paper

Quantum causality and the arrows of time and thermodynamics

arXiv:2003.09047 · doi:10.1016/j.ppnp.2020.103812

Abstract

In the understanding of the fundamental interactions, the origin of an arrow of time is viewed as problematic. However, quantum field theory has an arrow of causality, which tells us which time direction is the past lightcone and which is the future. This direction is tied to the conventions used in the quantization procedures. The different possible causal directions have related physics - in this sense they are covariant under time-reversal. However, only one causal direction emerges for a given set of conventions. This causal arrow tells us the direction that scattering reactions proceed. The time direction of scattering in turn tells us the time direction for which entropy increases - the so-called arrow of thermodynamics. This connection is overlooked in most discussions of the arrow of time.

This second version has a re-ordered and expanded discussion (to enhance the QFT perspective) and two new sections. The title is slightly changed. This is the version which was published in Progress in Particle and Nuclear Physics, Vol 115, 103812 (2020). 15 pages, 2 figures

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