Spacetime foam: a review

Carlip, Steven

doi:10.1088/1361-6633/acceb4

Cited by 15 publications

(6 citation statements)

References 284 publications

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“…whose specific form for our GW-detector setup is known from previous results [18,26]. At this point, it is important to highlight, as a logical possibility, that this simplified unitary model could be modified by quantum gravitational fluctuations originating from a UVcomplete description of spacetime, for instance as envisioned by Wheeler in the spacetime foam paradigm [27,28]. In this context, our model would provide only a simplified picture and should be augmented by the physics of open quantum systems [29], for example as in stochastic gravity [30].…”

Section: Introductionmentioning

confidence: 94%

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The quantum optics of gravitational waves

Abrahão,

Coradeschi,

Micol Frassino

et al. 2023

Class. Quantum Grav.

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By utilizing quantum optics techniques, we examine the characteristics of a quantum gravitational wave (GW) signature at interferometers. In particular, we study the problem by analyzing the equations of motion of a GW interacting with an idealized interferometer. Using this method, we reconstruct the classical GW signal from a representation of the quantum version of an almost classical monochromatic wave (a single-mode coherent state), then we discuss the experimental signatures of some specific, more general quantum states. We calculate the observables that could be used at future interferometers to probe possible quantum states carried by the GWs.

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Section: Introductionmentioning

confidence: 94%

“…We can express this as equation (27), which represents the effect of the detector's noise. Essentially, we have determined how the gravitational vacuum affects the interferometer's sensitivity curve.…”

Section: Vacuum Statementioning

confidence: 99%

The quantum optics of gravitational waves

Abrahão,

Coradeschi,

Micol Frassino

et al. 2023

Class. Quantum Grav.

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“…The Λ term possibly represents [25,[40][41][42][43][44] the non-trivial ground state (Wheeler spacetime foam [45,46]) of the spacetime. The perturbative quantum gravitational field fluctuates upon such a ground state, and the classical gravitational field varies in such a ground state.…”

Section: Geometric Nature Of λ Dark Energy As Gravitational Ground Statementioning

confidence: 99%

Holographic massive plasma state in Friedman universe: cosmological fine-tuning and coincidence problems

Xue 生

2024

J. Cosmol. Astropart. Phys.

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Massive particle and antiparticle pair production and oscillation on the horizon form a holographic and massive pair plasma state in the Friedman Universe. Via this state, the Einstein cosmology term (dark energy) interacts with matter and radiation and is time-varying Λ̃ in the Universe's evolution. It is determined by a close set of ordinary differential equations for dark energy, matter, and radiation energy densities. The solutions are unique, provided the initial conditions given by observations. In inflation and reheating, dark energy density decreases from the inflation scale, converting to matter and radiation energy densities. In standard cosmology, matter and radiation energy densities convert to dark energy density, reaching the present Universe. By comparing with ΛCDM, quintessence and dark energy interacting models, we show that these results can be the possible solutions for cosmological fine-tuning and coincidence problems.

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“…Although general relativity (GR) neglects the quantum nature of particles, requiring a smooth metric, a successful theory of quantum gravity (QG) must account for inherent uncertainty as energies, lengths and timescales approach the Planck scale: an irreducible "foamy" microscopic spacetime structure, as first proposed by Wheeler [1]. See [2] for a recent review. One phenomenology that may probe this is whether tiny, continual, random distance fluctuations ±δl proportional to the Planck length l P ∼ 10 −35 m (or, equivalently, the timescale t P ∼ 10 −44 s) accumulate in electromagnetic wavefronts, as they travel long distances through the spacetime foam.…”

Section: Introductionmentioning

confidence: 99%

Holographic Quantum-Foam Blurring Is Consistent with Observations of Gamma-Ray Burst GRB221009A

Steinbring

2023

Galaxies

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Gamma-ray burst GRB221009A was of unprecedented brightness in the γ-rays and X-rays through to the far ultraviolet, allowing for identification within a host galaxy at redshift z=0.151 by multiple space and ground-based optical/near-infrared telescopes and enabling a first association—via cosmic-ray air-shower events—with a photon of 251 TeV. That is in direct tension with a potentially observable phenomenon of quantum gravity (QG), where spacetime “foaminess” accumulates in wavefronts propagating cosmological distances, and at high-enough energy could render distant yet bright pointlike objects invisible, by effectively spreading their photons out over the whole sky. But this effect would not result in photon loss, so it remains distinct from any absorption by extragalactic background light. A simple multiwavelength average of foam-induced blurring is described, analogous to atmospheric seeing from the ground. When scaled within the fields of view for the Fermi and Swift instruments, it fits all z≤5 GRB angular-resolution data of 10 MeV or any lesser peak energy and can still be consistent with the highest-energy localization of GRB221009A: a limiting bound of about 1 degree is in agreement with a holographic QG-favored formulation.

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Spacetime foam: a review

Cited by 15 publications

References 284 publications

The quantum optics of gravitational waves

The quantum optics of gravitational waves

Holographic massive plasma state in Friedman universe: cosmological fine-tuning and coincidence problems

Holographic Quantum-Foam Blurring Is Consistent with Observations of Gamma-Ray Burst GRB221009A

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