On the stability of high Lewis number combustion fronts

We consider wavefronts that arise in a mathematical model for high Lewis number combustion processes. An e�cient method for the proof of the existence and uniqueness of combustion fronts is provided by geometric singular perturbation theory. The fronts supported by the model with very large Lewis numbers are small perturbations of the front supported by the model with in nite Lewis number. The question of stability for the fronts is more complicated. Besides discrete spectrum, the system possesses essential spectrum up to the imaginary axis. We show how a geometric approach which involves construction of the Stability Index Bundles can be used to relate the spectral stability of wavefronts with high Lewis number to the spectral stability of the front in the case of in nite Lewis number