TILTED EULER CHARACTERISTIC DENSITIES FOR CENTRAL LIMIT RANDOM FIELDS, WITH APPLICATION TO BUBBLES

• 成果类型: Article
• 署名作者: Chamandy, N.; Worsley, K. J.; Taylor, J.; Gosselin, F.
• 署名单位: McGill University; Alphabet Inc.; Google Incorporated; University of Chicago; Stanford University; Universite de Montreal
• 刊物名称: ANNALS OF STATISTICS
• ISSN/ISSBN: 0090-5364
• DOI: 10.1214/07-AOS549
• 发表日期: 2008
• 页码: 2471-2507
• 关键词: excursion sets; RECOGNITION; statistics

摘要

Local increases in the mean of a random field are detected (conservatively) by thresholding a field of test statistics at a level u chosen to control the tail probability or p-value of its maximum. This p-value is approximated by the expected Euler characteristic (EC) of the excursion set of the test statistic field above u, denoted E phi (A(u)). Under isotropy, one can use the expansion E phi(A(u)) = Sigma(k) V(k rho k()u), where V-k is an intrinsic volume of the parameter space and rho(k) is an EC density of the field. EC densities are available for a number of processes, mainly those constructed from (multivariate) Gaussian fields via smooth functions. Using saddlepoint methods, we derive an expansion for (rho k)(u) for fields which are only approximately Gaussian, but for which higher-order cumulants are available. We focus on linear combinations of n independent non-Gaussian fields, whence a Central Limit theorem is in force. The threshold u is allowed to grow with the sample size n, in which case our expression has a smaller relative asymptotic error than the Gaussian EC density. Several illustrative examples including an application to bubbles data accompany the theory.