Some attempts to construct coherent states of a string

The possibility of constructing coherent states for a closed bosonic string is studied. The investigation is carried out in the orthonormal covariant gauge so that the Virasoro conditions must be imposed in order to eliminate ghosts. These conditions are incompatible with the simple usual construction of such states: A simple example is worked out to show a family of states which are as coherent as possible, compatible with the constraints, but in trying to generalize the result severe difficulties are found. (orig.)