3
$\begingroup$

I am trying to calculate the following asymptotic behaviour:

Normal@Series[BesselK[1, r \[CapitalLambda]] / BesselK[1, \[CapitalLambda]], {r, 0, 1}]

but for $\Lambda$ real and positive. I have tried with:

Assuming[{\[CapitalLambda] \[Element] Reals, \[CapitalLambda] > 0;},Normal@Series[BesselK[1, r \[CapitalLambda]] /   BesselK[1, \[CapitalLambda]], {r, 0, 1}]]

but I still get a complex output. Any ideas?

$\endgroup$
1
$\begingroup$
Normal@Series[BesselK[1, r Λ]/BesselK[1, Λ], {r, 0, 1}, Assumptions -> Λ > 0]

gives

Mathematica graphics

You can also use

Simplify@Normal@Series[BesselK[1, r Λ]/BesselK[1, Λ], {r, 0, 1}, Assumptions -> Λ > 0]

or

Simplify[Normal@ Series[BesselK[1, r Λ]/ BesselK[1, Λ], {r, 0, 1}], 
    Assumptions ->  Λ > 0]

or

Assuming[{ Λ > 0}, 
  Simplify[Normal@ Series[BesselK[1, r Λ] / BesselK[1, Λ], {r, 0, 1}]]]

to get

Mathematica graphics

or

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.