An Uneven Vacuum Energy Fluid as Λ, Dark Matter, MOND and Lens

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1. On galaxy scales the gravity attributed to dark matter and the gravity of the known matter are tied together by a single empirical relation — the dark gravity is roughly the geometric mean of the known gravity and a fixed acceleration a0 of about one angstrom per second squared — and that relation fits the rotation curves of both faint and bright spiral galaxies.Section 1.1, equation 1, with the fits in Figure 1 (arXiv:0802.1775v3)

2. The acceleration scale where dark matter effects appear, the square root of the cosmological constant, and the product of the speed of light with the Hubble constant are all the same number. Zhao writes that these empirical facts should not be treated as random coincidences of the fundamental parameters of the universe.Section 1.1, equation 2 (arXiv:0802.1775v3)

3. Light can be bent by the vacuum itself, because the vacuum is not empty and can be a fluid with an energy density — and that density is measurable in the laboratory. Zhao notes that the Casimir pressure between two neutral plates one hundredth of a centimetre apart is about ten to the minus ten erg per cubic centimetre, the same order as the cosmological constant’s energy density, although the cosmic value sits a factor of ten to the twelve below current Casimir sensitivity.Section 2, opening paragraphs and the paragraph on gravitational energy density (arXiv:0802.1775v3)

4. Any spatial variation in the vacuum energy density curves some patches of spacetime more than others and so produces a dark-matter-like effect. Zhao expresses it as an effective gravitational coupling that varies with place and time, a dielectric-like parameter, and proposes measuring it with a table-top Cavendish torsion experiment carried out at different depths in the gravitational environment — on Earth, at the edge of the solar system, and in the void between galaxies.Section 2, the Gedanken experiment paragraphs, and Section 3 (arXiv:0802.1775v3)

5. TeVeS-like theories are single-metric theories that can be recast entirely inside the standard general-relativity framework, with the cosmological constant replaced by a non-trivial non-uniform vacuum energy. The vector field then contributes a Maxwell-like term, and the galaxy equation becomes electrostatics with a polarisation field whose susceptibility depends on field strength and on a characteristic column density comparable to that of a sheet of paper.Section 3, equation 4, and Section 4.1, equations 8 to 12 (arXiv:0802.1775v3)

6. An uneven dark-energy fluid and a real dark-matter halo can be told apart by observation. For an edge-on razor-thin Kuzmin disk the two produce the same rotation curve but different lensing convergence — a ratio of one over the square root of two at an impact parameter equal to the disk scale — so a combined lensing and kinematics study of a single lens decides between them, and the smaller convergence would also allow a larger Hubble constant to fit the same time-delay data.Section 6, equations 33 to 37 (arXiv:0802.1775v3)

The way in

How to cite it

HongSheng Zhao (2008) An Uneven Vacuum Energy Fluid as Λ, Dark Matter, MOND and Lens doi:10.1142/s021773230802656x

Where it sits in the curriculum

• The vacuum at cosmic scale
• The vacuum as a quantum fluid