Quasi-Intersection Problems and Fixed Point Theorems Concerning Separately Scalar Weakly l.s.c and u.s.c Mappings

In this paper, we first prove a new result on quasi-variational inequality problems; then, we use it to show the existence of solutions to quasi-intersection problems. In particular, we establish several results on the existence of solutions to generalized quasi-equilibrium problems and fixed point problems concerning separately scalar weakly lower and upper semi-continuous mappings. The results in this paper generalize some well-known existence theorems from the literature.