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Bessel function K convergence to Laguerre polynomials

  1. Aug 29, 2013 #1
    I am interested to know whether the modified Bessel functions of the second kind, also known as BesselK, defined as
    [tex] K_\alpha(x) = \frac{\pi}{2} \frac{I_{-\alpha} (x) - I_\alpha (x)}{\sin (\alpha \pi)} [/tex]
    [tex] I_\alpha(x) = i^{-\alpha} J_\alpha(ix) =\sum_{m=0}^\infty \frac{1}{m! \Gamma(m+\alpha+1)}\left(\frac{x}{2}\right)^{2m+\alpha} [/tex]
    [tex] \frac{J_\alpha(x)}{\left( \frac{x}{2}\right)^\alpha}= \frac{e^{-t}}{\Gamma(\alpha+1)} \sum_{k=0} \frac{L_k^{(\alpha)}\left( \frac{x^2}{4 t}\right)}{{k+ \alpha \choose k}} \frac{t^k}{k!} [/tex]
    can be shown to converge to the Laguerre polynomials written on the above equation with the symbol
    [tex] L [/tex]
    [tex] \alpha \rightarrow \infty \;. [/tex]
    Note that the above equations make use of the GAMMA function
    [tex] \Gamma(n) = (n-1)! [/tex]
  2. jcsd
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