Octonion algebras over rings are not determined by their norms

Answering a question of H. Petersson, we provide a class of examples of pair of octonion algebras over a ring having isometric norms.Comment: 8 page

The Implications of Accession for Waste Policies and Industrial Practices : Hungary and the European Union

The hope that prevailed immediately after the collapse of state socialism was that Eastern Europe's environmental pollution would be "swept away by democracy and economic rationality." While with time such expectations have become more modest, some of the same hopes are now resurfacing as the accession of most former socialist countries to the European Union becomes imminent. Most environmentalists and policy experts anticipate an improvement in regulatory standards, in law enforcement, and in the availability of funding for environmental purposes. The purpose of this paper is to evaluate whether and how such expectations are being met in one area of environmental policies in Hungary, a country among the first wave of candidates to be admitted to the EU.published or submitted for publicationnot peer reviewe

On Segregation during Crystal Growth from a Solution Zone

The distribution in a mixed crystal A1-xBxC grown from an either (A, B)-rich or C-rich solution zone (e.g. travelling heater method or related techniques) is to be described by Pfann's zone melting function which depends on the segregation coefficient and a characteristic length. Using pseudobinary mole fractions x the characteristic length of the distribution function is not the actual length of the liquid solution zone but an effective zone length is to be regarded which may be considerably smaller or much bigger for C-rich or (A, B)-rich solutions zones, respectively

Education spillovers in farm productivity: empirical evidence in rural India

Empirical evidence of education spillovers in developing countries and rural contexts is scarce and focuses on specific channels. This paper provides evidence of such spillovers in rural India, by evaluating the overall impact of education of neighbors on farm productivity. We use cross-sectional data from the India Human Development Survey of 2005. Spatial econometric tools are used to take into account social distance between neighbors. To be sure that our definition of the neighborhood does not drive our results, we test three different definitions of neighbors. Our results show that education spillovers are substantial: one additional year in the mean level of education of neighbors increases households' farm productivity by 3%. These findings are robust to changes in specification and open the way to further research. In particular, the paper does not explore the channels through which this spillover effect happens. This paper confirms the choice of improving education in developing countries: giving a child education will certainly provide him greater revenues but it may also provide his neighbors greater revenues. It also shows the importance for policy makers of taking into account education spillovers and policies' complementarity when facing political trade-offs. This paper is one of the few to underline that education externalities do not only exist in urban contexts and that education spillovers do not only occur between workers of the manufacturing and service sectors. There are also spillovers in sectors considered as more traditional such as agriculture. --Education externalities,Rural India,Farm productivity

A lower bound on the essential dimension of a connected linear group

Let G be a connected linear algebraic group defined over an algebraically closed field k and H be a finite abelian subgroup of G whose order is prime to char(k). We show that the essential dimension of G is bounded from below by rank(H) - rank C_G(H)^0, where rank C_G(H)^0 denotes the rank of the maximal torus in the centralizer C_G(H). This inequality, conjectured by J.-P. Serre, generalizes previous results of Reichstein -- Youssin (where char(k) is assumed to be 0 and C_G(H) to be finite) and Chernousov -- Serre (where H is assumed to be a 2-group).Comment: 21 page

The isotropic correlation function of plane figures: the triangle case

The knowledge of the isotropic correlation function of a plane figure is useful to determine the correlation function of the cylinders having the plane figure as right-section and a given height as well as to analyze the out of plane intensity collected in grazing incidence small-angle scattering from a film formed by a particulate collection of these cylinders. The correlation function of plane polygons can always be determined in closed algebraic form. Here we report its analytic expression for the case of a triangle. The expressions take four different forms that depend on the relative order among the sides and the heights of the triangle.Comment: 11 pages, 2 figure

A signature invariant for knotted Klein graphs

We define some signature invariants for a class of knotted trivalent graphs using branched covers. We relate them to classical signatures of knots and links. Finally, we explain how to compute these invariants through the example of Kinoshita's knotted theta graph.Comment: 23 pages, many figures. Comments welcome ! Historical inaccuracy fixe