Steplike contrast structures for a singularly perturbed elliptic equation in an annulus (Q5954342)

The authors consider a singularly perturbed boundary value problem for an elliptic differential equation in an annulus involving a steplike internal transition layer. An asymptotic form that is linear with respect to the derivative is used for the construction of the solution. The proof of the basic existence theorem relies on the method of barrier functions, which was extensively employed in recent scientific paper on singularly perturbed differential equations.