Cores of Geometric Graphs.

Cameron and Kazanidis have recently shown that rank-three graphs are either cores or have complete cores, and they asked whether this holds for all strongly regular graphs. We prove that this is true for the point graphs and line graphs of generalized quadrangles and that when the number of points is sufficiently large, it is also true for the block graphs of Steiner systems and orthogonal arrays. [ABSTRACT FROM AUTHOR]