Re: global real variables

*To*: mathgroup at smc.vnet.net*Subject*: [mg22046] Re: global real variables*From*: "Kevin J. McCann" <kevin.mccann at jhuapl.edu>*Date*: Fri, 11 Feb 2000 02:38:26 -0500 (EST)*Organization*: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA*References*: <87trds$5o3@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

There are other ways, but here is one that I use. It employs the Algebra`ReIm` Package and uses Upsets to tell Mathematica that x and p are reals: << Algebra`ReIm` Re[x] ^= x; Im[x] ^= 0; Re[p] ^= p; Im[p] ^= 0; Now you can do this: Conjugate[x] x Conjugate[ x + x * p^-1 ] x + x/p Note, however Conjugate[y] just gives Conjugate[y] because Mathematica doesn't know enough about y to do any more. Hope this helps, Kevin -- Kevin J. McCann Johns Hopkins University APL Naum Phleger <naum at cava.physics.ucsb.edu> wrote in message news:87trds$5o3 at smc.vnet.net... > I asked a dumb question a few weeks ago about making variables real and > found that Mathematica 4 took care of this better. I have been using it > since. I still have a couple of problems with it though. First, I can have > variables be treated as real by using the assumption Element[x,Reals] in a > simplify command, but I want x to be real in all commands so I don't have to > keep using Simplify each time I want x to be recognized as real. Second, > even this doesn't seem to work quite right. Here is what I mean. > > > Say I have tow var.s, x and p. Both are real so I can do this. > > Simplify[ Conjugate[ x ] , Element[ x , Reals ] ] ----> x > > amd I get the same thing for p, but it stops working if I have functions of > x and p, for instance I get > > > Simplify[ Conjugate[ x + x * p^-1 ] , Element[ {x,p} , Reals ] ] ----> > > Conjugate[ x + x * p^-1 ] > > > It works if I use FullSimplify AND put p^-1 into the list of variables > that I want to have real. How can I get around this without listing every > negative power of every variable and wasting time with FullSimplify. Thanks > for any help. Thanks. > > > -NAUM >