Non-existence of quasi-symmetric designs having certain pseudo-geometric block graphs

Abstract

The block graph of a quasi-symmetric design is strongly regular. It is a challenging problem to decide which strongly regular graphs are block graphs of quasi-symmetric designs. We rule out the possibility of quasi-symmetric designs with non-zero intersection numbers whose block graphs have the parameters as certain pseudo-geometric graphs.

Keywords

• Strongly regular graphs
• quasi-symmetric designs
• block graph
• quadrics
• 05B05