Cosmological constant in a quantum fluid model

TL;DR

This paper explores a quantum fluid model as an analogy for vacuum energy, showing that vacuum energy density is not naturally aligned with matter energy density and emphasizing the need for microscopic physics understanding.

Contribution

It introduces a quantum fluid analogy to study vacuum energy density and highlights the importance of microscopic physics in explaining the cosmological constant.

Findings

Vacuum energy density in the model is not naturally of the order of matter energy density.

Higher-order quantum back-reaction corrections influence vacuum energy density.

Cosmological expansion is linked to a universe out of mechanical equilibrium.

Abstract

Possible analogies between vacuum state and quantum fluid provide a model to study vacuum energy density induced by thermal corrections, space-time curvature, boundary conditions and quantum back-reaction. We find that vacuum energy density in this quantum fluid model is not naturally of the order of the matter energy density. We show how higher-order corrections in quantum back-reaction can also contribute to vacuum energy density, and how the cosmological expansion is a manifestation of an universe out of mechanical equilibrium. This last fact implies that simple thermodynamic arguments are not enough to explain the cosmological constant problem due to the calculation of the associated vacuum energy density requires first the knowing of the underlying microscopic physics of vacuum.