Basepoint freeness for nef and big line bundles in positive characteristic.
Let be a cubic, monic and separable polynomial over a field of characteristic and let be the elliptic curve given by . In this paper we prove that the coefficient at in the –th division polynomial of equals the coefficient at in . For elliptic curves over a finite field of characteristic , the first coefficient is zero if and only if is supersingular, which by a classical criterion of Deuring (1941) is also equivalent to the vanishing of the second coefficient. So the zero loci...
Soit un polynôme en deux variables, de degré et à coefficients entiers dans pour . Alors le nombre de zéros rationnels de est soit infini soit plus petit que . Nous montrons aussi une version plus générale sur les corps de nombres.
We investigate Bruhat-Tits buildings and their compactifications by means of Berkovich analytic geometry over complete non-Archimedean fields. For every reductive group over a suitable non-Archimedean field we define a map from the Bruhat-Tits building to the Berkovich analytic space associated with . Composing this map with the projection of to its flag varieties, we define a family of compactifications of . This generalizes results by Berkovich in the case of split groups. Moreover,...