       Re: (x-y) DiracDelta[x-y] does not simplify to 0

• To: mathgroup at smc.vnet.net
• Subject: [mg56296] Re: (x-y) DiracDelta[x-y] does not simplify to 0
• From: Alain Cochard <alain at geophysik.uni-muenchen.de>
• Date: Thu, 21 Apr 2005 05:36:15 -0400 (EDT)
• References: <d42kg5\$39t\$1@smc.vnet.net> <d45agf\$ieu\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Dr. Wolfgang Hintze writes:
> Alain,
>
> may I add the strangest case I found up to now:
>
> case wh01
> In:=Simplify[(x - y)*DiracDelta[x - y], {x, y}]
> Out=0
>
> But also these are strange enough
>
> case wh02
> In:=Simplify[(x - y)*DiracDelta[x - y], {x && y}]
> Out=0
>
> case wh03
> In:=Simplify[(x - y)*DiracDelta[x - y], {x || y}]
> Out=(x - y)*DiracDelta[x - y]
>
> case wh04
> In:=Simplify[I*x*DiracDelta[I*x]]
> Out=0
>
> But
> case wh05
> In:=Simplify[I*DiracDelta[I]]
> Out=I*DiracDelta[I]
>
> Can't explain ...
> Wolfgang

I have not much experience with delta functions with complex numbers,
so I don't have an opinion on wh04 and wh05, but I indeed find
wh01->03 funny.  Hope some will tell us what's going on.

Alain

```

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