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Functional Analysis

Banach and Hilbert spaces, operators, spectral theory.

Lessons

Advanced Normed and Banach spaces Vector spaces with a length; completeness; the classical sequence and function spaces. sqrt(3^2 + 4^2) Advanced Hilbert spaces and the spectral theorem Inner products, orthonormal bases, Fourier series, and eigenvalues of operators. eigenvalues of [[2,1],[1,2]]

Linear algebra in infinitely many dimensions, where functions are the vectors. Quantum mechanics, PDEs and signal processing all live here; the spectral theorem is the eigenvalue story told for operators.

More lessons

Spaces of functions

Functional analysis Normed vector space Banach space Hilbert space Inner product space Complete metric space Sequence space Orthonormal basis Separable space

Operators

Bounded operator Linear map Dual space Compact operator Adjoint Self-adjoint operator Unitary operator Operator norm

The big theorems

Hahn–Banach theorem Open mapping theorem (functional analysis)Closed graph theorem Uniform boundedness principle Spectral theorem Riesz representation theorem Weak topology Banach fixed-point theorem

Fourier and applications

Fourier series Fourier transform Convolution Sobolev space Distribution (mathematics)

Some of these lessons are adapted from open texts: Wikipedia. Each lesson page names its source and licence.

Symbols used here

Tap any symbol for the full definition, a picture, and what every letter in it means.

Questions people ask

What is a Hilbert space?

A vector space with an inner product (so lengths and angles make sense) that is complete (no missing limit points). Square-integrable functions form one; quantum states live in one.

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