Live soap: stability, order, and fluctuations in apolar active smectics
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Updated: Apr 25, 2026

Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Tapan Chandra Adhyapak1, Sriram Ramaswamy2, John Toner3
1Centre 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.
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.
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