Axions In String Theory

الأصل · EN

In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter Fₐ is several orders of magnitude higher than the standard cosmological bounds. We re-examine this problem in a variety of models, showing that Fₐ is close to the GUT scale or above in many models that have GUT-like phenomenology, as well as some that do not. On the other hand, in some models with Standard Model gauge fields supported on vanishing cycles, it is possible for Fₐ to be well below the GUT scale.