# I Scale of a in MOND and cosmological constant

1. Dec 7, 2016

### kodama

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?

2. Dec 7, 2016

### Garth

May we have the references to the papers you quote?

Garth

3. Dec 7, 2016

### kodama

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.
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]