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Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State

Chen, Eddy Keming (2018) Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State. [Preprint]

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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 unique initial condition in such a world. First, I introduce Density Matrix Realism, the thesis that the quantum universe is described by a fundamental density matrix (a mixed state) that represents something objective. This stands in sharp contrast to Wave Function Realism, the thesis that the quantum universe is described by a wave function (a pure state) that represents something objective. Second, I suggest that the Past Hypothesis is sufficient to determine a unique and simple density matrix. This is achieved by what I call the Initial Projection Hypothesis: the initial density matrix of the universe is the normalized projection onto the special low-dimensional Hilbert space. Third, because the initial quantum state is unique and simple, we have a strong case for the \emph{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, the dynamic unity of the universe and the subsystems, and the alleged conflict between Humean supervenience and quantum entanglement.


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Item Type: Preprint
Creators:
CreatorsEmailORCID
Chen, Eddy Kemingeddy.chen@rutgers.edu
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: Keming Chen
Date Deposited: 09 Jun 2018 18:44
Last Modified: 09 Jun 2018 18:44
Item ID: 14764
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: 8 June 2018
URI: http://philsci-archive.pitt.edu/id/eprint/14764

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