Existence of positive solutions for singular eigenvalue problems.
In this paper we deal with the four-point singular boundary value problem where , , , , , , , and may be singular at . By using the well-known theory of the Leray-Schauder degree, sufficient conditions are given for the existence of positive solutions.
We revisit the existence problem for shock profiles in quasilinear relaxation systems in the case that the velocity is a characteristic mode, implying that the profile ODE is degenerate. Our result states existence, with sharp rates of decay and distance from the Chapman–Enskog approximation, of small-amplitude quasilinear relaxation shocks. Our method of analysis follows the general approach used by Métivier and Zumbrun in the semilinear case, based on Chapman–Enskog expansion and the macro–micro...