DECENTRALIZATION WITHOUT COORDINATION.

In hierarchical control theory, decomposition into subproblems is generally followed by coordination because of interactions. For linear quadratic stationary optimal control problems, manipulations like state space basis change or replacement of the criterion by an equivalent one are allowed to get a new problem with the same solution. A simple test is exhibited to know whether it is possible by those manipulations to obtain a new problem which separates into independent smaller ones thus avoiding coordination. Also it is shown how to find the partition of control and state vectors and the good formulation of the problem.