Functional Analysis can mean different things, depending on who you ask. The core of the subject, however, is to study linear spaces with some topology which allows us to do analysis; ones like spaces of functions, spaces of operators acting on the space of functions, etc. Our interest in those spaces is twofold: those linear spaces with topology (i) often exhibit interesting properties that are worth investigating for their own sake, and (ii) have important application in other areas of mathematics (e.g., partial differential equations) as well as theoretical physics; in particular, quantum mechanics. (i) arises because linear vectors spaces that are of interest to analysts are infinitedimensional in nature, and this requires careful investigation of geometry. (More on this in Chapter 2 and 4.) (ii) was what initially motivated the development of the field; Functional Analysis has its historical roots in linear algebra and the mathematical formulation of quantum mechanics in the early 20 century. (See w:Mathematical formulation of quantum mechanics) The book aims to cover these two interests simultaneously.
The book consists of two parts. The first part covers the basics of Banach spaces theory with the emphasis on its applications. The second part covers topological vector spaces, especially locally convex ones, generalization of Banach spaces. In both parts, we give principal results e.g., the closed graph theorem, resulting in some repetition. One reason for doing this organization is that one often only needs a Banachversion of such results. Another reason is that this approach seems more pedagogically sound; the statement of the results in their full generality may obscure its simplicity. Exercises are meant to be an unintegrated part of the book. They can be skipped altogether, and the book should be fully read and understood. Some alternative proofs and additional results are relegated as exercises when their inclusion may disrupt the flow of the exposition.
Knowledge of measure theory will not be needed except for Chapter 6, where we formulate the spectrum theorem in the language of measure theory. As for topology, knowledge of metric spaces suffices for Chapter 1 and Chapter 2. The solid background in general topology is required for the ensuing chapters.
ContentsEdit
Part 1:
 Chapter 1. Preliminaries
 Zorn's lemma, Topology, Hamel basis, HahnBanach theorem
 Chapter 2. Banach spaces
 Open mapping theorem, closed graph theorem, compact operators
 Chapter 3. Hilbert spaces
 Unbounded operators, adjoint operators, orthonormal basis, Parseval theorem
 Chapter 4. Geometry of Banach spaces
 Reflexive spaces, KreinMilman theorem, Bishop's theorem, Separable Banach spaces, Schauder basis, James' theorem, uniformly convex spaces, monotonic operators, strictly singular operators
Part 2:
 Chapter 5. Topological vector spaces
 Locally convex spaces, metrization theorem
 Chapter 6. C*algebras
 Gelfand transformation, Spectrum of a commutative Banach algebra, Functional calculus, GNS construction
 Chapter 7. Integration theory
 von Neumann double centralizer theorem
Part 3:
 Chapter 8. Special topics

 Fredholm theory  Index of a bounded and unbounded operator, compact perturbation
 Representations of compact groups  Unitary representation, Peter–Weyl theorem
 Sobolev spaces