Bounds are found for a solution y, to the ordinary differential equation $(r^k p(r,y)y')' + r^k q(r,y) = 0(' = {d / {dr}})$, with initial conditions $y(0) = y_0 > 0$, $y'(0) = 0$. The principal assumptions are that $k \geqq 1,q(r,y(r))$ is decreasing for $0 \leqq r \leqq a$ and $q(a,y(a)) \geqq 0$. Also, r-independent bounds on p and q are assumed to exist. Lower bounds on y valid for $0 \leqq r \leqq a$ are found, and, also, upper bounds valid on a possibly smaller interval. They will be applied to Bessel’s equation to show how close they are. The bounds will further be applied to boundary value problems arising in gas glow discharge theory and tubular chemical reactor theory.
Read full abstract