On real logarithms of nearby matrices and structured matrix interpolation

Theoretical and algorithmic results are given for the numerical computation of real logarithms of nearby matrices. As an application, and an original motivation for this study, interpolation for sequences of invertible matrices is considered particularly for matrices with a given structure (for example, orthogonal, symplectic, or positive definite), so that the resulting interpolants share the structural properties of the data. Error analysis, implementation details and examples are provided.