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