Symmetric Bimetric Cosmology: A Minimal Extension of {\Lambda}CDM

TL;DR

This paper introduces a symmetric bimetric cosmological model that extends the DM framework by connecting AdS and dS regimes via a scalar field, reproducing key cosmological phenomenology with natural screening.

Contribution

It presents a minimal bimetric extension of DM that incorporates dual geometries and scalar field dynamics, aligning with observational constraints.

Findings

Reproduces DM phenomenology with small dynamical corrections

Ensures local gravity constraints via Vainshtein screening

Provides a theoretical framework connecting AdS and dS regimes

Abstract

We construct and analyze a symmetric bimetric cosmological model connecting Anti-de Sitter (AdS) and de Sitter (dS) regimes through a coupled scalar field. Starting from a Lagrangian with Einstein-Hilbert terms for two FLRW metrics and an inter-metric potential, we derive modified Friedmann and Klein-Gordon equations governing their evolution. In the symmetric effective-fluid limit, the model reproduces the main phenomenology of the $\Lambda$CDM cosmology with a small dynamical correction proportional to $(1+z)^{-3}$, and naturally satisfies local-gravity constraints through Vainshtein screening. This article outlines the theoretical structure and calibration of the model within a dual-geometry cosmological setting.