Comparison theorems of Kolmogorov type and exact values of n-widths on Hardy-Sobolev classes

Widths and shape-preserving widths of Sobolev-type classes of s-monotone functions

Abstract. Let I be a finite interval, r, n ∈ N, s ∈ N0 and 1 ≤ p ≤ ∞. Given a set M , of functions defined on I, denote by ∆+M the subset of all functions y ∈ M such that the s-difference ∆τ y(·) is nonnegative on I, ∀τ > 0. Further, denote by W r p the Sobolev class of functions x on I with the seminorm ‖x‖Lp ≤ 1. We obtain the exact orders of the Kolmogorov and the linear widths, and of the s...

Kolmogorov and Linear Widths of Weighted Sobolev-Type Classes on a Finite Interval, II

On the Metric Complexity of Continuous-time Systems

In this paper, metric complexities of certain classes of continuous-time systems are studied, using the time-domain sampling approach and the concepts of Kolmogorov, Gel’fand and sampling n-widths for certain classes of Sobolev space. A sampling theorem is obtained which extends Shannon’s sampling theorem to systems with possibly non-band-limited spectra. The theorem demonstrates that continuou...

n - Widths of Sobolev Spaces in L p

Let W~ r) = {f:fecr-J[O, l ] , f (rl) abs. cont., Ilftr)IIp < oo}, and set B~) = {f: f~ ~ ' ) , I[/~r)llp ~ 1}. We find the exact Kolmogorov, Gerfand, linear, and Bernstein n-widths of B~p r) in L p for all pE(l, oo). For the Kolmogorov n-width we show that for n _> r there exists an optimal subspace of splines of degree r 1 with n r fixed simple knots depending on p,

Optimal spline spaces of higher degree for L2 n-widths

In this paper we derive optimal subspaces for Kolmogorov n-widths in the L2 norm with respect to sets of functions defined by kernels. This enables us to prove the existence of optimal spline subspaces of arbitrarily high degree for certain classes of functions in Sobolev spaces of importance in finite element methods. We construct these spline spaces explicitly in special cases. Math Subject C...