Relating the thermodynamic arrow of time to the causal arrow
Abbreviated Journal Title
J. Stat. Mech.-Theory Exp.
new applications of statistical mechanics; QUANTUM SYSTEMS; 2ND-LAW; ENTROPY; THEOREM; CHAOS; GIBBS; PROOF; Mechanics; Physics, Mathematical
Consider a Hamiltonian system that consists of a slow subsystem S and a fast subsystem F. The autonomous dynamics of S is driven by an effective Hamiltonian, but its thermodynamics is unexpected. We show that a well-defined thermodynamic arrow of time (second law) emerges for S whenever there is a well-defined causal arrow from S to F and the back-action is negligible. This is because the back-action of F on S is described by a non-globally Hamiltonian Born Oppenheimer term that violates the Liouville theorem, and makes the second law inapplicable to S. If S and F are mixing, under the causal arrow condition they are described by microcanonical distributions P(S) and P(S|F). Their structure supports a causal inference principle proposed recently in machine learning.
Journal of Statistical Mechanics-Theory and Experiment
"Relating the thermodynamic arrow of time to the causal arrow" (2008). Faculty Bibliography 2000s. 65.