We follow the point of view that superstring theory, as the theory of quantum gravity in the number of spacetime dimensions bigger than 4, serves as mathematics for both, 4 dimensional QG and exotic smoothness on open 4-manifolds. Extra-dimensions, supersymmetry or some other string techniques, belong to the mathematical toolkit suitable for the above purposes. Physics in dimension 4 is reached via exotic 4-geometries on R~4. In the paper we discuss the techniques of exact superstring backgrounds, CFT and SU(2)_k WZW models, as suitable for the description of effects assigned to the magnetic field and its gravitational backreactions on exotic Euklidean R~4 which is the underlying smoothness for the 4-dimensional spacetime.
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