JOURNAL OF
ALGEBRAIC
COMBINATORICS

Home > Vol 19, No 3 (2004)

Colin L. Starr¹ and Galen E. III Turner²

¹Department of Mathematics Willamette University 900 State Street Salem OR 97302 USA
²Program of Mathematics and Statistics Louisiana Tech University P.O. Box 3189 Ruston LA 71272 USA

In abstract algebra courses, teachers are often confronted with the task of drawing subgroup lattices. For purposes of instruction, it is usually desirable that these lattices be planar graphs (with no crossings). We present a characterization of abelian groups with this property. We also resolve the following problem in the abelian case: if the subgroup lattice is required to be drawn hierarchically (that is, in monotonic order of index within the group), when is it possible to draw the lattice without crossings?

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