Complex time route to quantum backreaction
arXiv:2001.02543 · doi:10.1140/epjc/s10052-019-7480-2
Abstract
We consider the backreaction of a quantum system on an effectively classical degree of freedom that is interacting with it. The backreaction equation based on the standard path integral formalism gives the so-called `in-out' backreaction equation, which has several serious pathologies. One can use a different backreaction prescription, referred to as the `in-in' approach, which resolves all the issues of `in-out' backreaction equation. However, this procedure is usually invoked in a rather ad hoc manner. Here we provide a rigorous path integral derivation of the `in-in' approach by exploiting the concept of quantum evolution along complex time contours. It turns out that, this approach can also be used to study both the `in-in' and `in-out' backreaction equations in a unified manner.
arXiv comment23 pages, 2 figures, published version
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