In algebraic geometry, Barsotti–Tate groups or p-divisible groups are similar to the points of order a power of p on an abelian variety in characteristic p. They were introduced by Barsotti (1962) under the name equidimensional hyperdomain and by Tate (1967) under the name p-divisible groups, and named Barsotti–Tate groups by Grothendieck (1971).
Definition
Tate (1967) defined a p-divisible group of height h (over a scheme S) to be an inductive system of groups Gn for n≥0, such that Gn is a finite group scheme over S of order p and such that Gn is (identified with) the group of elements of order divisible by p in Gn+1.
More generally, Grothendieck (1971) defined a Barsotti–Tate group G over a scheme S to be an fppf sheaf of commutative groups over S that is p-divisible, p-torsion, such that the points G(1) of order p of G are (represented by) a finite locally free scheme. The group G(1) has rank p for some locally constant function h on S, called the rank or height of the group G. The subgroup G(n) of points of order p is a scheme of rank p, and G is the direct limit of these subgroups.
Example
- Take Gn to be the cyclic group of order p (or rather the group scheme corresponding to it). This is a p-divisible group of height 1.
- Take Gn to be the group scheme of pth roots of 1. This is a p-divisible group of height 1.
- Take Gn to be the subgroup scheme of elements of order p of an abelian variety. This is a p-divisible group of height 2d where d is the dimension of the Abelian variety.
References
- Barsotti, Iacopo (1962), "Analytical methods for abelian varieties in positive characteristic", Colloq. Théorie des Groupes Algébriques (Bruxelles, 1962), Librairie Universitaire, Louvain, pp. 77–85, MR 0155827
- Demazure, Michel (1972), Lectures on p-divisible groups, Lecture Notes in Mathematics, vol. 302, Berlin, New York: Springer-Verlag, doi:10.1007/BFb0060741, ISBN 978-3-540-06092-5, MR 0344261
- Dolgachev, I.V. (2001) , "P-divisible group", Encyclopedia of Mathematics, EMS Press
- Grothendieck, Alexander (1971), "Groupes de Barsotti-Tate et cristaux", Actes du Congrès International des Mathématiciens (Nice, 1970), vol. 1, Gauthier-Villars, pp. 431–436, MR 0578496, archived from the original on 2017-11-25, retrieved 2010-11-25
- de Jong, A. J. (1998), "Barsotti-Tate groups and crystals", Documenta Mathematica, Proceedings of the International Congress of Mathematicians, Vol. II (Berlin, 1998), II: 259–265, ISSN 1431-0635, MR 1648076
- Messing, William (1972), The crystals associated to Barsotti-Tate groups: with applications to abelian schemes, Lecture Notes in Mathematics, vol. 264, Berlin, New York: Springer-Verlag, doi:10.1007/BFb0058301, MR 0347836
- Serre, Jean-Pierre (1995) , "Groupes p-divisibles (d'après J. Tate), Exp. 318", Séminaire Bourbaki, vol. 10, Paris: Société Mathématique de France, pp. 73–86, MR 1610452
- Tate, John T. (1967), "p-divisible groups.", in Springer, Tonny A. (ed.), Proc. Conf. Local Fields( Driebergen, 1966), Berlin, New York: Springer-Verlag, MR 0231827