Open Questions Regarding the Arrow of Time

Zeh, H. D.

doi:10.1007/978-3-642-23259-6_11

Cited by 6 publications

(11 citation statements)

References 25 publications

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“…Independently of technical aspects, it is about the question whether there is an unambiguous degree of freedom in generally relativistic theories which can play the role of time, or of a parameter whose values arrange causally related events and thus separate the past, present and future. This is to be distinguished from the question of the arrow of time [3], which irreversibly orders events already separated into past, present and future by the time variable. Such an arrow is often related to thermodynamical questions via entropy, or to the selection of special initial states in quantum cosmology.…”

Section: The Problem and The Arrow Of Timementioning

confidence: 99%

“…The logical conflict was resolved by the atomists who accepted the notion of empty space and were led to the concept of material atoms. 3 A different perspective on the importance of gravitatational degrees of freedom is discussed in [11].…”

Section: Classical Dynamicsmentioning

confidence: 99%

“…Cosmic forgetfulness may be interpreted as forcing us to coarse-grain over many of the quantum variables. One should also note that cosmic forgetfulness is much stronger than decoherence (see e.g [3]…”

mentioning

confidence: 99%

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A Momentous Arrow of Time

Bojowald

2011

The Arrows of Time

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Quantum cosmology offers a unique stage to address questions of time related to its underlying (and perhaps truly quantum dynamical) meaning as well as its origin. Some of these issues can be analyzed with a general scheme of quantum cosmology, others are best seen in loop quantum cosmology. The latter's status is still incomplete, and so no full scenario has yet emerged. Nevertheless, using properties that have a potential of pervading more complicated and realistic models, a vague picture shall be sketched here. It suggests the possibility of deriving a beginning within a beginningless theory, by applying cosmic forgetfulness to an early history of the universe.

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Section: The Problem and The Arrow Of Timementioning

confidence: 99%

Section: Classical Dynamicsmentioning

confidence: 99%

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A Momentous Arrow of Time

Bojowald

2011

The Arrows of Time

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“…We now offer a few brief speculations concerning the role of the Planck power if the Universe, or at least our L-region and O-region, is oscillating with two-time low-entropy boundary conditions at the Big Bang and at the Big Crunch [16,88-94, [101][102][103][104][105]. It is important to note that there exist oscillating cosmological models, including those with thermodynamic rejuvenation, both in conjunction with and apart from the concept of an inflationary Multiverse [16,[88][89][90][91][92][93][94][101][102][103][104][105]. Some of these models [16,88,89,[101][102][103][104] were developed well before inflationary cosmology, when our observable Universe or O-region was construed to be the entire Universe or at least a major fraction thereof.…”

Section: Planck Power and Kinetic Control Versus Heat Death: Big-bangmentioning

confidence: 99%

The Planck Power – A Numerical Coincidence or a Fundamental Number in Cosmology?

Denur¹

2015

Recent Advances in Thermo and Fluid Dynamics

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The Planck system of units has been recognized as the most fundamental such system in physics ever since Dr. Max Planck first derived it in 1899. The Planck system of units in general, and especially the Planck power in particular, suggest a simple and interesting cosmological model. Perhaps this model may at least to some degree represent the real Universe; even if it does not, it seems interesting conceptually. The Planck power equals the Planck energy divided by the Planck time, or equivalently the Planck mass times c 2 divided by the Planck time. We show that the nongravitational mass-energy of our local region (L-region) of the Universe is, at least approximately, to within a numerical factor on the order of 2, equal to the Planck power times the elapsed cosmic time since the Big Bang. This result is shown to be consistent, to within a numerical factor on the order of 2, with results obtained via alternative derivations. We justify employing primarily L-regions within an observer's cosmological event horizon, rather than O-regions (observable regions) within an observer's cosmological particle horizon. Perhaps this might imply that as nongravitational mass-energy leaves the cosmological event horizon of our L-region via the Hubble flow, it is replaced at the rate of the Planck power and at the expense of negative gravitational energy. Thus the total mass-energy of our L-region, and likewise of all L-regions, is conserved at the value zero. Some questions concerning the Second Law of Thermodynamics and possible thwarting of the heat death of the Universe predicted thereby, whether via Planck-power input or via some other agency, are discussed.

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“…Despite this fundamental invariance, most classes of phenomena observed in Nature distinguish a specific direction of time. These are the famous "arrows of time" which are discussed at length in [1], see also [2] and other contributions to this volume. This observed discrepancy between the symmetric laws and the asymmetric facts does not constitute an inconsistency; asymmetric phenomena are compatible with symmetric laws, and most solutions of the fundamental equations are not symmetric by themselves.…”

Section: Introductionmentioning

confidence: 96%

Can the Arrow of Time Be Understood from Quantum Cosmology?

Kiefer¹

2011

The Arrows of Time

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I address the question whether the origin of the observed arrow of time can be derived from quantum cosmology. After a general discussion of entropy in cosmology and some numerical estimates, I give a brief introduction into quantum geometrodynamics and argue that this may provide a sufficient framework for studying this question. I then show that a natural boundary condition of low initial entropy can be imposed on the universal wave function. The arrow of time is then correlated with the size of the Universe and emerges from an increasing amount of decoherence due to entanglement with unobserved degrees of freedom. Remarks are also made concerning the arrow of time in multiverse pictures and scenarios motivated by dark energy.

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Open Questions Regarding the Arrow of Time

Cited by 6 publications

References 25 publications

A Momentous Arrow of Time

A Momentous Arrow of Time

The Planck Power – A Numerical Coincidence or a Fundamental Number in Cosmology?

Can the Arrow of Time Be Understood from Quantum Cosmology?

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