Unified dark sector and Hubble-tension alleviation in scalar-vector-tensor gravity

TL;DR

This paper proposes a scalar-vector-tensor gravity model that modifies late-time cosmic expansion, alleviating the Hubble tension by connecting dark energy, vector fields, and screening mechanisms, without disrupting early universe physics.

Contribution

It introduces a unified framework where late-time scalar dynamics and vector fields address the Hubble tension while satisfying local gravity constraints.

Findings

The model enhances the effective Hubble constant at late times.

Scalar potential acts as a dynamical dark energy component.

Vector contribution behaves as pressureless matter at cosmological scales.

Abstract

We investigate a scalar-vector-tensor theory in which matter is minimally coupled to a Jordan-frame metric, while a massive vector sector interacts with the baryonic current. We show that the conformal scalar coupling modifies the physical expansion rate measured by matter observers, leading to a late-time enhancement of the effective Hubble constant. By constructing a phenomenological scalar evolution that becomes relevant only at low redshifts, the model provides a purely late-time mechanism for alleviating the Hubble tension without significantly affecting early-universe cosmology. The scalar potential naturally acts as a dynamical dark-energy sector, while the vector contribution behaves effectively as a pressureless component at cosmological scales through a density-dependent vector mass. Hence, the framework connects late-time scalar dynamics, effective dark-energy evolution, and Hubble-tension alleviation within a unified setup. Finally, local gravitational constraints can be suppressed through a chameleon-type screening mechanism, allowing the theory to remain compatible with Solar-System tests while retaining nontrivial cosmological effects.