Huggett offers 2 alternative interpretations of T-duality, in connection with the 3rd question. Two interpretive decisions need to be made:
- First interpretive decision: either the T-duals agree on the physical world, or they do not. If they do . . .
- Second interpretive decision: do both say that strings literally live in a space of radius R (but represent that fact dierently); or do they represent facts the same way, and so say nothing beyond their shared consequences (so that the radius is indeterminate between R and 1=R.)
Either way, both interpretations agree that the target space’s radius (i.e., the phenomenal space we live in) is very very big. Whew!