We address two properties for Abelian topological groups: “every closed subgroup is dually closed” and “every closed subgroup is dually embedded.” We exhibit a pair of topological groups such that each has both of the properties and the product has neither, which refutes a remark of N. Noble. These examples are the additive group of integers topologized with respect to a convergent sequence as ...

We prove the following two conjectures. 1. (The Ehrenpreis Conjecture) Let ǫ > 0 and let S1, S2 be two closed Riemann surfaces of the same genus. Then there exists finite covers S̃i of Si (for i = 1, 2) such that there is a (1 + ǫ)-quasiconformal homeomorphism between S̃1 and S̃2. 2. (The Surface Subgroup Conjecture) Let M be a closed hyperbolic 3-manifold. Then there exists a subgroup G < π1(M) s...

For G = SL(3, R) and G = SO(2, n), we give explicit, practical conditions that determine whether or not a closed, connected subgroup H of G has the property that there exists a compact subset C of G with CHC = G. To do this, we fix a Cartan decomposition G = KA + K of G, and then carry out an approximate calculation of (KHK) ∩ A + for each closed, connected subgroup H of G.

We give explicit, practical conditions that determine whether or not a closed, connected subgroup H of G = SU(2, n) has the property that there exists a compact subset C of G with CHC = G. To do this, we fix a Cartan decomposition G = KA + K of G, and then carry out an approximate calculation of (KHK) ∩ A + for each closed, connected subgroup H of G. This generalizes the work of H. Oh and D. Wi...

The theorems of M. Ratner, describing the finite ergodic invariant measures and the orbit closures for unipotent flows on homogeneous spaces of Lie groups, are extended for actions of subgroups generated by unipotent elements. More precisely: Let G be a Lie group (not necessarily connected) and Γ a closed subgroup of G. Let W be a subgroup of G such that AdG(W ) is contained in the Zariski clos...

In this paper a particular case of z-ideals, called strongly z-ideal, is defined by introducing zero sets in pointfree topology. We study strongly z-ideals, their relation with z-ideals and the role of spatiality in this relation. For strongly z-ideals, we analyze prime ideals using the concept of zero sets. Moreover, it is proven that the intersection of all zero sets of a prime ideal of C(L),...

Let G be a connected, semisimple algebraic group defined over an algebraically closed field k of characteristic p > 0. We assume that G is defined and split over the prime field k0. In general, for any positive integer r, and any affine fc-group scheme H defined over k0, the r-th infinitesimal subgroup scheme Hr of H is defined to be the (scheme-theoretic) kernel of the r-th power of the Froben...

For a compact Hausdorff abelian group K and its subgroup H ≤ K, one defines the g-closure g K (H) of H in K as the subgroup consisting of χ ∈ K such that χ(a n) −→ 0 in T = R/Z for every sequence {a n } inˆK (the Pontryagin dual of K) that converges to 0 in the topology that H induces onˆK. We prove that every countable subgroup of a compact Hausdorff group is g-closed, and thus give a positive...

Let G be a compact connected Lie group and let K closed subgroup of G. In this paper, we study whether the functional

Let p be a prime. A group is called p-closed if it has a normal Sylow p-subgroup and it is called p-exponent closed if the elements of order dividing p form a subgroup. A group is minimal non-p-closed if it is not p-closed but its proper subgroups and homomorphic images are. Similarly, a group is called minimal non-p-exponent closed if it is not p-exponent closed but all its proper subgroups an...