Abstract
We study a pathwise local time of even integer order \(p \ge 2\), defined as an occupation density, for continuous functions with finite pth variation along a sequence of time partitions. With this notion of local time and a new definition of the Föllmer integral, we establish Tanaka-type change-of-variable formulas in a pathwise manner. We also derive some identities involving this high-order pathwise local time, each of which generalizes a corresponding identity from the theory of semimartingale local time. We then use collision local times between multiple functions of arbitrary regularity to study the dynamics of ranked continuous functions.
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Acknowledgements
The author would like to thank Professor Ioannis Karatzas for suggesting this topic and for numerous discussions regarding the material in this paper, and Professors Rama Cont and Nicolas Perkowski for helpful comments and for correcting errors in an earlier version of this paper. Thanks also go to Professors Hans Föllmer and Nicolas Perkowski for sending us the unpublished thesis of Würmli.
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This study was supported by the Department of Mathematics at Columbia University.
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Kim, D. Local Times for Continuous Paths of Arbitrary Regularity. J Theor Probab 35, 2540–2568 (2022). https://doi.org/10.1007/s10959-022-01159-z
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DOI: https://doi.org/10.1007/s10959-022-01159-z
Keywords
- Pathwise Itô calculus
- Pathwise local time
- Pathwise Tanaka–Meyer formulas
- Ranked functions of arbitrary regularity
- Fractional Brownian motion