===firstname: Elizabeth ===firstname3: Martin ===affil6: ===lastname3: Grepl ===email: elizqian@mit.edu ===keyword_other2: ===lastname6: ===affil5: MIT ===lastname4: Veroy ===lastname7: ===affil7: ===postal: 77 Massachusetts Avenue Room 37-312 Cambridge, MA 02139 ===ABSTRACT: Parameter optimization problems constrained by partial differential equations (PDEs) appear in many science and engineering applications. Solving these optimization problems may require a prohibitively large number of computationally expensive PDE solves, especially if there are many variable parameters. It is therefore advantageous to replace expensive high-dimensional PDE solvers (e.g.\ finite element) with lower-dimension surrogate models. In this paper, we use the reduced basis (RB) model reduction method in conjunction with a trust region optimization framework to accelerate PDE-constrained parameter optimization. New \emph{a posteriori }error bounds on the RB cost and cost gradient for quadratic cost functionals are presented, and used to guarantee convergence to the optimum of the high-fidelity model. The proposed certified RB trust region approach thus requires only a minimal number of high-order solves, used to update the RB model if the approximation is no longer sufficiently accurate. We consider problems governed by elliptic PDEs and present numerical results for a thermal fin model problem with six parameters. ===affil3: RWTH Aachen University, Germany ===title: A Certified Reduced Basis Approach to PDE-constrained Parameter Optimization with Quadratic Cost Functionals ===affil2: RWTH Aachen University, Germany ===lastname2: Qian ===firstname4: Karen ===keyword1: Optimization of Complex Problems/Systems ===workshop: no ===lastname: Qian ===firstname5: Karen ===keyword2: Surrogate modeling/model reduction ===otherauths: ===affil4: RWTH Aachen University, Germany ===competition: yes ===firstname7: ===firstname6: ===keyword_other1: ===lastname5: Willcox ===affilother: ===firstname2: Elizabeth