Partial and complete observables for Hamiltonian constrained systems
The author is picking up the concepts of partial and complete observables introduced by \textit{C. Rovelli} [in A. Ashtekar (ed.) et al., ``Conceptional problems in quantum gravity'', Cambridge: Cambridge University Press, 126--140 (1991; Zbl 0837.53060)] in order to construct Dirac observables in gauge systems. One generalizes these ideas to an arbitrary number of gauge degrees of freedom. Different methods to calculate such Dirac observables are developed. For background independent field theories one shows that partial and complete observables can define a non-trivial gauge action on the space of complete observables and also states the Poisson brackets of these functions. Additionally one investigates, whether it is possible to calculate Dirac observables starting with partially invariant partial observables, for instance functions, which are invariant under the spatial diffeomorphism group.
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