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P. 137

Duality for robust multi-dimensional vector variational control problem under invexity

            (ζ, ϱ, χ, λ, τ, ¯ a, b, µ)∈T w such that                Z
                                                                                                  ¯
                                                                             ¯
                                                                                  ¯
                                                                                             T
                                                                  +   ξ(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) ¯χ Ψ ϱ Π, ¯ a +
            Z

                                          T
                           T
                Ψ(Π, ¯ a)+λ θ(Π, ζ κ , b) +τ β(Π, ζ κ , µ) dν ≧      Ω
                                                                                                !
              Ω
                                                                   ¯ T
            Z                                                            ¯ ¯ ¯      T   ¯ ¯
                                                                  λ θ ϱ (Π, ζ κ , b)+ ¯τ β ϱ (Π, ζ κ , ¯µ) dν =0
                                      ¯
                                ¯
                  ¯
                                               ¯
                           ¯ T
                                           T

               Ψ Λ, ¯ a dν +λ θ(Λ, ¯σ κ , b) + ¯τ β(Λ, ¯σ κ , ¯µ) dν
              Ω
                                                              which is equivalent to the following, using the fact
                       ¯      m
                                                                                    ¯
            From (3), λ(t)∈R  +  and feasibility of (¯σ, ¯ω) to  that η =0 when ¯σ(t)=ζ(t) ,
            (RUVP), we obtain                                       Z

                                                                                   ¯
                                                                                                  ¯
                                                                             ¯
                                                                                             T
                                                                       η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) ¯χ Ψ ζ Π, ¯ a
                                                                     Ω
            Z

                                          T
                           T
                Ψ(Π, ¯ a)+λ θ(Π, ζ κ , b) +τ β(Π, ζ κ , µ) dν ≧       ¯ T   ¯ ¯ ¯     T    ¯ ¯
                                                                    +λ θ ζ (Π, ζ κ , b)+ ¯τ β ζ (Π, ζ κ , ¯µ) dν
              Ω
                             Z                                    Z

                                   ¯
                                                                              ¯
                                                                                    ¯
                                                                                             ¯ T
                                                                                                   ¯ ¯ ¯

                                Ψ Λ, ¯ a dν                     +    D κ η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) λ θ ζ κ (Π, ζ κ , b)
                               Ω                                   Ω

                                                                                    ¯ ¯
            contradicting Theorem 3.                                          T    (Π, ζ κ , ¯µ) dν
                                                                           +¯τ β ζ κ
                                                                    Z
                                 ¯
                           ¯
                                                                                                  ¯
                                                                                   ¯
                                                                             ¯
                                                                                             T
            Hence, (¯σ, ¯ω, ¯χ,λ,¯τ,¯ a,b, ¯µ) is a robust weak effi-  +  ξ(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) ¯χ Ψ ϱ Π, ¯ a +

            cient solution to (WD).                                  Ω

            Further, from (3) it follows that the objective      λ θ ϱ (Π, ζ κ , b)+ ¯τ β ϱ (Π, ζ κ , ¯µ) dν =0  (19)
                                                                       ¯ ¯ ¯
                                                                                       ¯ ¯
                                                                                  T
                                                                  ¯ T
            function values of (RUVP) and (WD) are equal         Z
                       ¯
                              ¯
            at (¯σ, ¯ω, ¯χ, λ, ¯τ, ¯ a, b, ¯µ).          □
                                                              As    Ψ(., ¯ a)dν is strictly invex w.r.t. η and ξ at
                                                                  Ω
                                                               ¯
            Theorem 5. [Strict Converse Duality Theorem]      (ζ, ¯ϱ) and ¯χ>0,
                                       ¯
                                              ¯
                                ¯
            Assume (¯σ, ¯ω) and (ζ, ¯ϱ, ¯χ, λ, ¯τ, ¯ a, b, ¯µ) to be ro-
            bust weak efficient solutions of (RUVP) and (WD)       Z   T    ¯       Z   T   ¯
            respectively, such that                                   ¯ χ Ψ Λ, ¯ a dν −  ¯ χ Ψ Π, ¯ a  dν >
                                                                    Ω                 Ω
                                                                   Z
                                                                            ¯
                                                                                                ¯
                                                                                  ¯
                                                                                           T

                                                                      η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)¯χ Ψ ζ Π, ¯ a dν

              Z             Z                                     Ω
                                     ¯
                                            ¯ T
                 ¯ ¯
                                                ¯ ¯ ¯
                 Ψ Λ, ¯ a dν ≦    Ψ Π, ¯ a +λ θ(Π, ζ κ , b)+      Z
                                                                                 ¯
                                                                           ¯
                                                                                               ¯
                                                                                         T

