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A question on weight function from Ashcroft and Mermin book

  1. Feb 8, 2015 #1
    I am not able to understand the top 2 lines on page 536 that are mentioned regarding the weight function mentioned in chapter 27 of ashcroft and mermin solid state physics book.

    I don't get the statement where the authors state Igrad(f)I/f should not be appreciably greater than the minimum value, of order 1/ro ? Why inverse of length is used ?

    I know grad(f) gives me the direction of maximum change in f but why has the author used Igrad(f)I/f for a slowly varying function ?
  2. jcsd
  3. Feb 13, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. Feb 18, 2015 #3
    What chapter-section is that? What edition of the book?
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