Widths of embeddings of 2-microlocal Besov spaces
  We consider the asymptotic behaviour of the approximation, Gelfand and Kolmogorov numbers of compact embeddings between 2-microlocal Besov spaces with weights defined in terms of the distance to a $d$-set $U\subset \mathbb{R}^n$. The sharp estimates are shown in most cases, where the quasi-Banach setting is included. 
Shun Zhang, Gensun Fang
math.FA math.NA