Blake Barker

Shantia Yarahmadian, Blake Barker, Kevin Zumbrun et al.

We generalize the Dogterom-Leibler model for microtubule dynamics [DL] to the case where the rates of elongation as well as the lifetimes of the elongating and shortening phases are a function of GTP-tubulin concentration. We study also the effect of nucleation rate in the form of a damping term which leads to new steady-states. For this model, we study existence and stability of steady states satisfying the boundary conditions at x = 0. Our stability analysis introduces numerical and analytical Evans function computations as a new mathematical tool in the study of microtubule dynamics.

Blake Barker, Kevin zumbrun

We carry out a systematic numerical stability analysis of ZND detonations of Majda's model with Arrhenius-type ignition function, a simplified model for reacting flow, as heat release and activation energy are varied. Our purpose is, first, to answer a question of Majda whether oscillatory instabilities can occur for high activation energies as in the full reacting Euler equations, and, second, to test the efficiency of various versions of a numerical eigenvalue-finding scheme suggested by Humpherys and Zumbrun against the standard method of Lee and Stewart. Our results suggest that instabilities do not occur for Majda's model with Arrhenius-type ignition function, nor with a modified Arrhenius-type ignition function suggested by Lyng--Zumbrun, even in the high-activation energy limit. We find that the algorithm of Humpherys--Zumbrun is in the context of Majda's model $100$-$1,000$ times faster than the one described in the classical work of Lee and Stewart and $1$-$10$ times faster than an optimized version of the Lee--Stewart algorithm using an adaptive-mesh ODE solver

Blake Barker, Rose Nguyen, Björn Sandstone et al.

The Evans function has been used extensively to study spectral stability of travelling-wave solutions in spatially extended partial differential equations. To compute Evans functions numerically, several shooting methods have been developed. In this paper, an alternative scheme for the numerical computation of Evans functions is presented that relies on an appropriate boundary-value problem formulation. Convergence of the algorithm is proved, and several examples, including the computation of eigenvalues for a multi-dimensional problem, are given. The main advantage of the scheme proposed here compared with earlier methods is that the scheme is linear and scalable to large problems.