Irreversibility in biological active matter

Nonequilibrium dynamics is an essential physical feature of living matter. Living systems harness energy at the molecular-scale through ATP hydrolysis and dissipate it on much larger spatiotemporal scales, often in the form of heat. The energetic loss can be cast as an increase in entropy of the environment, and the entropy production is associated with broken time-reversal symmetry in the system’s dynamics. Here we estimate the entropy production rate by analyzing statistical properties of a time series observed in a nonequilibrium steady state. The Kullback-Leibler divergence (KLD) between the time series and its time reversed is a lower bound to the entropy production rate. We use a lossless compression algorithm to quantify the information loss between forward and backward processes. The compression algorithm provides a universal measurement of irreversibility independent of the underlying models.