Wednesday, 20 January 2010

ca.analysis and odes - Derivate Bessel Function with respect to order

Abramowitz and Stegun give a couple of special cases but don't give a general result. Starting from some of the integral or series representations and differentiating you can get a corresponding integral or series for the derivative, but I would guess that it's unlikely to simplify to a "known" function in the general case. An example they give is (for the spherical Bessel function $j_nu(x)$):



$$[ frac{d}{dnu} j_nu(x) ]_{nu=0} = frac{pi}{2x}(operatorname{Ci}(2x)sin x - operatorname{Si}(2x)cos x)$$



They also give examples evaluated at $nu=-1$ and similar results for the case of the "other" spherical bessel $y_nu(x)$.

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