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Concerning the gravitational corrections to the running of gauge couplings two different results were reported. Some authors claim that gravitational correction at the one-loop level indicates an interesting effect of universal gravitational decreasing of gauge couplings, that is, gravitational correction works universally in the direction of asymptotic freedom no matter how the gauge coupling behaves without gravity, while others reject the presence of gravitational correction at the one-loop level at all. Being these calculations done in the framework of an effective field theory approach to general relativity, we wanted to draw attention to a recently discovered profound quantum-gravitational effect of space-time dimension running that inevitably affects the running of gauge couplings. The running of space-time dimension indicating gradual reduction of dimension as one gets into smaller scales acts on the coupling constants in the direction of asymptotic freedom and therefore in any case manifests the plausibility of this quantum-gravitational effect. Curiously enough, the results are also in perfect quantitative agreement with those of Robinson and Wilczek.
We give a direct microscopic derivation of the F-theory background that corresponds to four D7 branes of type I theory by taking into account the D-instanton contributions to the emission of the axio-dilaton field in the directions transverse to the
We discuss a string model where a conformal four-dimensional N=2 gauge theory receives corrections to its gauge kinetic functions from stringy instantons. These contributions are explicitly evaluated by exploiting the localization properties of the i
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The quantum contributions to the gravitational action are relatively easy to calculate in the higher derivative sector of the theory. However, the applications to the post-inflationary cosmology and astrophysics require the corrections to the Einstei