English

Pathwise non-uniqueness for Brownian motion in a quadrant with oblique reflection

Probability 2024-05-13 v1

Abstract

Consider the Skorokhod equation in the closed first quadrant: Xt=x0+Bt+0tv(Xs)dLs, X_t=x_0+ B_t+\int_0^t{\bf v}(X_s)\, dL_s, where BtB_t is standard 2-dimensional Brownian motion, XtX_t takes values in the quadrant for all tt, and LtL_t is a process that starts at 0, is non-decreasing and continuous, and increases only at those times when XtX_t is on the boundary of the quadrant. Suppose v{\bf v} equals (a1,1)(-a_1,1) on the positive xx axis, equals (1,a2)(1,-a_2) on the positive yy axis, and v(0){\bf v}(0) points into the closed first quadrant. Let θi=arctanai\theta_i=\arctan a_i, i=1,2i=1,2. It is known that there exists a solution to the Skorokhod equation for all t0t\geq 0 if and only if θ1+θ2<π/2\theta_1+\theta_2<\pi/2 and moreover the solution is unique if a1a2<1|a_1a_2|<1. Suppose now that θ1+θ2<π/2\theta_1+\theta_2<\pi/2, θ2<0\theta_2<0, θ1>θ2>0\theta_1>-\theta_2>0 and a1a2>1|a_1a_2|>1. We prove that for a large class of (a1,a2)(a_1,a_2), namely those for which loga1+loga2a1+a2>π/2,\frac{\log|a_1|+\log|a_2|}{a_1+a_2}>\pi/2, pathwise uniqueness for the Skorokhod equation fails to hold.

Keywords

Cite

@article{arxiv.2405.06144,
  title  = {Pathwise non-uniqueness for Brownian motion in a quadrant with oblique reflection},
  author = {Richard F. Bass and Krzysztof Burdzy},
  journal= {arXiv preprint arXiv:2405.06144},
  year   = {2024}
}
R2 v1 2026-06-28T16:22:42.707Z