1997/08/31 by Ariel Edery, A. Edery, M. B. Paranjape · 3 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Relativity and Gravitational Theory #astro-ph
paper · pdf · doi:10.1103/physrevd.58.024011
published as Phys.Rev.D58:024011,1998 · 17 pages, one figure, version to be published in Phys. Rev. D
arxiv created 1998/04/21 · openalex publication_date 1998/06/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Weyl gravity has been advanced in the recent past as an alternative to general relativity. The theory has had some success in fitting galactic rotation curves without the need for copious amounts of dark matter. To check the viability of Weyl gravity, we propose two additional classical tests of the theory: the deflection of light and time delay in the exterior of a static spherically symmetric source. The result for the deflection of light is remarkably simple: in addition to the usual positive (attractive) Einstein deflection of 4GM/r0 we obtain an extra deflection term of \ensuremath-\ensuremathγr0 where \ensuremathγ is a constant and r0 is the radius of closest approach. With a negative \ensuremathγ, the extra term can increase the deflection on large distance scales (galactic or greater) and therefore imitate the effect of dark matter. Notably, the negative sign required for \ensuremathγ is opposite to the sign of \ensuremathγ used to fit galactic rotation curves. The experimental constraints show explicitly that the magnitude of \ensuremathγ is of the order of the inverse Hubble length something already noted as an interesting numerical coincidence in the fitting of galactic rotation curves.