2,013 research outputs found
The Reading Preferences of Third, Fourth, and Fifth Graders
The purpose of this study was to investigate whether sex, grade, race, and teacher variables influenced the reading interests of children in the intermediate grades. It was hypothesized that each of the four listed variables would have an independent effect on children\u27s preferences
The Random-bond Potts model in the large-q limit
We study the critical behavior of the q-state Potts model with random
ferromagnetic couplings. Working with the cluster representation the partition
sum of the model in the large-q limit is dominated by a single graph, the
fractal properties of which are related to the critical singularities of the
random Potts model. The optimization problem of finding the dominant graph, is
studied on the square lattice by simulated annealing and by a combinatorial
algorithm. Critical exponents of the magnetization and the correlation length
are estimated and conformal predictions are compared with numerical results.Comment: 7 pages, 6 figure
Analytic Solution of Emden-Fowler Equation and Critical Adsorption in Spherical Geometry
In the framework of mean-field theory the equation for the order-parameter
profile in a spherically-symmetric geometry at the bulk critical point reduces
to an Emden-Fowler problem. We obtain analytic solutions for the surface
universality class of extraordinary transitions in for a spherical shell,
which may serve as a starting point for a pertubative calculation. It is
demonstrated that the solution correctly reproduces the Fisher-de Gennes effect
in the limit of the parallel-plate geometry.Comment: (to be published in Z. Phys. B), 7 pages, 1 figure, uuencoded
postscript file, 8-9
Universality of the Crossing Probability for the Potts Model for q=1,2,3,4
The universality of the crossing probability of a system to
percolate only in the horizontal direction, was investigated numerically by
using a cluster Monte-Carlo algorithm for the -state Potts model for
and for percolation . We check the percolation through
Fortuin-Kasteleyn clusters near the critical point on the square lattice by
using representation of the Potts model as the correlated site-bond percolation
model. It was shown that probability of a system to percolate only in the
horizontal direction has universal form for
as a function of the scaling variable . Here,
is the probability of a bond to be closed, is the
nonuniversal crossing amplitude, is the nonuniversal metric factor,
is the nonuniversal scaling index, is the correlation
length index.
The universal function . Nonuniversal scaling factors
were found numerically.Comment: 15 pages, 3 figures, revtex4b, (minor errors in text fixed,
journal-ref added
Quantum Phase Transitions in the U(5)-O(6) Large N limit
The U(5)-O(6) transitional behavior of the Interacting Boson Model in the
large N limit is revisited. Some low-lying energy levels, overlaps of the
ground state wavefunctions, B(E2) transition rate for the decay of the first
excited energy level to the ground state, and the order parameters are
calculated for different total numbers of bosons. The results show that
critical behaviors of these quantities are greatly enhanced with increasing of
the total number of bosons N, especially fractional occupation probability for
d bosons in the ground state, the difference between the expectation value of
n_d in the first excited 0^+ state and the ground state, and another quantity
related to the isomer shift behave similarly in both the O(6)-U(5) large N and
U(5)-SU(3) phase transitions.Comment: 7 Pages LaTeX, 3 figure
Quantum field theory of metallic spin glasses
We introduce an effective field theory for the vicinity of a zero temperature
quantum transition between a metallic spin glass (``spin density glass'') and a
metallic quantum paramagnet. Following a mean field analysis, we perform a
perturbative renormalization-group study and find that the critical properties
are dominated by static disorder-induced fluctuations, and that dynamic
quantum-mechanical effects are dangerously irrelevant. A Gaussian fixed point
is stable for a finite range of couplings for spatial dimensionality ,
but disorder effects always lead to runaway flows to strong coupling for . Scaling hypotheses for a {\em static\/} strong-coupling critical field
theory are proposed. The non-linear susceptibility has an anomalously weak
singularity at such a critical point. Although motivated by a perturbative
study of metallic spin glasses, the scaling hypotheses are more general, and
could apply to other quantum spin glass to paramagnet transitions.Comment: 16 pages, REVTEX 3.0, 2 postscript figures; version contains
reference to related work in cond-mat/950412
Scaling properties in off equilibrium dynamical processes
In the present paper, we analyze the consequences of scaling hypotheses on
dynamic functions, as two times correlations . We show, under general
conditions, that must obey the following scaling behavior , where the scaling variable is
and , two
undetermined functions. The presence of a non constant exponent
signals the appearance of multiscaling properties in the dynamics.Comment: 6 pages, no figure
Spin glass models with Kac interactions
In this paper I will review my work on disordered systems -spin glass model
with two body and body interactions- with long but finite interaction
range . I will describe the relation of these model with Mean Field Theory
in the Kac limit and some attempts to go beyond mean field.Comment: Proceedings of the Stat-phys23 conferenc
Reaction-diffusion processes in zero transverse dimensions as toy models for high-energy QCD
We examine numerically different zero-dimensional reaction-diffusion
processes as candidate toy models for high-energy QCD evolution. Of the models
examined -- Reggeon Field Theory, Directed Percolation and Reversible Processes
-- only the latter shows the behaviour commonly expected, namely an increase of
the scattering amplitude with increasing rapidity. Further, we find that
increasing recombination terms, quantum loops and the heuristic inclusion of a
running of the couplings, generically slow down the evolution.Comment: 17 pages, 7 figure
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