Dark energy and Josephson junctions

TL;DR

The paper critically examines claims that dark energy can be detected via noise measurements in Josephson junctions, concluding that such claims are based on misunderstandings and that no such detection is possible.

Contribution

It provides a theoretical analysis clarifying the physical origin of spectral functions in Josephson junctions, refuting previous claims of dark energy detection in these experiments.

Findings

Dark energy has not been observed in Josephson junction experiments.

No deviation from linear behavior in spectral noise is expected in future experiments.

Previous claims are based on misunderstandings of the fluctuation-dissipation theorem.

Abstract

It has been recently claimed that dark energy can be (and has been) observed in laboratory experiments by measuring the power spectrum $S_I(\omega)$ of the noise current in a resistively shunted Josephson junction and that in new dedicated experiments, which will soon test a higher frequency range, $S_I(\omega)$ should show a deviation from the linear rising observed in the lower frequency region because higher frequencies should not contribute to dark energy. Based on previous work on theoretical aspects of the fluctuation-dissipation theorem, we carefully investigate these issues and show that these claims are based on a misunderstanding of the physical origin of the spectral function $S_I(\omega)$. According to our analysis, dark energy has never been (and will never be) observed in Josephson junctions experiments. We also predict that no deviation from the linear rising behavior of $S_I(\omega)$ will be observed in forthcoming experiments. Our findings provide new (we believe definite) arguments which strongly support previous criticisms.