Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0802.2682

Comment on "An Arrow of Time Operator for Standard Quantum Mechanics" - a sign of the time!

Michael J. W. Hall

Published Feb 19, 2008• 2 citations
arXivHTMLPDF

Abstract

It is shown that the `arrow of time' operator, M_F, recently suggested by Strauss et al., in arXiv:0802.2448v1 [quant-ph], is simply related to the sign of the canonical `time' observable, T (apparently first introduced by Holevo). In particular, the monotonic decrease of < M_F > corresponds to the fact that < sgn T > increases monotonically with time. This relationship also provides a physical interpretation of the property M_F < 1. Some further properties and possible generalisations are pointed out, including to almost-periodic systems.

DOI
10.48550/arxiv.0802.2682

Related papers

An Arrow of Time Operator for Standard Quantum Mechanics

Y. Strauss, Jonathan Silman, Shai Machnes +1 more

We introduce a self-adjoint operator that indicates the direction of time within the framework of standard quantum mechanics. That is, as a function of time its expectation value decreases monotonically for any initial state. This operator can be defined for any system governed by a Hamiltonian with a uniformly finitely degenerate, absolutely continuous and semibounded spectrum. We study some of the operator's properties and illustrate them for a large equivalence class of scattering problems. We also discuss some previous attempts to construct such an operator, and show that the no-go theorems developed in this context are not applicable to our construction.

arXiv:0802.2448•Feb 18, 2008•2 citations

Study of a self-adjoint operator indicating the direction of time within standard quantum mechanics

Y. Strauss, Jonathan Silman, Shai Machnes +1 more

In [Y. Strauss, Self-adjoint Lyapunov variables, temporal ordering and irreversible representations of Schrödinger evolution, J. Math. Phys. 51 (2010) 022104] a self-adjoint operator was introduced that has the property that it indicates the direction of time within the framework of standard quantum mechanics, in the sense that as a function of time its expectation value decreases monotonically for any initial state. In this paper we study some of this operatorʼs properties. In particular, we derive its spectrum and generalized eigenstates, and treat the example of the free particle.

arXiv:1101.3969•Comptes Rendus Mathématique•Oct 1, 2011•10 citations

On the statistical arrow of time

Andreas Henriksson

What is the physical origin of the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of entropy as it appears in the statistical interpretation of the second law of thermodynamics. At the same time, the subjective information-theoretical interpretation of probability, and hence entropy, is a standard viewpoint in the foundations of statistical mechanics. In this article, it is argued that the subjective interpretation is incompatible with the philosophical point of view that the arrow of time is a fundamental property of Nature. The subjectivist can only uphold this philosophy if the role played by the second law of thermodynamics in defining time's arrow is abandoned.

•Apr 18, 2023•0 citations

On the statistical arrow of time

Andreas Henriksson

What is the physical origin of the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of entropy as it appears in the statistical interpretation of the second law of thermodynamics. At the same time, the subjective information-theoretical interpretation of probability, and hence entropy, is a standard viewpoint in the foundations of statistical mechanics. In this article, it is argued that the subjective interpretation is incompatible with the philosophical point of view that the arrow of time is a fundamental property of Nature. The subjectivist can only uphold this philosophy if the role played by the second law of thermodynamics in defining time's arrow is abandoned.

•Apr 18, 2023•0 citations

On the statistical arrow of time

Henriksson, Andreas

What is the physical origin of the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of entropy as it appears in the statistical interpretation of the second law of thermodynamics. At the same time, the subjective information-theoretical interpretation of probability, and hence entropy, is a standard viewpoint in the foundations of statistical mechanics. In this article, it is argued that the subjective interpretation is incompatible with the philosophical point of view that the arrow of time is a fundamental property of Nature. The subjectivist can only uphold this philosophy if the role played by the second law of thermodynamics in defining time's arrow is abandoned.

arXiv:1905.06187•May 13, 2019•0 citations

On the statistical arrow of time

Andreas Henriksson

What is the physical origin for the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of disorder, or entropy, as it appears in the statistical interpretation of the second law of thermodynamics. In this article, it is argued that the philosophical point of view that the arrow of time is a fundamental property of Nature is incompatible with the subjective information-theoretical interpretation of probability and entropy in statistical mechanics, where they arise due to the ignorance of the observer. This conclusion, however, relies on the premise that time's arrow has a statistical mechanical origin. If this assumption is abandoned, then there is no conflict between the belief in the fundamental character of time's arrow and the belief in the subjective information-theoretical interpretation.

