Let $X$ be a simply connected closed oriented manifold of rationally elliptic homotopy type. We prove that the string topology bracket on the $S^1$-equivariant homology $\overline{ H}_{ \ast}^{ S^1}(\mathcal{ L}X,\mathbb{ Q}) $ of the free loop space of $X$ preserves the Hodge decomposition of $\overline{ H}_{ \ast}^{ S^1}(\mathcal{ L}X,\mathbb{ Q}) $ , making it a bigraded Lie algebra. We deduce this result from a general theorem on derived Poisson structures on the universal enveloping algebras of homologically nilpotent finite-dimensional DG Lie algebras. Our theorem settles a conjecture proposed in our earlier work.
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