Self-adjoint spectral measures and functional calculus
Research context
postgraduate concept · established · As of 2026-10-10
A self-adjoint operator has a projection-valued spectral measure E on R and can be represented as an integral of lambda dE(lambda).
Key knowledge
A self-adjoint operator has a projection-valued spectral measure E on R and can be represented as an integral of lambda dE(lambda). Its domain consists of vectors with finite integral lambda² d<x,E(lambda)x>. A continuous spectrum need not have normalizable eigenvectors spanning H; the multiplication operator x on L2(R) illustrates why a finite-matrix eigenbasis statement does not extend unchanged.
Values and equations
T=integral_R lambda dE(lambda); D(T)={x:integral lambda² d<x,E(lambda)x><infinity}
- E
- Projection-valued spectral measure
- lambda
- Real spectral parameter
- x
- Hilbert-space vector
Conditions and scope
- The operator is self-adjoint, including its domain; arbitrary symmetric operators do not have this conclusion.
- The spectral integral for an unbounded function is defined only on its specified domain.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
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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- research-math-spectral-measures
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- Postgraduate & research reference