Abstract

Normal subgroups can be thought of as the primary building blocks for decomposing mathematicalgroups into quotient groups. The properties of the resulting quotient groups are oftenused to determine properties of the group itself. This thesis considers normal subgroups of threedimensionalcrystallographic space groups that are themselves three-dimensional crystallographicspace groups; for convenience, we refer to such a subgroup as a csg-normal subgroup. We identifypractical restrictions on csg-normal subgroups that facilitate their tabulation. First, the point groupof an csg-normal subgroup must be a normal subgroup of the crystallographic point group of thespace group, which we refer to for convenience as a cpg-normal subgroup. For each of the cpgnormalsubgroups, which are all well known, we identify the abstract quotient group. Secondly,we identify necessary conditions on the sublattice basis of any csg-normal subgroup, and tabulatethe “normally supportive“ sublattices that meet these conditions, where some tables are symbolicforms that represent infinite families of sublattices. For a given space group, every csg-normalsubgroup must be an extension of such a normally supportive sublattice, though some normallysupportive sublattices may not actually support such extensions.

Degree

College and Department

Physical and Mathematical Sciences; Physics and Astronomy

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