https://doi.org/10.1140/epjc/s10052-019-7480-2
Regular Article - Theoretical Physics
Complex time route to quantum backreaction
IUCAA, Pune University Campus, Post Bag 4, Ganeshkhind, Pune, 411007, India
* e-mail: karthik@iucaa.in
Received:
28
June
2019
Accepted:
11
November
2019
Published online:
22
November
2019
We consider the backreaction of a quantum system q on an effectively classical degree of freedom C 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.
© The Author(s), 2019
