Virtual surface bundle groups and Johnson's trichotomy


J. A. Hillman


Research Report 98-8
Date: 27 March 1998


We give a new exposition of Johnson's trichotomy for torsion free groups which are virtually extensions of one surface group by another, and show that all groups in his first two classes may be realized by aspherical closed smooth 4-manifolds.

Key phrases

aspherical. bundle. extension. 4-manifold. orbifold. surface.

AMS Subject Classification (1991)

Primary: 57N13
Secondary: 20F34 20J05


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