Machian gravity and a cosmology without dark matter and dark energy
  The standard model of cosmology is based on the general theory of relativity
and demands more than 95\% of the universe to consist of dark matter and dark
energy that has no direct observational evidence till date. The foundation of
the concept these dark components are based on a fixed relation between the
strength of the gravitational field and the matter density. Alternate models
are put forward in past to explain the observations without dark components in
the universe. Though they have their own merits and draw backs. In this paper
we propose a new cosmological model based on Mach's principle. It provides a
similar cosmology as that of the standard cosmological model without any ad-hoc
dark matter or dark energy. We show that the theory naturally provides some
geometric terms that behave like dark mater and dark energy and dark radiation.
The presence of dark radiation provides new observational features in
cosmology. We show that the theory is supported by observational data from Big
Bang Nucleosynthesis and Cosmic Microwave Background, and provides an
explanations for excess number of effective neutrino species and higher Helium
mass fraction in the universe. We also calculate the best fit cosmological
parameters for our model using Planck+WP data.
