Fakeons and microcausality: light cones, gravitational waves and the Hubble constant

TL;DR

This paper explores the implications of fakeons in quantum gravity, showing that microcausality violations are short-range and undetectable with current technology, with some effects linked to the universe's expansion.

Contribution

It demonstrates that violations of microcausality due to fakeons are practically unobservable and connects the positivity of the Hubble constant to the arrow of time.

Findings

Microcausality violations are short-range and undetectable.

The universe's expansion can suppress observable effects.

The Hubble constant influences the direction of time.

Abstract

The concept of fake particle, or "fakeon", allows us to make sense of quantum gravity as an ultraviolet complete theory, by renouncing causality at very small distances. We investigate whether the violation of microcausality can be amplified or detected in the most common settings. We show that it is actually short range for all practical purposes. Due to our experimental limitations, the violation does not propagate along the light cones or by means of gravitational waves. In some cases, the universe even conspires to make the effect disappear. For example, the positivity of the Hubble constant appears to be responsible for the direction of time in the early universe.