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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2509.23086 |
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| _version_ | 1866909812540833792 |
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| author | Kang, Wei Yang Lim, Tau Shean |
| author_facet | Kang, Wei Yang Lim, Tau Shean |
| contents | We study the optimal Markovian coupling problem for two Pi-valued Feller processes {X_t} and {Y_t}, which seeks a coupling process {(X_t, Y_t)} that minimizes the right derivative at t = 0 of the expected cost E^{(x,y)}[c(X_t, Y_t)], for all initial states (x,y) in Pi^2 and a given cost function c on Pi. This problem was first formulated and solved by Chen (1994) for drift-diffusion processes and later extended by Zhang (2000) to Markov processes with bounded jumps. In this work, we resolve the case of Levy processes under the quadratic cost c(x,y) = 1/2 |x - y|^2 by introducing a new formulation of the "Levy optimal transport problem" between Levy measures. We show that the resulting optimal coupling process {(X_t*, Y_t*)}_{t >= 0} satisfies a minimal growth property: for each t >= 0 and x,y in R^d, the expectation E^{(x,y)}|X_t* - Y_t*|^2 is minimized among all Feller couplings. A key feature of our approach is the development of a dual problem, expressed as a variational principle over test functions of the generators. We prove strong duality for this formulation, thereby closing the optimality gap. As a byproduct, we obtain a Wasserstein-type metric on the space of Levy generators and Levy measures with finite second moment, and establish several of its fundamental properties. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_23086 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | On Optimal Markovian Couplings of Levy Processes Kang, Wei Yang Lim, Tau Shean Probability Functional Analysis Optimization and Control 60G51, 49Q22 We study the optimal Markovian coupling problem for two Pi-valued Feller processes {X_t} and {Y_t}, which seeks a coupling process {(X_t, Y_t)} that minimizes the right derivative at t = 0 of the expected cost E^{(x,y)}[c(X_t, Y_t)], for all initial states (x,y) in Pi^2 and a given cost function c on Pi. This problem was first formulated and solved by Chen (1994) for drift-diffusion processes and later extended by Zhang (2000) to Markov processes with bounded jumps. In this work, we resolve the case of Levy processes under the quadratic cost c(x,y) = 1/2 |x - y|^2 by introducing a new formulation of the "Levy optimal transport problem" between Levy measures. We show that the resulting optimal coupling process {(X_t*, Y_t*)}_{t >= 0} satisfies a minimal growth property: for each t >= 0 and x,y in R^d, the expectation E^{(x,y)}|X_t* - Y_t*|^2 is minimized among all Feller couplings. A key feature of our approach is the development of a dual problem, expressed as a variational principle over test functions of the generators. We prove strong duality for this formulation, thereby closing the optimality gap. As a byproduct, we obtain a Wasserstein-type metric on the space of Levy generators and Levy measures with finite second moment, and establish several of its fundamental properties. |
| title | On Optimal Markovian Couplings of Levy Processes |
| topic | Probability Functional Analysis Optimization and Control 60G51, 49Q22 |
| url | https://arxiv.org/abs/2509.23086 |