Let BH={BH(t), t∈ℝ+N} be an (N, d)-fractional Brownian sheet with index H=(H1, …, HN)∈(0, 1)N defined by BH(t)=(BH1(t), …, BHd(t)) (t∈ℝ+N), where BH1, …, BHd are independent copies of a real-valued fractional Brownian sheet B0H. We prove that if d<∑ℓ=1NHℓ−1, then the local times of BH are jointly continuous. This verifies a conjecture of Xiao and Zhang (Probab. Theory Related Fields 124 (2002)).
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We also establish sharp local and global Hölder conditions for the local times of BH. These results are applied to study analytic and geometric properties of the sample paths of BH.