In this paper we give an explicit construction of a symplectic Lefschetz fibration whose total space is a smooth compact four dimensional manifold with a prescribed fundamental group. We also study the numerical properties of the sections in symplectic Lefschetz fibrations and their relation to the structure of the monodromy group. Partially supported by DGYCYT grant PB96-0234 Partially support...

We compute the irreducible constituents of the restrictions of all unipotent characters of the groups Sp4(q) and Sp6(q) and odd q to their maximal parabolic subgroups stabilizing a line. It turns out that these restrictions are multiplicity free. We also obtain general information about the restrictions of Harish-Chandra induced characters.

The projective orthogonal and symplectic groups POn(F ) and PSpn(F ) have a natural action on the F vector space V ′ = Mn(F ) ⊕ . . . ⊕ Mn(F ). Here we assume F is an infinite field of characteristic not 2. If we assume there is more than one summand in V , then the invariant fields F (V )n and F (V )n are natural objects. They are, for example, the centers of generic algebras with the appropri...

In this paper we shall give a simple and concrete realization of a set of representatives of all irreducible holomorphic representations of G. This realization, which involves the G-module structure of a symmetric algebra of polynomial functions is inspired by the work of B. Kostant [1] and follows the general scheme formulated in [2]. Detailed proofs will appear elsewhere. 1. The symmetric alg...

Let I7 = Sp(2m, 2) and I’ = X7, where Z is the translation group of the affine space AG(2m, 2). 17 acts 2-transitively on the cosets of each orthogonal subgroup G@(2m, 2), E = *l, and r has a second class of subgroups isomorphic to 17 ([lo, pp. 236, 2401, [6], and [14]). By considering a certain symmetric design P(2m) having r as its full automorphism group, we will prove these results. The sym...

Symplectic manifolds which are homogeneous spaces of Poisson-Lie groups are studied in this paper. We show that these spaces are, under certain assumptions, covering spaces of dressing orbits of the Poisson-Lie groups which act on them. The effect of the Poisson induction procedure on such spaces is also examined, thus leading to an interesting generalization of the notion of homogeneous space....

An invariant for symplectic involutions on central simple algebras of degree divisible by 4 over fields of characteristic different from 2 is defined on the basis of Rost’s cohomological invariant of degree 3 for torsors under symplectic groups. We relate this invariant to trace forms and show how its triviality yields a decomposability criterion for algebras with symplectic involution.

We construct and study the holomorphic discrete series representation and the principal series representation of the symplectic group Sp(2n, F) over a p-adic field F as well as a duality between some sub-representations of these two representations. The constructions of these two representations generalize those defined in Morita and Murase’s works. Moreover, Morita built a duality for SL(2, F)...

For a positive integer g, let Sp2g(R) denote the group of 2g× 2g symplectic matrices over a ring R. Assume g ≥ 2. For a prime number , we give a self-contained proof that any closed subgroup of Sp2g(Z ) which surjects onto Sp2g(Z/ Z) must in fact equal all of Sp2g(Z ). The result and the method of proof are both motivated by group-theoretic considerations that arise in the study of Galois repre...

We construct analogues of FI-modules where the role of the symmetric group is played by the general linear groups and the symplectic groups over finite rings and prove basic structural properties such as Noetherianity. Applications include a proof of the Lannes– Schwartz Artinian conjecture in the generic representation theory of finite fields, very general homological stability theorems with t...