Math @ Duke

Publications [#246890] of JianGuo Liu
Papers Published
 Frouvelle, A; Liu, JG, Dynamics in a kinetic model of oriented particles with phase transition,
Siam Journal on Mathematical Analysis, vol. 44 no. 2
(May, 2012),
pp. 791826, Society for Industrial & Applied Mathematics (SIAM), ISSN 00361410 [doi]
(last updated on 2021/05/17)
Abstract: Motivated by a phenomenon of phase transition in a model of alignment of selfpropelled particles, we obtain a kinetic meanfield equation which is nothing more than the Smoluchowski equation on the sphere with dipolar potential. In this selfcontained article, using only basic tools, we analyze the dynamics of this equation in any dimension. We first prove global wellposedness of this equation, starting with an initial condition in any Sobolev space. We then compute all possible steady states. There is a threshold for the noise parameter: over this threshold, the only equilibrium is the uniform distribution, and under this threshold, the other equilibria are the Fishervon Mises distributions with arbitrary direction and a concentration parameter determined by the intensity of the noise. For any initial condition, we give a rigorous proof of convergence of the solution to a steady state as time goes to infinity. In particular, when the noise is under the threshold and with nonzero initial mean velocity, the solution converges exponentially fast to a unique Fisher von Mises distribution. We also found a new conservation relation, which can be viewed as a convex quadratic entropy when the noise is above the threshold. This provides a uniform exponential rate of convergence to the uniform distribution. At the threshold, we show algebraic decay to the uniform distribution. © 2012 Society for Industrial and Applied Mathematics.


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