Introductory Linear Functional Analysis
2026 Edition - DU - B.Sc. (H) Mathematics - VII Semester

This is a foundational textbook designed to introduce students to the core ideas and techniques of linear analysis with clarity and mathematical rigour. The text bridges the gap between elementary linear algebra and advanced functional analysis, making it suitable for advanced undergraduates and beginning graduates in mathematics, physics and engineering. The book is designed to serve as one-semester course text in linear functional analysis. It will also be valuable to research scholars, faculties of university, colleges and various engineering institutes as well as professionals who wish to acquire a solid foundation in functional analysis and its applications. It will help the readers, familiar with finite-dimensional concepts to move towards rich and subtle theory of normed and inner product spaces, bounded linear operators and fundamental theorems that govern them. The concepts of normed linear spaces and inner product spaces are discussed emphasising geometric intuition alongside formal proofs. Key topics such as Banach and Hilbert spaces are explained, followed by a systematic study of bounded linear operators, dual spaces and continuous linear functionals. Important theorems like Hahn-Banach theorem, the open mapping theorem, the uniform boundedness principle and the closed graph theorem are presented with detailed proofs and illustrative examples. The theory is reinforced by several examples and exercises. All exercises have been solved at the end of the book. Special attention is given to operators on Hilbert spaces including self-adjoint, unitary and normal operators as well as projections and spectral ideas. The book also serves as a solid foundation for further study and research in functional analysis, operator theory, harmonic analysis and related fields.