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MathGroup Archive 2003

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Re: ProductLog[-Pi/2]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44176] Re: [mg44160] ProductLog[-Pi/2]
  • From: "Peter Pein" <nospam at spam.no>
  • Date: Sat, 25 Oct 2003 06:26:26 -0400 (EDT)
  • References: <200310240824.EAA04419@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

onlinehelp:
ProductLog[z] has a branch cut discontinuity in the complex z plane running
from -infinity to -1/e. ProductLog[k, z] for integer k>0 has a branch cut
discontinuity from -infinity to 0.

Peter Pein, Berlin
petsie at arcAND.de
replace && by || to write to me

----- Original Message -----
From: "Jean-Claude Poujade" <poujadej at yahoo.fr>
To: mathgroup at smc.vnet.net
Subject: [mg44176] [mg44160] ProductLog[-Pi/2]


> ProductLog[-Pi/2] should return I Pi/2 but doesn't...
>
> In[1] := w E^w /. w -> I Pi/2
> Out[1] = -Pi/2
>
> In[2] := ProductLog[-Pi/2] // FullSimplify
> Out[2] = ProductLog[-Pi/2]
>
> In[3] := ProductLog[-Pi/2] // N // Chop
> Out[3] = 1.5708 I
>
> Could someone explain ? (I use Mathematica 4.1)
>
> ---
> jcp
>


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