               Ω              Ω                                 +    ξ(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)¯χ Ψ ϱ Π, ¯ a dν,  (20)
                                                                   Ω
                                        !
                                ¯ ¯
                             T
                           ¯ τ β(Π, ζ κ , ¯µ) dν       (18)   Similarly, as  Z  ¯ T  ¯       Z  ¯ τ β(., ., ¯µ)dν
                                                                                                 T
                                                                             λ θ(., ., b)dν and
                                                                           Ω                   Ω
                                                                                         ¯
                            Z                                 are invex w.r.t. η and ξ at (ζ, ¯ϱ),
                               ¯
            Further,    if     Ψ(., ¯ a)dν  is  strictly  in-
                             Ω
                    Z                       Z                     Z                   Z
                                                                               ¯
                                                                                             ¯ ¯ ¯
                              ¯
                                                                     ¯ T
                                                                                        ¯ T
                                                                         ¯
                      ¯ T
                                                T
            vex,      λ θ(., ., b)dν  and      ¯ τ β(., ., ¯µ)dν     λ θ(Λ, ¯σ κ , b)dν −  λ θ(Π, ζ κ , b)dν ≧
                     Ω                       Ω                     Ω                   Ω
                                         ¯
                                              ¯
            are invex w.r.t.      η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) and  Z
                                                                                         ¯ T
                                                                                 ¯
                                                                            ¯
                                                                                              ¯ ¯ ¯
                                       ¯
                   ¯
                        ¯
            ξ(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) at (ζ, ¯ϱ), then (¯σ, ¯ω)=  η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)λ θ ζ (Π, ζ κ , b)dν
             ¯
            (ζ, ¯ϱ).                                             Z  Ω
                                                                                                ¯ ¯ ¯
                                                                                  ¯
                                                                                          ¯ T
                                                                             ¯
                                                               +   D κ η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)λ θ ζ κ (Π, ζ κ , b)dν+
                                                                  Ω
                                                                 Z
            Proof. Suppose to the contrary that (¯σ, ¯ω)̸=         ξ(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)λ θ ϱ (Π, ζ κ , b)dν  (21)
                                                                               ¯
                                                                          ¯
                                                                                       ¯ T
                                                                                            ¯ ¯ ¯
                                          ¯
             ¯
                            ¯
                                   ¯
            (ζ, ¯ϱ).  Since (ζ, ¯ϱ, ¯χ, λ, ¯τ, ¯ a, b, ¯µ) is a robust  Ω
            weak efficient solution of (WD), therefore by us-  and
            ing equation (10), (11) and multiplying them by
                        ¯
                                             ¯
                                                   ¯
                   ¯
            η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) and ξ(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ),  Z  Z
                                                                                             ¯ ¯
                                                                     T
                                                                                         T
                                                                         ¯
            respectively, adding them and thereafter integrat-      ¯ τ β(Λ, ¯σ κ , ¯µ)dν −  ¯ τ β(Π, ζ κ , ¯µ)dν ≧
            ing, we obtain                                         Ω                   Ω
                                                                  Z
                                                                                              ¯ ¯
                                                                                          T
                                                                                 ¯
                                                                           ¯
                                                                     η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)¯τ β ζ (Π, ζ κ , ¯µ)dν

                  Z
                                                                   Ω
                                 ¯
                           ¯
                                           T
                                                 ¯

                     η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ) ¯χ Ψ ζ Π, ¯ a  Z
                                                                                  ¯
                                                                                                ¯ ¯
                                                                                           T
                                                                             ¯
                   Ω                                           +   D κ η(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)¯τ β ζ κ (Π, ζ κ , ¯µ)dν+
                                           ¯ ¯
                            ¯ ¯ ¯
                                       T
                      ¯ T
                    +λ θ ζ (Π, ζ κ , b)+ ¯τ β ζ (Π, ζ κ , ¯µ)   Z Ω
                                                                   ξ(t, ¯σ, ζ, ¯σ κ , ζ κ , ¯ω, ¯ϱ)¯τ β ϱ (Π, ζ κ , ¯µ)dν. (22)
                                                    !                    ¯     ¯       T    ¯ ¯
                    h                              i
                                           ¯ ¯
                     ¯ T   ¯ ¯ ¯      T   (Π, ζ κ , ¯µ)  dν      Ω
               −D κ λ θ ζ κ  (Π, ζ κ , b)+ ¯τ β ζ κ
                                                              Adding the inequalities (20)−(22),
                                                           131
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