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Re: Integrating DiracDelta to get UnitStep

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91263] Re: Integrating DiracDelta to get UnitStep
  • From: amzoti <amzoti at gmail.com>
  • Date: Tue, 12 Aug 2008 04:46:48 -0400 (EDT)
  • References: <g7p2tm$arr$1@smc.vnet.net>

On Aug 11, 3:05 am, CRC <cr... at this-is-bogus.sbcglobal.net> wrote:
> Hi:
>
> I am a bit confused by Mathematica 6.0.3 behavior.  I expect that:
>
> In[n]:= Integrate[DiracDelta[x], {x, -\[Infinity], t},
>   Assumptions -> Im[t] == 0]
>
> Will produce:
>
> Out[n]= UnitStep[t]
>
> But instead it produces:
>
> Out[n]= 1
>
> However,
>
> In[n+1]:= Plot[ Integrate[DiracDelta[x], {x, -\[Infinity], t},
>    Assumptions -> Im[t] == 0], {t, -2, 2} ]
>
> produces the expected plot of UnitStep[t].
>
> Why doesn't the integration output the UnitStep function?
>
> Thanks for input.
>
> --
> _____________________
> CRC
> cr... at REMOVE-THIS.sbcglobal.net
> SuSE 10.3 Linux 2.6.22.17

In Mathematica V4.0.0.0, the first input does produce the UnitStep[t] result.

Not sure why this has changed.


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