16G20 16G60 15A63 the quadratic Tits form (min 15A 15A21 16G 16G60; 15A21 20C20 46K10 46L05 \(inj\)-finite poset bunch of modules bundle of semichaines category of representations constant Jordan type critical poset dispersing representation elementary abelian groups extended Dynkin diagram idempotent matrix representations,representation type max)-equivalent posets minimax (semiminimax) sum minimax equivalence minimax sum poset positive definite form positive form