On a CPT-Symmetric Interpretation of Two-Sector Dynamics in Ghost-Free Bimetric Cosmology

Abstract: We present a CPT-symmetric bimetric cosmological framework in which the classical equivalence principle is generalized to the modular form Mi = |Mg|, introducing an exotic matter sector (hereafter exomatter) with positive inertial mass and negative gravitational charge. Each sector couples exclusively to its own metric tensor (gμν for SM, fμν for EXO), with ghost-freedom guaranteed by the dRGT-class interaction potential Sᵢntg, f. Gravitational repulsion between sectors emerges as a macroscopic consequence of bimetric mixing under CPT symmetry — not as a violation of the Weak Equivalence Principle. Both sectors maintain strictly positive inertial mass and energy, preserving vacuum stability. We present the full bimetric action, modified field equations, and N-body simulation framework. We further identify a set of independently observed cosmological anomalies — including anomalous void lensing, the integrated Sachs-Wolfe effect in supervoids, and the absence of the Lyman-alpha forest in cosmic voids — that are qualitatively consistent with the predictions of this model. The framework presented here should be understood as a speculative extension of ghost-free bimetric gravity that offers an alternative effective interpretation of Dark Matter and Dark Energy phenomenology. Rather than introducing additional fundamental particle species or vacuum energy components, the observed large-scale gravitational effects are interpreted as macroscopic consequences of cross-sector interactions within a CPT-symmetric two-metric structure. We do not claim observational confirmation; instead, the model provides a self-consistent theoretical construction together with potentially discriminating empirical signatures.