Comment on: "How the huge energy of quantum vacuum gravitates to drive the slow accelerating expansion of the Universe"

TL;DR

This paper critiques a recent claim that quantum vacuum fluctuations can explain the universe's accelerated expansion, emphasizing the dependence of results on the choice of cutoff in vacuum energy calculations.

Contribution

It highlights the critical role of the cutoff method in vacuum energy calculations and challenges the universality of previous conclusions about vacuum energy's gravitational effects.

Findings

Results depend on the type of cutoff used in vacuum energy calculations.

Covariant cutoff leads to positive definite zero point energy density.

Previous claims about vacuum energy driving acceleration are not universally valid.

Abstract

In a recent paper (Phys. Rev. D95, 103504 (2017)) it is argued that, due to the fluctuations around its mean value, vacuum energy gravitates differently from what previously assumed. As a consequence, the universe would accelerate with a small Hubble expansion rate, solving the cosmological constant and dark energy problems. We point out here that the results depend on the type of cutoff used to evaluate the vacuum energy. In particular, they are not valid when one uses a covariant cutoff such that the zero point energy density is positive definite.