A projective variety with discrete, non-finitely generated automorphism group

Finitely Smooth Reinhardt Domains with Non-compact Automorphism Group

We give a complete description of bounded Reinhardt domains of finite boundary smoothness that have non-compact automorphism group. As part of this program, we show that the classification of domains with non-compact automorphism group and having only finite boundary smoothness is considerably more complicated than the classification of such domains that have infinitely smooth boundary. Let D ⊂...

Non-finitely Generated Projective Modules over Generalized Weyl Algebras

We classify infinitely generated projective modules over generalized Weyl algebras. For instance, we prove that over such algebras every projective module is a direct sum of finitely generated modules.

The Modular Group A Finitely Generated Group with Interesting Subgroups

The action of Möbius transformations with real coefficients preserves the hyperbolic metric in the upper half-plane model of the hyperbolic plane. The modular group is an interesting group of hyperbolic isometries generated by two Möbius transformations, namely, an order-two element, g2 HzL = -1 ê z, and an element of infinite order, g• HzL = z + 1. Viewing the action of the group elements on a...

Periodic rings with finitely generated underlying group

We study periodic rings that are finitely generated as groups. We prove several structure results. We classify periodic rings that are free of rank at most 2, and also periodic rings R such that R is finitely generated as a group and R/t(R) Z. In this way, we construct new classes of periodic rings. We also ask a question concerning the connection to periodic rings that are finitely generated a...

Ring With All Finitely Generated Modules Retractable