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Bounds on differences of adjacent zeros of Bessel functions and iterative relations between consecutive zeros
Authors:Javier Segura.
Affiliation:Instituto de Bioingeniería, Universidad Miguel Hernández, Edificio La Galia, 03202-Elche, Alicante, Spain
Abstract:

Bounds for the distance $vert c_{nu ,s}-c_{nu pm 1 , s^{prime}}vert$ between adjacent zeros of cylinder functions are given; $s$ and $s^{prime}$ are such that $nexists c_{nu,s^{primeprime}}in ]c_{nu ,s},c_{nupm 1,s^{prime}}[$; $c_{nu ,k}$ stands for the $k$th positive zero of the cylinder (Bessel) function $mathcal{C}_{nu}(x)=cosalpha J_{nu}(x) - sinalpha Y_{nu}(x)$, $alpha in [0,pi[$, $nu in {mathbb R}$.

These bounds, together with the application of modified (global) Newton methods based on the monotonic functions $f_{nu}(x)=x^{2nu -1}mathcal{C}_{nu}(x)/mathcal{C}_{nu -1}(x)$ and $g_{nu}(x)=-x^{-(2nu +1)}mathcal{C}_{nu}(x)/mathcal{C}_{nu +1}(x)$, give rise to forward ( $c_{nu ,k} rightarrow c_{nu ,k+1}$) and backward ( $c_{nu ,k+1} rightarrow c_{nu ,k}$) iterative relations between consecutive zeros of cylinder functions.

The problem of finding all the positive real zeros of Bessel functions $mathcal{C}_{nu}(x)$ for any real $alpha$ and $nu$ inside an interval $[x_{1},x_{2}]$, $x_{1}>0$, is solved in a simple way.

Keywords:Bessel functions   cylinder functions   adjacent and consecutive zeros   global Newton method
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