Search results for "J2"
showing 10 items of 137 documents
The Linearized Calderón Problem in Transversally Anisotropic Geometries
2017
In this article we study the linearized anisotropic Calderon problem. In a compact manifold with boundary, this problem amounts to showing that products of harmonic functions form a complete set. Assuming that the manifold is transversally anisotropic, we show that the boundary measurements determine an FBI type transform at certain points in the transversal manifold. This leads to recovery of transversal singularities in the linearized problem. The method requires a geometric condition on the transversal manifold related to pairs of intersecting geodesics, but it does not involve the geodesic X-ray transform which has limited earlier results on this problem.
Algebraic models of the Euclidean plane
2018
We introduce a new invariant, the real (logarithmic)-Kodaira dimension, that allows to distinguish smooth real algebraic surfaces up to birational diffeomorphism. As an application, we construct infinite families of smooth rational real algebraic surfaces with trivial homology groups, whose real loci are diffeomorphic to $\mathbb{R}^2$, but which are pairwise not birationally diffeomorphic. There are thus infinitely many non-trivial models of the euclidean plane, contrary to the compact case.
Regularity of sets under a reformulation in a product space of reduced dimension
2023
Different notions on regularity of sets and of collection of sets play an important role in the analysis of the convergence of projection algorithms in nonconvex scenarios. While some projection algorithms can be applied to feasibility problems defined by finitely many sets, some other require the use of a product space reformulation to construct equivalent problems with two sets. In this work we analyze how some regularity properties are preserved under a reformulation in a product space of reduced dimension. This allows us to establish local linear convergence of parallel projection methods which are constructed through this reformulation.
Demand for life annuities from married couples with a bequest motive
2006
The aim of this paper is to explain the ‘annuities puzzle’ in greater depth by introducing the bequest motive. It will try to determine whether this motive really is a relevant feature influencing the demand for life annuities from married couples. With this aim in mind, we develop an optimization model of the utility provided by purchasing a life annuity with contingent survivor benefit or a joint survivor life annuity. Our model is based on that first put forward by Brown and Poterba (2000), to which we have added elements from other models, such as Friedman and Warshawsky's (1990) and Vidal and Lejárraga's (2004), which include the bequest motive. This will enable us to calculate the ann…
The labour market consequences of self-employment spells:European evidence
2008
Hundreds of thousands of Europeans enter self-employment each year, but because self-employment spells are typically brief, many of them exit soon after entry. We examine how those who return to paid-employment fare on the labour market using the European Community Household Panel (ECHP). Like earlier evidence for the US, ours indicate that, in general, brief spells of self-employment do not increase average hourly earnings upon return to paid-employment. For highly educated men, an additional year of self-employment actually decreases their earnings by 4-5% relative to a year of continued wage employment. We also find that brief spells of self-employment are associated with increased proba…
The Return-to-Entrepreneurship Puzzle
2013
The returns to entrepreneurship are monetary and non-monetary. We offer new evidence on these returns using a large sample of genetically identical male twins. Our within-twin analysis suggests that OLS estimates are downwards, and traditional first-differenced panel data estimates upwards biased. We find no differences in the earnings of men with either low or high education. Our within-twin analysis of non-monetary returns shows that entrepreneurs with low education work longer hours and have greater responsibilities, but also face a reduced risk of divorce and less monotonous work tasks. The same does not apply to highly educated entrepreneurs.
Employment sector and pay gaps: Genetic and environmental influences
2012
This paper examines the role of genetic factors and shared environment in explaining the choice of working in the public sector and public-private sector pay gaps. The analyses are done using data for Finnish twins that span the period from 1990 to 2004. The data are based on two sources. The first data are Finnish Twin Cohort conducted by Department of Public Health in University of Helsinki. These data have been matched with the Finnish Longitudinal Employer-Employee Data (FLEED) kept by Statistics Finland. The standard behavioural genetics decomposition and DF (DeFries and Fulker 1985) analyses indicate that public sector employment is broadly influenced by the genetic factors by around …
How individual characteristics shape the structure of social networks
2015
Abstract We study how students’ social networks emerge by documenting systematic patterns in the process of friendship formation of incoming students; these students all start out in a new environment and thus jointly create a new social network. As a specific novelty, we consider cooperativeness, time and risk preferences – elicited experimentally – together with factors like socioeconomic and personality characteristics. We find a number of robust predictors of link formation and of the position within the social network (local and global network centrality). In particular, cooperativeness has a complex association with link formation. We also find evidence for homophily along several dim…
Long-term pulse profile study of the Be/X-ray pulsar SAX J2103.5+4545
2007
Aims. We present the first long-term pulse profile study of the X-ray pulsar SAX J2103.5+4545. Our main goal is to study the pulse shape correlation either with luminosity, time or energy. Methods. This Be/X-ray binary system was observed from 1999 to 2004 by RXTE PCA, and by INTEGRAL from 2002 to 2005, during the Performance and Verification (PV) phase and the Galactic Plane Scan survey (GPS). X-ray pulse profiles were obtained in different energy ranges. The long-term spectral variability of this source is studied. The long-term flux, frequency and spin-up rate histories are computed. A new set of orbital parameters are also determined. Results. The pulse shape is complex and highly varia…
Multiplicity of positive solutions for a degenerate nonlocal problem with p-Laplacian
2021
Abstract We consider a nonlinear boundary value problem with degenerate nonlocal term depending on the L q -norm of the solution and the p-Laplace operator. We prove the multiplicity of positive solutions for the problem, where the number of solutions doubles the number of “positive bumps” of the degenerate term. The solutions are also ordered according to their L q -norms.