Functional Analysis 106 Functional analysis Mathematical optimization Calculus of Variations and Optimization 78 Calculus of variations 78 Differential Equations 43 Differential equations 43 Optimization 40 Mathematical analysis 22 Analysis 21 Operator Theory 21 Operator theory 21 Mathematical physics 13 System theory 13 Numerical Analysis 12 Numerical analysis 12 Applications of Mathematics 11 Mathematics 11 Control theory 10 Systems Theory, Control 10 Topology 10 Approximation theory 8 Approximations and Expansions 8 Convex and Discrete Geometry 8 Convex geometry  8 Discrete geometry 8 Mathematical Methods in Physics 8 Measure and Integration 8 Measure theory 8 Probabilities 7