## Section: New Results

### Convergence rates with singular parameterizations for solving elliptic boundary value problems in isogeometric analysis

Participant : Bernard Mourrain.

In [15], we present convergence rates for solving elliptic boundary value problems with singular parameterizations in isogeometric analysis. First, the approximation errors with the ${L}^{2}\left(\Omega \right)$-norm and the ${H}^{1}\left(\Omega \right)$-seminorm are estimated locally. The impact of singularities is considered in this framework. Second, the convergence rates for solving PDEs with singular parameterizations are discussed. These results are based on a weak solution space that contains all of the weak solutions of elliptic boundary value problems with smooth coefficients. For the smooth weak solutions obtained by isogeometric analysis with singular parameterizations and the finite element method, both are shown to have the optimal convergence rates. For non-smooth weak solutions, the optimal convergence rates are reached by setting proper singularities of a controllable parameterization, even though convergence rates are not optimal by finite element method, and the convergence rates by isogeometric analysis with singular parameterizations are better than the ones by the finite element method.

This a joint work with Meng Wu, Yicao Wang, Boniface Nkonga, Changzheng Cheng.