The "Applications" part of the keyword is crucial. This mathematical rigour is applied in:
Linear functional analysis focuses on linear operators between normed spaces. Key concepts usually covered in a standard PDF or textbook include: The "Applications" part of the keyword is crucial
Linear and Nonlinear Functional Analysis with Applications: A Comprehensive Guide The "Applications" part of the keyword is crucial
Finding solutions by minimizing or maximizing functionals (the basis of the Calculus of Variations). The "Applications" part of the keyword is crucial
Using Sobolev spaces to find weak solutions to physical phenomena.