Gg. Magarililyaev, MEAN DIMENSION, WIDTHS, AND OPTIMAL RECOVERY OF SOBOLEV CLASSES OF FUNCTIONS ON THE LINE, Mathematics of the USSR. Sbornik, 74(2), 1993, pp. 381-403
The concept of mean dimension is introduced for a broad class of subsp
aces of L(p)(R) , and analogues of the Kolmogorov widths, Bernstein wi
dths, Gel'fand widths, and linear widths are defined. The precise valu
es of these quantities are computed for Sobolev classes of functions o
n R in compatible metrics, and the corresponding extremal spaces and o
perators are described. A closely related problem of optimal recovery
of functions in Sobolev classes is also studied.