We have decided to discontinue the publication of preprints on our preprint server end of 2024. The publication culture within mathematics has changed so much due to the rise of repositories such as ArXiV (www.arxiv.org) that we are encouraging all institute members to make their preprints available there. An institute's repository in its previous form is, therefore, unnecessary. The preprints published to date will remain available here, but we will not add any new preprints here.
We use singular entropies, and the connection with the fundamental solution of the entropy equation and its adjoint operator, in order to derive a new formula describing the coupling of oscillations between the two characteristic fields in systems of two conservation laws.