1
$\begingroup$

How do I interpret this form of sigma notation? Do e1 and e2 take on all combinations of 1 and -1? If they do, what's the point? They just get multiplied inside the sum! FYI, this comes from equation 8 in the following paper: http://personal.mecheng.adelaide.edu.au/will.robertson/research/2012-magcoil.pdf

weird notation

$\endgroup$
  • $\begingroup$ Yes, they take on $\pm 1$ values. There are 4 terms in the sum. $\endgroup$ – user147263 Dec 26 '14 at 6:20
2
$\begingroup$

The meaning is $$\sum_{e_1=-1,+1}\sum_{e_2=-1,+1}e_1e_2m_1...$$

Look at equation 10 underneath that, $m_1$ depends on $e_1$ and $e_2$, so the succeeding factor is not constant as $e_1$ and $e_2$ vary.

$\endgroup$
  • $\begingroup$ And the notation indicates that they vary independently over the set $\{1,-1\}$. $\endgroup$ – Brian M. Scott Dec 26 '14 at 6:21
  • $\begingroup$ Oh wow! I didn't see that. Am I right in thinking that (e1,e2) will be (1,1) then (1,-1) then (-1, 1) and finally (-1, -1)?? $\endgroup$ – Jordan Dec 26 '14 at 6:22
  • $\begingroup$ @Jordan Yes, I've added a clarification. $\endgroup$ – Suzu Hirose Dec 26 '14 at 6:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.