TY - JOUR AB - We consider a Boltzmann model introduced by Bertin, Droz and Grégoire as a binary interaction model of the Vicsek alignment interaction. This model considers particles lying on the circle. Pairs of particles interact by trying to reach their mid-point (on the circle) up to some noise. We study the equilibria of this Boltzmann model and we rigorously show the existence of a pitchfork bifurcation when a parameter measuring the inverse of the noise intensity crosses a critical threshold. The analysis is carried over rigorously when there are only finitely many non-zero Fourier modes of the noise distribution. In this case, we can show that the critical exponent of the bifurcation is exactly 1/2. In the case of an infinite number of non-zero Fourier modes, a similar behavior can be formally obtained thanks to a method relying on integer partitions first proposed by Ben-Naïm and Krapivsky. AU - Carlen,E AU - Carvalho,MC AU - Degond,P AU - Wennberg,B DO - 6/1783 EP - 1803 PY - 2015/// SN - 1361-6544 SP - 1783 TI - A Boltzmann model for rod alignment and schooling fish T2 - Nonlinearity UR - http://dx.doi.org/10.1088/0951-7715/28/6/1783 UR - http://hdl.handle.net/10044/1/23581 VL - 28 ER -