2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/225933We compute the cotorsion product of the mod 2 cohomology of spinor group spin(n), which is the E_2-term of the Rothenberg-Steenrod spectral sequence for the mod 2 cohomology of the classifying space of the spinor group spin(n). As a consequence of this computation, we show the non-collapsing of the Rothenberg-Steenrod spectral sequence for n > 16.This is the version published by Geometry & Topology Monographs on 25 February 2008Algebraic Topology55R40, 55T99text