Switched graphs of some strongly regular graphs related to the symplectic graph

Abstract

Applying a method of Godsil and McKay \cite{GM} to some graphs related to the symplectic graph, a series of new infinite families of strongly regular graphs with parameters $(2^n\pm 2^{(n-1)/2},2^{n-1}\pm 2^{(n-1)/2},2^{n-2}\pm 2^{(n-3)/2},2^{n-2}\pm 2^{(n-1)/2})$ are constructed for any odd $n\ge 5$. The construction is described in terms of geometry of quadric in projective space. The binary linear codes of the switched graphs are $[2^n\mp 2^{\frac{n-1}{2}},n+3,2^{t+1}{]}_2$-code or $[2^n\mp 2^{\frac{n-1}{2}},n+3,2^{t+2}{]}_2$-code.