Equation 3 · Part 1 · Decoherence: The Quiet Selection That Makes the World Look Solid
Symbol ρ
What this part means
ρ is part of the quantity the equation computes from the expression on the right.
Its job in the formula
ρ is part of the quantity the equation computes from the expression on the right.
Full expression→Symbol ρ→Article meaning
The passage around this formula
Joos and Zeh made this quantitative in 1985 by deriving a genuine, non-phenomenological master equation for the reduced density matrix of an object’s centre-of-mass position under repeated recoil-free scattering [ 7 ] . For the off-diagonal elements of that density matrix — the very quantity whose survival or destruction is the entire question of macroscopic superposition — their result, in the short-time, many-collisions regime, takes the form of a simple exponential decay in the separation between the two positions being superposed: . Here is what Joos and Zeh call the localization rate: a single number, with units of inverse length squared per unit time, built…
Learn the underlying idea
A function assigns an output to each allowed input. The expression f(x) means “apply f to x”.
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Sources cited in the surrounding passage
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