Nonequilibrium fluctuations and nonlinear response of an active bath

Activity driven transport in harmonic chains

“…Active reservoirs refer to a special class of nonequilibrium reservoirs, consisting of self-propelled particles like bacteria or Janus beads, which are inherently out of equilibrium by consuming energy from the environment at an individual level [22][23][24]. Recent studies, both theoretical and experimental, show that individual probe particles immersed in such active reservoirs exhibit many unusual features including emergence of negative friction, modification of equipartition theorem and anomalous relaxation dynamics [26][27][28][29][30][31][32][33][34][35]. A natural question is how the transport properties of an extended system are affected when connected to active reservoirs at the boundaries.…”

Trapped tracer in a non-equilibrium bath: dynamics and energetics

“…[5][6][7] Employing microrheology and single-particle tracking techniques, it is possible to measure the fluctuations of a tracer trapped in a medium and thus check the validity of the FDT. [8][9][10] Any deviation from the usual FDT indicates a non-equilibrium nature of the observed dynamics, found earlier in a wide class of systems, e.g., aging glasses, 11,12 sheared materials, 13,14 externally driven colloids, 15,16 active matter, 17,18 and others. 1,[19][20][21] Based on the knowledge from equilibrium physics, a generalised version of the FDT was proposed, [22][23][24][25][26][27] and the notion of an effective temperature is introduced in the theorem as a substitute for the ambient temperature.…”

Trapped-particle microrheology of active suspensions

“…(45) It can be seen from equations (44) and (45) that in order to calculate the mean and mean-squared displacements, one needs to obtain the net polar order q 1 and the covariance of the position and orientation Cov(q 1 , r 1 ). The governing equation for Cov(q 1 , r 1 ) follows from (29) and is given by…”

“…Because biological materials examined by microrheology such as the microenvironment inside living cells often contain active "particles", we model the suspension as an active colloidal suspension. Compared to passive suspensions, the study of the microrheology of active suspensions is more recent 17,18,[21][22][23][24][25][26][27][28][29] . The colloidal particles in an active suspension are able to self-propel, which can be a model for either biologically active microswimmers or synthetic phoretic particles.…”