for spin glasses and other systems which have to cope with similar
problems of conflicting constraints.
| 1992-07-21
| 2015-06-25
|
[
"hep-lat",
"cond-mat"
] |
B.A. Berg and T. Celik
|
hep-lat/9207021
|
Numerical simulation of heavy fermions in an SU(2)_L x SU(2)_R symmetric
Yukawa model
|
An exploratory numerical study of the influence of heavy fermion doublets on
the mass of the Higgs boson is performed in the decoupling limit of a chiral
$\rm SU(2)_L \otimes SU(2)_R$ symmetric Yukawa model with mirror fermions. The
behaviour of fermion and boson masses is investigated at infinite bare quartic
coupling on $4^3 \cdot 8$, $6^3 \cdot 12$ and $8^3 \cdot 16$ lattices. A first
estimate of the upper bound on the renormalized quartic coupling as a function
of the renormalized Yukawa-coupling is given.
| 1992-07-21
| 2010-12-23
|
[
"hep-lat"
] |
C. Frick, L. Lin, I. Montvay, G. Munster, M. Plagge, T. Trappenberg,
H. Wittig
|
hep-lat/9207020
|
Topography of the hot sphaleron Transitions
|
By numerical simulations in {\it real time} we provide evidence in favour of
sphaleron like transitions in the hot, symmetric phase of the electroweak
theory. Earlier performed observations of a change in the Chern-Simons number
are supplemented with a measurement of the lowest eigenvalues of the
three-dimensional staggered fermion Dirac operator and observations of the
spatial extension of energy lumps associated with the transition. The
observations corroborate on the interpretation of the change in Chern-Simons
numbers as representing continuum physics, not lattice artifacts. By combining
the various observations it is possible to follow in considerable detail the
time-history of thermal fluctuations of the classical gauge-field
configurations responsible for the change in the Chern-Simons number.
| 1992-07-20
| 2009-10-22
|
[
"hep-lat"
] |
J. Ambjorn and K. Farakos
|
hep-lat/9207019
|
High Precision Verification of the Kosterlitz Thouless Scenario
|
We verify the Kosterlitz Thouless scenario for three different SOS
(solid-on-solid) models, including the dual transforms of XY-models with
Villain and with cosine action. The method is based on a matching of the
renormalization group (RG) flow of the candidate models with the flow of a bona
fide KT model, the exactly solvable BCSOS model. We obtain high precision
estimates for the critical couplings and other non-universal quantities.
| 1992-07-19
| 2009-10-22
|
[
"hep-lat",
"cond-mat"
] |
M. Hasenbusch, M. Marcu and K. Pinn
|
hep-lat/9207018
|
Fermion Interactions in the Wilson Yukawa Approach for Lattice Chiral
Gauge Theories
|
We consider fermion-gauge couplings in the Wilson-Yukawa approach for lattice
chiral gauge theories. At the leading order of a fermionic hopping parameter
expansion we find that the fermion-gauge coupling has a chiral and tree-like
structure. We argue that this fermion-gauge coupling remains non-zero in the
continuum limit taken in the Higgs phase. Possible fermion-scalar couplings in
this approach are considered. We also evaluate the fermion interaction with an
external gauge field in the slightly modified model and show that it has a
chiral structure in general.
| 1992-07-18
| 2017-02-01
|
[
"hep-lat"
] |
Sinya Aoki
|
hep-lat/9207017
|
The equivalence of the SU(N) Yang Mills Theory with a Purely Fermionic
Model
|
We investigate the detailed conditions under which a purely fermionic model
with current-current interaction goes over to a renormalizable, asymptotically
free SU$(N)$ gauge theory.
| 1992-07-17
| 2009-10-22
|
[
"hep-lat"
] |
Anna Hasenfratz, Peter Hasenfratz
|
hep-lat/9207016
|
Improving Multigrid and Conventional Relaxation Algorithms for
Propagators
|
Practical modifications of deterministic multigrid and conventional
relaxation algorithms are discussed. New parameters need not be tuned but are
determined by the algorithms themselves. One modification can be thought of as
``updating on a last layer consisting of a single site''. It eliminates
critical slowing down in computations of bosonic and fermionic propagators in a
fixed volume. Here critical slowing down means divergence of asymptotic
relaxation times as the propagators approach criticality. A remaining volume
dependence is weak enough in case of bosons so that conjugate gradient can be
outperformed. However, no answer can be given yet if the same is true for
staggered fermions on lattices of realizable sizes. Numerical results are
presented for propagators of bosons and of staggered fermions in 4-dimensional
$SU(2)$ gauge fields.
