General Relativity and Quantum Cosmology (gr-qc)

Abstract: Previous discussions of charged dark matter neglected PBH spin and employed the Reissner-Nordstrom metric. In Nature we expect the PBHs to possess spin which require use of the technically more challenging Kerr-Newman metric. It is shown that the use of K-N metric retains the principal properties already obtained using the R-N metric, in particular the dominance of Coulomb repulsion requires super-extremality and the presence of naked singularities. In this sense, the spin of the PBHs is not an essential complication.

Abstract: Einstein formulated the general theory of relativity (GR) with an aim to mathematically incorporate Mach's principle. Despite early hopes, it became evident that GR did not follow Mach's proposition. Nevertheless, due to its accurate explanation of various observational results, Einstein refrained from further attempts to formulate Mach's principle. Over time, multiple researchers attempted to develop gravity theories aligned with the Machian model of inertia. However, each of these theories possessed its own strengths and weaknesses. This paper presents a novel theory of gravity that fully embraces Mach's principle. This metric-based theory, termed as Machian Gravity (MG), can be derived from the action principle, ensuring compliance with all conservation laws. The theory demonstrates its efficacy by providing precise explanations for galactic rotation curves. Moreover, it effectively resolves the discrepancy between dynamic mass and photometric mass in galaxy clusters without resorting to dark matter. It also presents a resolution for the expansion history of the universe without requiring any dark matter and dark energy. Consequently, MG presents a viable and compelling alternative to the standard gravity theory.