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Equation 3 · Part 4 · Decoherence: The Quiet Selection That Makes the World Look Solid

Symbol Lambda

ρ(x,x′,t)=ρ(x,x′,0) exp⁡ ⁣[−Λ(x−x′)2t]\rho(x, x', t) = \rho(x, x', 0)\, \exp\!\left[-\Lambda (x - x')^2 t\right]
Λ\Lambda

What this part means

what Joos and Zeh call the localization rate: a single number.

Its job in the formula

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

Where the article explains it

Here Λ\Lambda is what Joos and Zeh call the localization rate: a single number, with units of inverse length squared per unit time, built from the scattering cross-section of the object, the flux and momentum of whatever is doing the scattering, and nothing else [ 7 ] .

The passage around this formula

…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: ρ(x,x′,t)=ρ(x,x′,0) exp⁡ ⁣[−Λ(x−x′)2t]\rho(x, x', t) = \rho(x, x', 0)\, \exp\!\left[-\Lambda (x - x')^2 t\right]. Here Λ\Lambda is what Joos and Zeh call the localization rate: a single number, with units of inverse length squared per unit time, built from the scattering cross-section of the object, the flux and momentum of whatever is doing the scattering, and nothing else [ 7 ] . Everything about how fast a given…

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Learn the underlying idea

A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.