| 1992-07-17
| 2009-10-22
|
[
"hep-lat"
] |
Thomas Kalkreuter
|
hep-lat/9207015
|
1/N Expansion and Particle Spectrum in Induced QCD
|
We study the 1/N expansion in the recently proposed model of the lattice
gauge theory induced by heavy scalar field in adjoint representation. In the
first approximation the fluctuations of the density of eigenvalues of the
scalar field are Gaussian, so that the scalar glueball spectrum is defined from
the corresponding linear wave equation.
| 1992-07-16
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
A.A. Migdal
|
hep-lat/9207014
|
Lattice Charge Overlap: Towards the Elastic Limit
|
A numerical investigation of time-separated charge overlap measurements is
carried out for the pion in the context of lattice QCD using smeared Wilson
fermions. The evolution of the charge distribution function is examined and the
expected asymptotic time behavior $\sim e^{-(E_{q}-m_{\pi})t}$, where $t$
represents the charge density relative time separation, is clearly visible in
the Fourier transform. Values of the pion form factor are extracted using
point-to-smeared correlation functions and are seen to be consistent with the
expected monopole form from vector dominance. The implications of these results
for hadron structure calculations is briefly discussed.
| 1992-07-16
| 2009-10-22
|
[
"hep-lat"
] |
Walter Wilcox
|
hep-lat/9207012
|
A Proposal for Simulating Chiral Fermions
|
We describe a method for evaluating chiral gauge theories that is not plagued
by the doubling problem. To demonstrate the efficiency of the approach, we
apply our ideas to the chiral Schwinger model.
| 1992-07-15
| 2009-10-22
|
[
"hep-lat"
] |
M. Goeckeler and G. Schierholz
|
hep-lat/9207013
|
The Topological Susceptibility of the Lattice CP(n-1) Model on the Torus
and the Sphere
|
The topological vacuum structure of the two-dimensional $~CP^{n-1}~$ model
for $~n = 3,5,7~$ is studied on the lattice. In particular we investigate the
small-volume limit on the torus as well as on the sphere and compare with
continuum results. For $~n \ge 5~$ , where lattice artifacts should be
suppressed, the topological susceptibility shows unexpectedly strong deviations
from asymptotic scaling. On the other hand there is an indication for a
convergence to values obtained analytically within the limit $~n \rightarrow
\infty~$ .
| 1992-07-15
| 2009-10-22
|
[
"hep-lat"
] |
N. Schultka and M. M\"uller-Preussker
|
hep-lat/9207009
|
The Schr\"odinger Functional - a Renormalizable Probe for Non-Abelian
Gauge Theories
|
Following Symanzik we argue that the Schr\"odinger functional in lattice
gauge theories without matter fields has a well-defined continuum limit. Due to
gauge invariance no extra counter terms are required. The Schr\"odinger
functional is, moreover, accessible to numerical simulations. It may hence be
used to study the scaling properties of the theory and in particular the
evolution of the renormalized gauge coupling from low to high energies. A
concrete proposition along this line is made and the necessary perturbative
analysis of the Schr\"odinger functional is carried through to 1-loop order.
| 1992-07-09
| 2016-08-14
|
[
"hep-lat"
] |
Martin L\"uscher and Rajamani Narayanan (DESY), Peter Weisz (MPI,
Munich), Ulli Wolff (CERN)
|
hep-lat/9207011
|
On Heteropolymer Shape Dynamics
|
We investigate the time evolution of the heteropolymer model introduced by
Iori, Marinari and Parisi to describe some of the features of protein folding
mechanisms. We study how the (folded) shape of the chain evolves in time. We
find that for short times the mean square distance (squared) between chain
configurations evolves according to a power law, $D \sim t ^\nu$. We discuss
the influence of the quenched disorder (represented by the randomness of the
coupling constants in the Lennard-Jones potential) on value of the critical
exponent. We find that $\nu$ decreases from $\frac{2}{3}$ to $\frac{1}{2}$ when
the strength of the quenched disorder increases.
