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

Labor Market Regimes and Mobility through a Markov Chain in Chile

In this paper we analyze the dynamics of labor markets in Chile. Our goal is to understand how flexibility in the labor market has changed over time, and in particular, to relate this change with the legislation framework. We analyze mobility in four different periods, each of them associated with different labor regimes. Based on flows, we estimate transition probabilities across three relevant possible states: unemployment, employment, and out of the labor force. Our finding shows that since 1974 employment became less secure. The probability for an employed person of becoming unemployed almost doubled since 1974 and remained thereafter. Also, the probability of remaining unemployed increased from 26,1% in the period 1962-73, to over 40% in the periods 1974-79 and 1980-89, but felt to 25,6% after 1990. This in spite the average unemployment rate doubled between these two periods. The probabilities related with discourage and added worker effects were stable in the different periods considered, except since 1990, where the hypothesis of discouraged workers is challenged. Finally, whilst the natural rate of unemployment doubled after the reforms in 1974, it remained high until the last period, starting in 1990. Changes in participation compensated such changes, and hence, the expected length of unemployment did not increase dramatically in the period, remaining stable around two quarterslabor markets, transition probabilities, unemployment.

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

Measuring the impact of minimum wage policies on the economy

This paper undertakes a statistical analysis of the effect of minimum wages (MWs) on different population groups. The underlying question for this analysis relates to the probability bias exerted by certain protective government regulations in terms of the unemployment prospects of specific groups. Several cross-sectional data and a standard human capital model corrected for selectivity bias are used to analyze the case of Chile, where high structural unemployment has been a remarkable feature of the 1970s and 1980s. The main conclusions show that the coverage of the MW is more significant for the young and the less educated, and there exists a negative relationship between human capital stock and actual coverage of MWs. It is also shown that previous statistical analysis of this issue, both in the case of Chile and in industrial countries may have underestimated the negative impact of MWs because they do not correct for selectivity bias.Environmental Economics&Policies,Economic Theory&Research,Labor Markets,Banks&Banking Reform,Poverty Assessment

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

Sueños en Polaroid

La memoria nos hace descubrir tres encuentros que, en primera instancia, justifican la escritura de este ensayo, ya que acá subscribimos la impronta diltheyana de la centralidad de la vivencia como constituyente de la experiencia vital. En primer lugar, está el ya nostálgico 1997 cuando, en su caluroso verano, fui invitado a enriquecer teóricamente una argumentación sociológica desde la cual iluminar la poética narración cinematográfica de Michelangelo Antonioni (sobre un exitoso fotógrafo de modas en pleno "Swinging London", quien de manera azarosa se involucra en la fotografía documental), para luego alabar indirectamente la capacidad intuitiva de este artista visual para prever los cambios culturales y sociales que distinguen las aristas utópicas y distópicas de la condición postmoderna

Public institutions and private transactions : the legal and regulatory environment for business private transactions in Brazil and Chile

Drawing on the new institutional economics, the authors examine the impact on businesses of Brazil's relatively complex, nontransparent legal and regulatory institutions and compare their costs with those of Chile's institutions, which are relatively simple. They examine four basic areas where legal and regulatory institutions could create critical obstacles to efficiency in the garment industries of Sao Paulo and Santiago: (a) the start-up of a new business (entry); (b) the regulation of business; (c) orders by customers of garment firms; and (d) sales with credit. They find that Chilean business transactions benefit from legal simplicity and more consistent enforcement than in Brazil, but that these perceived advantages are offset because of the differences between formal law and practice in Brazil. In two of these areas, Brazil has evolved some effective institutional substitutes to reduce the costs that would otherwise have been imposed by inefficient formal institutions. In the entry of new businesses, professions have evolved to transform the process of registering a new business from a potentially tortuous obstacle path into a fairly affordable one-stop process. In debt collection, information systems limit the need to resort to the formal legal system. Nevertheless, regulation raises the cost of transactions for Brazilian businesses. Costs are further raised by greater uncertainty and frequent renegotiation of orders.National Governance,Environmental Economics&Policies,Legal Products,Private Participation in Infrastructure,Small Scale Enterprise

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

Includes bibliograph