Johnson-Nyquist noise and the Casimir force between real metals at nonzero temperature

TL;DR

This paper explores how Johnson-Nyquist noise influences the thermal Casimir force between real metals at nonzero temperature, proposing that capacitive effects are crucial for resolving related thermodynamic inconsistencies.

Contribution

It introduces a physical model linking Johnson-Nyquist noise to the Casimir force and highlights the importance of capacitive effects in resolving thermodynamic issues.

Findings

Johnson-Nyquist noise induces a repulsive force between conductors.

Capacitive effects resolve thermodynamic inconsistencies in the model.

Capacitive effects are likely essential in understanding the thermal Casimir force.

Abstract

It is well known since a long time that all lossy conductors at finite temperature display an electronic noise, the Johnson-Nyquist noise, arising from the thermal agitation of electric charges inside the conductor. The existence of this noise implies that two nearby discharged conductors at finite temperature should repel each other, as a result of the electrodynamic interaction between the Johnson-Nyquist currents in either conductor and the eddy currents they induce in the other. It is suggested that this force is at the origin of the recently discovered large repulsive correction to the thermal Casimir force between two lossy metallic plates. Further support for this physical picture is obtained by studying a simple system of two linear noisy antennas. Using elementary concepts from circuit theory, we show that the repulsive force engendered by the Johnson-Nyquist noise results in the same kind of thermodynamic inconsistencies found in the Casimir problem. We show that all inconsistencies are however resolved if account is taken of capacitive effects associated with the end points of the antennas. Our findings therefore suggest that capacitive effects resulting from the finite size of the plates, may be essential for a resolution of the analogous problems met in the thermal Casimir effect.