| 1992-07-09
| 2009-10-22
|
[
"hep-lat",
"cond-mat",
"q-bio.QM"
] |
Pawel Pliszka and Enzo Marinari
|
hep-lat/9207010
|
Computation of the Running Coupling in the SU(2) Yang-Mills Theory
|
A finite-size scaling technique is applied to the SU(2) gauge theory (without
matter fields) to compute a non-perturbatively defined running coupling
alpha(q) for a range of momenta q given in units of the string tension K. We
find that already at rather low q, the evolution of alpha(q) is well described
by the 2-loop approximation to the Callan-Symanzik beta-function. At the
highest momentum reached, q=20 sqrt(K), we obtain alpha_MSbar(q)=0.187 +/-
0.005 +/- 0.009 for the running coupling in the MSbar scheme of dimensional
regularization.
| 1992-07-09
| 2016-08-14
|
[
"hep-lat"
] |
Martin L\"uscher (DESY), Peter Weisz (MPI, Munich), Rainer Sommer and
Ulli Wolff (CERN)
|
hep-lat/9207008
|
The Theory of Dynamical Random Surfaces with Extrinsic Curvature
|
We analyze numerically the critical properties of a two-dimensional
discretized random surface with extrinsic curvature embedded in a
three-dimensional space. The use of the toroidal topology enables us to enforce
the non-zero external extension without the necessity of defining a boundary
and allows us to measure directly the string tension. We show that a phase
transition from the crumpled phase to the smooth phase observed earlier for a
spherical topology appears also for a toroidal surface for the same finite
value of the coupling constant of the extrinsic curvature term. The phase
transition is characterized by the vanishing of the string tension. We discuss
the possible non-trivial continuum limit of the theory, when approaching the
critical point. Numerically we find a value of the critical exponent $\n$ to be
between .38 and .42. The specific heat, related to the extrinsic curvature term
seems not to diverge (or diverge slower than logarithmically) at the critical
point.
| 1992-07-08
| 2009-10-22
|
[
"hep-lat",
"hep-th"
] |
J. Ambjorn, A, Irback, J. Jurkiewicz and B. Petersson
|
hep-lat/9207007
|
Recent Results of Multimagnetical Simulations of the Ising Model
|
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the $2D$ and $3D$ Ising model. Stringent tests of the numerical
methods are performed by reproducing with high precision exact $2D$ results. In
the physically more interesting $3D$ case we estimate the amplitude $F^s_0$ of
the critical interfacial tension.
| 1992-07-08
| 2015-06-25
|
[
"hep-lat"
] |
U. Hansmann, B.A. Berg and T. Neuhaus
|
hep-lat/9207006
|
The Phase Diagram of a U(1) Higgs-Yukawa Model at Finite $\lambda$
|
In this paper we investigate how the phase diagram of a U(1) symmetric
Higgs-Yukawa system depends on the scalar self coupling $\lambda$. The phase
diagram of similar models with continuous symmetry were extensively studied in
the infinite scalar self coupling $\lambda=\infty$ limit. Recent analytical and
numerical calculations at zero self coupling showed qualitatively different
phase diagram, raising the question of the $\lambda$ dependence of the phase
diagram. Here we use analytical (large $N_f$, perturbative and mean field)
approximations as well as numerical simulations to investigate the system.
| 1992-07-06
| 2009-10-22
|
[
"hep-lat"
] |
A. Hasenfratz, K. Jansen and Y. Shen
|
hep-lat/9207004
|
Fermions in Models with Wilson--Yukawa Couplings
|
Our work on models with Wilson--Yukawa couplings is reviewed. Conclusions
include the failure of such models to produce continuum chiral gauge theories.
| 1992-07-04
| 2009-10-22
|
[
"hep-lat"
] |
M.F.L. Golterman and D.N. Petcher
|
hep-lat/9207005
|
On the Eichten--Preskill Proposal for Lattice Chiral Gauge Theories
|
We have studied the Eichten--Preskill proposal for constructing lattice
chiral gauge theories using both strong and weak coupling methods. The results
indicate that this proposal is unlikely to work due to a dynamical behavior
similar to that of the Smit--Swift proposal, which also does not give rise to
chiral fermions.
| 1992-07-04
| 2009-10-22
|
[
"hep-lat"
] |
M.F.L. Golterman, D.N. Petcher and E. Rivas
|
hep-lat/9207002
|
Gauge Dependence of Effective Quark Mass and Matrix Elements in
Gaugefixed Large $N$ Strong Coupling Lattice QCD
|
In conjunction with recent numerical \hbox{$\lambda~\partial_0 A_0 +
\nabla\cdot\vec{A} =0$} ``$\lambda$-gauge'' results reported in a companion
paper, we construct an $N\to\infty$ Wilson loop picture of
$\lambda$-gaugefixing in which (I)the $\lambda$-gauge expectation value of a
link chain $C$ is the weighted sum over Wilson loops made by joining to $C$ all
selfavoiding chains $\widetilde{C}$ closing $C$. (II)Weights
$A_{\widetilde{C}}$, containing all the $\lambda$-dependence, are given by the
$\beta=0$ $\lambda$-gauge expectation value of $\widetilde{C}$.
