New constructions of strongly regular graphs
Date
2014
Authors
Lane-Harvard, Elizabeth, author
Penttila, Tim, advisor
Gloeckner, Gene, committee member
Hulpke, Alexander, committee member
Peterson, Chris, committee member
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Abstract
There are many open problems concerning strongly regular graphs: proving non-existence for parameters where none are known; proving existence for parameters where none are known; constructing more parameters where examples are already known. The work addressed in this dissertation falls into the last two categories. The methods used involve symmetry, geometry, and experimentation in computer algebra systems. In order to construct new strongly regular graphs, we rely heavily on objects found in finite geometry, specifically two intersection sets and generalized quadrangles, in which six independent successes occur. New two intersection sets are constructed in finite Desarguesian projective planes whose strongly regular graph parameters correspond to previously unknown and known ones. An infinite family of new two intersection sets is also constructed in finite projective spaces in 5 dimensions. The infinite family of strongly regular graphs have the same parameters as Paley graphs. Next, using the point graph of the classical GQ H(3,q2), q even, a new infinite family of strongly regular graphs is constructed. Then we generalize three infinite families of strongly regular graphs from large arcs in Desarguesian projective planes to the non-Desarguesian case. Finally, a construction of strongly regular graphs from ovoids of generalized quadrangles of Godsil and Hensel is applied to non-classical generalized quadrangles to obtain new families of strongly regular graphs.
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Subject
generalized quadrangle
strongly regular graph