ε-weakly chebyshev subspaces and quotient spaces

ε-weakly Chebyshev subspaces and quotient spaces

Approximating weak Chebyshev subspaces by Chebyshev subspaces

We examine to what extent finite-dimensional spaces defined on locally compact subsets of the line and possessing various weak Chebyshev properties (involving sign changes, zeros, alternation of best approximations, and peak points) can be uniformly approximated by a sequence of spaces having related properties. r 2003 Elsevier Science (USA). All rights reserved.

Some Natural Subspaces and Quotient Spaces of L

We show that the space Lip0(R) is the dual space of L(R;R)/N where N is the subspace of L(R;R) consisting of vector fields whose divergence vanishes identically. We prove that although the quotient space L(R;R)/N is weakly sequentially complete, the subspace N is not nicely placed in other words, its unit ball is not closed for the topology τm of local convergence in measure. We prove that if Ω...

On the Dimension of Almost Hilbertian Subspaces of Quotient Spaces

The question of the dimension of almost Hilbertian subspaces is resolved in [1] where it is shown that every Banach space E of dimension n possesses almost Hilbertian subspaces of dimension c(logn), where c is an absolute constant, and that this estimate is the best possible. When the net is spread wider to include quotient spaces and subspaces of quotient spaces we should expect to find instan...

WEAK CHEBYSHEV SUBSPACES AND , 4 - SUBSPACES OF C [ a , b ]

In this paper we show some very interesting properties of weak Chebyshev subspaces and use them to simplify Pinkus's characterization of Asubspaces of C[a, b]. As a consequence we obtain that if the metric projection PG from C[a, b] onto a finite-dimensional subspace G has a continuous selection and elements of G have no common zeros on (a, b), then G is an /4-subspace.

Almost Euclidean Quotient Spaces of Subspaces of a Finite-dimensional Normed Space

The main result of this article is Theorem 1 which states that a quotient space Y, dim Y = k, of a subspace of any finite dimensional normed space X, dim X — n, may be chosen to be J-isomorphic to a euclidean space even for k = [Xn] for any fixed X < 1 (and d depending on X only). The following theorem is proved. 1. Theorem. For every d > 1 there exists X(d) > 0 such that every n-dimensional no...