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Time Symmetry and Asymmetry in Quantum Mechanics and Quantum Cosmology

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Paper breakdownThe authors' claims, conditions and measurements, as JSON Signed receiptProof this review has not been altered
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Murray Gell-Mann, James B. Hartle

General Relativity and Quantum Cosmology · Submitted 18 Apr 1993

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim A special initial condition and a final condition of indifference would be sufficient to explain the observed time asymmetries of the universe.

how it is stated · hedged possibility 0.50 read the record →

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arXiv IDgr-qc/9304023 (version 2)
Pith IDVV5QEIQB, Pith's permanent record of this paper and its review
CitationJames B. Hartle, Murray Gell-Mann. "Time Symmetry and Asymmetry in Quantum Mechanics and Quantum Cosmology." arXiv:gr-qc/9304023 (1993). https://pith.science/paper/VV5QEIQB
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The compiled record

The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

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Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 7,537 input tokens, $0.0003 reported.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.82 · human participants 0.01 · controlled comparison 0.03 · randomized assignment 0.01 · states quantitative result 0.03 · compares with prior results 0.47 · mentions code or data availability 0.01.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; .

We investigate the origin of the arrow of time in quantum mechanics in the context of quantum cosmology. The ``Copenhagen'' quantum mechanics of measured subsystems incorporates a fundamental arrow of time. Extending discussions of Aharonov, Bergmann and Lebovitz, Griffiths, and others we investigate a generalized quantum mechanics for cosmology that utilizes both an initial and a final density matrix to give a time-neutral formulation without a fundamental arrow of time. Time asymmetries can arise for particular universes from differences between their initial and final conditions. Theories for both would be a goal of quantum cosmology. A special initial condition and a final condition of indifference would be sufficient to explain the observed time asymmetries of the universe. In this essay we ask under what circumstances a completely time symmetric universe, with T-symmetric initial and final condition, could be consistent with the time asymmetries of the limited domain of our experience. We discuss the approach to equilibrium, the electromagnetic system, and T-violation in the weak interactions in such universes. The decoherence of alternatives that is necessary for the prediction of probabilities in the quantum mechanics of closed systems is the origin of a fundamental limitation on quantum cosmologies with initial and final conditions. The initial and final density matrices cannot both be pure; if they are there is no decoherence and no prediction.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We investigate the origin of the arrow of time in quantum mechanics in the context of quantum cosmology. contribution 0.80 0.81 0.05 unclear 0.56
s1 The ``Copenhagen'' quantum mechanics of measured subsystems incorporates a fundamental arrow of time. background 1.00 0.06 0.05 asserted 1.00
s2 Extending discussions of Aharonov, Bergmann and Lebovitz, Griffiths, and others we investigate a generalized quantum mechanics for cosmology that utilizes both an initial and a final density matrix to give a time-neutral formulation without a fundamental arrow of time. contribution 0.71 0.61 0.16 asserted 0.84
s3 Time asymmetries can arise for particular universes from differences between their initial and final conditions. result 0.61 0.27 0.23 hedged possibility 0.77
s4 Theories for both would be a goal of quantum cosmology. future work 0.84 0.05 0.06 asserted 0.41
s5 A special initial condition and a final condition of indifference would be sufficient to explain the observed time asymmetries of the universe. result 0.51 0.25 0.33 hedged possibility 0.50
s6 In this essay we ask under what circumstances a completely time symmetric universe, with T-symmetric initial and final condition, could be consistent with the time asymmetries of the limited domain of our experience. contribution 0.81 0.32 0.09 hedged possibility 0.80
s7 We discuss the approach to equilibrium, the electromagnetic system, and T-violation in the weak interactions in such universes. contribution 0.92 0.41 0.04 unclear 0.63
s8 The decoherence of alternatives that is necessary for the prediction of probabilities in the quantum mechanics of closed systems is the origin of a fundamental limitation on quantum cosmologies with initial and final conditions. result 0.55 0.57 0.32 asserted 1.00
s9 The initial and final density matrices cannot both be pure; if they are there is no decoherence and no prediction. result 0.60 0.61 0.26 asserted 1.00

What kind of paper the classifier reports this is: position or commentary 0.77 · evidence from argument 0.97.

What was examined, and what was not

sources read
  • arXiv listing abstract v2
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper
Original abstract

We investigate the origin of the arrow of time in quantum mechanics in the context of quantum cosmology. The ``Copenhagen'' quantum mechanics of measured subsystems incorporates a fundamental arrow of time. Extending discussions of Aharonov, Bergmann and Lebovitz, Griffiths, and others we investigate a generalized quantum mechanics for cosmology that utilizes both an initial and a final density matrix to give a time-neutral formulation without a fundamental arrow of time. Time asymmetries can arise for particular universes from differences between their initial and final conditions. Theories for both would be a goal of quantum cosmology. A special initial condition and a final condition of indifference would be sufficient to explain the observed time asymmetries of the universe. In this essay we ask under what circumstances a completely time symmetric universe, with T-symmetric initial and final condition, could be consistent with the time asymmetries of the limited domain of our experience. We discuss the approach to equilibrium, the electromagnetic system, and T-violation in the weak interactions in such universes. The decoherence of alternatives that is necessary for the prediction of probabilities in the quantum mechanics of closed systems is the origin of a fundamental limitation on quantum cosmologies with initial and final conditions. The initial and final density matrices cannot both be pure; if they are there is no decoherence and no prediction.

Human review

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References
How the literature uses it

19 arXiv papers cite this in 25 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 17 sentences without a confident label

Cites it as support 1 paper
  • DHQM of the universe can be formulated time neutrally with initial and final conditions playing symmetric roles in the formulation [ref] and no built in arrows of time.

    Quantum Buzzwords · The Quantum Arrow of Time · 0.99

Cites it as background 7 papers
  • Setting $ρ^(f)$ to the identity reproduces the usual formulation of quantum mechanics and has been termed by Gell-Mann and Hartle [ref] as the principle of indifference.

    No Future in Black Holes · Introduction · 0.86

  • Such time-symmetric cosmologies have been proposed by Gold, Wheeler, Hawking and Hartle and Gell-Mann, the latter two in the context of quantum cosmology [ref] .

    Teleocosmology and quantum post-selection · Physical interpretation and discussion · 0.97

  • Several distinct arrows of time can be identified in nature, based on intrinsic temporal asymmetries observed in different classes of physical phenomena [ref] :

    Arrows of time in bouncing cosmologies · Arrows of time and their cosmological origin · 0.89

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