Variational ground-energy bound
For a self-adjoint Hamiltonian bounded below, every normalized trial state with a finite energy expectation satisfies ⟨ψ_trial|H|ψ_trial⟩≥E₀.
Key knowledge
For a self-adjoint Hamiltonian bounded below, every normalized trial state with a finite energy expectation satisfies ⟨ψ_trial|H|ψ_trial⟩≥E₀. Minimizing a chosen trial family's expectation provides an upper bound on the ground energy, not proof that the trial state is exact.
Values and equations
E_trial=⟨ψ_trial|H|ψ_trial⟩≥E₀
- E_trial,H,E₀
- Trial expectation, Hamiltonian and ground energy J
- ψ_trial
- Normalized trial state
Conditions and scope
- Trial state belongs to the appropriate operator or quadratic-form domain and satisfies physical boundary/particle-symmetry constraints.
- E₀ is the lowest spectral energy; unrestricted trial families or excited-state bounds require additional reasoning.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Quantum Mechanics (2010): Variational principle: Spectral expansion of a normalized trial and lower-energy inequality.
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Entry details
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