Physical running of couplings in quadratic gravity

TL;DR

This paper re-examines the beta functions in quadratic gravity, deriving the correct physical versions, and shows that asymptotic freedom can coexist with the absence of tachyons, challenging previous assumptions.

Contribution

It provides a new derivation of the physical beta functions in quadratic gravity, clarifying their relation to scattering amplitudes and physical properties.

Findings

Correct physical beta functions differ from traditional ones.

Asymptotic freedom is compatible with no tachyons.

Revised beta functions impact understanding of quadratic gravity.

Abstract

We argue that the well-known beta functions of quadratic gravity do not correspond to the physical dependence of scattering amplitudes on external momenta, and derive the correct physical beta functions. Asymptotic freedom turns out to be compatible with the absence of tachyons.