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abstract: |
    We combine I. background independent [**Loop Quantum Gravity (LQG)**]{} quantization techniques, II. the mathematically rigorous framework of [**Algebraic Quantum Field Theory (AQFT)**]{} and III. the theory of integrable systems resulting in the invariant [**Pohlmeyer Charges**]{} in order to set up the general representation theory (superselection theory) for the closed bosonic quantum string on flat target space.

    While we do not solve the, expectedly, rich representation theory completely, we present a, to the best of our knowledge new, non – trivial solution to the representation problem. This solution exists 1. for any target space dimension, 2. for Minkowski signature of the target space, 3. without tachyons, 4. manifestly ghost – free (no negative norm states), 5. without fixing a worldsheet or target space gauge, 6. without (Virasoro) anomalies (zero central charge), 7. while preserving manifest target space Poincaré invariance and 8. without picking up UV divergences. The existence of this stable solution is, on the one hand, exciting because it raises the hope that among all the solutions to the representation problem (including fermionic degrees of freedom) we find stable, phenomenologically acceptable ones in lower dimensional target spaces, possibly without supersymmetry, that are much simpler than the solutions 