Theory of Fundamental Bessel Functions of High Rank

In this article, we shall study fundamental Bessel functions for ${\mathrm{G}\mathrm{L}}_n(\mathbb{F})$ arising from the Vorono"i summation formula for any rank $n$ and field $\mathbb{F}=\mathbb{R}$ or $\mathbb{C}$, with focus on developing their analytic and asymptotic theory. The main implements and subjects of our study of fundamental Bessel functions are their formal integral representations and Bessel differential equations. We shall prove the asymptotic formulae for fundamental Bessel functions and explicit connection formulae for the Bessel differential equations.