## [astro-ph/0604055] Can the Brans-Dicke gravity possibly with $\Lambda$ be a theory of Dark Matter ?

 Authors: Hongsu Kim Abstract: The pure Brans-Dicke (BD) gravity with or without the cosmological constant $\Lambda$ has been taken as a model theory for the dark matter. Indeed, there has been a consensus that unless one modifies either standard theory of gravity, namely, the general relativity or standard model for particle physics, or both, one can never achieve a satisfying understanding of the phenomena associated with dark matter and dark energy. Along this line, our dark matter model in this work can be thought of as an attempt to modify the gravity side alone in the simplest fashion to achieve the goal. As is well-known, the mysterious flattened rotation curves observed for so long in the outer region of galactic halos have been the primary cause that called for the existence of dark matter. Among others, therefore, it is demonstrated that our model theory can successfully predict the emergence of dark matter halo-like configuration in terms of a self-gravitating spacetime solution to the BD field equations and reproduce the flattened rotation curve in this dark halo-like object in terms of the non-trivial energy density of the BD scalar field which was absent in the context of general relativity where the Newton's constant is strictly a constant'' having no dynamics. [PDF]  [PS]  [BibTex]  [Bookmark]

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Garth Antony Barber
Posts: 59
Joined: July 19 2005
Affiliation: Published independent

### [astro-ph/0604055] Can the Brans-Dicke gravity possibly with

An interesting paper, will it go the same way as Cooperstock & Lieu?

Note that as well as explaining the flat galactic rotation curves, it has yet to explain galaxy/cluster lensing of distant quasars, and BB nucleosynthesis and be concordant with WMAP etc.

Garth

Ruth Lazkoz
Posts: 14
Joined: January 02 2006
Affiliation: University of the Basque Country

### Re: [astro-ph/0604055] Can the Brans-Dicke gravity possibly

Hi,

I have a question. I understand that the velocity curves are obtained from Doppler shift measurements, which are frame invariant quantities.
Should then this Brans-Dicke explanation of the flatness of the curves lead to the same conclusions both in the Einstein or in the Jordan frame?
Put another way, if one were to present the results of this paper in terms of Doppler shift, then one should not care for what frame has been chosen, right?

Thanks,

Ruth
Garth Antony Barber wrote:An interesting paper, will it go the same way as Cooperstock & Lieu?

Note that as well as explaining the flat galactic rotation curves, it has yet to explain galaxy/cluster lensing of distant quasars, and BB nucleosynthesis and be concordant with WMAP etc.

Garth