We review the progress which has recently been made in determining the spacetime backgrounds in which strings may consistently propagate. At the no-string-loop level, satisfactory backgrounds correspond to conformally invariant non-linear signal models and the condition of conformal invariance can be expressed as a field equation for the background spacetime. The problem of finding the effect of string loops on this picture is discussed.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Mathematical Physics
- Condensed Matter Physics