Abstract
We argue that a technique called analytic perturbation theory leads to a well-defined method for analytically continuing the running coupling constant from the spacelike to the timelike region, which allows us to give a self-consistent definition of the running coupling constant for timelike momentum. The corresponding function is proportional to the spectral density, which confirms a hypothesis due to Schwinger.
- Received 27 November 1996
DOI:https://doi.org/10.1103/PhysRevD.55.5295
©1997 American Physical Society