Scale of a in MOND and cosmological constant

In summary, Lee Smolin and Erik Verlinde have proposed that the scale of acceleration required by MOND theories is similar to the cosmological constant. They suggest that MOND-like effects are due to quantum gravity effects, with Verlinde proposing entanglement entropy as the cause and Smolin proposing modifications of general relativity in the deep infrared regime. Verlinde's paper, "Emergent Gravity and the Dark Universe," discusses the emergence of spacetime and gravity from entanglement structures and the role of dark energy. Smolin's paper, "Four Principles for Quantum Gravity," proposes four principles that can recover the Einstein equations and suggests that MOND may result from a modification of the equivalence principle due to quantum gravity effects.
  • #1
kodama
978
132
in 2 recent papers by Lee Smolin and Erik Verlinde

it is claimed that the scale of acceleration as required by various MOND theories is on the same order as the cosmological constant

both researchers suggest that instead of cold dark matter, or even modified Newtonian dynamics, MOND-like effects are QG effects, in Verlinde's case the result of entanglement entropy. for Smolin MOND-like modifications of GR is QG in deep IR regime

How is MOND's scale of acceleration related to the cc, and any theories to explain this?
 
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  • #2
May we have the references to the papers you quote?

Garth
 
  • #3
Garth said:
May we have the references to the papers you quote?

Garth
Emergent Gravity and the Dark Universe
Erik P. Verlinde
(Submitted on 7 Nov 2016 (v1), last revised 8 Nov 2016 (this version, v2))
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional `dark' gravitational force describing the `elastic' response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton's constant and the Hubble acceleration scale a_0 =cH_0, and provide evidence for the fact that this additional `dark gravity~force' explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
Comments: 5 figures
Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
Cite as: arXiv:1611.02269 [hep-th]
(or arXiv:1611.02269v2 [hep-th] for this version)
Four principles for quantum gravity
Lee Smolin
(Submitted on 6 Oct 2016)
Four principles are proposed to underlie the quantum theory of gravity. We show that these suffice to recover the Einstein equations. We also suggest that MOND results from a modification of the classical equivalence principle, due to quantum gravity effects.
Comments: 26 pages, one figure and caption taken from McGaugh, Lelli, Schombert, arXiv:1609.05917v1
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
Cite as: arXiv:1610.01968 [gr-qc]
 

What is the MOND theory?

The MOND (MOdified Newtonian Dynamics) theory is an alternative theory of gravity that seeks to explain the observed discrepancies between the predictions of Newtonian mechanics and the observed motions of galaxies and clusters of galaxies. It proposes a modification to Newton's laws of gravity at low accelerations, rather than invoking the existence of dark matter.

What is the cosmological constant?

The cosmological constant, denoted by the Greek letter lambda (Λ), is a term in the equations of general relativity that represents the energy density of the vacuum of space. It was first introduced by Albert Einstein to explain the observed expansion of the universe and is now commonly associated with dark energy.

How does MOND explain the scale of a in cosmology?

MOND provides an alternative explanation for the observed scale of a in cosmology, which is the parameter that determines the expansion rate of the universe. In MOND, the scale of a is not determined by the amount of matter in the universe, as in the standard cosmological model, but rather by the distribution of matter and the acceleration of gravity at large scales.

What is the significance of the scale of a in MOND and the cosmological constant?

The scale of a in MOND and the cosmological constant are important parameters in understanding the evolution and structure of our universe. These parameters impact the expansion rate, density, and overall dynamics of the universe, and provide insights into the nature of gravity and dark energy.

What are the implications of MOND and the cosmological constant for our understanding of the universe?

MOND and the cosmological constant provide alternative explanations for the observed properties of the universe, such as the accelerated expansion and the distribution of matter. These theories challenge the current understanding of gravity and may lead to a deeper understanding of the fundamental laws of physics and the nature of the universe.

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