Reduction for flag-transitive 2-( v , k , λ ) designs with ( r , λ ) = 2

摘要

This paper studies flag-transitive 2- ( v , k , lambda ) designs with ( r , lambda ) = 2. We prove that if D is a flag-transitive nontrivial 2- ( v , k , lambda ) design with ( r , lambda ) = 2, then G is of affine or almost simple type. Furthermore, we analyze the flag-transitive automorphism groups of almost simple type with S o c ( G ) = A n for n >= 5, and obtain that, up to isomorphism, there are 11 designs.

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