Perturbation Dynamics and Structure Formation in Extended Proca-Nuevo Gravity

TL;DR

This paper investigates the Extended Proca-Nuevo gravity model, analyzing cosmological perturbations and structure formation, revealing modifications to expansion history and stability conditions, and providing a basis for observational tests.

Contribution

It introduces a comprehensive linear perturbation analysis of the EPN framework, highlighting its effects on cosmological evolution and structure growth.

Findings

EPN modifies background expansion interpolating between ΛCDM and deviations at intermediate redshifts.

The matter growth equation remains GR-like but with a modified expansion history.

Stability conditions for scalar perturbations are discussed.

Abstract

A comprehensive analysis of cosmological perturbations and structure formation is presented for the Extended Proca-Nuevo (EPN) framework, a vector-tensor extension of General Relativity with a massive spin-1 field. In this scenario, the vector field modifies the background expansion through an algebraic constraint, leading to a characteristic Hubble evolution that interpolates between $\Lambda$CDM limits while introducing deviations at intermediate redshifts. Assuming minimal matter coupling, the linear perturbation equations are derived in gauge-invariant form and the resulting growth of matter inhomogeneities is analyzed. The EPN sector induces effective anisotropic stress and couples a single propagating scalar mode to the metric potentials, leaving the matter growth equation in its GR form but with a modified expansion history. The full scalar perturbation system is presented, stability conditions are discussed, and the results provide a foundation for testing the EPN framework against current and future cosmological observations.