On explicit integral formulas for \(\text{GL}(n, \mathbb R)\)-Whittaker functions. With an appendix by Daniel Bump, Solomon Friedberg, and Jeffrey Hoffstein
The author considers the Whittaker functions \(W_{(n,\nu)}(y)\) associated with nonramified principal series representations of the group \(\text{GL}(n, \mathbb R)\). The main result is: Theorem. Let \(n\geq 2\). If \(\nu \in {\mathbb C}^{n-1}\), put \(\lambda_{j-1}=n\nu_ j/(n-2)\) for \(2\leq j\leq n- 2\) and \(\lambda =(\lambda_ 1,\lambda_ 2,...,\lambda_{n-3})\). Also define \(u_ 0=1/u_{n-1}=0\) and \(u^ 0_{n-1}=1\). Then \[ W^*_{(n,\nu)}(y)=2^{n-1}\int_{({\mathbb R}_+)^{n-2}}\prod^{n- 1}_{i=1}u_ i^{r_{i,1}-r_{i,n-i}}K_{\mu_ 1}(2\pi y_ i\sqrt{(1+u^ 2_{i-1})(1+1/u_ i^ 2)}) \] \[ \times W^*_{(n- 2,\lambda)}(\frac{y_ 2}{u_ 2}u_ 1,\frac{y_ 3}{u_ 3}u_ 2,...,\frac{y_{n-2}}{u_{n-2}}u_{n-3})\prod^{n- 2}_{i=1}\frac{du_ i}{u_ i} \] where \(K\) denotes the \(K\)-Bessel function \(K_{\mu}(2\pi y)=\frac{1}{2}\int^{\infty}_{0}t^{\mu}\exp (-\pi y(t+1/t))\frac{dt}{t}\) \((y>0)\). Here \(W^*_{(n,\nu)}\) is \(W_{(n,\nu)}\) divided by some powers of the \(y_ i\)'s. As applications of the above theorem, he expresses the local factors at the archimedean places for the exterior square automorphic \(L\)-function on \(\text{GL}(n)\) and for automorphic functions for \(\text{GL}(2,\mathbb R)\times \text{GL}(3,\mathbb R)\) as products of Gamma functions. He also gives growth estimates for \(W_{(n,\nu)}\).
scientific article; zbMATH DE number 4208165
scientific article