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Doob decomposition, Dirichlet processes, and entropies on Wiener space. (English) Zbl 1497.60065

Chen, Zhen-Qing (ed.) et al., Dirichlet forms and related topics, in honor of Masatoshi Fukushima’s beiju, IWDFRT 2022, Osaka, Japan, August 22–26,2022. Singapore: Springer. Springer Proc. Math. Stat. 394, 119-141 (2022).
Summary: As an extension of the Doob-Meyer decomposition of a semimartingale and the Fukushima representation of a Dirichlet process, we introduce a general Doob decomposition in continuous time, where a square-integrable process is represented as the sum of a martingale and a process with “vanishing local risk”. For a probability measure \(Q\) on Wiener space, we discuss how entropy conditions on \(Q\) formulated with respect to Wiener measure \(P\) are connected with the Doob decomposition of the coordinate process \(W\) under \(Q\). The situation is well understood if the relative entropy \(H(Q|P)\) is finite; in this case the decomposition is classical and yields an immediate proof of Talagrand’s transport inequality on Wiener space. To go beyond this restriction, we consider the specific relative entropy \(h(Q|P)\) on Wiener space that was introduced by N. Gantert in [Einige große Abweichungen der Brownschen Bewegung. Bonn: Univ. Bonn, Math.-Naturwiss. Fak. (1991; Zbl 0746.60026)]. We discuss its interplay with the Doob decomposition of \(W\) under \(Q\) and a corresponding version of Talagrand’s inequality, with special emphasis on the case where \(W\) is a Dirichlet process under \(Q\).
For the entire collection see [Zbl 1493.11005].

MSC:

60G44 Martingales with continuous parameter
60G48 Generalizations of martingales
60J65 Brownian motion
60F10 Large deviations
46G12 Measures and integration on abstract linear spaces

Citations:

Zbl 0746.60026

References:

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