Majorizing measures and proprtional subsets of bounded orthonormal systems

Abstract

In this article we prove that for any orthonormal system (φj)j=1n ⊂ L2. that is bounded in L∞, and any 1 < k < n, there exists a subset I of cardinality greater than n - k such that on span{φi} i∈I, the L1 norm and the L2 norm are equivalent up to