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Re: Simplifying Conjugate[] with 5.2 Mac

  • To: mathgroup at smc.vnet.net
  • Subject: [mg59760] Re: [mg59725] Simplifying Conjugate[] with 5.2 Mac
  • From: "David Park" <djmp at earthlink.net>
  • Date: Sat, 20 Aug 2005 03:13:49 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Steuard,

Why don't you use...

ComplexExpand[Conjugate[x + I y]]
x - I*y

and you don't even have to set $Assumptions?

ComplexExpand is the workhorse routine for complex algebra - but often
overlooked.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/


From: Steuard Jensen [mailto:sbjensen at midway.uchicago.edu]
To: mathgroup at smc.vnet.net


I've just upgraded from Mathematica 5.0 to 5.2 for the Mac, and I
discovered that a notebook that ran fine before (finishing in ten or
fifteen minutes) was now being tremendously slow.  I'm sure I haven't
tracked down everything that I need to fix by hand to speed it back up
again (I did a lot of tuning when I wrote it), but it seems that part
of the problem can be tracked back to what looks like a bug in
Simplify[] (or at least an awfully annoying behavior).

Specifically, I have used $Assumptions to define some variables as
real.  I apply Conjugate to various expressions, and then Simplify the
results.  In version 5.0, I _never_ saw a case in which Conjugate[]
remained after this step.  But in 5.2, I find that even simple forms
like Conjugate[x + I y] often remain unsimplified.  (Refine[x + I y]
still seems to work, though.)

I've cut and pasted a simple example below, and I'd be interested to
know if other people experience the same behavior.  I'd appreciate any
advice or comments on how to handle this, or on where I should write
to report this strange behavior to Wolfram if you think that's
appropriate.  Thanks in advance for any help you can give.

						Steuard Jensen

------------------------------------------------------------

In[1]:= $Assumptions={Element[{x,y},Reals]};

In[2]:= Simplify[Conjugate[x]]

Out[2]= x

In[3]:= Simplify[Conjugate[I y]]

Out[3]= -I y

In[4]:= Simplify[Conjugate[x+y]]

Out[4]= x+y

In[5]:= Simplify[Conjugate[x+I y]]

Out[5]= Conjugate[x + I y]

In[6]:= Refine[Conjugate[x+I y]]

Out[6]= x - I y

------------------------------------------------------------



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