Surjective rational Hurewicz homomorphism gives a wedge of spheres

ID: surjective-rational-hurewicz-homomorphism-gives-a-wedge-of-spheres

If is simply connected and is onto, choose a homogeneous homology basis and representing sphere maps into . Their wedge sum gives a rational homology equivalence, hence a rational homotopy equivalence by the rational Whitehead theorem. All positive cup products therefore vanish. In a minimal model, the induced map from cohomology to the indecomposable quotient is injective; replacing a set of generators by cocycle representatives produces a quasi-isomorphism to the square-zero cohomology algebra, proving formality of a topological space.

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