Gelfand Theory and Commutative C Star Algebras
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1 · Prerequisites
Abstract Algebra
- Binary Operations, Monoids, Groups and Subgroups
- Cosets, Index and Lagrange's Theorem
- Divisibility, Euclidean Domains, Principal Ideal Domains and Unique Factorisation
- Ideals, Quotient Rings and the Isomorphism Theorems for Rings
- Normal Subgroups and Quotient Groups
- Polynomial Rings, the Division Algorithm and Roots
- Rings, Subrings, Integral Domains and Fields
- Simple Field Extensions and the Construction of the Complex Numbers
Complex Analysis
- Analyticity of Holomorphic Functions; Liouville and Morera
- Complex Coordinate and Path Transport
- Complex Differentiability and the Cauchy–Riemann Equations
- Complex Power Series and Analytic Functions
- Contour Integration
- Goursat's Theorem and Cauchy's Theorem in a Convex Domain
- The Identity Theorem, the Maximum Principle and the Open Mapping Theorem
Functional Analysis
- Banach Alaoglu Goldstine and Krein Milman
- Banach Algebras Spectrum and Holomorphic Functional Calculus
- Banach Valued Integration and the Radon Nikodym Property
- Bounded Linear Operators and Quotient Spaces
- Complex Norms and Realification
- Complex Subspace Realification
- Dual Spaces Adjoint Operators and Annihilators
- Locally Convex Spaces and Continuous Separation
- Normed and Banach Spaces
- The Analytic Hahn Banach Theorem
Linear Algebra
- Complexification, Realification and Real Structures
- Dual Spaces, Bilinear and Quadratic Forms, and Sylvester's Law of Inertia
- Linear Independence, Bases and Dimension
- Linear Transformations, Rank-Nullity and Quotient Spaces
- Matrices, the Matrix of a Linear Map, and Change of Basis
- Triangularisation, Generalised Eigenspaces and Jordan Canonical Form
- Vector Spaces, Linear Subspaces, Span and Direct Sums
Measure Theory
- Measurable Functions and Simple Approximation
- Measures and Their Basic Properties
- Outer Measure and the Caratheodory Extension Theorem
- Pointwise Extended-Real Function Products
- Radon Measures and the Riesz Markov Kakutani Theorem
- Sigma Algebras and Borel Sets
- Signed and Complex Measures Hahn and Jordan
- The Lebesgue Integral and the Convergence Theorems
Real Analysis
- Absolute and Conditional Convergence; Rearrangement; Products
- Approximation and Compactness in C(K)
- Arc Length and Rectifiable Curves
- Bounded Variation and the Riemann–Stieltjes Integral
- Construction of the Real Numbers via Cauchy Sequences
- Construction of the Real Numbers via Dedekind Cuts
- Continuity, IVT, EVT, and Uniform Continuity
- Countability and Uncountability
- Foundations of the Real Numbers for Analysis
- Fundamental Trigonometric Identities
- Limits of Real Functions
- limsup, liminf, and Subsequential Limits
- Line Integrals and the Gradient Theorem
- Mixed Partials, Taylor Formulae, and Extrema
- Monotone Functions, Discontinuities, and Continuity Sets
- Monotone Sequences, Bolzano-Weierstrass, and Cauchy Completeness
- pi: the Equivalent Characterizations
- Power Series and Real-Analytic Functions
- Properties of the Integral and the Working FTC
- Rⁿ as a Normed Space; Vector-Valued Functions
- Roots, Rational Powers, and Classical Inequalities
- Sequences and Limits
- Sequences and Series of Functions; Uniform Convergence
- Series: Convergence and the Nonnegative Tests
- Sine, Cosine, and the Definition of Pi
- Suprema and Infima
- The Cantor Set, Baire Category, and Measure Zero in ℝ
- The Complex Exponential and Euler's Formula
- The Derivative and the Mean Value Theorems
- The Exponential Function
- The Fundamental Theorems of Calculus
- The Inverse and Implicit Function Theorems
- The Logarithm and General Powers
- The Riemann Integral: Definition and Integrability
- The Total Derivative in ℝᵐ → ℝⁿ
- Topology of ℝ
Set Theory
Topology
- Compactness
- Compactness in Metric Spaces
- Completeness, Completion, and Uniform Continuity
- Connectedness
- Convergence: Nets and Filters
- Function Space Topologies and the Exponential Law
- Hausdorff via the Diagonal
- Hereditary and Productive Behaviour of the Separation Axioms
- Metric Spaces
- Partitions of Unity and Paracompactness
- Separation Axioms: the Hierarchy
- Stone–Weierstrass in General
- Subspaces, Products, and Quotients
- The Topology of Euclidean Space
- The Tychonoff Embedding and the Stone–Čech Compactification
- Topological Spaces and Continuity
- Urysohn's Lemma and the Tietze Extension Theorem
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
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Chapter 3 §3.1 and §3.3, printed pp. 54–69 and 80–87
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Chapter 5 §5.5, printed pp. 258–267
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Theorem 3.1.11 proof and Proposition 3.1.12(i), printed pp. 54–61
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Chapter 5 §5.5.1, printed pp. 258–262
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Proposition 3.1.4, printed pp. 54–57
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Theorem 5.58 and §5.5.1, printed pp. 258–262
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Propositions 3.1.4, 3.1.7, 3.1.9, printed pp. 54–61
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Theorem 5.58, printed pp. 258–262
- Dana P. Williams, Lecture Notes on the Spectral Theorem — Theorem 3.1, printed pp. 7–8
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Corollary 3.1.8 and §3.1, printed pp. 54–61
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Theorem 5.63, printed pp. 262–266
