Bessel function Errors reproducing Wronskian

12 vues (au cours des 30 derniers jours)
Matthew King
Matthew King le 26 Fév 2021
Commenté : Matthew King le 2 Mar 2021
I am trying to reproduce the Wronskians of the Bessel functions.
this should hold true for any complex argument Z to my knowledge.
I am making use of
m=5; % I have the same issue for other values of m.
Z=linspace(-200,200,400)+1i*(linspace(-200,200,400).');
JmZ=besselj(m,Z);
H1mZ=besselh(m,1,Z);
H2mZ=besselh(m,2,Z);
dJmZ=(1/2).*(besselj(m-1,Z)-besselj(m+1,Z));
dH1mZ=(1/2).*(besselh(m-1,1,Z)-besselh(m+1,1,Z));
dH2mZ=(1/2).*(besselh(m-1,2,Z)-besselh(m+1,2,Z));
figure
contour(linspace(-200,200,400),linspace(-200,200,400),log10(abs(1-(JmZ.*dH1mZ-H1mZ.*dJmZ)./(2i./(pi.*Z)))),[-16,-8,0,1,10])
figure
contour(linspace(-200,200,400),linspace(-200,200,400),log10(abs(1-(JmZ.*dH2mZ-H2mZ.*dJmZ)./(-2i./(pi.*Z)))),[-16,-8,0,1,10])
in order to evaluate the error.
For the first expression I am retrieiving a large error in the Lower Half Plane for the first expression and in the Upper Half Plane for the second expression.
Are there any ways to reduce this error in order to get reasonable accuracy in these regions?
I have tried using different expressions for the derivatives such as
% dJmZ=(m./Z).*JmZ - besselj(m+1,Z);
% dJmZ= (JmZ - besselj(m,Z+sqrt(eps)))./(-sqrt(eps));
and the equivalent for the derivatives of the Hankel functions.
I have also attempted intoducing the scalings into the problem
JmZS=besselj(m,Z,1);
H1mZS=besselh(m,1,Z,1);
H2mZS=besselh(m,2,Z,1);
dJmZS=(1/2).*(besselj(m-1,Z,1)-besselj(m+1,Z,1));
dH1mZS=(1/2).*(besselh(m-1,1,Z,1)-besselh(m+1,1,Z,1));
dH2mZS=(1/2).*(besselh(m-1,2,Z,1)-besselh(m+1,2,Z,1));
figure
contour(linspace(-200,200,400),linspace(-200,200,400),log10(abs(1-(JmZS.*dH1mZS-H1mZS.*dJmZS)./(2i./(pi.*Z).*(exp(abs(imag(alpha))+1i.*Z))))),[-16,-8,0,1,10])
figure
contour(linspace(-200,200,400),linspace(-200,200,400),log10(abs(1-(JmZS.*dH2mZS-H2mZS.*dJmZS)./(-2i./(pi.*Z).*(exp(abs(imag(alpha))+1i.*Z)))),[-16,-8,0,1,10])
However this makes little to no difference.
  2 commentaires
Walter Roberson
Walter Roberson le 26 Fév 2021
Use the symbolic toolbox?
Matthew King
Matthew King le 2 Mar 2021
I was not, although trying this did not improve the accuracy.

Connectez-vous pour commenter.

Réponses (0)

Catégories

En savoir plus sur Bessel functions dans Help Center et File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by