Renormalisation group calculation of correlation functions for the 2D random bond Ising and Potts models

We find the cross-over behavior for the spin-spin correlation function for the 2D Ising and 3-states Potts model with random bonds at the critical point. The procedure employed is the renormalisation approach of the perturbation series around the conformal field theories representing the pure models. We obtain a crossover in the amplitude for the correlation function for the Ising model which doesn't change the critical exponent, and a shift in the critical exponent produced by randomness in the case of the Potts model. A comparison with numerical data is discussed briefly

Estudio de sesgo de una prueba para evaluar memoria de trabajo fonologica y visoespacial, en ninos entre 4 anos y 5 anos 11 meses, con desarrollo tipico, de la ciudad de Talca

87 p.La memoria de trabajo es el “espacio mental” necesario para el recuerdo episódico y semántico, para el pensamiento y la toma de decisión, para la comprensión del lenguaje y el cálculo mental, y en general para todas las actividades cognitivas que requieren atención y procesamiento controlado (Miyake y Shah, 1999). Se encuentra directamente relacionada con el desarrollo de habilidades de procesamiento lingüístico, adquisición de lectura y comprensión de lectura, así como también en la adquisición de nuevas palabras. Se realizó un estudio de sesgo de la prueba creada, específicamente relacionado con la edad y género de los menores, en donde se analizó la existencia de diferencias significativas en el rendimiento en la prueba para evaluar memoria de trabajo, entre ambos géneros y entre 2 rangos etáreos (uno de 4 años a 4 años 11 meses y otro de 5 años a 5 años 11 meses de edad), luego ésto se comparó con la teoría existente sobre el tema. Finalmente, el análisis arroja la existencia de sesgo relacionado con la edad de los menores y no así con el sexo de los menores

Magnetization Process of the Classical Heisenberg Model on the Shastry-Sutherland Lattice

We investigate classical Heisenberg spins on the Shastry-Sutherland lattice and under an external magnetic field. A detailed study is carried out both analytically and numerically by means of classical Monte-Carlo simulations. Magnetization pseudo-plateaux are observed around 1/3 of the saturation magnetization for a range of values of the magnetic couplings. We show that the existence of the pseudo-plateau is due to an entropic selection of a particular collinear state. A phase diagram that shows the domains of existence of those pseudo-plateaux in the $(h, T)$ plane is obtained.Comment: 9 pages, 11 figure

Hubbard ladders in a magnetic field

The behavior of a two leg Hubbard ladder in the presence of a magnetic field is studied by means of Abelian bosonization. We predict the appearance of a new (doping dependent) plateau in the magnetization curve of a doped 2-leg spin ladder in a wide range of couplings. We also discuss the extension to N-leg Hubbard ladders

CW laser operation around 2-μm in (Tm,Yb):KLu(WO4) 2

Laser generation in continuous wave (CW) regime at 1.94-μm from (Tm,Yb) codoped system has been investigated in two different hosts: KLu(WO 4)2 and KY(WO4)2. The high quality crystals were grown by the Top-Seeded Solution Growth Slow Cooling (TSSG-SC) method with doping levels of 2.5 at. %Tm and 5 at. %Yb. The active media were pumped with a diode laser at 980 nm. We demonstrated the superior performance of KLu(WO4)2 compared to that of KY(WO4) 2 and improved the results already obtained in the literature. The maximum laser output power reached was 157 mW for (Tm,Yb):KLu(WO 4)2 and 123 mW for (Tm,Yb):KY(WO4)2. © 2010 Published by Elsevier Ltd

A Non-Perturbative Approach to the Random-Bond Ising Model

We study the N -> 0 limit of the O(N) Gross-Neveu model in the framework of the massless form-factor approach. This model is related to the continuum limit of the Ising model with random bonds via the replica method. We discuss how this method may be useful in calculating correlation functions of physical operators. The identification of non-perturbative fixed points of the O(N) Gross-Neveu model is pursued by its mapping to a WZW model.Comment: 17 pages LaTeX, 1 PostScript figure included using psfig.st

CW laser operation around 2-μm in (Tm,Yb):KLu(WO4) 2

Laser generation in continuous wave (CW) regime at 1.94-μm from (Tm,Yb) codoped system has been investigated in two different hosts: KLu(WO 4)2 and KY(WO4)2. The high quality crystals were grown by the Top-Seeded Solution Growth Slow Cooling (TSSG-SC) method with doping levels of 2.5 at. %Tm and 5 at. %Yb. The active media were pumped with a diode laser at 980 nm. We demonstrated the superior performance of KLu(WO4)2 compared to that of KY(WO4) 2 and improved the results already obtained in the literature. The maximum laser output power reached was 157 mW for (Tm,Yb):KLu(WO 4)2 and 123 mW for (Tm,Yb):KY(WO4)2. © 2010 Published by Elsevier Ltd

Increasing of entanglement entropy from pure to random quantum critical chains

It is known that the entropy of a block of spins of size $L$ embedded in an infinite pure critical spin chain diverges as the logarithm of $L$ with a prefactor fixed by the central charge of the corresponding conformal field theory. For a class of strongly random spin chains, it has been shown that the correspondent block entropy still remains universal and diverges logarithmically with an "effective" central charge. By computing the entanglement entropy for a family of models which includes the $N$-states random Potts chain and the $Z_N$ clock model, we give some definitive answer to some recent conjectures about the behaviour of the effective central charge. In particular, we show that the ratio between the entanglement entropy in the pure and in the disordered system is model dependent and we provide a series of critical models where the entanglement entropy grows from the pure to the random case.Comment: 4 pages, 2 eps figures, added reference