Foundations of advanced analysis · Graduate course · Staged public deployment

Measure Theory and Integration

Size, integration, and limits, made rigorous.

Measure theory is the rigorous foundation of modern analysis, probability, and functional analysis. Beginning from countable set operations and the axioms of sigma-algebras and measures, this course constructs Lebesgue measure through the Caratheodory extension, builds the Lebesgue integral and its convergence theorems, develops product measures, differentiation, and signed measures, proves the Radon-Nikodym theorem and Lp duality, and closes with the probability and Fourier structures that measure theory makes possible.

14Chapters
56Visual investigations
420Exercises with detailed corrections
GraduateLevel
Chapter 1 is free now. All 14 chapters are built. Chapters 2 through 14 will be released progressively as public deployment continues.
xf∫ f dμ = sup ∫ s dμsimple s ↑ f

Where this course sits

Real Analysis→General Topology→Measure Theory→Distribution Theory→Probability & Functional Analysis

What you will master

Three capabilities the course builds

I
Measure what length cannot

Assign a rigorous notion of size to sets far beyond intervals, and understand exactly which sets can and cannot be measured.

II
Integrate and pass to the limit

Build the Lebesgue integral from simple functions and wield the monotone convergence, Fatou, and dominated convergence theorems with confidence.

III
Open the door to probability

Prove Radon-Nikodym and Lp duality, then read probability, densities, and Fourier analysis as measure theory in disguise.

The syllabus

Fourteen chapters, built in sequence

Each chapter opens with visual investigations, states every definition and theorem with complete proofs, and closes with thirty exercises, each carrying three progressive hints and a full correction.

Chapter 01
Foundations for Measure Theory

Set operations, indexed families, inverse images, countability, and the limsup and liminf of sets. Extended real numbers, indicator functions, and the proof techniques on which measurable structures rest.

Countabilitylimsup / liminfExtended reals
Free · Open chapter
Chapter 02
Sigma-Algebras and Measurable Spaces

Algebras and sigma-algebras of sets, generated sigma-algebras, and the Borel sigma-algebra. Trace, initial, and final measurable structures, and measurable spaces as information structures.

Sigma-algebrasBorel setsGeneration
Built · Not yet released
Chapter 03
Measures and Their Fundamental Properties

Finite, sigma-finite, probability, counting, and Dirac measures. Continuity from below and above, subadditivity, null sets, completeness, and the completion of a measure space.

ContinuityNull setsCompletion
Built · Not yet released
Chapter 04
Outer Measures and the Caratheodory Construction

Outer measures and Caratheodory measurability, Caratheodory's theorem, the construction of measures from premeasures, extension principles, and uniqueness under sigma-finiteness.

Outer measureCaratheodoryExtension
Built · Not yet released
Chapter 05
Lebesgue Measure on Euclidean Space

Intervals, length, area, and volume. Lebesgue outer measure and measurable sets, translation invariance, scaling, regularity, Borel versus Lebesgue sets, null sets, and Cantor-type examples.

Lebesgue measureRegularityCantor set
Built · Not yet released
Chapter 06
Measurable Functions

Equivalent characterizations of measurability, extended-real-valued functions, operations preserving measurability, pointwise limits, simple functions, positive and negative parts, and almost-everywhere equivalence.

PreimagesSimple functionsa.e. equivalence
Built · Not yet released
Chapter 07
Integration of Nonnegative Functions

Integrals of simple functions, approximation by increasing simple functions, the Lebesgue integral of nonnegative functions, monotonicity, additivity, Fatou's lemma, and the monotone convergence theorem.

MCTFatouSimple approx.
Built · Not yet released
Chapter 08
Product Measures

Product sigma-algebras and measurable rectangles, measurability of sections, the product measure, and the theorems of Tonelli and Fubini, with the counterexamples that show why sigma-finiteness and integrability are required.

TonelliFubiniSections
Built · Not yet released
Chapter 09
Differentiation

The Vitali covering lemma and the Hardy-Littlewood maximal function, the Lebesgue differentiation theorem, bounded variation, absolute continuity, and the fundamental theorem of calculus for the Lebesgue integral.

Lebesgue diff.Bounded variationAbsolute continuity
Built · Not yet released
Chapter 10
Signed Measures

Signed measures, positive and negative sets, the Hahn and Jordan decompositions, total variation, mutual singularity, and integration with respect to signed and complex measures.

HahnJordanTotal variation
Built · Not yet released
Chapter 11
Radon-Nikodym

Absolute continuity and singularity of measures, the Radon-Nikodym theorem and derivative, the Lebesgue decomposition, change of measure, and applications to probability densities.

Radon-NikodymLebesgue decomp.Density
Built · Not yet released
Chapter 12
Modes of Convergence

Pointwise, almost-everywhere, in-measure, Lp, and uniform convergence; Egorov and Lusin; the Riesz subsequence theorem; uniform integrability and the Vitali convergence theorem; and counterexamples separating each mode.

EgorovLusinIn measure
Built · Not yet released
Chapter 13
Lp Duality

Holder duality and the Riesz representation of the dual of Lp via Radon-Nikodym, weak convergence, L2 as a Hilbert space, and conditional expectation as an orthogonal projection with Jensen's inequality.

DualityWeak convergenceConditional exp.
Built · Not yet released
Chapter 14
Probability and Fourier

Probability spaces and random variables as measurable functions, expectation as a Lebesgue integral, independence via product measures, the Borel-Cantelli lemmas, and L2 Fourier series with Parseval's identity.

ProbabilityBorel-CantelliParseval
Built · Not yet released
Visual first

Four premium investigations per chapter, on light crisp backgrounds.

Complete proofs

Every theorem stated with all hypotheses and proved in full.

Guided practice

Thirty exercises per chapter with three hints and a full correction each.

Bilingual

Full English and French presentation sharing one mathematical corpus.