History of variational principles in physics involves integrals over an interval of time and (for fields) extended region of space. Moreover, in the usual formulation of classical action principles, the initial and final states of the system are fixed, e.g., In particular, the fixing of the "final" state appears to give the action principle a teleological character which has been controversial historically. This apparent teleology is eliminated in the quantum mechanical version of the action principle. History of variational principles in physics A variational principle in physics is an alternative method for determining the state or dynamics of a physical system, by identifying it as an
Interaction information Interaction information The interaction information (McGill 1954), or amounts of information (Hu Kuo Ting, 1962) or co-information (Bell 2003) or information interaction (Licina 2017) is one of several generalizations of the mutual information. In fact, the definition of interaction information is identical to that of multivariate mutual information except for a change in sign in the case of an odd number of random variables except in the work of Licina where information is more like a physical entitiy. Interaction information expresses the amount information (redundancy or synergy) bound up in a set of variables, "beyond" that which is present in