TY - JOUR ID - Majewski2023 LB - Majewski2023 AU - Majewski, Marek TI - On the existence of optimal solutions to the Lagrange problem governed by a nonlinear Goursat-Darboux problem of fractional order ST - On the existence of optimal solutions to the Lagrange problem governed by a nonlinear Goursat-Darboux problem of fractional order JO - Opuscula Math. JA - Opuscula Math. JF - Opuscula Mathematica PY - 2023 VL - 43 IS - 4 SP - 547 EP - 558 DO - https://doi.org/10.7494/OpMath.2023.43.4.547 UR - https://doi.org/10.7494/OpMath.2023.43.4.547 AB - In the paper, the Lagrange problem given by a fractional boundary problem with partial derivatives is considered. The main result is the existence of optimal solutions based on the convexity assumption of a certain set. The proof is based on the lower closure theorem and the appropriate implicit measurable function theorem. KW - fractional partial derivative KW - fractional boundary problem KW - existence of optimal solutions KW - Lagrange problem KW - lower closure theorem SN - 1232-9274 ER -