On Conditions for Strict Feasibility in Nonlinear Complementarity Problems 1

The strict feasibility plays an important role in the development of theory and algorithms of complementarity problems. In this paper, we establish suucient conditions to ensure the strict feasibility of a nonlinear complemen-tarity problem. Our analytical method, based on a newly introduced concept of-antifeasible sequence, can be viewed as a uniied approach in proving the existence of a strictly feasible point. Some equivalent conditions of strict feasibility are also established for certain complementarity problems. Among others, we show that a P complementarity problem is strictly feasible if and only if its solution set is nonempty and bounded. This result extends a well-known result in monotone situation.