An exact sequence from the nth to the (n-1)-st fundamental group
We give an example of a space with the property that every orientable fibration with the fiber is rationally totally non-cohomologous to zero, while there exists a nontrivial derivation of the rational cohomology of of negative degree.
In this paper we present an approximation to the de Rham theorem for simplicial sets with any coefficients based, using simplicial techniques, on Poincaré's lemma and q-extendability.