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The polar surface set function on the unit sphere
Definition
Assume the Axiom of Countable Choice (The Axiom of Countable Choice ()). Fix and write Let This map is continuous. If is Borel, then is Borel and is Borel in by A continuous map has Borel preimages of Borel sets, hence Borel in by The Borel sigma-algebra of a subspace is the trace of the ambient Borel sigma-algebra. It is therefore Lebesgue measurable by Assuming countable choice, every Borel subset of is Lebesgue measurable. Define
The next theorem proves that this is a Borel measure on and that it is exactly the surface measure needed for polar coordinates.
Depends on
- The Borel product of R^m and R^n is the Borel sigma-algebra of R^{m+n}
- The Borel sigma-algebra of a subspace is the trace of the ambient Borel sigma-algebra
- Assuming countable choice, every Borel subset of $\mathbb{R}^n$ is Lebesgue measurable
- A continuous map has Borel preimages of Borel sets
- The Borel sigma-algebra of a topological space
- The Axiom of Countable Choice ($\mathrm{AC}_\omega$)
Used by
- Polar integration may discard the cut locus Corollary
- Morrey's inequality has no p=n endpoint Counterexample
- The fundamental Hessian is not absolutely locally integrable Counterexample
- Fourier restriction and adjoint extension operators Definition
- Fundamental solution for the positive operator minus Laplacian Definition
- Model space radial area and ball volume Definition
- Spherical averages and local ball means in Rn Definition
- Spherical means and the weighted ball integral of space-dependent data Definition
- Wave equation, Cauchy data and wave speed Definition
- A compact-support Cauchy–Pompeiu calculation Example
- A Dirac mass has precisely sufficiently negative Sobolev order Example
- An explicit ∂̄ solution with an L² estimate Example
- Bishop gromov ratio is constant in the model space Example
- Hörmander estimate with a Gaussian weight Example
- Newton shell theorem from harmonic mean values Example
- Projective-plane curvature via a hemisphere Example
- Radial powers approach the Morrey borderline exponent Example
- Sharp Sobolev threshold for a radial power Example
- Volume growth in euclidean and hyperbolic space Example
- Archimedean product region, volume and norm bound Lemma
- Ball-mean oscillation bound by the Riesz potential of the gradient Lemma
- Heat-ball representation formula Lemma
- Monomial integrals on the sphere and orthonormality on the distinguished torus Lemma
- Pointwise potential bound for compactly supported smooth functions Lemma
- Radial derivative of a spherical average Lemma
- Reflection invariance and vanishing first moment of the sphere measure Lemma
- Sphere graph charts, surface density, and a finite partition Lemma
- Sphere integrals of a cylindrical function project to weighted ball integrals Lemma
- The level-set kernel measure estimate for the Slobodeckij kernel Lemma
- The mean-value L² bound for holomorphic functions on a polydisc Lemma
- The truncated Riesz kernel is bounded on Lᵖ of a bounded set Lemma
- The unit sphere is Lebesgue null Lemma
- Weighted monomial integrals and monomial norms for the disc, ball and polydisc Lemma
- Bishop gromov volume comparison Theorem
- Calderon-Zygmund operators map L-infinity to BMO Theorem
- Polar coordinates decompose Lebesgue measure into rⁿ⁻¹ dr d sigma Theorem
- Strong parabolic maximum principle Theorem
- The critical Sobolev embedding into every finite L^q Theorem
Dependency tree · two levels
26 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
- Gerald B. Folland, Real Analysis, 2nd ed., Theorem 2.49 (standard reference, not scraped)