Re: assumptions question

• To: mathgroup at smc.vnet.net
• Subject: [mg21909] Re: assumptions question
• From: "Allan Hayes" <hay at haystack.demon.co.uk>
• Date: Fri, 4 Feb 2000 02:54:40 -0500 (EST)
• References: <87b0rh\$o6c@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Peter,

Options must come last

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

Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

"Peter Jay Salzman" <psalzman at landau.ucdavis.edu> wrote in message
news:87b0rh\$o6c at smc.vnet.net...
> 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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