Measuring non-linear dependence for two random variables distributed along a curve

The final publication is available at link.springer.comWe propose new dependence measures for two real random variables not necessarily linearly related. Covariance and linear correlation are expressed in terms of principal components and are generalized for variables distributed along a curve. Properties of these measures are discussed. The new measures are estimated using principal curves and are computed for simulated and real data sets. Finally, we present several statistical applications for the new dependence measures.Peer ReviewedPostprint (author's final draft

Which quantum states are dual to classical spacetimes?

It is commonly accepted that states in a conformal field theory correspond to classical spacetimes with Anti-de-Sitter asymptotics. In this work we give a prescription for the CFT states with a dual classical spacetime and, using basic holographic rules, show that they are holographically connected to coherent states in the large-N limit, or by considering linearized perturbations. We also point out implications in the spacetime emergence mechanism, for instance, the (entangled) state dual to the black hole should be properly described as a quantum superposition of products of these states. This also complements the quantum interpretation of the Hawking-Page transition.Comment: 14 pages, 8 figure

Wind Risk Assessment in Urban Environments: The Case of Falling Trees During Windstorm Events in Lisbon

Trees bring many benefits to the urban environment. However, they may also cause hazards to human population, being the major causes of injuries and infrastructural damage during strong wind events. In the city of Lisbon, strong winds rather frequently result in tree falls, depending on the season and meteorological conditions. This paper presents a methodology to analyse tree damage due to strong wind events in urban environments. Each occurrence has been recorded by the Lisbon Fire Brigade and Rescue Services (Regimento de Sapadores Bombeiros de Lisboa - RSBL). Information provided by RSBL relating to the period of 1990-2005 was considered along with hourly wind speed and direction, species, fitossanitary conditions and urban parameters. To ensure that the fallen trees were caused by strong winds, only days with three or more occurrences of fallen trees were selected. It was found that in summer, northerly winds are responsible for 11% of tree falls, with winds from other directions (west, southwest and south) responsible for 5%. From autumn to spring, perturbed weather conditions originating from the west, southwest and south are responsible for 84% of fallen trees. The majority of tree falls occurred when wind speed surpassed 7 m/s in the six hours prior to their fall. Some recommendations to the Civil Protection Agency and the Fire Department are presented to improve the mission of collecting information. This research is a contribution to the assessment of wind risk in Lisbon

The Effect of social security, demography and technology on retirement

This article investigates the causes in the reduction of labor force participation ofthe old. We argue that the changes in social security policy, in technology and indemography may account for most of the changes in retirement over the second partof the last century in the U.S. economy. We develop a dynamic general equilibriummodel with endogenous retirement that embeds social security legislation. The modelis able to match very closely the increase in the retirement rate of males aged 65 andolder. It also quanti es the isolated impact on retirement and on the solvency of thesocial security system of the di¤erent factors. The model suggests that technologicaland demographic changes had a strong in uence on retirement, so that it would haveincreased signi cantly even if the social security rules had not changed. However, asthe latter became much more generous in the past, changes in social security policycan account not only for a sizeable part of the expansion of retirement, but also for themost of the observed increase in the social security expenses as a share of GDP.

Sobre la formación y la inserción laboral de los historiadores: desacoples problemáticos

Se pasa revista a una serie de desacoples entre las prácticas institucionales relacionadas con la formación profesional y la inserción laboral de los historiadores en nuestro país: desarticulación entre carreras de grado y posgrado, entre maestrías y doctorados, entre universidades y agencias de financiamiento, clientelismo y endogamia intrainstitucional, escaso pensamiento acerca del perfil del egresado respecto del sistema educativo y otros ámbitos alternativos de inserción. Se considera también algunas acciones emprendidas en la Universidad de Buenos Aires que apuntan a reducir ese tipo de desacoples.A series of disconnections between institutional practices related to professional training and ways of employment of historians in Argentina is considered: disconnections between undergraduate and post-graduate careers; between M.A. and Ph.D. studies; between universities and fund agencies; clientelism and intra-institutional endogamy; little thought about the graduate’s profile regarding the educational system and other alternative areas of job placement. Some actions undertaken at the University of Buenos Aires are also mentioned, which aim to reduce that kind of disconnections.Fil: Campagno, Marcelo Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentina. Universidad de Buenos Aires. Facultad de Filosofía y Letras; Argentin

Business cycles in a small open economy with a banking sector

This paper studies the interest-rate-driven business cycles of a small open economy (SOE). For than end a costly operated banking system is added to the standard real-business-cycles model. Banks are the only domestic agents considered worthy of credit in international capital markets. They borrow from the rest of the world and lend domestically in a competitive credit market. Existent quantitative models of business cycles in SOE's indicate that interest-rate shocks are unable to cast the kind of output variability produced by productivity or terms-of-trade shocks. Contrary to this finding, it seems that the macroeconomic performances of several SOE's are tightly related to international interest rates and capital flows. Neumeyer and Perri (1999) points out that the introduction of working capital needs may close the gap between the standard model's predictions and the observed consequences of interest-rate shocks. This paper shows that a more careful analysis of the microfoundations of working capital may give rise to an intermediate position where working capital matters in explaining output fluctuations, but not as much as Neumayer and Perri suggest. For that end, the model is calibrated to the Argentinean economy.Departamento de Economí

The Effect of Social Security, Demography and Technology on Retirement

This article investigates the causes in the reduction of labor force participation ofthe old. We argue that the changes in social security policy, in technology and indemography may account for most of the changes in retirement over the second partof the last century in the U.S. economy. We develop a dynamic general equilibriummodel with endogenous retirement that embeds social security legislation. The modelis able to match very closely the increase in the retirement rate of males aged 65 andolder. It also quanti es the isolated impact on retirement and on the solvency of thesocial security system of the di¤erent factors. The model suggests that technologicaland demographic changes had a strong in uence on retirement, so that it would haveincreased signi cantly even if the social security rules had not changed. However, asthe latter became much more generous in the past, changes in social security policycan account not only for a sizeable part of the expansion of retirement, but also for themost of the observed increase in the social security expenses as a share of GDP.