An inherent disadvantage of the vastness of the space of all regularisers combined with the absence of a variational principle is that there is no straightforward method to access the best possible regularisers. We therefore propose to build regularising terms from components with clear physical interpretation, i. e. it should be a tensor contraction only consisting of tensor components with well-defined physical meaning. To summarise the previous discussion, we can identify the following necessary requirements for any regulariser R = R pq â † p âq :