On maximal curves having classical Weierstrass gaps

We study geometrical properties of maximal curves having classical Weierstrass gaps.Comment: 9 pages, Latex2

On maximal curves

We study arithmetical and geometrical properties of maximal curves, that is, curves defined over the finite field F_{q^2} whose number of F_{q^2}-rational points reaches the Hasse-Weil upper bound. Under a hypothesis on non-gaps at a rational point, we prove that maximal curves are F_{q^2}-isomorphic to y^q + y = x^m, for some $m \in Z^+$. As a consequence we show that a maximal curve of genus g=(q-1)^2/4 is F_{q^2}-isomorphic to the curve y^q + y = x^{(q+1)/2}.Comment: LaTex2e, 17 pages; this article is an improved version of the paper alg-geom/9603013 (by Fuhrmann and Torres

Neural Network identification of halo white dwarfs

The white dwarf luminosity function has proven to be an excellent tool to study some properties of the galactic disk such as its age and the past history of the local star formation rate. The existence of an observational luminosity function for halo white dwarfs could provide valuable information about its age, the time that the star formation rate lasted, and could also constrain the shape of the allowed Initial Mass Functions (IMF). However, the main problem is the scarce number of white dwarfs already identified as halo stars. In this Letter we show how an artificial intelligence algorithm can be succesfully used to classify the population of spectroscopically identified white dwarfs allowing us to identify several potential halo white dwarfs and to improve the significance of its luminosity function.Comment: 15 pages, 3 postscript figures. Accepted for publication in ApJ Letters, uses aasms4.st

The Diffusion of Informal Knowledge and Innovation Performance: A sectoral approach

This paper tries to quantify the effect of diffusion of informal knowledge on the innovative performance of European firms using data derived from the 3rd Community Innovation Survey. When firms are asked whether or not they have introduced new products or processes, they were also asked to which degree such innovations were developed in-house. These degrees were captured by the CIS variables InPdtW and InPcsW. These variables ranged from 1 (Mainly done by the firm) to 3 (Mainly done by other enterprises). The focus of this paper is to investigate the impact of diffusion of informal knowledge. We combine the previous variables with another variable which reflects firms that were not doing any formal collaboration with other institutions. If an innovative firm has no formal collaboration arrangements and the innovation has not been done mainly by the firm, then diffusion of informal knowledge is considered to be the main driver of the innovation. The idea is that informal channels are accessible to all firms. This paper tries to quantify the impact of such flows of knowledge on firms' innovation performance. To do this, a two step procedure is followed: -In a first step, a latent variable for diffusion of informal knowledge is defined and estimated based on firms' characteristics. -In a second step, the latent diffusion variable is introduced as a regressor in a probit/tobit model.Knowledge flows, innovation, dynamic equations, sectoral innovation, CIS