Probing scale-dependent liveliness with nonequilibrium thermospectroscopy

TL;DR

This paper introduces a method using nonequilibrium thermospectroscopy to probe scale-dependent activity in living matter, revealing multiple effective temperatures linked to energy injection at different scales.

Contribution

It demonstrates how spectral noise temperatures can be identified and related to activity landscapes using a generalized Langevin equation and harmonic traps.

Findings

Multiple effective temperatures emerge in active polymer simulations.

Spectral noise temperatures relate to the underlying activity landscape.

Harmonic traps can selectively scan and resolve scale-dependent activity.

Abstract

Probing the spatially heterogeneous activity across scales is a major challenge in living matter. Energy injection at diverse length scales leads to mode coupling, inter-modal energy transfer, and entropy production. We demonstrate the emergence of multiple effective (``active'') temperatures in nonequilibrium molecular- and Brownian-dynamics simulations of an active polymer. Via a generalised Langevin equation for a labelled monomer we identify spectral noise temperatures and their relation to the underlying activity landscape. A harmonic trap of variable stiffness can serve as a minimally invasive prototypical spectroscopic device to selectively scan through the emergent effective temperatures and thereby resolve the scale-dependent activity.