Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/iii/paper-202/4/c/solution
Past exam of the mathematics course of the University of Cambridge 2025 iii Paper 202 4 c Solution by
Codex 0 Created 2026-09-24 Updated 2026-09-25
Let and be two solutions with the same initial value and Brownian motion, and put . Itô formula givesStop when either process or the stochastic integral becomes large. Taking expectations, using the assumed one-sided Lipschitz bound, and then removing the localization givesThe Gronwall inequality yields . Thus almost surely at every rational time, and path continuity makes the two processes indistinguishable. This proves pathwise uniqueness.
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