>>12828040>>12828063>>12828180>>12828190>>12828737>>12828844>According to string theory, there are 10 or 11 dimensions.>What are the other dimensions suppose to be? Are they spatial, temporal or something different?The extra dimensions are there because of how black holes oscillate.
The string is a black hole, and the number of degrees of freedom of a black hole are constrained. The string black hole can shake in any one of the dimensions of space, and when there are more than 10 dimensions (and Fermionic currents on the worldsheet), the black hole has too much entropy. You can see that there is a strict mass bound because the number of oscillation directions gives a new scalar field, and each one contributes to the entropy of the string.
The dimension can go up to 26 for a string, if you give up on Fermions and allow a non-stable vacuum. The 26 dimensional bosonic string is not viable by itself, but it can perhaps be given a cosmological interpretation. The limit is just that the number of degrees of freedom of the string can't grow without bound (or shrink either), because there is a self-consistency requirement that the string describe a surrounding spacetime holographically, with the right entropy relation for a black hole in the classical limit.
This argument does not appear in the literature in exactly this form, and it is not 100% clear it can be made mathematically precise, so take it with a grain of salt. It's a framework for giving a more physical interpretation to the mathematical calculations in the existing formalisms that pick out a certain fixed amount of degrees of freedom as required by the duality between world-sheet and space-time to work.
