The Infinite-dimensional σ-widthsof Besov Classes

Let (X(Rd), x) be a normed space of real functions on Rd. Let > 0 and P be theoperator in X(Rd) defined by P f(x) = x(x)f(x) (where (x) is the characteristic functionof the cube Id = [- , ]d). Let L be a subspace of X(Rd). Set P L= {P f: f L}. SupposeL is locally-finite dimensional, i.e., dim(P L,X) < for every > 0. Then the followingquantity is said to be the average dimension of L in X (in the sense of LED)(see [1]).Let > 0, and C be a centrally symmetric subset of X(Rd). The i…