Chen, Eddy Keming (2018) Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State. The British Journal for the Philosophy of Science, 72 (4). ISSN 1464-3537

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Abstract

In a quantum universe with a strong arrow of time, we postulate a low-entropy boundary condition (the Past Hypothesis) to account for the temporal asymmetry. In this paper, I show that the Past Hypothesis also contains enough information to simplify the quantum ontology and define a natural initial condition.

First, I introduce Density Matrix Realism, the thesis that the quantum state of the universe is objective and impure. This stands in sharp contrast to Wave Function Realism, the thesis that the quantum state of the universe is objective and pure. Second, I suggest that the Past Hypothesis is sufficient to determine a natural density matrix, which is simple and unique. This is achieved by what I call the Initial Projection Hypothesis: the initial density matrix of the universe is the (normalized) projection onto the Past Hypothesis subspace (in the Hilbert space). Third, because the initial quantum state is unique and simple, we have a strong case for the Nomological Thesis: the initial quantum state of the universe is on a par with laws of nature.

This new package of ideas has several interesting implications, including on the harmony between statistical mechanics and quantum mechanics, theoretical unity of the universe and the subsystems, and the alleged conflict between Humean supervenience and quantum entanglement.

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Item Type:	Published Article or Volume
Creators:	Creators Email ORCID Chen, Eddy Keming eddykemingchen@ucsd.edu 0000-0001-5144-0952
Keywords:	time’s arrow, Past Hypothesis, Statistical Postulate, reduction, typicality, foundations of probability, quantum statistical mechanics, wave function realism, quantum ontology, density matrix, Weyl Curvature Hypothesis, Humean Supervenience
Subjects:	General Issues > Determinism/Indeterminism General Issues > Laws of Nature Specific Sciences > Physics > Quantum Mechanics General Issues > Realism/Anti-realism Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Depositing User:	Dr. Eddy Keming Chen
Date Deposited:	11 Mar 2022 02:14
Last Modified:	11 Mar 2022 02:14
Item ID:	20320
Journal or Publication Title:	The British Journal for the Philosophy of Science
Official URL:	https://doi.org/10.1093/bjps/axy068
DOI or Unique Handle:	10.1093/bjps/axy068
Subjects:	General Issues > Determinism/Indeterminism General Issues > Laws of Nature Specific Sciences > Physics > Quantum Mechanics General Issues > Realism/Anti-realism Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Date:	30 September 2018
Volume:	72
Number:	4
ISSN:	1464-3537
URI:	https://philsci-archive.pitt.edu/id/eprint/20320

Available Versions of this Item

• Time's Arrow in a Quantum Universe I: On the Simplicity and Uniqueness of the Initial Quantum State. (deposited 05 Dec 2017 18:18)
  • Time's Arrow in a Quantum Universe I: On the Simplicity and Uniqueness of the Initial Quantum State. (deposited 14 Dec 2017 03:35)
    • Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State. (deposited 09 Jun 2018 18:44)
      • Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State. (deposited 30 Sep 2018 15:27)
        • Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State. (deposited 11 Mar 2022 02:14) [Currently Displayed]

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