Reconstruction of aether scalar tensor theory for various cosmological scenarios

TL;DR

This paper reconstructs the aether scalar tensor (AeST) theory to replicate various cosmological scenarios, including the ΛCDM universe, using different fluid models and solutions, highlighting its flexibility in modeling cosmic evolution.

Contribution

It provides explicit reconstructions of the AeST theory for multiple cosmological backgrounds, showing its ability to reproduce ΛCDM and other expansion histories without requiring standard matter.

Findings

Einstein-Hilbert Lagrangian with positive cosmological constant uniquely reproduces ΛCDM expansion.

ΛCDM-era can be modeled with non-standard fluids in AeST theory.

Cosmic evolution can be achieved without real matter fields in AeST framework.

Abstract

In this paper, we present several explicit reconstructions for {the aether scalar tensor (AeST) theory} derived from the background of Friedmann-Lema$\hat{\text{\i}}$tre-Robertson-Walker cosmological evolution. It is shown that the Einstein-Hilbert Lagrangian with a positive cosmological constant is the only Lagrangian capable of accurately replicating the exact expansion history of the $\Lambda$ cold dark matter ($\Lambda$CDM) universe filled solely with dust-like matter. However, the $\Lambda$CDM-era can be produced within the framework of the AeST theory for some other fluids, including a perfect fluid with $p=-(1/3)\rho$, multifluids, and nonisentropic perfect fluids. Moreover, we demonstrate that the $\Lambda$CDM-era also can be replicated with no real matter field for the AeST theory. The cosmic evolution resulting from both the power-law and de-Sitter solutions also can be obtained.