Algorithms for nonlinear piecewise polynomial approximation: Theoretical aspects

Authors:
Borislav Karaivanov, Pencho Petrushev and Robert C. Sharpley

Journal:
Trans. Amer. Math. Soc. **355** (2003), 2585-2631

MSC (2000):
Primary 41A17, 41A25, 65D18; Secondary 65D07, 42B35

Published electronically:
March 19, 2003

MathSciNet review:
1975391

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Abstract: In this article algorithms are developed for nonlinear -term Courant element approximation of functions in ( ) on bounded polygonal domains in . Redundant collections of Courant elements, which are generated by multilevel nested triangulations allowing arbitrarily sharp angles, are investigated. Scalable algorithms are derived for nonlinear approximation which both capture the rate of the best approximation and provide the basis for numerical implementation. Simple thresholding criteria enable approximation of a target function to optimally high asymptotic rates which are determined and automatically achieved by the inherent smoothness of . The algorithms provide direct approximation estimates and permit utilization of the general Jackson-Bernstein machinery to characterize -term Courant element approximation in terms of a scale of smoothness spaces (-spaces) which govern the approximation rates.

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Additional Information

**Borislav Karaivanov**

Affiliation:
Department of Mathematics, University of South Carolina, Columbia, South Carolina 29208

Email:
karaivan@math.sc.edu

**Pencho Petrushev**

Affiliation:
Department of Mathematics, University of South Carolina, Columbia, South Carolina 29208

Email:
pencho@math.sc.edu

**Robert C. Sharpley**

Affiliation:
Department of Mathematics, University of South Carolina, Columbia, South Carolina 29208

Email:
sharpley@math.sc.edu

DOI:
https://doi.org/10.1090/S0002-9947-03-03141-6

Keywords:
Nested irregular triangulations,
redundant representations,
nonlinear $n$-term approximation,
Courant elements,
Jackson and Bernstein estimates.

Received by editor(s):
May 2, 2002

Published electronically:
March 19, 2003

Additional Notes:
The second and third authors were supported in part by Grant NSF #DMS-0079549 and ONR N00014-01-1-0515.

All three authors were supported in part by ONR grant N00014-00-1-0470.

Article copyright:
© Copyright 2003
American Mathematical Society