## Abstract

The first-order div least squares finite element methods (LSFEMs) allow for an immediate a posteriori error control by the computable residual of the least squares functional. This paper establishes an adaptive refinement strategy based on some equivalent refinement indicators. Since the first-order div LSFEM measures the flux errors in H (div), the data resolution error measures the L ^{2} norm of the right-hand side f minus the piecewise polynomial approximation II f without a mesh-size factor. Hence the data resolution term is neither an oscillation nor of higher order and consequently requires a particular treatment, e.g., by the thresholding second algorithm due to Binev and DeVore. The resulting novel adaptive LSFEM with separate marking converges with optimal rates relative to the notion of a nonlinear approximation class.

Original language | English |
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Pages (from-to) | 43-62 |

Number of pages | 20 |

Journal | SIAM Journal on Numerical Analysis |

Volume | 53 |

Issue number | 1 |

DOIs | |

Publication status | Published - 2015 Jan 1 |

### Bibliographical note

Publisher Copyright:© 2015 Society for Industrial and Applied Mathematics.

## All Science Journal Classification (ASJC) codes

- Numerical Analysis
- Computational Mathematics
- Applied Mathematics