Dr. Constantin Christof

Dr. Constantin Christof
Universität Duisburg-Essen
Thea-Leymann-Straße 9
D-45127 Essen
+49 201 183 6893
Email: constantin.christof[at]uni-due.de

Research Interests: Variational Inequalities, Optimal Control, Numerical Analysis, PDE-Constrained Optimization, Nonsmooth Optimization

Teaching in the Summer Semester 2025

  • Mathematical Imaging​, lectures and exercises
  • Practical course in numerical mathematics, case studies
  • Bachelor Seminar Mathematics

 

Publications

[28] Brokate, M., and C. Christof: Directional Differentiability for Solution Operators of Sweeping Processes with Convex Polyhedral Admissible Sets, submitted, 2025

[27] Christof, C.: Optimal Control of Semilinear Elliptic Partial Differential Equations with Non-Lipschitzian Nonlinearities, Mathematical Control and Related Fields, to appear, 2025

[26] Christof, C., and G. Wachsmuth: Energy Space Newton Differentiability for Solution Maps of Unilateral and Bilateral Obstacle Problems, SIAM Journal on Control and Optimization, Volume 63, Number 1, pp. 292-320, 2025

[25]  Alphonse, A., C.  Christof, M. Hintermüller, and I. Papadopoulos: A Globalized Inexact Semismooth Newton Method for Nonsmooth Fixed-point Equations involving Variational Inequalities, submitted, 2024

[24] Christof, C., and J. Kowalczyk: On the Identification and Optimization of Non-smooth Superposition Operators in Semilinear Elliptic PDEs, ESAIM: Control, Optimisation and Calculus of Variations, Volume 30, Article Number 16, 2024

[23] Ruiz, V.P., P. Hinsen, T. Wiedemann, D. Shutin, and C. Christof: Gas Source Localization Using Physics-Guided Neural Networks,  In: Proceedings of the 2024 IEEE International Symposium on Olfaction and Electronic Nose (ISOEN), Grapevine, Texas, pp. 1-3, 2024

[22] Brokate, M., and C. Christof: Strong Stationarity Conditions for Optimal Control Problems Governed by a Rate-Independent Evolution Variational Inequality, SIAM Journal on Control and Optimization, Volume 61, Number 4, pp. 2222-2250, 2023

[21] Christof, C., and J. Kowalczyk: On the Omnipresence of Spurious Local Minima in Certain Neural Network Training Problems, Constructive Approximation,  Volume 60, Number 2, pp. 197-224, 2023

[20] Christof, C., and G. Wachsmuth: Semismoothness for Solution Operators of Obstacle-Type Variational Inequalities with Applications in Optimal Control, SIAM Journal on Control and Optimization, Volume 61, Number 3, pp. 1162-1186, 2023

[19] Christof, C., and G. Wachsmuth: Lipschitz Stability and Hadamard Directional Differentiability for Elliptic and Parabolic Obstacle-Type Quasi-Variational Inequalities, SIAM Journal on Control and Optimization, Volume 60, Number 6, pp. 3430-3456, 2022

[18] Christof, C., and D. Hafemeyer: On the Nonuniqueness and Instability of Solutions of Tracking-Type Optimal Control Problems, Mathematical Control and Related Fields, Volume 12, Number 2, pp. 421-431, 2022

[17] Christof, C., C. Meyer, B. Schweizer, and S. Turek: Strong Stationarity for Optimal Control of Variational Inequalities of the Second Kind, In: M. Hintermüller, R. Herzog, C. Kanzow, M. Ulbrich, and S. Ulbrich (eds.), Non-Smooth and Complementarity-Based Distributed Parameter Systems, International Series of Numerical Mathematics, Volume 172, Birkhäuser, Cham, 2022

[16] Christof, C.: On the Stability Properties and the Optimization Landscape of Training Problems with Squared Loss for Neural Networks and General Nonlinear Conic Approximation Schemes, Journal of Machine Learning Research, Volume 22, Article Number 263, pp. 1-77, 2021

[15] Christof, C., and B. Vexler: New Regularity Results and Finite Element Error Estimates for a Class of Parabolic Optimal Control Problems with Pointwise State Constraints, ESAIM: Control, Optimisation and Calculus of Variations, Volume 27, Article Number 4, 2021

[14] Christof, C., and G. Müller: Multiobjective Optimal Control of a Non-Smooth Semilinear Elliptic Partial Differential Equation, ESAIM: Control, Optimisation and Calculus of Variations, Volume 27, Article Number S13, 2021

[13] Christof, C., and G. Wachsmuth: On Second-Order Optimality Conditions for Optimal Control Problems Governed by the Obstacle Problem, Optimization, Taylor & Francis, Volume 70, Number 10, pp. 2247-2287, 2021

[12]  Christof, C., C. Meyer, and J.C. De los Reyes: A Non-Smooth Trust Region Method for Locally Lipschitz Functions with Application to Optimization Problems Constrained by Variational Inequalities, SIAM Journal on Optimization, Volume 30, Number 3, pp. 2163-2196, 2020

[11] Christof, C., and C. Haubner: Finite Element Error Estimates in Non-Energy Norms for the Two-Dimensional Scalar Signorini Problem, Numerische Mathematik, Volume 145, pp. 513-551, 2020

[10] Christof, C.: Gradient-Based Solution Algorithms for a Class of Bilevel Optimization and Optimal Control Problems with a Non-Smooth Lower Level, SIAM Journal on Optimization, Volume 30, Number 1, pp. 290-318, 2020

[9] Christof, C., and G. Wachsmuth: Differential Sensitivity Analysis of Variational Inequalities with Locally Lipschitz Continuous Solution Operators, Applied Mathematics & Optimization, Volume 81, Issue 1, pp. 23-62, 2020

[8] Christof, C.: Sensitivity Analysis and Optimal Control of Obstacle-type Evolution Variational Inequalities, SIAM Journal on Control and Optimization, Volume 57, Number 1, pp. 192-218, 2019

[7] Christof, C., and C. Meyer: Sensitivity Analysis for a Class of H_0^1-Elliptic Variational Inequalities of the Second Kind, Set-Valued and Variational Analysis, Volume 27, Issue 2, pp. 469-502, 2018

[6] Christof, C., and G. Wachsmuth: No-Gap Second-Order Conditions via a Directional Curvature Functional, SIAM Journal on Optimization, Volume 28, Number 3, pp. 2097-2130, 2018

[5] Christof, C., and G. Wachsmuth: On the Non-Polyhedricity of Sets with Upper and Lower Bounds in Dual Spaces, GAMM-Mitteilungen, Volume 40, Issue 4, pp. 339-350, 2018 

[4] Christof, C., and G. Müller:  A Note on the Equivalence and the Boundary Behavior of a Class of Sobolev Capacities, GAMM-Mitteilungen, Volume 40, Issue 3, pp. 238-266, 2018

[3] Christof, C., C. Clason, C. Meyer, and S. Walther:  Optimal Control of a Non-Smooth Semilinear Elliptic Equation, Mathematical Control and Related Fields, Volume 8, Number 1, pp. 247-276, 2018

[2] Christof, C., and C. Meyer:  A Note on A Priori L^p-Error Estimates for the Obstacle Problem, Numerische Mathematik, Volume 139, pp. 27-45, 2018

[1]  Christof, C.:  L^\infty-Error Estimates for the Obstacle Problem Revisited, Calcolo, Volume 54, Issue 4, pp. 1243-1264, 2017