Paper 4, Section II, A

Asymptotic Methods
Part II, 2020

Consider the differential equation

yy2(x+1)x2y=0y^{\prime \prime}-y^{\prime}-\frac{2(x+1)}{x^{2}} y=0

(i) Classify what type of regularity/singularity equation ()(\dagger) has at x=x=\infty.

(ii) Find a transformation that maps equation ( \dagger to an equation of the form

u+q(x)u=0u^{\prime \prime}+q(x) u=0

(iii) Find the leading-order term of the asymptotic expansions of the solutions of equation ()(*), as xx \rightarrow \infty, using the Liouville-Green method.

(iv) Derive the leading-order term of the asymptotic expansion of the solutions yy of ( \dagger ). Check that one of them is an exact solution for ()(\dagger).