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MathGroup Archive 2005

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Re: Multiple integration of UnitStep fails

  • To: mathgroup at smc.vnet.net
  • Subject: [mg63203] Re: Multiple integration of UnitStep fails
  • From: Bhuvanesh <lalu_bhatt at yahoo.com>
  • Date: Sun, 18 Dec 2005 07:34:39 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

For multiple integrals, it's always a good idea to use a single Integrate call, not nested ones, as inner integrations may spawn conditions that the outer ones may not be able to handle. This works for me in versions 5.1 and 5.2:

In[1]:= (4!*Integrate[UnitStep[p4 - Pi, p5 - p2 - Pi, Pi - p3, Pi - p4 + p2, Pi - p5 + p3], {p2, 0, 2*Pi}, {p3, p2, 2*Pi}, {p4, p3, 2*Pi}, {p5, p4, 2*Pi}])/(2*Pi)^4

        1
Out[1]= --
        16

The n=6 case does take much longer, and it will probably return unevaluated.

Bhuvanesh,
Wolfram Research.


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