Vacuum fluctuation, microcyclic universes, and the cosmological constant problem

Wang, Qingdi; Unruh, W. G.

doi:10.1103/physrevd.102.023537

Cited by 22 publications

(35 citation statements)

References 40 publications

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“…Note added: After the completion of this work we have became aware 3 of a series of papers in [51][52][53][54] who questioned the assumption of the homogeneity of the spacetime in the presence of the vacuum zero point energy. It was concluded, among other things, that a uniform cosmological constant can not cover the large scale spacetime and the local spacetime is very inhomogeneous as in Wheeler's spacetime foam.…”

Section: Summary and Discussionmentioning

confidence: 99%

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Cosmological constant problem on the horizon

Firouzjahi¹

2022

Preprint

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We revisit the quantum cosmological constant problem and highlight the important roles played by the dS horizon of zero point energy. We argue that fields which are light enough to have dS horizon of zero point energy comparable to the FLRW Hubble radius are the main contributor to dark energy. On the other hand, the zero point energy of heavy fields develop nonlinearities on sub-Hubble scales and can not contribute to dark energy. Our proposal provides a simple resolution for both the old and new cosmological constant problems by noting that there exits a field, the (lightest) neutrino, which happens to have a mass comparable to the present background photon temperature. The natures of dark energy and dark matter are unified in this proposal in which the zero point energy of light fields are the source of dark energy while dark matter is sourced by the zero point energy of heavy fields. The proposal predicts multiple transient periods of dark energy in early and late expansion history of the universe yielding to a higher value of the current Hubble expansion rate which can resolve the H 0 tension problem.

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Section: Summary and Discussionmentioning

confidence: 99%

“…We are grateful to Jerome Martin for bringing to our attention the papers by Unruh and his collaborators[51][52][53][54].…”

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confidence: 99%

Cosmological constant problem on the horizon

Firouzjahi¹

2022

Preprint

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“…With such a review the experimental efforts dedicated to CRE could be prioritized accordingly so that appropriate detection and monitoring algorithms could be developed, including the alerting mechanisms on a sub-threshold level to be analyzed in accordance with the multi-messenger astrophysics strategies. The latter direction gives promising perspectives for new advances in astrophysics, reflected also in the new attention of theorists, also those addressing the questions related to space time structure (see e.g., [146][147][148]) and private interest in discussions (P. Homola's private communication with S. Carlip, Y. J. Ng, and Q. Wang.…”

Section: Uhecr As the Spacetime Structure Probe?mentioning

confidence: 99%

Cosmic-Ray Extremely Distributed Observatory

et al. 2020

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The Cosmic-Ray Extremely Distributed Observatory (CREDO) is a newly formed, global collaboration dedicated to observing and studying cosmic rays (CR) and cosmic-ray ensembles (CRE): groups of at least two CR with a common primary interaction vertex or the same parent particle. The CREDO program embraces testing known CR and CRE scenarios, and preparing to observe unexpected physics, it is also suitable for multi-messenger and multi-mission applications. Perfectly matched to CREDO capabilities, CRE could be formed both within classical models (e.g., as products of photon–photon interactions), and exotic scenarios (e.g., as results of decay of Super-Heavy Dark Matter particles). Their fronts might be significantly extended in space and time, and they might include cosmic rays of energies spanning the whole cosmic-ray energy spectrum, with a footprint composed of at least two extensive air showers with correlated arrival directions and arrival times. As the CRE are predominantly expected to be spread over large areas and, due to the expected wide energy range of the contributing particles, such a CRE detection might only be feasible when using all available cosmic-ray infrastructure collectively, i.e., as a globally extended network of detectors. Thus, with this review article, the CREDO Collaboration invites the astroparticle physics community to actively join or to contribute to the research dedicated to CRE and, in particular, to pool together cosmic-ray data to support specific CRE detection strategies.

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“…In the second part of our work we generalize our treatment to include the effect of quantum spacetime fluctuations. It was very properly pointed in [15] and [16], as well as in some earlier investigations of this topic in [17] and [18], that at small (Planck) scales, one should not take the usual, highly idealized FRWL metric as a justified approximation. In other words, due to the fact that at such scales the spacetime should be expected to wildly fluctuate, it is problematic to analyse the question of cosmological constant in the framework of the large scale FRWL metric, which is assuming homogeneity and isotropicity.…”

Section: Introductionmentioning

confidence: 98%

“…In other words, due to the fact that at such scales the spacetime should be expected to wildly fluctuate, it is problematic to analyse the question of cosmological constant in the framework of the large scale FRWL metric, which is assuming homogeneity and isotropicity. It was argued in [15] and [16] that this fact, implying the usage of a more general metric -containing the quantum fluctuations of both vacuum energy density and spacetime -can explain the cosmological constant problem, since the large value of the cosmological constant can become hidden in the quantum fluctuations (however, note that the proposals made in [15] and [16] for the realization of this idea are quite different in their nature). However, we are here not concerned with the details and potential difficulties of the idea of fluctuating vacuum density, since we will study only the consequences of the fluctuations of the spacetime metric.…”

Section: Introductionmentioning

confidence: 99%

Cosmological bounce and the cosmological constant problem

Pavlović¹,

Sossich²

2021

Preprint

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We demonstrate that the famous cosmological constant problem of the standard cosmology naturally vanishes in the suitable model-independent effective approach towards quantum gravity, while also studying the effect of quantum space-time fluctuations on the cosmological evolution. We start from the general list of assumptions required for a consistent and complete model of the Universe, which replaces the big bang singularity with a bounce, and thus invokes a modification of the classical field equations for gravity. We first concentrate on the case of the classical FRWL spacetime and show that in a bouncing cosmology, where the modification of the Einstein-Hilbert action can be represented by some general continuous function of time, S(t), the cosmological constant problem is absent if this function at late cosmological times approaches a sufficiently large value. Motivated by the recent studies of cosmological constant problem in the context of quantum vacuum and spacetime fluctuations in the standard cosmology, we then generalize our study to incorporate the effects of quantum spacetime fluctuations. We show that some problems of the earlier proposals, like singularities and negative values of the scale factor, are also naturally resolved in the approach proposed here.

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Vacuum fluctuation, microcyclic universes, and the cosmological constant problem

Cited by 22 publications

References 40 publications

Cosmological constant problem on the horizon

Cosmological constant problem on the horizon

Cosmic-Ray Extremely Distributed Observatory

Cosmological bounce and the cosmological constant problem

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