Hubble drift in Palatini $f(\mathcal{R})$-theories

TL;DR

This paper investigates the effects of atomic clock choices on Hubble drift measurements within Palatini $f( ext{R})$ gravity models, proposing a formalism to distinguish these effects from dark energy contributions and discussing the physical frame concept.

Contribution

It introduces a formalism to separate clock-induced effects from dark sources in Palatini $f( ext{R})$ theories and analyzes the implications for the physical frame in extended gravity.

Findings

Atomic clock choices influence Hubble drift measurements.

The formalism effectively isolates clock effects from dark energy signals.

The Jordan frame is suitable for cosmology but not for solar system tests.

Abstract

In a Palatini $f(\mathcal{R})$-model, we define chonodynamical effects due to the choice of atomic clocks as standard reference clocks and we develop a formalism able to quantitatively separate them from the usual effective dark sources one has in extended theories. We apply the formalism to Hubble drift and briefly discuss the issue about the physical frame. In particular, we argue that there is no physical frame in the sense one does different things in different frames and that, in a sense, is the physical characteristic of extended gravity. As an example, we discuss how Jordan frame may be well suited to discuss cosmology, though it fails within the solar system.