THE UNIFORM DIMENSION OF THE LEVEL SETS OF A BROWNIAN SHEET

Let WN(t) denote the N-parameter Brownian sheet (Wiener process) taking values in R'. For 0 < T < 1, set A(T) = {teRN: 0 < ti ? T, i = 1, * * *, N} and let E(x, T) = {t e A(T): WN(t) = x}, the set of t where the process is at the level x. Then we show that, with probability one, the Hausdorff dimension of E(x, T) equals N I for all 0 < T ? 1 and every x in the interior of the range of WN(t), t e A(T). This provides an answer to a question raised earlier by Pyke.