Lower bounds for widths of classes of convolutions of periodic functions in the metrics ofC andL

@article{Stepanets1995LowerBF,
  title={Lower bounds for widths of classes of convolutions of periodic functions in the metrics ofC andL},
  author={A. I. Stepanets and A. Serdyuk},
  journal={Ukrainian Mathematical Journal},
  year={1995},
  volume={47},
  pages={1271-1282}
}
We give new sufficient conditions for kernels to belong to the set Cy,2n introduced by Kushpel'. These conditions give the possibility of extending the set of kernels belonging to Cy,2n. On the basis of these results, we obtain lower bounds for the Kolmogorov widths of classes of convolutions with these kernels. We show that these estimates are exact in certain important cases. 
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