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Weak Dirichlet solutions for a divergence-form operator
Definition
Assume Countable Choice (The Axiom of Countable Choice ()), and let and its form be as in Uniformly elliptic divergence-form operators and their sesquilinear forms on an open set . Homogeneous problem. Given (The negative Sobolev space ), a weak solution of with zero boundary values is a class (Zero-boundary Sobolev space as a norm closure, Integer-order Sobolev spaces and their norms) with Inhomogeneous problem. Additionally assume the Axiom of Choice (The Axiom of Choice) for the trace supplier, and let and be a bounded domain (Bounded C^k domains and boundary charts), let in the boundary scale of The fractional Sobolev space on a compact boundary and let be the trace operator of The trace operator on a bounded domain. A weak solution with boundary data is a class with and for every . The defining identities are identities between functionals on the classes, so they are independent of the chosen almost-everywhere representatives of , of the coefficients and of the data (Weak differentiation ignores null-set changes, Complex Lp classes and Euclidean test-function conventions); the boundary condition is imposed through the trace of The trace operator on a bounded domain, never by pointwise evaluation. The Dirichlet condition is imposed by in the homogeneous problem and by in the inhomogeneous problem; testing against expresses the weak equation and does not by itself impose boundary data; the integrals are the ones proved absolutely convergent in The elliptic form is well defined and bounded on .
Depends on
- The Axiom of Choice
- Bounded C^k domains and boundary charts
- Complex Lp classes and Euclidean test-function conventions
- The Axiom of Countable Choice ($\mathrm{AC}_\omega$)
- The fractional Sobolev space on a compact $C^1$ boundary
- The negative Sobolev space $H^{-1}(\Omega)$
- Integer-order Sobolev spaces and their norms
- Uniformly elliptic divergence-form operators and their sesquilinear forms
- Zero-boundary Sobolev space as a norm closure
- Weak differentiation ignores null-set changes
- The $L^p$ trace operator on a bounded $C^1$ domain
Used by
- Minimisers are classical when elliptic regularity applies Corollary
- Smooth coefficients and boundary make elliptic eigenfunctions smooth Corollary
- Smooth weak Dirichlet solutions are classical Corollary
- The global H² estimate without the L² term under uniqueness Corollary
- The inhomogeneous weak Dirichlet problem by a trace lifting Corollary
- Weak comparison and uniqueness for the Dirichlet problem Corollary
- Weak solutions depend continuously on the data Corollary
- Boundary H² regularity needs domain regularity Counterexample
- Boundary W^2,p regularity needs more than Lipschitz boundary Counterexample
- Elliptic Fredholm solvability can fail at an eigenvalue Counterexample
- Smooth interior data do not repair incompatible Dirichlet corner values Counterexample
- The H² estimate needs the L² kernel term without injectivity Counterexample
- The weak maximum principle needs the zero-order sign condition Counterexample
- Local weak solutions of a divergence-form operator Definition
- The formal adjoint and the adjoint weak Dirichlet problem Definition
- The L² operator associated with a symmetric elliptic form Definition
- Weak subsolutions and supersolutions of a divergence-form equation Definition
- A nonsymmetric coercive elliptic form Example
- Poisson's equation with L² data gains two interior derivatives Example
- Classical solutions satisfy the weak formulation Lemma
- On bounded domains, the unshifted equation is an identity-minus-compact equation Lemma
- Testing a coercive weak solution with itself gives the energy bound Lemma
- Regularity estimates do not create boundary compatibility Remark
- De Giorgi local boundedness with a scale-correct forcing term Theorem
- Existence and uniqueness for the weak Dirichlet Poisson problem Theorem
- Global H² Dirichlet regularity Theorem
- Higher-order boundary regularity for Dirichlet problems Theorem
- Lax--Milgram solvability for coercive divergence-form equations Theorem
- Spectral series solution of an invertible symmetric elliptic problem Theorem
- The Dirichlet principle for the Poisson equation Theorem
- The Fredholm alternative for weak elliptic Dirichlet problems Theorem
- Weak global W^2,p regularity for the Dirichlet Laplacian Theorem
- Weak Harnack inequality for nonnegative supersolutions Theorem
Dependency tree · two levels
59 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
- John K. Hunter, Notes on Partial Differential Equations (UC Davis, revised 18 June 2014, complete 242-page two-quarter notes) (standard reference, not scraped)
- John K. Hunter, Notes on Partial Differential Equations (UC Davis, revised 18 June 2014, complete 242-page two-quarter notes) (standard reference, not scraped)
- Richard S. Laugesen, Linear Analysis and Partial Differential Equations (University of Illinois, 2020, complete 158-page graduate notes) (standard reference, not scraped)
- Haim Brezis, Functional Analysis, Sobolev Spaces and Partial Differential Equations (Springer Universitext, 2011, complete 614-page text) (standard reference, not scraped)
- Gerald Teschl, Partial Differential Equations: From Classical to Modern (archived 2025 author manuscript) (standard reference, not scraped)