Abstract
Our Modified Gravity Theory (MOG) is a gravitational theory without exotic dark matter, based on an action principle. MOG has been used successfully tomodel astrophysical phenomena, such as galaxy rotation curves, galaxy cluster masses and lensing. MOG may also be able to account for cosmological observations. We assume that the MOG point source solution can be used to describe extended distributions of matter via an appropriately modified Poisson equation. We use this result to model perturbation growth in MOG and find that it agrees well with the observed matter power spectrum at present. As the resolution of the power spectrum improves with increasing survey size, however, significant differences emerge between the predictions of MOG and the standard Λ-cold dark matter (Λ-CDM) model, as in the absence of exotic darkmatter, oscillations of the power spectrum in MOG are not suppressed. We can also use MOG to model the acoustic power spectrum of the cosmic microwave background. A suitably adapted semi-analytical model offers a first indication that MOG may pass this test and correctly model the peak of the acoustic spectrum.
Highlights
The preferred model of cosmology today, the Λ-cold dark matter (Λ-CDM) model, provides an excellent fit to cosmological observations, but at a substantial cost: according to this model, about 95% of the Universe is either invisible or undetectable, or possibly both [1]
Do such theories have to explain successfully the velocity dispersions, rotational curves and gravitational lensing of galaxies and galaxy clusters, the theories must be in accord with cosmological observations, notably, the acoustic power spectrum of the cosmic microwave background (CMB), the matter power spectrum of galaxies and the recent observation of the luminosity-distance relationship of high-z supernovae, which is seen as evidence for “dark energy”
A χ2 comparison suggests that Modified Gravity Theory (MOG) offers a better fit (χ2MOG = 0.03, χ2ΛCDM = 0.09 per degree of freedom), we must be cautious: the Λ-CDM approximation we used is not necessarily the best approximation available, and the MOG result is dependent on the validity of the analysis presented which was developed without the benefit of an interior solution
Summary
The preferred model of cosmology today, the Λ-cold dark matter (Λ-CDM) model, provides an excellent fit to cosmological observations, but at a substantial cost: according to this model, about 95% of the Universe is either invisible or undetectable, or possibly both [1]. For gravitational theories designed to challenge the Λ-CDM model, the bar is set increasingly higher by recent discoveries Do such theories have to explain successfully the velocity dispersions, rotational curves and gravitational lensing of galaxies and galaxy clusters, the theories must be in accord with cosmological observations, notably, the acoustic power spectrum of the cosmic microwave background (CMB), the matter power spectrum of galaxies and the recent observation of the luminosity-distance relationship of high-z supernovae, which is seen as evidence for “dark energy”. A concluding section summarizes our results and maps out future steps
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