is super symmetry real or has been predicted by string theory?
- It's not a prediction by string theory but a necessary component of some string models. It's not something unique to string theory, though. You can apply supersymmetry more or less directly to the SM
Taking the maximum extension of spacetime symmetries already appears relatively natural () to me. How does it "arise naturally" in string theory (also in the sense of "what does that mean?") and what does that mean about string models without susy? If susy automatically arises from a string approach, then it seems that non-susy string models shouldn't be possible.