Nematic phase transitions in two-dimensional systems

Simulations of nematic-isotropic transition of liquid crystals in two dimensions are performed using an O(2) vector model characterised by non linear nearest neighbour spin interaction governed by the fourth Legendre polynomial $P\_4$. The system is studied through standard Finite-Size Scaling and conformal rescaling of density profiles or correlation functions. The low temperature limit is discussed in the spin wave approximation and confirms the numerical results, while the value of the correlation function exponent at the deconfining transition seems controversial.Comment: Talk given at Statphys 2005, Lviv, Ukrain

Effects of aerogel-like disorder on the critical behavior of O(m)-vector models. Recent simulations and experimental evidences

We review some results on the effect of a specific type of quenched disorder on well known O(m)-vector models in three dimension. Evidences of changes of criticality in both systems, when confined in aerogel pores, are briefly referenced. The 3DXY model (m=2) represents the universality class to which the \lambda-transition of bulk superfluid $^4$He belongs. Experiments report changes of critical exponents for this transition, when superfluid $^4$He is confined in aerogels. Numerical results of the 3DXY model, confined in aerogel-like structures, are in agreement with experiments. Both results seem to contradict Harris criterion: being the specific heat exponent negative for the pure system, changes must be explained in terms of the extended criterion due to Weinrib and Halperin, which requires disorder to be long-range correlated (LRC) at all scales. Aerogels are fractal through some decades only, and present crossovers to homogeneous regimes at finite scales, so the violation to Harris criterion persists. The apparent violation has been explained in terms of hidden LRC subsets within aerogels $[$Phys. Rev. Lett., 2003, {\bf 90}, 170602$]$. On the other hand, experiments on the liquid-vapor (LV) transition of $^4$He and N$_2$ confined in aerogels, also showed changes in critical-point exponents. Being the LV critical-point in the O(1) universality class, criticality may be affected by both, short-range correlated (SRC) and LRC subsets ofdisorder. Simulations of the 3DIS in DLCA aerogels can corroborate experimental results. Experiments and simulations both suggest a shift in critical exponents to values closer to the SRC instead of those of the LRC fixed point.Comment: 14 pages, 7 figures. Contribution to the "Mochima theoretical physics spring school". Joint CEA-IVIC-SFP workshop on Foundations of Statistical and Mesoscopic Physics. Venezuela. 200

Favored child? School choice within the family

We study school choice within the family, analyzing how birth order, gender, innate talent, and family financial restrictions impact the parents´ decision to prioritize the education of one or more of the children over the rest. We find that parents, particularly from lower income homes, are more likely to select more prestigious, higher cost schools for their eldest child, male children and the most talented children. This behavior may explain part of the positive “male bias” in learning and may have a relevant impact on income distribution among family members.School Choice; Siblings; Chile

Government Concession Contracts in Chile: The Role of Competition in the Bidding Process

Over the last 12 years, Chile has been very successful in attracting private participation into the provision of Public Infrastructure. Private capital has gone into road infrastructure, ports and airports all over the country in the form of Concessions. The aim of the 1991 Concession Law, and that of the specific contracts associated with each project, has been to provide much-needed infrastructure efficiently and without committing government resources better employed elsewhere. Using the contracts of four infrastructure projects involving the private sector in Chile, we show that even though these projects and the Concessions Program are positively evaluated, design flaws in the auction setup directly or indirectly reduced competition in the bidding process, negatively affected performance, created incentives for ex-post renegotiation and precluded welfare maximization.Contracts, concessions, bidding

Investigación Multidisciplinaria: Voces en el Aire, Apuntes para Conocer la Radio

Se exploran las posibilidades de la investigación científica de la radio, en tanto medio de comunicación y lenguaje contemporáneo, enmarcando la presentación temática en el emergente campo multidisciplinario de los radio studies. Se delinean dos tradiciones analíticas de la radio, sugiriendo que la potencialidad de una antropología de la radio debiera profundizar las tempranas observaciones y reflexiones de Rudolf Arnheim

Chile: academic performance and educational management under a rigid employment regime

Includes bibliograph

Anti-jesuitismo al sur del mundo. Las polémicas públicas en torno a la Compañía de Jesús en Puerto Montt, Chile (1859-1919)

Las actividades de los jesuitas, su influencia social y las reacciones adversas que provocan son con frecuencia de interés historiográfico.  Por ello, muchas  investigaciones toman como tema su accionar en la capital, Santiago de Chile.  No obstante, existió en el siglo XIX otra comunidad jesuita localizada en Puerto Montt, menos conocida. Esta investigación busca describir sus características, sus semejanzas y diferencias con su par de Santiago, apuntando a  exponer e interpretar las expresiones de rechazo (anti-jesuitismo) que surgen a su presencia en el lugar, analizando las discusiones religiosas que originaron en la comunidad sureña a través de prensa, la principal fuente local preservada.Puerto Montt, fundada mil km. al sur de Santiago de Chile en 1853, recibió a la comunidad de jesuitas en 1859 procedentes de Alemania, con un último rectorado alemán que finaliza en 1919. Desde su inicio protagonizaron importantes actividades misioneras y educativas con reconocida estima entre en sus fieles. No obstante, un rechazo ideológico siempre los acompañaba desde una prensa hostil.Los hallazgos son abundantes, intensos, de influjo ideológico muy europeo, y marcan una sección especial dentro del fenómeno mundial del anti-jesuitismo