824 research outputs found
Spins coupled to a -Regge lattice in 4d
We study an Ising spin system coupled to a fluctuating four-dimensional
-Regge lattice and compare with the results of the four-dimensional Ising
model on a regular lattice. Particular emphasis is placed on the phase
transition of the spin system and the associated critical exponents. We present
results from finite-size scaling analyses of extensive Monte Carlo simulations
which are consistent with mean-field predictions.Comment: Lattice2001(surfaces), 3 pages, 2 figure
Orbiting Geophysical Observatory Attitude Control Subsystem Design Survey. NASA/ERC Design Criteria Program, Guidance and Control
This design survey summarizes the history of the Orbiting Geophysical Observatories' (OGO) Attitude Control Subsystem (ACS) from the proposal phase through current flight experience. Problems encountered in design, fabrication, test, and on orbit are discussed. It is hoped that the experiences of the OGO program related here will aid future designers
Orbiting Geophysical Observatory Attitude Control Subsystem design survey
Development history and design modifications for attitude control subsystem of OG
Absence of logarithmic scaling in the ageing behaviour of the 4D spherical model
The non-equilibrium dynamics of the kinetic spherical model, quenched to
T<=T_c, with a non-conserved order-parameter is studied at its upper critical
dimension d=d*=4. In the scaling limit where both the waiting time s and the
observation time t are large and the ratio y=t/s>1 is fixed, the scaling
functions of the two-time autocorrelation and autoresponse functions do not
contain any logarithmic correction factors and the typical size of correlated
domains scales for large times as L(t) ~ t^0.5 .Comment: Latex2e, 12 pages, 2 figures included, (final form
Universal Amplitude Ratios in the Ising Model in Three Dimensions
We use a high-precision Monte Carlo simulation to determine the universal
specific-heat amplitude ratio A+/A- in the three-dimensional Ising model via
the impact angle \phi of complex temperature zeros. We also measure the
correlation-length critical exponent \nu from finite-size scaling, and the
specific-heat exponent \alpha through hyperscaling. Extrapolations to the
thermodynamic limit yield \phi = 59.2(1.0) degrees, A+/A- = 0.56(3), \nu =
0.63048(32) and \alpha = 0.1086(10). These results are compatible with some
previous estimates from a variety of sources and rule out recently conjectured
exact values.Comment: 17 pages, 5 figure
Scaling and Density of Lee-Yang Zeroes in the Four Dimensional Ising Model
The scaling behaviour of the edge of the Lee--Yang zeroes in the four
dimensional Ising model is analyzed. This model is believed to belong to the
same universality class as the model which plays a central role in
relativistic quantum field theory. While in the thermodynamic limit the scaling
of the Yang--Lee edge is not modified by multiplicative logarithmic
corrections, such corrections are manifest in the corresponding finite--size
formulae. The asymptotic form for the density of zeroes which recovers the
scaling behaviour of the susceptibility and the specific heat in the
thermodynamic limit is found to exhibit logarithmic corrections too. The
density of zeroes for a finite--size system is examined both analytically and
numerically.Comment: 17 pages (4 figures), LaTeX + POSTSCRIPT-file, preprint UNIGRAZ-UTP
20-11-9
Beyond the Ubiquitous Relapse Curve: A Data-Informed Approach
Relapse to alcohol and other substances has generally been described by curves that resemble one another. However, these curves have been generated from the time to first use after a period of abstinence without regard to the movement of individuals into and out of drug use. Instead of measuring continuous abstinence, we considered post-treatment functioning as a more complicated phenomenon, describing how people move in and out of drinking states on a monthly basis over the course of a year. When we looked at time to first drink we observed the ubiquitous relapse curve. When we classified clients (N = 550) according to drinking state however, they frequently moved from one state to another with both abstinent and very heavy drinking states as being rather stable, and light or moderate drinking and heavy drinking being unstable. We found that clients with a family history of alcoholism were less likely to experience these unstable states. When we examined the distribution of cases crossed by the number of times clients switched states we found that a power function explained 83% of that relationship. Some of the remainder of the variance seems to be explained by the stable states of very heavy drinking and abstinence acting as attractors
Universality of the Ising Model on Sphere-like Lattices
We study the 2D Ising model on three different types of lattices that are
topologically equivalent to spheres. The geometrical shapes are reminiscent of
the surface of a pillow, a 3D cube and a sphere, respectively. Systems of
volumes ranging up to O() sites are simulated and finite size scaling is
analyzed. The partition function zeros and the values of various cumulants at
their respective peak positions are determined and they agree with the scaling
behavior expected from universality with the Onsager solution on the torus
(). For the pseudocritical values of the coupling we find significant
anomalies indicating a shift exponent for sphere-like lattice
topology.Comment: 24 pages, LaTeX, 8 figure
Testing fixed points in the 2D O(3) non-linear sigma model
Using high statistic numerical results we investigate the properties of the
O(3) non-linear 2D sigma-model. Our main concern is the detection of an
hypothetical Kosterlitz-Thouless-like (KT) phase transition which would
contradict the asymptotic freedom scenario. Our results do not support such a
KT-like phase transition.Comment: Latex, 7 pgs, 4 eps-figures. Added more analysis on the
KT-transition. 4-loop beta function contains corrections from D.-S.Shin
(hep-lat/9810025). In a note-added we comment on the consequences of these
corrections on our previous reference [16
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