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Inverse theorems in the theory of approximation of vectors in a Banach space with exponential type entire vectors


Abstract

An arbitrary operator $A$ on a Banach space $X$ which is a generator of a $C_0$-group with a certain growth condition at infinity is considered. A relationship between its exponential type entire vectors and its spectral subspaces is found. Inverse theorems on the connection between the degree of smoothness of a vector $x\in X$ with respect to the operator $A$, the rate of convergence to zero of the best approximation of $x$ by exponential type entire vectors for operator $A$, and the $k$-module of continuity with respect to $A$ are established. Also, a generalization of the Bernstein-type inequality is obtained. The results allow to obtain Bernstein-type inequalities in weighted $L_p$ spaces.


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Article Information

TitleInverse theorems in the theory of approximation of vectors in a Banach space with exponential type entire vectors
SourceMethods Funct. Anal. Topology, Vol. 16 (2010), no. 1, 69-82
MathSciNet MR2656133
CopyrightThe Author(s) 2010 (CC BY-SA)

Authors Information

S. Torba
Institute of Mathematics, National Academy of Sciences of Ukraine, 3 Tereshchenkivs'ka, Kyiv, 01601, Ukraine


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Citation Example

S. Torba, Inverse theorems in the theory of approximation of vectors in a Banach space with exponential type entire vectors, Methods Funct. Anal. Topology 16 (2010), no. 1, 69-82.


BibTex

@article {MFAT490,
    AUTHOR = {Torba, S.},
     TITLE = {Inverse theorems in the theory of approximation of vectors in a Banach space with exponential type entire vectors},
   JOURNAL = {Methods Funct. Anal. Topology},
  FJOURNAL = {Methods of Functional Analysis and Topology},
    VOLUME = {16},
      YEAR = {2010},
    NUMBER = {1},
     PAGES = {69-82},
      ISSN = {1029-3531},
       URL = {http://mfat.imath.kiev.ua/article/?id=490},
}


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