arXiv:quant-ph/9804003 · Physical Review A
Fluctuations, time-correlation functions, and geometric phase
Arun Kumar Pati
Abstract
The adiabatic approximation usually applies to a collection of lighter particles (the ``fast'' system) and heavier particles (the ``slow'' system), where the geometric phase naturally appears. With the help of the recently introduced gauge potential in the context of adiabatic Berry phase for open paths, we establish a fluctuation-correlation theorem by relating the quantum fluctuations in the generator of the parameter change (of the ``slow'' system) to the time integral of the quantum correlation function between the projection operator and force operator acting on the ``fast'' system. By taking a cue from linear response theory we relate the quantum fluctuation in the generator to the generalized susceptibility. The relation between the open-path geometric phase, diagonal elements of the quantum metric tensor, and the force-force correlation function are provided and the classical limit of the fluctuation-correlation theorem is discussed.