The following papers make the argument that, at least for systems with a low initial entropy, "within a quantum mechanical framework, all phenomena which leave

The following papers make the argument that, at least for systems with a low initial entropy, "within a quantum mechanical framework, all phenomena which leave a trail of information behind (and hence can be studied by physics) are those where entropy necessarily increases or remains constant. All phenomena where the entropy decreases must not leave any information of their having happened. This situation is completely indistinguishable from their not having happened at all." ---- Quantum Solution to the Arrow-of-Time Dilemma Lorenzo Maccone Phys. Rev. Lett. 103, 080401 – Published 17 August 2009 The arrow-of-time dilemma states that the laws of physics are invariant for time inversion, whereas the familiar phenomena we see everyday are not (i.e., entropy increases). I show that, within a quantum mechanical framework, all phenomena which leave a trail of information behind (and hence can be studied by physics) are those where entropy necessarily increases or remains constant. All phenomena where the entropy decreases must not leave any information of their having happened. This situation is completely indistinguishable from their not having happened at all. In the light of this observation, the second law of thermodynamics is reduced to a mere tautology: physics cannot study those processes where entropy has decreased, even if they were commonplace. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.080401 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.10... ---- [Submitted on 30 Dec 2009] A quantum solution to the arrow-of-time dilemma: reply Lorenzo Maccone I acknowledge a flaw in the paper "A quantum solution to the arrow of time dilemma": as pointed out by Jennings and Rudolph, (classical) mutual information is not an appropriate measure of information. This can be traced back to the quantum description underlying my analysis, where quantum mutual information is the appropriate measure of information. The core argument of my paper (summarized in its abstract) is not affected by this flaw. Nonetheless, I point out that such argument may not be adequate to account for all phenomena: it seems necessary to separately postulate a low entropy initial state. https://arxiv.org/abs/0912.5394 https://arxiv.org/abs/0912.5394