Exact Simulation of Diffusions via Brownian Bridge Range Reconstruction

Radu Herbei; Kumar Somnath

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arXiv · 2609.26739

Exact Simulation of Diffusions via Brownian Bridge Range Reconstruction

Radu Herbei·Kumar Somnath

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Abstract

We develop an exact simulation algorithm for scalar diffusion paths and diffusion bridges when the Poisson potential is unbounded in both tails. The method reconstructs the realized range of a Brownian bridge proposal by sampling its maximum and location, together with the maxima and locations of the two adjacent restricted Brownian meanders. Conditional on this finite information, the remaining path decomposes into four conditionally independent interval-constrained Brownian bridges, which can be sampled exactly at the Poisson times required by the rejection test. In contrast to constructions based on an enclosing range layer, the proposed representation retains the exact extrema and their locations. Our algorithm returns an exact finite-dimensional skeleton without time-discretization error and permits exact post-acceptance refinement at arbitrary finite collections of times. Numerical experiments validate the resulting finite-dimensional laws and identify the restricted-meander extremum simulation as the principal computational cost in the nonlinear example.

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Radu Herbei, Kumar Somnath. 2026-09-22. Exact Simulation of Diffusions via Brownian Bridge Range Reconstruction. https://arxiv.org/abs/2609.26739

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