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New Paper: Physical Review X

February 27, 2018 4:05 PM

Jarzynski Equality for Driven Quantum Field Theories

Phys. Rev. X 8, 011033

Anthony Bartolotta and Sebastian Deffner


Since the middle of the last century, quantum field theory—a theoretical framework for describing subatomic particles in terms of fields—has served as our most fundamental description of nature. The theory has been rigorously tested and encompasses particle physics, cosmology, and condensed matter. Thermodynamics, however, remained largely stagnant until about two decades ago when fluctuation theorems broadened our understanding of systems operating far from equilibrium. These two bodies of research remain largely separate. Here, we extend the existing literature on fluctuation theorems to the realm of quantum field theory, vastly expanding the range of possible systems to which these theorems can be applied. In our work, we reconcile the sometimes conflicting nature of quantum fluctuation theorems and quantum field theory. Quantum fluctuation theorems aim to describe the behavior of systems over short time scales when subject to time-dependent driving, whereas quantum field theories are usually used to describe the long-time behavior of time-independent systems. We require new calculation techniques because existing methods in quantum field theory are inadequate for calculating the quantities of interest. This culminates in the calculation of closed-form expressions for the probability distribution of work performed by subjecting a particular quantum field theory to a time-dependent driving. From the quark-gluon plasma produced in particle accelerators to the relativistic charge carriers of graphene and to the inflation of the early Universe, nonequilibrium systems described by quantum field theories abound across a vast range of scales. This work opens the door for future applications of quantum fluctuation theorems to the study of this diverse group of systems.
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