What are e-foldings and how are they used in various fields of study?

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E-foldings refer to the time interval in which an exponentially growing quantity increases by a factor of e, approximately 2.71828, commonly used in theoretical physics, particularly in the context of cosmic inflation. The discussion highlights the lack of comprehensive resources on e-foldings, with Wikipedia providing some basic information. It clarifies that e-folding time scales are determined by the proper time required for a region of space to expand by this factor. Additionally, the conversation notes that 60 e-folds equate to an increase by a factor of 10^26. Understanding e-foldings is crucial for grasping concepts in cosmology and exponential growth in various scientific fields.
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I've tried several searches on the term e-foldings, However I've been unable to find any decent write ups on the terminology or calculations. Surprisingly even Wiki doesn't have much on the subject.
 
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Well, let's look at two articles from wiki.

First: http://en.wikipedia.org/wiki/E_folding
In science, e-folding is the time interval in which an exponentially growing quantity increases by a factor of e; it is the base-e analog of doubling time. This term is often used in theoretical physics, especially when cosmic inflation is investigated. Physicists often talk about the e-folding time scale that is determined by the proper time in which the length of a patch of space or spacetime increases by the factor e mentioned above.

Second: http://en.wikipedia.org/wiki/E_(mathematical_constant)
The number e is an important mathematical constant, approximately equal to 2.71828, that is the base of the natural logarithm.

If I'm reading this correctly, it appears that e-folding is simply the amount of time it takes for space to expand by approximately 2.71828 times its original size. Does that help at all?
 
Ah yeah it does the second link provided the details I needed. I couldn't figure out how they derived the 2.71828 value thanks so much
 
Quite right! And loge 10 = 2.3
So 60 e-folds is the same as 26 "ten-folds"

Distances increasing by a factor of e60 is the same as their increasing
by a factor of 1026
 
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https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.

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