Tensor developments of a stochastic variational principle

A variational principle for lumped neutron stochastics is recast showing the role of the forward and backward Kolmogorov equations as the adjoint Euler-Lagrange pair. The generating function formalism can be introduced although the link between the pair is not maintained. To extend the variational principle to more complicated models, including delayed neutrons, detected events and feedback, the matrix-vector notation is put into tensor form. Three examples are given of the extension of the model in tensor notation that are covered by the variational formulation.