francesca said:
I'm going to attend this seminar:
Luca Lusanna
Canonical gravity, York map and non-inertial frames: is dark matter a relativistic inertial effect?
Abstract: ... the rotation curves of galaxies in a framework more general of the non-relativistic MOND model and ...
I am worried about Lusanna because he sounds out of touch with current MOND developments. He mentions only "non-relativistic MOND" and does not mention relativistic MOND in his abstract!
There have been some interesting talks and papers at Perimeter Institute about this recently. The authors to check, if you do a search, are John Moffat, Jacob Bekenstein, Joao Magueijo.
Bekenstein is famous because of the Bekenstein-Hawking BH entropy formula (his Princeton thesis introduced the ideas of BH thermodynamics). He has developed a relativistic MOND he calls TeVeS (tensor-vector-scalar).
Magueijo (Perimeter and London Imperial) is also prominent. He recently co-authored this
http://arxiv.org/abs/astro-ph/0602266
MOND habitats within the solar system
Jacob Bekenstein, Joao Magueijo
Phys.Rev. D73 (2006) 103513
"MOdified Newtonian Dynamics (MOND) is an interesting alternative to dark matter in extragalactic systems. We here examine the possibility that mild or even strong MOND behavior may become evident well inside the solar system, in particular near saddle points of the total gravitational potential. Whereas in Newtonian theory tidal stresses are finite at saddle points, they are expected to diverge in MOND, and to remain distinctly large inside a sizeable oblate ellipsoid around the saddle point. We work out the MOND effects using the nonrelativistic limit of the TeVeS theory, both in the perturbative nearly Newtonian regime and in the deep MOND regime. While strong MOND behavior would be a spectacular 'backyard' vindication of the theory, pinpointing the MOND-bubbles in the setting of the realistic solar system may be difficult. Space missions, such as the LISA Pathfinder, equipped with sensitive accelerometers, may be able to explore the larger perturbative region."
Recently Magueijo gave an interesting talk about this paper at Perimeter, video is available online.
the point is that the general category MOND includes relativistic MOND, such as TeVeS, and a relativistic MOND has a NONRELATIVISTIC LIMIT which is similar to but not exactly the same as Newton gravity, and this nonrelativistic limit can be TESTED by spaceprobe observations within the solar system. In fact, according to him, by the LISA probe in the inner solar system.
John Moffat, also at Perimeter, has a couple of different Scalar-Tensor-Vector versions of MOND which he has been working out ways to test in the solar system (by some outer planet mission)
He manages to fit his MOND both to the Pioneer anomaly data and to galaxy rotation curve data
http://arxiv.org/abs/gr-qc/0605141
Time Delay Predictions in a Modified Gravity Theory
J. W. Moffat
5 pages
"The time delay effect for planets and spacecraft is obtained from a
fully relativistic modified gravity theory including a fifth force skew symmetric field by fitting to the Pioneer 10/11 anomalous acceleration data. A possible detection of the predicted time delay corrections to general relativity for the outer planets and future spacecraft missions is considered. The time delay correction to GR predicted by the modified gravity is consistent with the observational limit of the Doppler tracking measurement reported by the Cassini spacecraft on its way to Saturn, and the correction increases to a value that could be measured for a spacecraft approaching Neptune and Pluto."
I see that Moffat makes a helpful distinction! In effect, he says MOG instead of MOND. He calls his "Scalar-Tensor-Vector" theory a kind of "Modified Gravity". But I fear other people would refer to it as a kind of MOND because that is the usual term---as witness Bekenstein.
http://arxiv.org/abs/gr-qc/0506021
Scalar-Tensor-Vector Gravity Theory
J. W. Moffat
Comments: 20 pages. Section on cosmology added.
JCAP 0603 (2006) 004
"A
covariant scalar-tensor-vector gravity theory is developed which allows the gravitational constant G, a vector field coupling $\omega$ and the vector field mass mu to vary with space and time. The equations of motion for a test particle lead to a modified gravitational acceleration law that can fit galaxy rotation curves and cluster data without non-baryonic dark matter. The theory is consistent with solar system observational tests. The linear evolutions of the metric, vector field and scalar field perturbations and their consequences for the observations of the cosmic microwave background are investigated."
If the other professionals in the field could be persuaded to say MOG instead of MOND when talking about relativistic versions of MOND, then the confusion would be straightened out.
