Bessel K expansion, large argument?
- To: mathgroup at smc.vnet.net
- Subject: [mg70088] Bessel K expansion, large argument?
- From: AES <siegman at stanford.edu>
- Date: Tue, 3 Oct 2006 06:16:28 -0400 (EDT)
- Organization: Stanford University
The function z BesselK[ 1, z ] / BesselK[ 0, z ] with z complex, magnitude several times unity or larger, and argument between -90 and 90 degrees, appears in optical fiber mode calculations. Experience shows that a quite good approximation to this is just w + 1/2 Can anyone suggest a next term or two in the expansion, e.g. w + 1/2 + a/w + b/w^2 ??? Been trying to get Mathematica to tell me this, but not figuring out how to get the Series command to do what I want.