In "Black Holes, Information and the String Theory Revolution"(adsbygoogle = window.adsbygoogle || []).push({});

by Leonard Susskind and James Lindesay, the authors give,

(Ch. 15: Entropy of Strings and Black Holes, pg. 170):

"The string and Planck length scales are related by

g^2* (l_s)^D-2 = (l_p)^D-2 (15.0.23) "

They then find the consequences of varying g while keeping

string length l_s fixed, saying, "This implies that the Planck

length varies." [D is dimensionality of the system, g is the

dimensionless string coupling constant, and l_p is the Planck

length.]

Variation of g and l_s seems pretty standard in such studies,

but the implication of variation of l_p, the Planck length, struck

me as a surprising statement in mainstream physics, given

that

l_p = (hbar*G / c^3)^.5

IF the authors are actually suggesting that the Planck length

might vary under certain conditions in our universe, they are

also suggesting changes in one or more of the 'constants' on

the right hand side of the above equation. Unfortunately, they

do not further develop this statement in the book, as far as I

can see.

Is my interpretation correct? Have some authors posited actual

variation in l_p?

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# Susskind on 'variation in Planck length'?

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