Search results for "j30"
showing 10 items of 11 documents
Infinitesimal deformations of double covers of smooth algebraic varieties
2003
The goal of this paper is to give a method to compute the space of infinitesimal deformations of a double cover of a smooth algebraic variety. The space of all infinitesimal deformations has a representation as a direct sum of two subspaces. One is isomorphic to the space of simultaneous deformations of the branch locus and the base of the double covering. The second summand is the subspace of deformations of the double covering which induce trivial deformations of the branch divisor. The main result of the paper is a description of the effect of imposing singularities in the branch locus. As a special case we study deformations of Calabi--Yau threefolds which are non--singular models of do…
Integrability of the one dimensional Schrödinger equation
2018
We present a definition of integrability for the one dimensional Schroedinger equation, which encompasses all known integrable systems, i.e. systems for which the spectrum can be explicitly computed. For this, we introduce the class of rigid functions, built as Liouvillian functions, but containing all solutions of rigid differential operators in the sense of Katz, and a notion of natural boundary conditions. We then make a complete classification of rational integrable potentials. Many new integrable cases are found, some of them physically interesting.
A Mountain Pass Theorem for a Suitable Class of Functions
2009
La mujer en los consejos de administración: evidencia para el mercado bursátil español
2019
Antecedentes: durante decadas se ha luchado por la incorporacion de la mujer al mercado laboral, lo que promueve la igualdad de genero. Sin embargo, una mayor presencia de la mujer en el mercado laboral no indica una plena igualdad, pues es evidente la existencia del conocido techo de cristal y de una brecha salarial. El articulo proporciona evidencia de estas dos caracteristicas en los consejos de administracion de las empresas del mercado continuo espanol. Metodologia: se estima un modelo de regresion multiple con observaciones por consejero, empresa y ano, controlando efectos fijos temporales de la empresa y del sector. En el estudio consideramos especificamente la presencia de diversida…
Les étudiants anticipent-ils correctement la valeur de leur diplôme sur le marché du travail ?
2013
Documents de travail de l'IREDU, n°2013-1; Ce travail analyse la manière dont les étudiants de première année d'université anticipent leurs salaires futurs, puis compare ces salaires à ceux qu'ils peuvent réellement observer sur le marché du travail. Nos résultats montrent globalement une surestimation des salaires anticipés d'environ 9 pour cent en début de carrière, ce qui est cohérent avec des travaux réalisés dans d'autres pays. En revanche, les salaires anticipés après dix ans de carrières sont supérieurs de 28 pour cent aux salaires observés des diplômés à ancienneté comparable. Les résultats soulignent également l'importance de l'environnement familial lors du choix des études supéri…
Integrability and non integrability of some n body problems
2015
We prove the non integrability of the colinear $3$ and $4$ body problem, for any masses positive masses. To deal with resistant cases, we present strong integrability criterions for $3$ dimensional homogeneous potentials of degree $-1$, and prove that such cases cannot appear in the $4$ body problem. Following the same strategy, we present a simple proof of non integrability for the planar $n$ body problem. Eventually, we present some integrable cases of the $n$ body problem restricted to some invariant vector spaces.
Bi-homogeneity and integrability of rational potentials
2020
Abstract In this paper we consider natural Hamiltonian systems with two degrees of freedom for which Hamiltonian function has the form H = 1 2 ( p 1 2 + p 2 2 ) + V ( q 1 , q 2 ) and potential V ( q 1 , q 2 ) is a rational function. Necessary conditions for the integrability of such systems are deduced from integrability of dominate term of the potential which usually is appropriately chosen homogeneous term of V. We show that introducing weights compatible with the canonical structure one can find new dominant terms which can give new necessary conditions for integrability. To deduce them we investigate integrability of a family of bi-homogeneous potentials which depend on two integer para…
High Wage Workers Match with High Wage Firms: Clear Evidence of the Effects of Limited Mobility Bias
2012
Positive assortative matching implies that high productivity workers and firms match together. However, there is almost no evidence of a positive correlation between the worker and firm contributions in two-way fixed-effects wage equations. This could be the result of a bias caused by standard estimation error. Using German social security records we show that the effect of this bias is substantial in samples with limited inter-firm movement. The correlation between worker and firm contributions to wage equations is unambiguously positive.
School aspirations, cognitive skills and wage expectations of French Undergraduates
2013
en ligne : http://cemapre.iseg.utl.pt/educonf/2e3/files/submissions_to_web/Bonnard%20Claire_%20Giret%20Jean-Francois_Lambert-Le%20Mener%20Marielle.pdf; This paper aims to study the earnings expectations of first-year students at a French university and to compare them with the observed earnings of young people in the labour market for that same year. Our findings highlight the importance of the environment in which students make their choices about education. Expected earnings are proportionally higher when their parents seem to be involved in the careers guidance, even controlling for the effect of parental socio-economic status. The positive opinion of parents about the orientation or the…
An unbounded family of log Calabi–Yau pairs
2016
We give an explicit example of log Calabi-Yau pairs that are log canonical and have a linearly decreasing Euler characteristic. This is constructed in terms of a degree two covering of a sequence of blow ups of three dimensional projective bundles over the Segre-Hirzebruch surfaces ${\mathbb F}_n$ for every positive integer $n$ big enough.