Cosmic structure formation in massive conformal gravity

Abstract

We study the evolution of cosmological density perturbations in massive conformal gravity (MCG). We show that conformal fermionic matter alone does not generate growing density perturbations in the subhorizon regime. By introducing a conformally coupled scalar field, however, an effective cold dark matter component emerges at the effective level. The resulting coupled perturbation equations admit growing solutions with a stronger effective gravitational interaction, allowing cosmic structure formation in MCG and potentially favoring earlier structure formation at high redshifts.

13 pages, no figures; v2: 15 pages, no figures, improved results analysis; v3: 22 pages, no figures, corrected version to match the published version