Jorge Talamantes writes:
> Dear all,
>
> I am trying to integrate the following function:
>
> I = \int_0^{x1} M (D, alpha, x, n) dx,
>
> where D, alpha and n are parameters to be passed to M, and
>
> M = x^(D-alpha-1) * [ j(x,n+0.5) ]^2.
>
> Here, j is the Bessel function of order (n + 0.5).
>
> For some combinations of D and alpha, the integrand M diverges at the
> origin. So, I am trying to use gsl_integration_qagp -- adaptive
> integration with known singular points.
>
> The problem I am having is that, for a given x, there is a maximum n for
> which I can compute j(x,n+0.5) -- increasing n leads to an underflow
> error from gsl_sf_bessel_Jnu.
Split up the integral (or integrand) to compute the part near x=0
using the asymptotic form of j(x,n) for small x to avoid underflow.
Or disable the underflow error if it doesn't affect the final results.
--
Brian Gough
Network Theory Ltd,
Publishing Free Software Manuals --- http://www.network-theory.co.uk/
_______________________________________________
Help-gsl mailing list
[email protected]
http://lists.gnu.org/mailman/listinfo/help-gsl
