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Equation 1 · Part 3 · The Entry a Relabeling Cannot Write

Symbol H_B

Hf=HS⊗HB\mathcal H_f = \mathcal H_S \otimes \mathcal H_B
HBH_B

What this part means

HBH_B is an input to the expression that computes the quantity on the left.

Its job in the formula

HBH_B is an input to the expression that computes the quantity on the left.

The passage around this formula

Start with the setting the open-quantum-systems literature calls a fine description: a Hilbert space Hf\mathcal H_f = HS\mathcal H_S ⊗\otimes HB\mathcal H_B holding a system S and everything else, B , that a working physicist has decided not to track in detail — a resonant bath, an environment, a set of nuclear spins, whatever “everything else” means for the apparatus at hand. The fine Hamiltonian is

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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 article section

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