Ergodic decomposition of Markov chains

AbstractWe explicitly find the spectral decomposition, when it exists, of a Markov operator P∗ : l1 → l1 using the asymptotic periodicity of the associated infinite Markov matrix. We give a simple condition under which an infinite Markov matrix is asymptotically periodic. We also determine the set of P∗-invariant distributions in l1 and the set of P∗-ergodic distributions

Evaluating Labor Market Reforms: A General Equilibrium Approach

Job security provisions are commonly invoked to explain the high and persistent European unemployment rates. This belief has led several countries to reform their labor markets and liberalize the use of fixed-term contracts. Despite how common such contracts have become after deregulation, there is a lack of quantitative analysis of their impact on the economy. To fill this gap, we build a general equilibrium model with heterogeneous agents and firing costs in the tradition of Hopenhayn and Rogerson (1993). We calibrate our model to Spanish data, choosing in part parameters estimated with firm-level longitudinal data. Spain is particularly interesting, since its labor regulations are among the most protective in the OECD, and both its unemployment and its share of fixed-term employment are the highest. We find that fixed term contracts increase unemployment, reduce output, and raise productivity. The welfare effects are ambiguous.Fixed-term contracts, Firing costs, General equilibrium, Heterogeneous agents

EVALUATING LABOR MARKET REFORMS: A GENERAL EQUILIBRIUM APPROACH

Job security provisions are commonly invoked to explain the high and persistent European unemployment rates. This belief has led several countries to reform their labor markets and liberalize the use of fixed-term contracts. Despite how common such contracts have become after deregulation, there is a lack of quantitative analysis of their impact on the economy. To fill this gap, we build a general equilibrium model with heterogeneous agents and firing costs in the tradition of Hopenhayn and Rogerson (1983). We calibrate our model to Spanish data, choosing in part parameters estimated with firm-level longitudinal data. Spain is particularly interesting, since its labor regulations are among the most protective in the OECD, and both its unemployment and its share of fixed-term employment are the highest. We find that fixedterm contracts increase unemployment, reduce output, and raise productivity. The welfare effects are ambiguous.

Modelo analítico para predecir el comportamiento de mechas arteriales

Un análisis matemático para predecir el comportamiento de mechas arteriales, para uso en tubos de calor, es presentado. El estudio está basado en el análisis del problema de penetración capilar bajo las consideraciones de flujo laminar paralelo de un fluido Newtoniano incomprensible en un conducto circular, lo cual conduce a una ecuación diferencial no-lineal cuya integración se obtuvo numéricamente. El análisis es primero restringido a mechas arteriales inclinadas, respecto a la horizontal, trabajando en un medio ambiente de un-g y bajo el efecto adverso de una aceleración constante; enseguida éste es generalizado a mechas arteriales que trabajan horizontalmente, o en un medio ambiente de cero-g. Las soluciones de la ecuación gobernante, la cual depende de los parámetros O, M y N, son presentadas para diferentes situaciones físicas y comparadas con soluciones correspondientes obtenidas a partir de modelos conocidos para el problema de penetración capilar. Finalmente, la aplicabilidad del análisis a mechas arteriales de sección no-circular es discutida

Nuclear masses, deformations and shell effects

We show that the Liquid Drop Model is best suited to describe the masses of prolate deformed nuclei than of spherical nuclei. To this end three Liquid Drop Mass formulas are employed to describe nuclear masses of eight sets of nuclei with similar quadrupole deformations. It is shown that they are able to fit the measured masses of prolate deformed nuclei with an RMS smaller than 750 keV, while for the spherical nuclei the RMS is, in the three cases, larger than 2000 keV. The RMS of the best fit of the masses of semi-magic nuclei is also larger than 2000 keV. The parameters of the three models are studied, showing that the surface symmetry term is the one which varies the most from one group of nuclei to another. In one model, isospin dependent terms are also found to exhibit strong changes. The inclusion of shell effects allows for better fits, which continue to be better in the prolate deformed nuclei regionComment: 10 pages, 8 tables, Proc. of the XXXIV Nuclear Physics Symposium, January 4-7 2011, Cocoyoc, Morelos, Mexico. IOP Journal of Physics: Conference Series (in press

Discrete Formulation for the dynamics of rods deforming in space

We describe the main ingredients needed to create, from the smooth lagrangian density, a variational principle for discrete motions of a discrete rod, with corresponding conserved Noether currents. We describe all geometrical objects in terms of elements on the linear Atiyah bundle, using a reduced forward difference operator. We show how this introduces a discrete lagrangian density that models the discrete dynamics of a discrete rod. The presented tools are general enough to represent a discretization of any variational theory in principal bundles, and its simplicity allows to perform an iterative integration algorithm to compute the discrete rod evolution in time, starting from any predefined configurations of all discrete rod elements at initial times

Functional approach to quantum friction: effective action and dissipative force

We study the Casimir friction due to the relative, uniform, lateral motion of two parallel semitransparent mirrors coupled to a vacuum real scalar field, $\phi$. We follow a functional approach, whereby nonlocal terms in the action for $\phi$, concentrated on the mirrors' locii, appear after functional integration of the microscopic degrees of freedom. This action for $\phi$, which incorporates the relevant properties of the mirrors, is then used as the starting point for two complementary evaluations: Firstly, we calculate the { in-out} effective action for the system, which develops an imaginary part, hence a non-vanishing probability for the decay (because of friction) of the initial vacuum state. Secondly, we evaluate another observable: the vacuum expectation value of the frictional force, using the { in-in} or Closed Time Path formalism. Explicit results are presented for zero-width mirrors and half-spaces, in a model where the microscopic degrees of freedom at the mirrors are a set of identical quantum harmonic oscillators, linearly coupled to $\phi