So, in QFT where the calculation involves noncommuting operators, we define normal ordering to remove the ambiguity. This is usually done by moving annihilation operators to the right of the creation operators.

In string theory, there is also another position operator apart from ladder operators of the excitation. It appears that X and Alpha_0 (momentum) don't commute. So how do we define the normal ordering for these two operators?


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.