Is the Hypothesis About a Low Entropy Initial State of the Universe Necessary for Explaining the Arrow of Time?

Goldstein, Sheldon; Tumulka, Roderich; Zanghi, Nino

doi:10.1103/PhysRevD.94.023520

Is the Hypothesis About a Low Entropy Initial State of the Universe Necessary for Explaining the Arrow of Time?

Feb 8, 2016

13 pages

Published in:

Phys.Rev.D 94 (2016) 023520

Published: Jul 20, 2016

e-Print:

1602.05601 [astro-ph.CO]

DOI:

10.1103/PhysRevD.94.023520

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Abstract: (arXiv)

According to statistical mechanics, micro-states of an isolated physical system (say, a gas in a box) at time

t_0

in a given macro-state of less-than-maximal entropy typically evolve in such a way that the entropy at time

t

increases with

|t-t_0|

in both time directions. In order to account for the observed entropy increase in only one time direction, the thermodynamic arrow of time, one usually appeals to the hypothesis that the initial state of the universe was one of very low entropy. In certain recent models of cosmology, however, no hypothesis about the initial state of the universe is invoked. We discuss how the emergence of a thermodynamic arrow of time in such models can nevertheless be compatible with the above-mentioned consequence of statistical mechanics, appearances to the contrary notwithstanding.

Note:

14 pages LaTeX, 3 figures; v2: first paragraph added, section 8 added, 9 references added; v3: further references added

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Figures(3)

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