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Equation 21 · Part 3 · The Entry a Relabeling Cannot Write

Symbol Lambda^dagger

DΛ:=Hf−Λ†(Hc).D_\Lambda := H_f - \Lambda^\dagger(H_c).
Λ†\Lambda^\dagger

What this part means

the define.

Its job in the formula

Lambdada^dagger is one of the signed contributions combined to compute the quantity on the left.

Where the article explains it

Define Λ†\Lambda^\dagger: B(Hc)\mathcal B(\mathcal H_c) →\to B(Hf)\mathcal B(\mathcal H_f) by the pairing that must hold for every fine state and every coarse observable OcO_c , Tr\mathrm{Tr}[\big[Λ(ρ)\Lambda(\rho)\,OcO_c]\big] = Tr\mathrm{Tr}[\big[ρ\rho\,Λ†(Oc)\Lambda^\dagger(O_c)]\big].

The passage around this formula

That pullback is the object this article is built around: DΛ:=Hf−Λ†(Hc)D_\Lambda := H_f - \Lambda^\dagger(H_c). DΛD_\Lambda is Hermitian on Hf\mathcal H_f — a positive, unital map applied to a self-adjoint input stays self-adjoint — and it carries units of energy, since both terms do. Its state-dependent reading,

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Learn the underlying idea

An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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Sources cited in the article section

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