Monday, July 22, 2013

1307.5124 (Edward Witten)

The Feynman $i ε$ in String Theory    [PDF]

Edward Witten
The Feynman $i\varepsilon$ is an important ingredient in defining perturbative scattering amplitudes in field theory. Here we describe its analog in string theory. Roughly one takes the string worldsheet to have Lorentz signature when a string is going on-shell although it has Euclidean signature generically.
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