Dual characterizations of norm minimization problems

The paper studies a general norm minimization problem on a product of normed vector spaces. We establish dual necessary and sufficient optimality conditions and derive explicit formulas for the corresponding solution sets. These formulas are obtained under the assumption that one optimal solution together with its associated dual vectors arising from the optimality conditions is known. Three important cases of product norms, namely the sum norm, maximum norm and $p$-norm, are also studied. Several examples in finite and infinite dimensional spaces equipped with various types of norms are presented to illustrate the established results.