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Topic: Summation in Mathematica
Replies: 2   Last Post: Apr 26, 2013 4:24 AM

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Roland Franzius

Posts: 586
Registered: 12/7/04
Re: Summation in Mathematica
Posted: Apr 26, 2013 4:24 AM
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Am 24.04.2013 13:02, schrieb Ben Blomberg:
> Hello All,
> I am trying to understand a piece of code I found but I am stuck on this
> summation. This is part of a larger do loop over n.
> UnderoverscriptBox[\(\[Sum]\), \(m = \(-10\)\),
> \(10\)]\(\(eigenfunctionsort[n, j]\)[\([m + 11]\)]
> Exp[I*2*\[Pi]*m*x/dp]\)\),{j,1,21}]
> What I mainly do not understand is what is happening with the [m+11]. Is
> that being multiplied with eigen function sort with each step in the sum,
> or is that simply adding 11 to m at each step in the sum?

The piece of code should be read in InputForm

Sum[eigenfunctionsort[n, j][[m + 1]] * Exp[2 *\[Pi] *I *m *x /dp],
{m, -10, 10}]

In FullForm, eigenfunctionsort[n, j][[m + 1]] means

Part[eigenfunctionsort[n, j],m+1],

the m+1-component of the vector of eigenfunctions probably with quantum
numbers n and j.


Roland Franzius

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