On the dimension and the index of the solution set of nonlinear equations
Petronije S. Milojevic · Transactions of the American Mathematical Society · 1995
We study the covering dimension and the index of the solution set to multiparameter nonlinear and semilinear operator equations involving Fredholm maps of positive index. The classes of maps under consideration are (pseudo) $A$-proper and either approximation-essential or equivariant approximation-essential. Applications are given to semilinear elliptic BVP’s.