Unipotent Elements of Nonprime Order in Representations of the Classical Algebraic Groups: Two Big Jordan Blocks.

For irreducible rational representations of the classical algebraic groups in characteristic p > 2, which are not equivalent to the composition of a group morphism and the standard representation, it is proved that usually the image of a unipotent element of order p > p has at least two Jordan blocks of size > p; all exceptions are indicated explicitly. As a corollary, irreducible rational representations of these groups whose images contain unipotent elements with just one Jordan block of size > 1 are classified. [ABSTRACT FROM AUTHOR]