Entropy and Correlators in Quantum Field Theory

Understand

It is well known that loss of information about a system, for some observer, leads to an increase in entropy as perceived by this observer.

• We use this to propose an alternative approach to decoherence in quantum field theory in which the machinery of renormalisation can systematically be implemented: neglecting observationally inaccessible correlators will give rise to an increase in entropy of the system.
• As an example we calculate the entropy of a general Gaussian state and, assuming the observer's ability to probe this information experimentally, we also calculate the correction to the Gaussian entropy for two specific non-Gaussian states.