•Mar 23, 2023•0 citations
It is shown that the arrow of time' operator, M_F, recently suggested by Strauss et al., in arXiv:0802.2448v1 [quant-ph], is simply related to the sign of the canonical time' observable, T (apparently first introduced by Holevo). In particular, the monotonic decrease of < M_F > corresponds to the fact that < sgn T > increases monotonically with time. This relationship also provides a physical interpretation of the property M_F < 1. Some further properties and possible generalisations are pointed out, including to almost-periodic systems.
We introduce a self-adjoint operator that indicates the direction of time within the framework of standard quantum mechanics. That is, as a function of time its expectation value decreases monotonically for any initial state. This operator can be defined for any system governed by a Hamiltonian with a uniformly finitely degenerate, absolutely continuous and semibounded spectrum. We study some of the operator's properties and illustrate them for a large equivalence class of scattering problems. We also discuss some previous attempts to construct such an operator, and show that the no-go theorems developed in this context are not applicable to our construction.
In [Y. Strauss, Self-adjoint Lyapunov variables, temporal ordering and irreversible representations of Schrödinger evolution, J. Math. Phys. 51 (2010) 022104] a self-adjoint operator was introduced that has the property that it indicates the direction of time within the framework of standard quantum mechanics, in the sense that as a function of time its expectation value decreases monotonically for any initial state. In this paper we study some of this operatorʼs properties. In particular, we derive its spectrum and generalized eigenstates, and treat the example of the free particle.
What is the physical origin of the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of entropy as it appears in the statistical interpretation of the second law of thermodynamics. At the same time, the subjective information-theoretical interpretation of probability, and hence entropy, is a standard viewpoint in the foundations of statistical mechanics. In this article, it is argued that the subjective interpretation is incompatible with the philosophical point of view that the arrow of time is a fundamental property of Nature. The subjectivist can only uphold this philosophy if the role played by the second law of thermodynamics in defining time's arrow is abandoned.
What is the physical origin of the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of entropy as it appears in the statistical interpretation of the second law of thermodynamics. At the same time, the subjective information-theoretical interpretation of probability, and hence entropy, is a standard viewpoint in the foundations of statistical mechanics. In this article, it is argued that the subjective interpretation is incompatible with the philosophical point of view that the arrow of time is a fundamental property of Nature. The subjectivist can only uphold this philosophy if the role played by the second law of thermodynamics in defining time's arrow is abandoned.
What is the physical origin of the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of entropy as it appears in the statistical interpretation of the second law of thermodynamics. At the same time, the subjective information-theoretical interpretation of probability, and hence entropy, is a standard viewpoint in the foundations of statistical mechanics. In this article, it is argued that the subjective interpretation is incompatible with the philosophical point of view that the arrow of time is a fundamental property of Nature. The subjectivist can only uphold this philosophy if the role played by the second law of thermodynamics in defining time's arrow is abandoned.
What is the physical origin for the arrow of time? It is a commonly held belief in the physics community that it relates to the increase of disorder, or entropy, as it appears in the statistical interpretation of the second law of thermodynamics. In this article, it is argued that the philosophical point of view that the arrow of time is a fundamental property of Nature is incompatible with the subjective information-theoretical interpretation of probability and entropy in statistical mechanics, where they arise due to the ignorance of the observer. This conclusion, however, relies on the premise that time's arrow has a statistical mechanical origin. If this assumption is abandoned, then there is no conflict between the belief in the fundamental character of time's arrow and the belief in the subjective information-theoretical interpretation.