= Formal space
= Formality of a topological space
{synonym}
A space is formal over $\mathbb Q$ if its rational cochain commutative <differential graded algebra> is joined to $(H^*(X;\mathbb Q),0)$ by <quasi-isomorphisms>. Equivalently in the usual <simply connected> Sullivan-model setting, its <minimal model> has a <quasi-isomorphism> to its <cohomology> algebra with zero differential. This says its <rational homotopy type> can be recovered from the <cohomology> algebra; zero <cup products> alone do not imply <formality of a topological space> without an additional argument.
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