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 > >