Unbounded operators: expression and domain
Research context
postgraduate concept · established · As of 2026-10-10
An unbounded operator is specified by a linear domain D(T) in a Hilbert space and a map T:D(T)→H.
Key knowledge
An unbounded operator is specified by a linear domain D(T) in a Hilbert space and a map T:D(T)→H. A densely defined operator has an adjoint with its own domain; symmetric means T is contained in T*, while self-adjoint means equality of operators and domains. For −d²/dx² on an interval, Dirichlet and Neumann domains yield different spectra even though the formal expression is identical.
Conditions and scope
- Adjoints require a dense domain; closedness refers to the graph in H×H.
- Boundary conditions belong to the domain, and symmetry alone does not prove self-adjointness.
Sources · 1
References
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Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: §§1–2 unbounded domains/adjoints, §§5–6 spectral measures, §11 deficiency indices/extensions. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
Entry details
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