Functional Analysis Functional analysis 85 Mathematics 72 Differential equations, Partial 24 Partial Differential Equations 24 Operator Theory 23 Operator theory 23 Mathematical physics 16 Probabilities 15 Probability Theory and Stochastic Processes 15 Harmonic analysis 14 MATHEMATICS 12 Abstract Harmonic Analysis 11 Mathematical Physics 11 Physics 11 Fourier Analysis 10 Approximation theory 9 Approximations and Expansions 9 Mathematical Methods in Physics 9 Applied mathematics 8 Differential equations 8 Engineering mathematics 8 Functions of complex variables 8 Ordinary Differential Equations 8 Calculus, Operational 7 Dynamical Systems and Ergodic Theory 7 Dynamics 7 Ergodic theory 7 Fourier analysis 7 Integral Transforms, Operational Calculus 7