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Equation 7 · Part 4 · The Corner of the Equivalence Principle No Experiment Has Touched

Symbol hateta_coh

η^=ηcl+η^diag+η^coh+η^sup+η^ent\hat\eta = \eta_{cl} + \hat\eta_{diag} + \hat\eta_{coh} + \hat\eta_{sup} + \hat\eta_{ent}
η^coh\hat\eta_{coh}

What this part means

hatetaca_coh is one of the signed contributions combined to compute the quantity on the left.

Its job in the formula

hatetaca_coh is one of the signed contributions combined to compute the quantity on the left.

The passage around this formula

…basis: it can make a clock in one internal state fall differently from the same species in another, which is what a clock-redshift test or a test comparing atoms prepared in different hyperfine states actually probes. η^coh\hat\eta_{coh} is off-diagonal in that same basis — it couples the coherences between internal states to free fall, so it only shows up in an experiment that keeps a system in superposition of two internal states long enough for gravity to act on the superposition itself, rather than on each state…

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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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