Abstract
A modified gravitational theory explains early universe and late time cosmology, galaxy and galaxy cluster dynamics. The modified gravity (MOG) theory extends general relativity (GR) by three extra degrees of freedom: a scalar field G, enhancing the strength of the Newtonian gravitational constant G_N, a gravitational, spin 1 vector graviton field phi _mu , and the effective mass mu of the ultralight spin 1 graviton. For t < t_mathrm{rec}, where t_mathrm{rec} denotes the time of recombination and re-ionization, the density of the vector graviton rho _phi > rho _b, where rho _b is the density of baryons, while for t > t_mathrm{rec} we have rho _b > rho _phi . The matter density is parameterized by Omega _M=Omega _b+Omega _phi +Omega _r where Omega _r=Omega _gamma +Omega _nu . For the cosmological parameter values obtained by the Planck Collaboration, the CMB acoustical oscillation power spectrum, polarization and lensing data can be fitted as in the Lambda CDM model. When the baryon density rho _b dominates the late time universe, MOG explains galaxy rotation curves, the dynamics of galaxy clusters, galaxy lensing and the galaxy clusters matter power spectrum without dominant dark matter.
Highlights
Dark matter was introduced to explain the stable dynamics of galaxies and galaxy clusters
In future galaxy surveys which utilize a large enough number of galaxies, with galaxies detected at sufficiently large redshift z, and with the use of a sufficiently narrow enough window function, it should be possible to detect any significant unit oscillations in the matter power spectrum, which can distinguish in the present universe between a dominant dark matter model and modified gravity (MOG) without dark matter
By assuming that the density of vector graviton (VG) associated with the massive and neutral vector field φμ in MOG theory is the dominant density in the early universe with a VG mass, mφ ∼ 10−22 eV, the perturbations δρφ satisfy the pressureless Jeans equation, allowing for an enhanced growth from the time of horizon entry and radiation-matter equality to produce large scale stellar and galaxy structure after the time of decoupling and recombination
Summary
Dark matter was introduced to explain the stable dynamics of galaxies and galaxy clusters. The second approach is to promote the gravitational VG (spin 1 vector graviton) degree of freedom as a dominant density ρφ in the early universe, so that it dominates the baryon density ρb for the time before the reionization phase when stars and galaxies are first formed [2,22]. After this time, there is a transition to modified gravity when ρb > ρφ. Where the VG de Broglie wave length λ/2π ∼ h /mφv
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