Positive Equation-of-state Parameter in the Accelerating Dilaton Cosmology

TL;DR

This paper demonstrates that in a two-dimensional quantum cosmological model, the equation-of-state parameter for an accelerating universe can be positive due to quantum effects, challenging conventional assumptions.

Contribution

It shows that quantum contributions can make the overall equation-of-state parameter positive and finite, even when quantum partial contributions are not positive definite.

Findings

The full parameter is positive and finite.

Quantum effects can alter the sign of the equation-of-state parameter.

The partial quantum contribution is not perturbatively additive.

Abstract

In a semiclassically quantized two-dimensional cosmological model, it can be shown that the parameter of the equation of state for the accelerating universe can be positive due to the negative energy density and the negative pressure, which is a little different from the conventional wisdom that the parameter is negative with the positivity of the energy density. Furthermore, we show that the full parameter composed of the classical and the quantum-mechanical contributions is positive and finite even though the partial state parameter from the quantum-mechanical contribution is not positive definite, which means that the state parameter is not perturbatively additive in this model.