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Susskind on 'variation in Planck length'?

  1. Oct 11, 2006 #1
    In "Black Holes, Information and the String Theory Revolution"
    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

    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

    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?
  2. jcsd
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