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Equation 49 · Part 2 · A Horizon Is a Toll Booth, Not a Loophole

Symbol f

E∞=f E0′E_\infty = \sqrt{f}\,E_0'
ff

What this part means

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

Its job in the formula

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

The passage around this formula

Now hold the asymptotic Killing energy fixed instead, at E∞E_\infty = f\sqrt{f}\,E0E_0' (the amount of energy it would cost a distant experimenter, at infinity, to deliver that same physical resource down to radius r ), and integrate over the corresponding coordinate interval Δ\Delta t = Δ\Deltaτ\tau/f\sqrt f :

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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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