2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67216The difference between the quadratic L-groups L_*(A) and the symmetric L-groups L^*(A) of a ring with involution A is detected by generalized Arf invariants. The special case A=Z[x] gives a complete set of invariants for the Cappell UNil-groups UNil_*(Z;Z,Z) for the infinite dihedral group D_{\infty}=Z_2*Z_2, extending the results of Connolly and Ranicki (math.AT/0304016) and Connolly and Davis.90 pages, LATEXAlgebraic Topology57N15, 57R67text