Equi-isoclinic planes in Euclidean even dimensional spaces

Abstract

Abstract Let . A p-set of equi-isoclinic planes with parameter λ in is a set of p planes spanning each pair of which has the same non-zero angle arccos . We prove that the maximum number of equi-isoclinic planes in is nine and that if λ > ¼, the maximum number of equi-isoclinic planes in with parameter λ is equal to that one of equiangular lines in with angle arccos .