KroneckerDelta in sum
- To: mathgroup at smc.vnet.net
- Subject: [mg31675] KroneckerDelta in sum
- From: Matthias Reichelt <reichelt at ax1348.physik.uni-marburg.de>
- Date: Fri, 23 Nov 2001 05:47:27 -0500 (EST)
- Organization: Uni Marburg
- Sender: owner-wri-mathgroup at wolfram.com
Hi all,
I guess I have a rather simple problem. If I write
Sum[a[i, j]KroneckerDelta[i - j], {i, -Infinity, Infinity}]
Mathematica answers
a[j, j]
Now, if I use a two-fold sum
Sum[a[i, j]KroneckerDelta[i - j], {i, -Infinity, Infinity}, {j, -Infinity,
Infinity}]
the expression is not simplified.
How can I force Mathematica to give results like
Sum[a[j,j],{j,-Infinity, Infinity}]
Thks,
Matthias Reichelt
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