  Simplest extensions of single particle dynamics in momentum conserving active
fluid - that of an active suspension of two colloidal particles or a single
particle confined by a wall - exhibit strong departures from Boltzmann
behavior, resulting in either a breakdown of an effective temperature
description or a steady state with nonzero entropy production rate. This is a
consequence of hydrodynamic interactions that introduce multiplicative noise in
the stochastic description of the particle positions. This results in
fluctuation induced interactions that depend on distance as a power law. We
find that the dynamics of activated colloids in a passive fluid, with
stochastic forcing localized on the particle, is different from that of passive
colloids in an active fluctuating fluid.
