title: Live soap: stability, order, and fluctuations in apolar active smectics.
abstract: We construct a hydrodynamic theory of noisy, apolar active smectics in bulk suspension or on a substrate. Unlike purely orientationally ordered active fluids, active apolar smectics can be dynamically stable in Stokesian bulk suspensions. Smectic order in these systems is quasilong ranged in dimension d=2 and long ranged in d=3. We predict reentrant Kosterlitz-Thouless melting to an active nematic in our simplest model in d=2, a nonzero second-sound speed parallel to the layers in bulk suspensions, and that there are no giant number fluctuations in either case. We also briefly discuss possible instabilities in these systems.
authors.affiliation: Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560 012, India and Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
authors.forename: Tapan Chandra
authors.initials: TC
authors.lastname: Adhyapak
authors.affiliation: Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560 012, India and TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 21 Brundavan Colony, Narsingi, Hyderabad 500 075, India.
authors.forename: Sriram
authors.initials: S
authors.lastname: Ramaswamy
authors.affiliation: Department of Physics and Institute of Theoretical Science, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: John
authors.initials: J
authors.lastname: Toner