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Fundamental theorem of calculus for absolutely continuous functions
Statement
Assume the Axioms of Countable Choice and Dependent Choice. For , the following are equivalent:
- is absolutely continuous.
- exists almost everywhere, , and
Facts & Assumptions
Given: Countable choice, dependent choice, and a real function on the compact interval .
Proof
Assume (1). By Absolutely continuous functions have integrable derivatives, put a.e.; the first FTC The indefinite integral of an function is differentiable almost everywhere says a.e.
The corollary The indefinite integral of an function is absolutely continuous makes AC, so is AC and has derivative zero a.e. The zero-derivative theorem makes constant; , giving (2).
Conversely, (2) says , and the same corollary makes it AC. The singleton interval satisfies both clauses directly.
Depends on
- The Axiom of Countable Choice ($\mathrm{AC}_\omega$)
- The axiom of dependent choice: a relation in which every element is related to something admits an $\mathbb{N}$-indexed chain
- The indefinite integral of an $L^1$ function is absolutely continuous
- The indefinite integral of an $L^1$ function is differentiable almost everywhere
- Absolutely continuous functions have integrable derivatives
- An absolutely continuous function with zero derivative almost everywhere is constant
Used by
- One-dimensional W^1,p functions have unique absolutely continuous representatives Corollary
- A symmetric closed operator that is not self-adjoint Counterexample
- The composition of two absolutely continuous functions need not be absolutely continuous Counterexample
- x² sin(1/x²) is differentiable everywhere but not absolutely continuous Counterexample
- Convex entropy--entropy flux pairs Definition
- The ACL and Sobolev analytic definition of quasiconformality Definition
- A one-dimensional obstacle problem and its contact set Example
- An integral constraint and its constant multiplier Example
- Periodic derivative and its unitary translation group Example
- The Neumann Laplacian has a zero constant mode Example
- The weak Dirichlet Poisson problem on an interval Example
- ACL representatives recover their weak gradients by Fubini Lemma
- Analytic quasiconformality gives both quadrilateral modulus bounds Lemma
- Brownian step-potential resolvent at zero Lemma
- Caputo and Volterra formulations are equivalent for absolutely continuous solutions Lemma
- Chain rule for an indefinite integral after an absolutely continuous composition Lemma
- Compact subsets of lines and round circles are removable for quasiconformal maps Lemma
- Exterior finite-energy functions have a trace controlled by their gradient Lemma
- Green identity and Kirchhoff flux cancellation on a metric graph Lemma
- Integrated pressure recovery and MINI pressure-primitive convergence Lemma
- Sobolev pullback and Green identity on Lipschitz graphs Lemma
- Solutions of projected contact dynamics are unique under the inherited choice assumptions Lemma
- The inverse of a quasiconformal map is quasiconformal with the same dilatation Lemma
- The translation estimate for W^1,p functions on ℝⁿ Lemma
- Whole-space support and the zero-boundary Sobolev closure Lemma
- Sharp and classical fundamental theorems of calculus agree Remark
- A posteriori ODE error bound from the continuous residual Theorem
- A square-root global error bound for projected Euler with certified projection tolerances Theorem
- Alexandrov second differentiability of locally semiconvex functions Theorem
- Chain rule for globally Lipschitz scalar maps of Sobolev functions Theorem
- Change of variables for an absolutely continuous map under an absolutely continuous composition hypothesis Theorem
- Change of variables for an increasing absolutely continuous function Theorem
- Compactness of the normalized K-quasiconformal self-maps of the sphere Theorem
- Countably exceptional differentiability and integrable derivative imply absolute continuity Theorem
- Existence and uniqueness for projected dynamics and convergence of projection Euler under countable and dependent choice Theorem
- Finite-dimensional Gaussian isoperimetric expansion Theorem
- Gross logarithmic Sobolev inequality for standard Gaussian measure Theorem
- Higher-order Rellich--Kondrachov compactness Theorem
- Integration by parts for absolutely continuous functions Theorem
- Lipschitz characterisation within absolutely continuous functions Theorem
…and 11 more results.
Dependency tree · two levels
28 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Christopher Heil, Absolute Continuity and the Banach--Zaretsky Theorem, Theorem 23 (standard reference, not scraped)