Stark-Wannier type operators with purely singular spectrum

We consider the one-dimensional Stark-Wannier type operators with potentials given by a smooth function with a logarithmic growth at infinity plus a periodic function with the Fourier coefficients of the form $(\ln |n|)^{-b}, 0<b<1/2$. We prove that in the case of rational electric field the spectrum of the corresponding operator is purely singular continuous.Comment: 42 page

Constant Capital and the Crisis in Contemporary Capitalism: Echoes from the Late Nineteenth Century

Because constant capital involves irreversible decisions, understanding this subject is essential for coming to grips with the complexity of the economy, especially crisis theory. This paper attempts to show how both Marx and late 19th century neoclassical economists in the United States realized that the relative growth of constant capital made competitive economies unsustainable.

Vey theorem in infinite dimensions and its application to KdV

We consider an integrable infinite-dimensional Hamiltonian system in a Hilbert space $H=\{u=(u_1^+,u_1^-; u_2^+,u_2^-;....)\}$ with integrals $I_1, I_2,...$ which can be written as $I_j={1/2}|F_j|^2$, where $F_j:H\to \R^2$, $F_j(0)=0$ for $j=1,2,...$ . We assume that the maps $F_j$ define a germ of an analytic diffeomorphism $F=(F_1,F_2,...):H\to H$, such that dF(0)=id$,$(F-id)$is a$\kappa$-smoothing map ($\kappa\geq 0$) and some other mild restrictions on$F$hold. Under these assumptions we show that the maps$F_j$may be modified to maps$F_j^\prime$such that$F_j-F_j^\prime=O(|u|^2)$and each$\frac12|F'_j|^2$still is an integral of motion. Moreover, these maps jointly define a germ of an analytic symplectomorphism$F^\prime: H\to H$, the germ$(F^\prime-id)$is$\kappa$-smoothing, and each$I_j$is an analytic function of the vector$(\frac12|F'_j|^2,j\ge1)$. Next we show that the theorem with$\kappa=1$ applies to the KdV equation. It implies that in the vicinity of the origin in a functional space KdV admits the Birkhoff normal form and the integrating transformation has the form `identity plus a 1-smoothing analytic map'

Measuring the technical efficiency of airports in Latin America

This paper studies the technical efficiency of airports in Latin America. The evolution of productive efficiency in the region has seldom been studied, mainly due to lack of publicly available data. Relying on a unique dataset that was obtained through questionnaires distributed to airport operators, the authors use Data Envelopment Analysis methods to compute an efficient production frontier and compare the technical efficiency of Latin American airports relative to airports around the world. In a second stage, they estimate a truncated regression to study the drivers of observed differences in airport efficiency. According to the results, institutional variables (private/public operation), the socioeconomic environment (level of gross domestic product), and airport characteristics (hub airport, share of commercial revenues) matter in explaining airport productive efficiency. Finally, the authors compute total factor productivity changes for Latin American airports for 1995-2007. The region has implemented a wide variety of private sector participation schemes for the operation of airports since the mid 1990s. The results show that private operators have not had higher rates of total factor productivity change.Airports and Air Services,Transport Economics Policy&Planning,Infrastructure Economics,Export Competitiveness,Knowledge for Development

Measuring educational efficiency at student level with parametric stochastic distance functions: An application to Spanish PISA results

This study explicitly considers that education is a multi-input multi-output production process subject to inefficient behaviors that can be identified at student level. Therefore a distance function allows us to calculate different aspects of educational technology. The paper presents an empirical application of this model using Spanish data from the Programme for International Student Assessment implemented by the OECD. The results provide insights into how student background, peer-group and school characteristics interact with educational outputs. Findings also suggest that, once educational inputs are taken into account; there is no statistically significant difference in efficiency levels across schools regarding public-private ownership.Secondary schools, technical efficiency, stochastic frontier, distance function.