10,228 research outputs found
On the number of metastable states in spin glasses
In this letter, we show that the formulae of Bray and Moore for the average
logarithm of the number of metastable states in spin glasses can be obtained by
calculating the partition function with coupled replicas with the symmetry
among these explicitly broken according to a generalization of the `two-group'
ansatz. This equivalence allows us to find solutions of the BM equations where
the lower `band-edge' free energy equals the standard static free energy. We
present these results for the Sherrington-Kirkpatrick model, but we expect them
to apply to all mean-field spin glasses.Comment: 6 pages, LaTeX, no figures. Postscript directly available
http://chimera.roma1.infn.it/index_papers_complex.htm
Phase Ordering Dynamics of the O(n) Model - Exact Predictions and Numerical Results
We consider the pair correlation functions of both the order parameter field
and its square for phase ordering in the model with nonconserved order
parameter, in spatial dimension and spin dimension .
We calculate, in the scaling limit, the exact short-distance singularities of
these correlation functions and compare these predictions to numerical
simulations. Our results suggest that the scaling hypothesis does not hold for
the model. Figures (23) are available on request - email
[email protected]: 23 pages, Plain LaTeX, M/C.TH.93/2
Corrections to Scaling in Phase-Ordering Kinetics
The leading correction to scaling associated with departures of the initial
condition from the scaling morphology is determined for some soluble models of
phase-ordering kinetics. The result for the pair correlation function has the
form C(r,t) = f_0(r/L) + L^{-\omega} f_1(r/L) + ..., where L is a
characteristic length scale extracted from the energy. The
correction-to-scaling exponent \omega has the value \omega=4 for the d=1
Glauber model, the n-vector model with n=\infty, and the approximate theory of
Ohta, Jasnow and Kawasaki. For the approximate Mazenko theory, however, \omega
has a non-trivial value: omega = 3.8836... for d=2, and \omega = 3.9030... for
d=3. The correction-to-scaling functions f_1(x) are also calculated.Comment: REVTEX, 7 pages, two figures, needs epsf.sty and multicol.st
Phase Ordering Kinetics with External Fields and Biased Initial Conditions
The late-time phase-ordering kinetics of the O(n) model for a non-conserved
order parameter are considered for the case where the O(n) symmetry is broken
by the initial conditions or by an external field. An approximate theoretical
approach, based on a `gaussian closure' scheme, is developed, and results are
obtained for the time-dependence of the mean order parameter, the pair
correlation function, the autocorrelation function, and the density of
topological defects [e.g. domain walls (), or vortices ()]. The
results are in qualitative agreement with experiments on nematic films and
related numerical simulations on the two-dimensional XY model with biased
initial conditions.Comment: 35 pages, latex, no figure
Item Wording and Internal Consistency of a Measure of Cohesion: The Group Environment Questionnaire
A common practice for counteracting response acquiescence in psychological measures has been to employ both negatively and positively worded items. However, previous research has highlighted that the reliability of measures can be affected by this practice (Spector, 1992). The purpose of the present study was to examine the effect that the presence of negatively worded items has on the internal reliability of the Group Environment Questionnaire (GEQ). Two samples (N = 276) were utilized, and participants were asked to complete the GEQ (original and revised) on separate occasions. Results demonstrated that the revised questionnaire (containing all positively worded items) had significantly higher Cronbach α values for three of the four dimensions of the GEQ. Implications, alternatives, and future directions are discussed
Role Ambiguity in Sport Teams
The general purpose of the present study was to examine the nature of role ambiguity in sport teams and to explore the construct validity of the operational definition of role ambiguity developed by Beauchamp, Bray, Eys, and Carron (2002). Role ambiguity was operationalized as a multidimensional construct (Scope of Responsibilities, Behavioral Responsibilities, Evaluation of Performance, and Consequences of Not Fulfilling Responsibilities) that occurs in two contexts, offense and defense. Consistent with the a priori hypothesis, perceptions of role ambiguity exhibited some degree of within-group consistency and group-level variability, but most of the variance in role ambiguity was seen at the individual level. Also, perceptions of role ambiguity decreased from early to late season. Finally, veteran athletes experienced less role ambiguity than first-year athletes at the beginning of the season, but not at the end. Implications of the findings and suggestions for future research are discussed
The Effect of Role Ambiguity on Competitive State Anxiety
The purpose of this study was to examine the relationship between role ambiguity and precompetition state anxiety (A-state). Consistent with multidimensional anxiety theory (Martens, Vealey, & Burton, 1990), it was hypothesized that role ambiguity would be positively related to cognitive but not to somatic A-state. Based on the conceptual model presented by Beauchamp, Bray, Eys, and Carron (2002), role ambiguity in sport was operationalized as a multidimensional construct (i.e., scope of responsibilities, role behaviors, role evaluation, and role consequences) potentially manifested in each of two contexts, offense and defense. Consistent with hypotheses, ambiguity in terms of the scope of offensive role responsibilities predicted cognitive A-state (R2 = .19). However, contrary to hypotheses, offensive role-consequences ambiguity also predicted somatic A-state (R2 = .09). Results highlight the importance of using a multidimensional approach to investigate role ambiguity in sport and are discussed in terms of both theory advancement and possible interventions
Persistence in a Random Bond Ising Model of Socio-Econo Dynamics
We study the persistence phenomenon in a socio-econo dynamics model using
computer simulations at a finite temperature on hypercubic lattices in
dimensions up to 5. The model includes a ` social\rq local field which contains
the magnetization at time . The nearest neighbour quenched interactions are
drawn from a binary distribution which is a function of the bond concentration,
. The decay of the persistence probability in the model depends on both the
spatial dimension and . We find no evidence of ` blocking\rq in this model.
We also discuss the implications of our results for possible applications in
the social and economic fields. It is suggested that the absence, or otherwise,
of blocking could be used as a criterion to decide on the validity of a given
model in different scenarios.Comment: 11 pages, 4 figure
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