(III)$A_{\widetilde{C}}$ equals path-products of coefficients from the trace
expansion of the gaugefixing Boltzmann weight. From (II) and (III) we deduce
formulas for $\beta =0$ quark matrix elements. We find that $M_q^{(\lambda)}$
decreases with increasing $\lambda$; the quark propagator dispersion relation
is not covariant when $\lambda\ne 1$; and $\Delta I=1/2$ matching coefficients
are $\lambda$-independent. These strong coupling features are qualitatively
consistent with numerical $\beta=5.7$ and $6.0$ results briefly described here
for comparison purposes but mainly presented in a companion paper.
| 1992-07-03
| 2011-07-19
|
[
"hep-lat"
] |
Ken Yee
|
hep-lat/9207003
|
Kinematics of Multigrid Monte Carlo
|
We study the kinematics of multigrid Monte Carlo algorithms by means of
acceptance rates for nonlocal Metropolis update proposals. An approximation
formula for acceptance rates is derived. We present a comparison of different
coarse-to-fine interpolation schemes in free field theory, where the formula is
exact. The predictions of the approximation formula for several interacting
models are well confirmed by Monte Carlo simulations. The following rule is
found: For a critical model with fundamental Hamiltonian H(phi), absence of
critical slowing down can only be expected if the expansion of <H(phi + psi)>
in terms of the shift psi contains no relevant (mass) term. We also introduce a
multigrid update procedure for nonabelian lattice gauge theory and study the
acceptance rates for gauge group SU(2) in four dimensions.
| 1992-07-03
| 2009-10-22
|
[
"hep-lat"
] |
M.Grabenstein and K.Pinn
|
hep-lat/9207001
|
The Effective String of 3D Z_2 Gauge Theory as a c=1 compactified CFT
|
We report on a high precision Montecarlo test of the three dimensional Ising
gauge model at finite temperature. The string tension $\sigma$ is extracted
from the expectation values of correlations of Polyakov lines. Agreement with
the string tension extracted from Wilson loops is found only if the quantum
fluctuations of the flux tube are properly taken into account. The central
charge of the underlying conformal field theory is c=1.
| 1992-07-01
| 2015-06-25
|
[
"hep-lat",
"hep-th"
] |
M. Caselle, R. Fiore, F. Gliozzi and S. Vinti
|
hep-lat/9206027
|
Numerical Analysis of the Quark Fraction of the Proton Spin
|
We report on a lattice QCD estimate of the quark spin fraction of the proton
spin. The estimate is arrived at by means of a lattice QCD simulation of the
polarized proton matrix element of the Adler-Bell-Jackiw anomaly. The
preliminary result of the simulation is that this fraction is rather small.
This is in accord with the interpretation of the EMC experiment that the quark
spins are responsible for very little, if any, of the proton spin. (Talk given
at the Adriatico Research Conference on Polarization Dynamics in Nuclear and
Particle Physics, Trieste, January, 1992) NOTE: This paper is available only in
postscript form.
| 1992-06-30
| 2007-05-23
|
[
"hep-lat",
"hep-ph"
] |
Jeffrey E. Mandula
|
hep-lat/9206026
|
The Universlity Class of Monopole Condensation in Non-Compact, Quenched
Lattice QED
|
Finite size scaling studies of monopole condensation in noncompact quenched
lattice $QED$ indicate an authentic second order phase transition lying in the
universality class of four dimensional percolation. Since the upper critical
dimension of percolation is six, the measured critical indices are far from
mean-field values. We propose a simple set of ratios as the exact critical
indices for this transition. The implication of these results for critical
points in Abelian gauge theories are discussed.
| 1992-06-30
| 2009-10-22
|
[
"hep-lat"
] |
Aleksandar Kocic (CERN), John Kogut (Illinois), Simon Hands (CERN)
|
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