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Proposition 3.1.12 and Remark 3.1.13, printed pp. 60–61
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Lemmas 5.61–5.62, printed pp. 262–265
- Dana P. Williams, Lecture Notes on the Spectral Theorem — Theorem 3.6, printed pp. 8–9
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Definition 3.1.17, printed pp. 61–62
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Definition 5.59 and §5.5.1, printed pp. 259–262
- Dana P. Williams, Lecture Notes on the Spectral Theorem — Definition 3.2 and §3, printed pp. 7–9
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Theorem 3.1.18, printed p. 62
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Definition 3.1.23 and Remark 3.1.24, printed pp. 62–63
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Theorem 5.63 and §5.5.1, printed pp. 262–266
- Dana P. Williams, Lecture Notes on the Spectral Theorem — Remark 3.7, printed p. 9
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Definitions 2.1.1, 2.1.18 and §3.1, printed pp. 11–13 and 54–61
- Dana P. Williams, Lecture Notes on the Spectral Theorem — Definitions 3.8 and 4.1, printed pp. 8–9
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Definition 3.1.27 and Remark 3.1.28, printed pp. 63–64
- Dana P. Williams, Lecture Notes on the Spectral Theorem — §4 and Theorem 4.5, printed pp. 9–11
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Lemma 3.1.30 and Proposition 3.1.32, printed pp. 64–65
- Dana P. Williams, Lecture Notes on the Spectral Theorem — §4, printed pp. 9–11
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Proposition 3.1.31, printed p. 64
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — §5.5.1, printed pp. 258–262
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Corollary 3.1.33 and Theorem 3.1.34 (unital case), printed pp. 65–66
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — Theorem 5.64, printed pp. 266–267
- Dana P. Williams, Lecture Notes on the Spectral Theorem — Theorem 4.5, printed pp. 10–11
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Remark 3.1.36 and §3.1, printed pp. 54–67
- Dana P. Williams, Lecture Notes on the Spectral Theorem — Example 4.3, printed p. 9
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Theorem 3.3.5 and Corollary 3.3.6 (compact case), printed pp. 80–81
- Marcus Tressl, Stone Duality for Boolean Algebras — §4, pp. 16–17 (naturality template)
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Lemma 3.1.10 (rescaled to a non-strict growth bound), printed pp. 58–59
- Theo Bühler and Dietmar A. Salamon, Functional Analysis — §5.5.1, printed pp. 258–267
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Theorem 3.1.11, printed pp. 59–61
- Orr Shalit, Advanced Analysis Notes 14: the isometric structure of C(K) — Theorem 2 and Exercises B–C, HTML lines 38–54; the extreme-point proof is stated as an exercise and is supplied locally
- Orr Shalit, Advanced Analysis Notes 14: the isometric structure of C(K) — Theorem 2 and Exercises B–C, HTML lines 38–54; the adjoint and extreme-point inputs are supplied locally
- L. Gillman, M. Henriksen and M. Jerison, On a Theorem of Gelfand and Kolmogoroff Concerning Maximal Ideals in Rings of Continuous Functions (1954) — §1, pp. 447–448. This endpoint was inaccessible in the current run; the exact local alternative and failed recovery record are in the Batch 4 coverage ledger.
- L. Gillman, M. Henriksen and M. Jerison, On a Theorem of Gelfand and Kolmogoroff Concerning Maximal Ideals in Rings of Continuous Functions (1954) — §2, Theorem 1 proof, pp. 448–449. This endpoint was inaccessible in the current run; the complete local alternative and failed recovery record are in the Batch 4 coverage ledger.
- L. Gillman, M. Henriksen and M. Jerison, On a Theorem of Gelfand and Kolmogoroff Concerning Maximal Ideals in Rings of Continuous Functions (1954) — §2, Theorem 1 and fixed-ideal consequences, pp. 448–449. This endpoint was inaccessible in the current run; the exact local proof and failed recovery record are in the Batch 4 coverage ledger.
- Marcus Tressl, Stone Duality for Boolean Algebras — Definition 2.2.13, Observation 2.2.14, Definition 2.3.1 and Characterization 2.3.3, pp. 7–9
- Marcus Tressl, Stone Duality for Boolean Algebras — Definitions 3.1.1 and 3.1.3, Remark 3.1.2(i), pp. 10–11
- Marcus Tressl, Stone Duality for Boolean Algebras — Proposition 2.2.10 and Corollary 2.2.11, pp. 7–8
- Marcus Tressl, Stone Duality for Boolean Algebras — Theorem 2.3.4, pp. 9–10; Proposition 3.2.4 and Theorem 3.2.5, pp. 11–12
- Marcus Tressl, Stone Duality for Boolean Algebras — Theorem 3.1.6, p. 12; Lemma 4.1, Definitions 4.2–4.3, p. 16; Theorem 4.4, pp. 16–17
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Definition 2.1.18 and Proposition 2.1.15, printed pp. 11–13
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Proposition 2.1.15 and Definition 2.1.18, printed pp. 11–13
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Exercise 3.1.15 and Lemma 3.1.20, printed pp. 60–62
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Theorem 3.1.34 and Proposition 3.1.35, printed pp. 65–66
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Definition 3.1.38 and Example 3.1.39, printed pp. 66–67
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Example 3.1.39 and §3.1, printed pp. 66–67
- Vahid Shirbisheh, Lectures on C-star Algebras, v2 — Theorem 3.3.5 and Corollary 3.3.6, printed pp. 80–81; Propositions 5.1.40–5.1.42, printed pp. 66–68