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On Zariski's theorem in positive characteristic

Ilya Tyomkin (2013)

Journal of the European Mathematical Society

In the current paper we show that the dimension of a family V of irreducible reduced curves in a given ample linear system on a toric surface S over an algebraically closed field is bounded from above by - K S . C + p g ( C ) - 1 , where C denotes a general curve in the family. This result generalizes a famous theorem of Zariski to the case of positive characteristic. We also explore new phenomena that occur in positive characteristic: We show that the equality 𝚍𝚒𝚖 ( V ) = - K S . C + p g ( C ) - 1 does not imply the nodality of C even if C belongs to the...

Optimality of the Width- w Non-adjacent Form: General Characterisation and the Case of Imaginary Quadratic Bases

Clemens Heuberger, Daniel Krenn (2013)

Journal de Théorie des Nombres de Bordeaux

We consider digit expansions j = 0 - 1 Φ j ( d j ) with an endomorphism Φ of an Abelian group. In such a numeral system, the w -NAF condition (each block of w consecutive digits contains at most one nonzero) is shown to minimise the Hamming weight over all expansions with the same digit set if and only if it fulfills the subadditivity condition (the sum of every two expansions of weight 1 admits an optimal w -NAF).This result is then applied to imaginary quadratic bases, which are used for scalar multiplication in elliptic...

Orbifolds, special varieties and classification theory

Frédéric Campana (2004)

Annales de l’institut Fourier

This article gives a description, by means of functorial intrinsic fibrations, of the geometric structure (and conjecturally also of the Kobayashi pseudometric, as well as of the arithmetic in the projective case) of compact Kähler manifolds. We first define special manifolds as being the compact Kähler manifolds with no meromorphic map onto an orbifold of general type, the orbifold structure on the base being given by the divisor of multiple fibres. We next show that rationally connected Kähler...

Orbifolds, special varieties and classification theory: an appendix

Frédéric Campana (2004)

Annales de l’institut Fourier

For any compact Kähler manifold X and for any equivalence relation generated by a symmetric binary relation with compact analytic graph in X × X , the existence of a meromorphic quotient is known from Inv. Math. 63 (1981). We give here a simplified and detailed proof of the existence of such quotients, following the approach of that paper. These quotients are used in one of the two constructions of the core of X given in the previous paper of this fascicule, as well as in many other questions.

Ordinary reduction of K3 surfaces

Fedor Bogomolov, Yuri Zarhin (2009)

Open Mathematics

Let X be a K3 surface over a number field K. We prove that there exists a finite algebraic field extension E/K such that X has ordinary reduction at every non-archimedean place of E outside a density zero set of places.

Ouverts analytiques d'une courbe algébrique en géométrie rigide

Qing Liu (1987)

Annales de l'institut Fourier

Nous étudions les espaces analytiques rigides de dimension 1, réguliers, de genre fini sur un corps valué complet k . Nous montrons qu’un tel espace X admet une réduction préstable. Si k est maximalement complet, X se plonge dans une courbe algébrique (analytifiée). On donne aussi une caractérisation des espaces analytiques qui sont le complémentaire d’une partie compacte dans une courbe algébrique.

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