In this article, we study calculus for gH-subdifferential of convex interval-valued functions
(IVFs) and apply it in a nonconvex composite model of an interval optimization problem
(IOP). Towards this, we define convexity, convex hull, closedness, and boundedness of a set
of interval vectors. In identifying the closedness of the convex hull of a set of interval vectors
and the union of closed sets, we analyze the convergence of the sequence of interval
vectors. We prove a relation on the gH-directional derivative of the maximum of finitely many …

In this article, we study $ gH $-subdifferential calculus of convex interval-valued functions
(IVFs) and apply it in a nonconvex composite model of interval optimization problems (IOPs).
It is found that the $ gH $-directional derivative of maximum of finitely many comparable IVFs
is the maximum of their $ gH $-directional derivative. Proposed concepts of $ gH $-
subdifferential are observed to be useful to derive Fritz-John-type and KKT-type efficiency
conditions for weak efficient solutions of IOPs. Further, we extract a necessary and sufficient …