Interaction of Sum/Plus and KroneckerDelta

*To*: mathgroup at smc.vnet.net*Subject*: [mg55178] Interaction of Sum/Plus and KroneckerDelta*From*: "Ofek Shilon" <ofek at simbionix.com>*Date*: Wed, 16 Mar 2005 05:35:53 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

I'm fighting Mathematica 5.1.0 to perform a (seemingly) elementary simplification, and Mathematica - so far - wins, so i thought i'd consult some veterans. Here's a simplified example of the problem. type: Sum[KroneckerDelta[i, j], {i, 1, 5}] and you get: KroneckerDelta[1, j] + KroneckerDelta[2, j] + KroneckerDelta[3, j] + KroneckerDelta[4, j] + KroneckerDelta[5, j] which i want to simplify to 1. The direct approach: Simplify[%, Assumptions -> {j â?? Integers, 0 < j < 3}] still gives: KroneckerDelta[1, j] + KroneckerDelta[2, j] Can Mathematica somehow automatically transform this to 1? modification of the original sum are welcome too, of course. thanks for any ideas, Ofek Shilon

**Follow-Ups**:**Re: Interaction of Sum/Plus and KroneckerDelta***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>