Infinite-dimensional linear spaces, Banach and Hilbert spaces.
Geometry of Hilbert spaces, lemma of Riesz for Banach spaces.
Linear functionals, Hahn-Banach theorem, weak convergence, uniform boundedness principle.
Linear operators, open mapping theorem and closed graph theorem for Hilbert spaces.
Compact operators, Fredholm theory.
Spectral theory for compact self-adjoint operators and applications to ODEs.
Introduction to Sobolev spaces