Is there a connection between “dark” and “light” physics?

Lake, Matthew J.

doi:10.1088/1742-6596/883/1/012001

Cited by 15 publications

(36 citation statements)

References 94 publications

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“…Hence, it is clear that, if the fundamental quanta of space-time are fermionic, universal expansion can also be viewed as a result of their continuous pair-production. Such a view is consistent with the model of particulate dark energy proposed in [48][49][50][51][52].…”

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confidence: 90%

Generalised Uncertainty Relations for Angular Momentum and Spin in Quantum Geometry

2020

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We derive generalised uncertainty relations (GURs) for orbital angular momentum and spin in the recently proposed smeared-space model of quantum geometry. The model implements a minimum length and a minimum linear momentum, and recovers both the generalised uncertainty principle (GUP) and extended uncertainty principle (EUP), previously proposed in the quantum gravity literature, within a single formalism. In this paper, we investigate the consequences of these results for particles with extrinsic and intrinsic angular momentum, and obtain generalisations of the canonical so(3) and su(2) algebras. We find that, although SO(3) symmetry is preserved on three-dimensional slices of an enlarged phase space, corresponding to a superposition of background geometries, individual subcomponents of the generalised generators obey nontrivial subalgebras. These give rise to GURs for orbital angular momentum while leaving the canonical commutation relations intact except for a simple rescaling, → + β. The value of the new parameter, β ≃ × 10 −61 , is determined by the ratio of the dark energy density to the Planck density and its existence is required by the presence of both minimum length and momentum uncertainties. Here, we assume the former to be of the order of the Planck length and the latter to be of the order of the de Sitter momentum ∼ √ Λ, where Λ is the cosmological constant, which is consistent with the existence of a finite cosmological horizon. In the smeared-space model, and β are interpreted as the quantisation scales for matter and geometry, respectively, and a quantum state vector is associated with the spatial background. We show that this also gives rise to a rescaled Lie algebra for generalised spin operators, together with associated subalgebras that are analogous to those for orbital angular momentum. Remarkably, consistency of the algebraic structure requires the quantum state associated with the background space to be fermionic. However, this is no way contradicts the standard result that the graviton is expected to be a spin-2 boson. (We explain why, at length, in the text.) Finally, the modified spin algebra leads to GURs for spin measurements. The potential implications of these results for cosmology and high-energy physics, and for the description of spin and angular momentum in relativistic theories of quantum gravity, are briefly discussed. Contents

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confidence: 90%

Generalised Uncertainty Relations for Angular Momentum and Spin in Quantum Geometry

2020

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“…as required. Here, modes with k > 2π/l Λ immediately stimulate the pair-production of dark energy particles [62,63], triggering universal expansion in place of increased energy density, as described above.…”

Section: A Cosmologymentioning

confidence: 89%

“…Second, m Λ is the unique mass-scale for which the Compton wavelength of a particle is equal to its gravitational turn-around radius, i.e., the radius at which dark energy repulsion overcomes canonical (Newtonian) gravitational attraction [60]. This gives a neat interpretation of the stability condition ρ part ≥ ρ Λ and suggests that m Λ is the unique scale for which the (positive) rest mass of a body is counter-balanced by its (negative) gravitational energy [61][62][63]. In this way, particles with rest mass m Λ can be pair-produced ad infinitum, leading to eternal universal expansion and the existence of an asymptotic de Sitter phase, a(τ ) ∝ e √ Λ/3cτ , where τ is the cosmic time and a(τ ) is the scale factor of the universe.…”

Section: A Cosmologymentioning

confidence: 99%

Generalised uncertainty relations from superpositions of geometries

Lake

Miller

Ganardi

et al. 2019

Class. Quantum Grav.

205

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Phenomenological approaches to quantum gravity implement a minimum resolvable length-scale but do not link it to an underlying formalism describing geometric superpositions. Here, we introduce an intuitive approach in which points in the classical spatial background are delocalised, or 'smeared', giving rise to an entangled superposition of geometries. The model uses additional degrees of freedom to parameterise the superposed classical backgrounds. Our formalism contains both minimum length and minimum momentum resolutions and we naturally identify the former with the Planck length. In addition, we argue that the minimum momentum is determined by the de Sitter scale, and may be identified with the effects of dark energy in the form of a cosmological constant. Within the new formalism, we obtain both the generalised uncertainty principle (GUP) and extended uncertainty principle (EUP), which may be combined to give an uncertainty relation that is symmetric in position and momentum. Crucially, our approach does not imply a significant modification of the positionmomentum commutator, which remains proportional to the identity matrix. It therefore yields generalised uncertainty relations without violating the equivalence principle, in contradistinction to existing models based on nonlinear dispersion relations. Implications for cosmology and the black hole uncertainty principle correspondence are briefly discussed, and prospects for future work on the smeared-space model are outlined.

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“…where m e is the electron mass. For a review of the relation between fundamental physics and the cosmological constant see [55]. The mass -radius relations, as well as the possible existence of a minimum mass have been in different theoretical contexts, and for different physical models, in [56][57][58][59][60][61].…”

Section: Introductionmentioning

confidence: 99%

Mass-radius ratio bounds for compact objects in Lorentz-violating dRGT massive gravity theory

2018

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We consider the mass-radius bounds for spherically symmetric static compact objects in the de Rham-Gabadadze-Tolley (dRGT) Massive Gravity theories, free of ghosts. In this type of gravitational theories the graviton, the quantum of gravity, may have a small, but non-vanishing mass. We derive the hydrostatic equilibrium and mass continuity equations in the Lorentz-violating Massive gravity in the presence of a cosmological constant and for a non-zero graviton mass. The case of the constant density stars is also investigated by numerically solving the equilibrium equations. The influence of the graviton mass on the global parameters (mass and radius) of these stellar configurations is also considered. The generalized Buchdahl relations, giving the upper and lower bounds of the mass-radius ratio are obtained, and discussed in detail. As an application of our results we obtain gravitational redshift bounds for compact stellar type objects in the Lorentz-violating dRGT Massive Gravity, which may (at least in principle) be used for observationally testing this theory in an astrophysical context.

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Is there a connection between “dark” and “light” physics?

Cited by 15 publications

References 94 publications

Generalised Uncertainty Relations for Angular Momentum and Spin in Quantum Geometry

Generalised Uncertainty Relations for Angular Momentum and Spin in Quantum Geometry

Generalised uncertainty relations from superpositions of geometries

Mass-radius ratio bounds for compact objects in Lorentz-violating dRGT massive gravity theory

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