A low-order discontinuous Petrov-Galerkin method for the Stokes equations. - Carsten Carstensen; Sophie Puttkammer (Numerische Mathematik, 2018)

Guaranteed lower bounds on eigenvalues of elliptic operators with a hybrid high-order method. - Carsten Carstensen; Alexandre Ern; Sophie Puttkammer (Numerische Mathematik, 2021)

Direct Guaranteed Lower Eigenvalue Bounds with Optimal a Priori Convergence Rates for the Bi-Laplacian. - Carsten Carstensen; Sophie Puttkammer (SIAM J. Numer. Anal., 2023)

Adaptive guaranteed lower eigenvalue bounds with optimal convergence rates. - Carsten Carstensen; Sophie Puttkammer (Numerische Mathematik, 2024)