The Kolmogorov-Chentsov theorem

Christian Pardillo-Laursen 📧 and Simon Foster 📧

April 6, 2025

Abstract

Continuous-time stochastic processes often carry the condition of having almost-surely continuous paths. If some process \(X\) satisfies certain bounds on its expectation, then the Kolmogorov-Chentsov theorem lets us construct a modification of \(X\), i.e. a process \(X'\) such that \(\forall t. X_t = X'_t\) almost surely, that has Hölder continuous paths.

In this work, we mechanise the Kolmogorov-Chentsov theorem. To get there, we develop a theory of stochastic processes, together with Hölder continuity, convergence in measure, and arbitrary intervals of dyadic rationals.

With this, we pave the way towards a construction of Brownian motion. The work is based on the exposition in Achim Klenke's probability theory text.

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BSD License

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Session Kolmogorov_Chentsov