Generalized energy equipartition in harmonic oscillators driven by   active baths
  We study experimentally and numerically the dynamics of colloidal beads confined by a harmonic potential in a bath of swimming E. coli bacteria. The resulting dynamics is well approximated by a Langevin equation for an overdamped oscillator driven by the combination of a white thermal noise and an exponentially correlated active noise. This scenario leads to a simple generalization of the equipartition theorem resulting in the coexistence of two different effective temperatures that govern dynamics along the flat and the curved directions in the potential landscape. 
Claudio Maggi, Matteo Paoluzzi, Nicola Pellicciotta, Alessia Lepore,   Luca Angelani, Roberto Di Leonardo
cond-mat.soft