Perturbation (Mathematics) Differential equations 3 Numerical solutions 2 Asymptotic theory 1 Boundary value problems 1 Differential equations, Linear 1 Differential equations, Partial 1 Equations 1 Linear operators 1 Markov processes 1 Mathematical optimization 1 Matrices 1 Operator theory 1 Regression analysis 1 Resolvents (Mathematics) 1 Spectral theory (Mathematics) 1 Stability 1