Is spacetime in string theory 4D or 12D?

[ensabah6]

Spacetime is 3D + 1T = 4D

Is spacetime in string theory 4D as a result of compactification, or 12D, 11D+1T?

 

[MTd2]

No one really knows how many dimensions m-theory has. The highest dimensional low energy limit is 11d (10 +1T) supergravity, the other 5 being the superstring theories in 10D (9+1T). There is a higher dimensional version of it,"E8 gauge theory", in 12D (11+1). I don't anything about it, but I am trying.

 

[javierR]

Is spacetime in string theory 4D as a result of compactification, or 12D, 11D+1T?

In superstring theory (the "usual" string theory) spacetime must be 10D, so we have to consider the extra six dimensions as being compact and small. Any other reason why they "should" be like this is unknown. M-theory is 11D and F-theory is 12D; these are not string theories, but are related to them by some compactifications to 10D.