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SUMMARY:Dynamics of topological defects in active nematic films - Luiza An
 gheluta-Bauer\, Univ. of Oslo
DTSTART:20211109T130000Z
DTEND:20211109T140000Z
UID:TALK162586@talks.cam.ac.uk
CONTACT:Camille Scalliet
DESCRIPTION:Swimming bacteria\, growing cell tissues\, molecular motors an
 d microtubule systems confined to a substrate are examples of active matte
 r films that exhibit long-range nematic (orientational) order. Intrinsic a
 ctivity in these systems builds mechanical stresses that tend to destroy l
 ocal nematic order through topological defects\, which act as sources of p
 ersistent active flows.  The overall evolution and functionality of biolog
 ical matter is greatly influenced by these orientational defects. Yet\, th
 eir formation and dynamics are driven by a complex interplay between topol
 ogical singularities in the nematic order and active flow instabilities\, 
 and this is not completely understood. \n \nIn this talk\, I will present 
 a generic field theory of topological defects as zeros of the order parame
 ter. The method is presented within the hydrodynamic model of active nemat
 ics\; however\, it also applies to superfluids\, crystals and other ordere
 d states with vanishing order parameter at the defect core. The dynamics o
 f these kinds of defects is entirely determined by tracking the evolution 
 of order parameter zeros. I will discuss how defect velocity is determined
  by flow and nematic distortions\, and how the self-propulsion of the +1/2
  defect depends on both friction and viscous dissipation. I will present a
 nalytical results on the active flows induced by isolated defects in infin
 ite domains and discuss finite-size effects. The defect densities and dens
 ity currents are easily derived with this formalism of tracking zeros\; th
 us\, it can be used as a theoretical framework for developing a hydrodynam
 ic theory of defects.
LOCATION:Center for Mathematical Sciences\, Lecture room MR11\, or https:/
 /maths-cam-ac-uk.zoom.us/j/98016675669
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