MULTIDIMENSIONAL KOLMOGOROV-PETROVSKY TEST FOR THE BOUNDARY REGULARITY AND IRREGULARITY OF SOLUTIONS

MULTIDIMENSIONAL KOLMOGOROV-PETROVSKY TEST FOR THE BOUNDARY REGULARITY AND IRREGULARITY OF SOLUTIONS TO THE HEAT EQUATION UGUR G. ABDULLA Received 25 August 2004 Dedicated to I. G. Petrovsky This paper establishes necessary and sufficient condition for the regularity of a characteristic top boundary point of an arbitrary open subset of RN+1 (N ≥ 2) for the diffusion (or heat) equation. The result implies asymptotic probability law for the standard Ndimensional Brownian motion. 1. Introduction and main result Consider the domain Ωδ = (x,t) ∈ RN+1 : |x| 0, N ≥ 2, x = (x1 ,...,xN ) ∈ RN , t ∈ R,...