Algebraicity of ratios of special $L$-values for $\mathrm{GL}(n)$

Abstract

We prove, under certain assumptions, algebraicity of the ratio $L(m, Π\times χ)/L(m, Π\times χ')$, where $Π$ is a cuspidal automorphic cohomological unitary representation of $\mathrm{GL}_n(\mathbb{A}_\mathbb{Q})$, and $χ$, $χ'$ are finite order Hecke characters such that $χ_{\infty} = χ'_{\infty} = \mathrm{sgn}^{r}$, and $m, r$ are specific positive integers which depends only on $Π_{\infty}$. The methods in this article are a generalization of those in the work of Mahnkopf [Cohomology of arithmetic groups, parabolic subgroups and the special values of $L$-functions of GL(n), J. Inst. Math. Jussieu, 4 (2005)].