"Modules Over Localized Group Rings for Groups Mapping Onto Free Groups" by Nicholas Davidson

Publication Date

5-2011

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Mathematics

Department Filter

Mathematics

Department

Mathematics

Supervisory Committee Chair

Jens Harlander, Ph.D.

Abstract

In 1964, Paul Cohn showed that if F is a finitely-generated free group, and Q a field, then all ideals in the group ring Q[F] are free as Q[F]-modules. In particular, all finitely-generated submodules of free Q[F]-modules are free. In 1990, Cynthia Hog-Angeloni reproved this theorem using techniques from geometric group theory. Leaning on Hog-Angeloni's methods, we prove an analogous statement for crossed products D * F, with D a division ring.

With this result in hand, we prove that if G = HF, the semi-direct product of H with F, so that the group ring D[G] may be localized at the sub-group ring k[H]―{0), then the resulting localized group ring also has the property that finitely-generated submodules of free modules are free.

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