First order signatures in 4D pure compact U(1) gauge theory with toroidal and spherical topologies

We study the pure compact U(1) gauge theory with the extended Wilson action (\beta, \gamma couplings) by finite size scaling techniques, in lattices ranging from L=6 to L=24 in the region of \gamma <= 0 with toroidal and spherical topologies. The phase transition presents a double peak structure which survives in the thermodynamical limit in the torus. In the sphere the evidence support the idea of a weaker, but still first order, phase transition. For negative values of gamma the transition becomes weaker and larger lattices are needed to find its asymptotic behaviour. Along the transient region the behaviour is the typical one of a weak first order transition for both topologies, with a region where 1/d < nu < 0.5, which becomes nu compatible with 1/d when larger lattices are used.Comment: Some references added; changes in the text mainly wording. To appear in Phys. Lett.

Productive Efficiency in 16 European Countries

We investigate in this paper differences in productive efficiency across sixteen European countries. In order to assess differences in productive efficiency, we have built a dynamic input-output model and computed for each country the balanced growth rate and the balanced output composition. After that, we investigate how the differences existing between the output composition for balanced growth and the actual one relate to the differences between the rate of balanced growth and the actual one. In the final part of the paper we examine the influence of individual sectors on the rate of balanced growth by looking for growth-sensitive sectors.Productive efficiency, input-output, growth, Europe

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 $\lambda\phi^2_1 \phi^2_2$ model in three dimensions. We find no trace of Inverse Symmetry Breaking in the region of negative $\lambda$'s for which the one-loop effective potential predicts this phenomenon. Moreover, for $\lambda$'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.

Repercusión de las opacidades vitreas yatrogénicas en pacientes con degeneración macular asociada a la edad en tratamiento antiangiogénico

El objetivo de este trabajo es estimar la frecuencia de las opacidades vítreas (fundamentalmente microburbujas de silicona) y las posibles repercusiones subjetivas de dichas opacidades (miodesopsias) en pacientes con Degeneración Macular Asociada a la Edad (DMAE) en tratamiento antiangiogénico (anti-VEGF). Además, analizar la relación del número de inyecciones con la observación más o menos abundante de microburbujas de silicona en el vítreo y con la percepción de miodesopsias. Estudio observacional, descriptivo y transversal de 101 pacientes, diagnosticados de DMAE de tipo neovascular, con al menos 1 año de tratamiento anti-VEGF intravítreo. Se estudió la frecuencia de las opacidades vítreas secundarias al tratamiento mediante la visualización directa de las microburbujas de silicona en lámpara de hendidura y la existencia de posibles artefactos producidos por opacidades vítreas en la tomografía de coherencia óptica (OCT). A través de un cuestionario administrado al paciente se estudió la percepción de miodesopsias. Para esto se dividió a la muestra en un grupo de estudio (miodesopsias sintomáticas post-tratamiento) y un grupo control (sin miodesopsias sintomáticas). Se realizó el estudio completo a 98 pacientes, con 142 ojos tratados que han recibido un total de 2.377 inyecciones. El tiempo medio de tratamiento fue de 44,7 meses. La media de inyecciones/ojo tratado fue de 16,7 durante este tiempo. Un 44,9% de los pacientes estaban o habían estado en tratamiento en ambos ojos. Un 88,4% de los ojos tratados (92,8% de los pacientes) presentaban microburbujas de silicona en la cavidad vítrea, encontrándose en casi la mitad de los casos un número incontables de microburbujas (43,6%). Se encontró una correlación positiva entre el número de inyecciones y la frecuencia de microburbujas (coeficiente de correlación de 0,7). A pesar de la gran incidencia de microburbujas, éstas sólo han producido artefactos en la OCT de forma excepcional (2,1%). No se han encontrado diferencias significativas entre el grupo de estudio y el grupo control en relación con la presencia de microburbujas. La inmensa mayoría de los pacientes presentaban microburbujas de silicona en cavidad vítrea. La presencia de microburbujas es más frecuente cuantas más inyecciones intravítreas haya recibido el paciente. En general, la presencia de microburbujas no conlleva una mayor frecuencia de percepción de miodesopsias.Departamento de Cirugía, Oftalmología, Otorrinolaringología y FisioterapiaMáster en Investigación en Ciencias de la Visió

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 $24^4$ in one case) and high statistics are used. We fix $\beta =1.15$ and explore specially a region of $\lambda$-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 $\lambda \gtrsim 0.005$, while for smaller values of $\lambda$ 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

The U(1) phase transition on toroidal and spherical lattices

We have studied the properties of the phase transition in the U(1) compact pure gauge model paying special atention to the influence of the topology of the boundary conditions. From the behavior of the energy cumulants and the observation of an effective \nu -> 1/d on toroidal and spherical lattices, we conclude that the transition is first order.Comment: LATTICE98(gauge

A proposal of a Renormalization Group transformation

We propose a family of renormalization group transformations characterized by free parameters that may be tuned in order to reduce the truncation effects. As a check we test them in the three dimensional XY model. The Schwinger--Dyson equations are used to study the renormalization group flow.Comment: Contribution to Lattice'94. uuencoded postscript fil

SMOOTHERS AND THEIR APPLICATIONS IN AUTONOMOUS SYSTEM THEORY

Abstract. In this paper the author introduces the concept of smoother. Roughly speaking, a smoother is a pair (s, K) consisting of a continuous map s sending each point p of its domain into a closed neighborhood Vp of p, and an operator K that transforms any function f into another Kf being smoother than f. This property allows us to remove the effect of a perturbation P from the solutions of an autonomous system the vector field of which is modified by P