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arXiv · 1712.01965

An isomorphism between branched and geometric rough paths

Horatio Boedihardjo·Ilya Chevyrev
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Abstract

We exhibit an explicit natural isomorphism between spaces of branched and geometric rough paths. This provides a multi-level generalisation of the isomorphism of Lejay-Victoir (2006) as well as a canonical version of the It\^o-Stratonovich correction formula of Hairer-Kelly (2015). Our construction is elementary and uses the property that the Grossman-Larson algebra is isomorphic to a tensor algebra. We apply this isomorphism to study signatures of branched rough paths. Namely, we show that the signature of a branched rough path is trivial if and only if the path is tree-like, and construct a non-commutative Fourier transform for probability measures on signatures of branched rough paths. We use the latter to provide sufficient conditions for a random signature to be determined by its expected value, thus giving an answer to the uniqueness moment problem for branched rough paths.

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Horatio Boedihardjo, Ilya Chevyrev. 2017-12-05. An isomorphism between branched and geometric rough paths. https://doi.org/10.1214/18-aihp912

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