title: Thermal and non-thermal fluctuations in active polar gels.
abstract: We discuss general features of noise and fluctuations in active polar gels close to and away from equilibrium. We use the single-component hydrodynamic theory of active polar gels built by Kruse and coworkers to describe the cytoskeleton in cells. Close to equilibrium, we calculate the response function of the gel to external fields and introduce Langevin forces in the constitutive equations with correlation functions respecting the fluctuation-dissipation theorem. We then discuss the breakage of the fluctuation-dissipation theorem due to an external field such as the activity of the motors. Active gels away from equilibrium are considered at the scaling level. As an example of application of the theory, we calculate the density correlation function (the dynamic structure factor) of a compressible active polar gel and discuss possible instabilities.
authors.affiliation: Theoretical Condensed Matter Physics Division and Centre for Advanced Research and Education, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, 700 064, Kolkata (Calcutta), India.
authors.forename: A
authors.initials: A
authors.lastname: Basu
authors.forename: J F
authors.initials: JF
authors.lastname: Joanny
authors.forename: F
authors.initials: F
authors.lastname: Jülicher
authors.forename: J
authors.initials: J
authors.lastname: Prost
mesh_terms: D001703:Biophysics; D003599:Cytoskeleton / Q000378:metabolism*; D005782:Gels; D016014:Linear Models; D008954:Models, Biological; D013816:Thermodynamics
chemical_list: D005782:Gels
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