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ohwilleke

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There has been a fair amount of publishing in the field recently, and here are a collection of recent papers on the topic:

**An alternative to the dark matter paradigm: relativistic MOND gravitation**

http://arxiv.org/abs/astro-ph/0412652

MOND, invented by Milgrom, is a phenomenological scheme whose basic premise is that the visible matter distribution in a galaxy or cluster of galaxies alone determines its dynamics. MOND fits many observations surprisingly well. Could it be that there is no dark matter in these systems and we witness rather a violation of Newton's universal gravity law ? If so, Einstein's general relativity would also be violated. For long conceptual problems have prevented construction of a consistent relativistic substitute which does not obviously run afoul of the facts. Here I sketch TeVeS, a tensor-vector-scalar field theory which seems to fit the bill: it has no obvious conceptual problems and has a MOND and Newtonian limits under the proper circumstances. It also passes the elementary solar system tests of gravity theory.

**Tidal streams in a MOND potential: constraints from Sagittarius**

http://arxiv.org/abs/astro-ph/0501273

We compare orbits in a thin axisymmetric disc potential in MOND to those in a thin disc plus near-spherical dark matter halo predicted by a $\Lambda$CDM cosmology. Remarkably, the amount of orbital precession in MOND is nearly identical to that which occurs in a a CDM Galactic halo with flattening q=0.95, consistent with recent constraints from the Sagittarius stream. Since very flattened mass distributions in MOND produce rounder potentials than in standard Newtonian mechanics, we show that it will be very difficult to use the tidal debris from streams to distinguish between a MOND galaxy and a standard CDM galaxy with a mildly oblate halo.

**The End of the Dark Ages in MOND**

http://arxiv.org/abs/astro-ph/0412614

We study the evolution of a spherically symmetric density perturbation in the Modified Newtonian Dynamics (MOND) model applied to the net acceleration over Hubble flow. The background cosmological model is a $\Lambda$-dominated, low-$\Omega_b$ Friedmann model with no Cold Dark Matter. We include thermal processes and non-equilibrium chemical evolution of the collapsing gas. We find that under these assumptions the first low-mass objects ($M \le 3\times 10^4 M_{\odot}$) may collapse already for $z\sim 30$, which is in quite good agreement with the recent WMAP results. A lower value of $a_0$ would lead to much slower collapse of such objects.

**Using distant globular clusters as a test for gravitational theories**

http://arxiv.org/abs/astro-ph/0501272

We propose to determine the stellar velocity dispersions of globular clusters in the outer halo of the Milky Way in order to decide whether the dynamics of the universe on large scales is governed by dark matter or modified Newtonian dynamics (MOND). We show that for a number of galactic globular clusters, both the internal and the external accelerations are significantly below the critical acceleration parameter $a_0$ of MOND. This leads to velocity dispersions in case of MOND which exceed their Newtonian counterparts by up to a factor of 3, providing a stringent test for MOND. Alternatively, in case high velocity dispersions are found, these would provide the first evidence that globular clusters are dark matter dominated.

**A tensor-vector-scalar framework for modified dynamics and cosmic dark matter**

http://arxiv.org/abs/astro-ph/0502222

I describe a tensor-vector-scalar theory that reconciles the galaxy scale success of modified Newtonian dynamics (MOND) with the cosmological scale evidence for CDM. The theory provides a cosmological basis for MOND in the sense that the predicted phenomenology only arises in a cosmological background. The theory contains an evolving effective potential, and scalar field oscillations in this potential comprise the cold dark matter; the de Broglie wavelength of these soft bosons, however, is sufficiently large that they cannot accumulate in galaxies. The theory predicts, inevitably, a constant anomalous acceleration in the outer solar system which, depending upon the choice of parameters, can be consistent with that detected by the Pioneer spacecraft s.