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Gelfand Theory and Commutative C Star Algebras

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1 · Prerequisites
Abstract Algebra
Combinatorics
Complex Analysis
Functional Analysis
Linear Algebra
Measure Theory
Real Analysis
Set Theory
Topology
2 · Logical flowchart

3 · Items

Definition

Character and maximal ideal space

Theorem

Characters on a unital Banach algebra are continuous

Lemma

Closed ideal quotient is a Banach algebra

Theorem

Maximal ideals and characters of a commutative Banach algebra

Theorem

Spectrum as character values

Theorem

Maximal ideal space is compact Hausdorff

Definition

Gelfand transform

Theorem

Gelfand transform is a contractive unital homomorphism

Definition

Jacobson radical and semisimple commutative Banach algebra

Theorem

Kernel of the Gelfand transform is the radical

Definition

C star algebra

Definition

Self-adjoint positive unitary and normal elements

Lemma

C star spectral radius equals norm for normal elements

Lemma

Characters on a unital commutative C star algebra preserve star

Theorem

Commutative Gelfand Naimark

Lemma

Characters of continuous functions are evaluations

Theorem

Commutative Gelfand duality

Lemma

Zero free entire function of exponential type is an exponential

Theorem

Gleason Kahane Zelazko

Lemma

Extreme points of the dual ball of C(K)

Theorem

Banach-Stone

Definition

Zero set filter and zero set ultrafilter

Lemma

Maximal ideals of C(X) and zero set ultrafilters

Lemma

Zero set ultrafilters and Stone-Cech points

Theorem

Gelfand-Kolmogorov for rings of continuous functions

Definition

Boolean algebra and Boolean ultrafilter

Definition

Stone space and clopen algebra

Lemma

Boolean ultrafilter extension

Theorem

Stone representation for Boolean algebras

Theorem

Stone duality

Definition

Algebraic unitization of a star algebra

Theorem

Minimal C star unitization

Theorem

Character space of the unitization is one-point compactification

Theorem

Nonunital commutative Gelfand Naimark

Definition

Approximate unit and proper C star morphism

Theorem

Every commutative C star algebra has an approximate unit

Theorem

Locally compact Gelfand duality

Sources