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Equation 132 · Part 3 · The Entry a Relabeling Cannot Write

subscript

ωr=0\omega_r = 0
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

the detuned Hamiltonian that governs spin precession in a frame rotating with an applied field — the identical construction I. I. Rabi used to analyze spin behavior in a gyrating magnetic field in 1937 [ 14 ] . Two checks confirm the recovery is exact rather than incidental: at ωr\omega_r = 0 , the non-rotating case, Δframe\Delta_{\rm frame} ≡\equiv 0 and HcH_c = HfH_f , the already-verified baseline; at ωr\omega_r = ω0\omega_0 , exact corotation, HcH_c = 0 and the spin’s energy in this frame vanishes identically, which is the ordinary resonance condition, not a puzzle, because Δframe\Delta_{\rm frame} = -ℏ\hbarω0\omega_0⟨\langleσz\sigma_z⟩\rangle/2 exactly cancels the lab-frame value for a state that starts, and stays,…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the surrounding passage

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