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MathGroup Archive 2000

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assumptions question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg21893] assumptions question
  • From: Peter Jay Salzman <psalzman at landau.ucdavis.edu>
  • Date: Wed, 2 Feb 2000 22:54:50 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear all,

I have an integral whose output contains things which look like:

	(Sign[m] - I Sign[h t])

Since m is mass, h is hbar and t > 0, I placed placed a:

	Assumptions -> {Sign[m] > 0, Sign[t h] > 0}

inside the Integrate[ ] command.

	Integrate[ Sin[k r]/(k r) * Exp[-I*(h k)^2 t /(2 m h)],
		Assumptions-> {Sign[m] > 0, Sign[t h] > 0},
			{k, 0, Infinity}]

It seems to be ignoring me.  The Sign[m]'s keep showing up.  Is there a way
to tell Mathematica that m is always positive?  I *thought* this was the way of
doing it...

pete



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