490 research outputs found
A lattice Monte Carlo study of Inverse Symmetry Breaking in a two-scalar model in three dimensions
We carry a Monte Carlo study of the coupled two-scalar model in three dimensions. We find no trace of Inverse Symmetry
Breaking in the region of negative 's for which the one-loop effective
potential predicts this phenomenon. Moreover, for 's negative enough,
but still in the stability region for the potential, one of the transitions
turns out to be of first order, both for zero and finite temperature.Comment: 23 pages, 7 figures included, Latex, epsfig. Minor changes in Sec.3
and in the conclusions. In press on Nuc.Phys.
Study of the Coulomb-Higgs transition in the Abelian Higgs Model
The order of the Coulomb-Higgs transition in the U(1)-Higgs model with
unfrozen modulus of the scalar field is studied. Large lattices (up to
in one case) and high statistics are used. We fix and explore
specially a region of -values where metastability is observed. We
study the thermodynamical limit of several observables, in particular, the
latent heat, the specific heat, the decrement of the free energy between the
maxima and the central minimum of the two-peaked histogram, the Binder cumulant
and the displacement of the critical coupling with the lattice size. The
results point towards a second order transition for ,
while for smaller values of the strong metastability growing with the
lattice size seems to derive from a first order character.Comment: 10 pages, Latex, epsfig, uuencoded gzipped tar file, 4 figures
include
G protein beta gamma subunits synthesized in Sf9 cells. Functional characterization and the significance of prenylation of gamma
Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) consist of a nucleotide-binding alpha subunit and a high- affinity complex of beta and gamma subunits. There is molecular heterogeneity of beta and gamma, but the significance of this diversity is poorly understood. Different G protein beta and gamma subunits have been expressed both singly and in combinations in Sf9 cells. Although expression of individual subunits is achieved in all cases, beta gamma subunit activity (support of pertussis toxin-catalyzed ADP-ribosylation of rGi alpha 1) is detected only when beta and gamma are expressed concurrently. Of the six combinations of beta gamma tested (beta 1 or beta 2 with gamma 1, gamma 2, or gamma 3), only one, beta 2 gamma 1, failed to generate a functional complex. Each of the other five complexes has been purified by subunit exchange chromatography using Go alpha-agarose as the chromatographic matrix. We have detected differences in the abilities of the purified proteins to support ADP- ribosylation of Gi alpha 1; these differences are attributable to the gamma component of the complex. When assayed for their ability to inhibit calmodulin-stimulated type-I adenylylcyclase activity or to potentiate Gs alpha-stimulated type-II adenylylcyclase, recombinant beta 1 gamma 1 and transducin beta gamma are approximately 10 and 20 times less potent, respectively, than the other complexes examined. Prenylation and/or further carboxyl-terminal processing of gamma are not required for assembly of the beta gamma subunit complex but are indispensable for high affinity interactions of beta gamma with either G protein alpha subunits or adenylylcyclases
A multisite microcanonical updating method
We have made a study of several update algorithms using the XY model. We find
that sequential local overrelaxation is not ergodic at the scale of typical
Monte Carlo simulation time. We have introduced a new multisite microcanonical
update method, which yields results compatible with those of random
overrelaxation and the microcanonical demon algorithm, which are very much
slower, all being incompatible with the sequential overrelaxation results.Comment: 13 pages, 4 figure
Leaders among the leaders in Economics: a network analysis of the Nobel Prize laureates
We analyse the production and networks of Nobel laureates in Economics, employing the Normalized Impact Factor (NIF) of their publications in the Journal of Citation Report (Economics), to identify the academic leaders among those laureates awarded between 1969 and 2016. Our results indicate that direct collaborations among laureates are, in general, rare, but when we add all the co-authors of the laureates, there appears a very large component containing 70% of the nodes, so that more than two thirds of the laureates can be connected through only two steps. Deaton, Tirole, Arrow, and Stiglitz are identified as leaders according to the total production of their respective networks
Continuum limit of finite temperature from lattice Monte Carlo
The model at finite temperature is simulated on the lattice. For
fixed we compute the transition line for by means of
Finite Size Scaling techniques. The crossings of a Renormalization Group
trajectory with the transition lines of increasing give a well defined
limit for the critical temperature in the continuum. By considering different
RG trajectories, we compute as a function of the renormalized
parameters.Comment: 26 pages, Latex, epsfig, 8 figures include
General properties of overlap probability distributions in disordered spin systems. Toward Parisi ultrametricity
For a very general class of probability distributions in disordered Ising
spin systems, in the thermodynamical limit, we prove the following property for
overlaps among real replicas. Consider the overlaps among s replicas. Add one
replica s+1. Then, the overlap q(a,s+1) between one of the first s replicas,
let us say a, and the added s+1 is either independent of the former ones, or it
is identical to one of the overlaps q(a,b), with b running among the first s
replicas, excluding a. Each of these cases has equal probability 1/s.Comment: LaTeX2e, 11 pages. Submitted to Journal of Physics A: Mathematical
and General. Also available at
http://rerumnatura.zool.su.se/stefano/ms/ghigu.p
Gobernanza urbana interactiva para la formulación de planes parciales en el municipio de Zapopan
Este trabajo aborda cómo los procesos de planeación urbana en las ciudades en la época contemporánea han respondido a procesos y modelos tecnocráticos alejados de las realidades de sus ciudadanos. Esto no ha sido ajeno a las ciudades mexicanas. Desde hace décadas, en grandes ciudades como Guadalajara se han adoptado procesos y metodologías disociadas con las exigencias, necesidades y deseos de la población a escala municipal. El presente trabajo busca fortalecer los mecanismos de gobernanza urbana a nivel municipal con el propósito de vincular a la población en la toma de decisiones sobre el uso y destino del suelo urbano a escala distrital de forma más interactiva. El trabajo se desarrolla desde una mirada crítica de un proceso de planeación en particular y analiza de forma cualitativa eventos, actores, acciones, discursos y valores que se derivan de la participación en la formulación de planes parciales de desarrollo del municipio de Zapopan, Jalisco. Se presenta la historia del proceso para determinar los usos del suelo del distrito 5 en Zapopan, la cual se plantea como una narrativa cronológica que da cuenta de factores críticos en los procesos y mecanismos de participación ciudadana enfocados en la planeación del territorio. Estos procesos se sistematizaron en proposiciones para la construcción de un modelo de “gobernanza urbana en red”.Consejo Nacional de Ciencia y Tecnologí
Numerical Simulations of the 4D Edwards-Anderson Spin Glass with Binary Couplings
We present numerical results that allow a precise determination of the
transition point and of the critical exponents of the 4D Edwards-Anderson Spin
Glass with binary quenched random couplings. We show that the low T phase
undergoes Replica Symmetry Breaking. We obtain results on large lattices, up to
a volume : we use finite size scaling to show the relevance of our
results in the infinite volume limit.Comment: 18 pages + 17 figures, revised bibliography and minor typos. Added
Journal Re
Antiferromagnetism in four dimensions: search for non-triviality
We present antiferromagnetism as a mechanism capable of modifying
substantially the phase diagram and the critical behaviour of statistical
mechanical models. This is particularly relevant in four dimensions, due to the
connection between second order transition points and the continuum limit as a
quantum field theory. We study three models with an antiferromagnetic
interaction: the Ising and the O(4) Models with a second neighbour negative
coupling, and the \RP{2} Model. Different conclusions are obtained depending
on the model.Comment: 4 pages LateX. Contribution to Lat9
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