For an eigenfunction of the Laplacian on a hyperbolic Riemann surface, the coefficients of the Fourier expansion are described as intertwining functionals. All intertwiners are classified. A refined growth estimate for the coefficients is given and a summation formula is proved.

This paper contains an application of Langlands’ functoriality principle to the following classical problem: which finite groups, in particular which simple groups appear as Galois groups over $\mathbb{Q}$? Let $\ell$ be a prime and $t$ a positive integer. We show that that the finite simple groups of Lie type $B_n\left({\ell }^k\right)=3DS{O}_{2n+1}{\left({𝔽}_{{\ell }^k}\right)}^{der}$ if $\ell \equiv 3,5(mod8)$ and $G_2\left({\ell }^k\right)$ appear as Galois groups over $\mathbb{Q}$, for some $k$ divisible by $t$. In particular, for each of the two Lie types and fixed $\ell$ we construct infinitely many Galois groups but we do not have a precise control...

Let $X$ be a smooth projective curve over an algebraically closed field of characteristic $\>2$. Consider the dual pair $H={\mathrm{SO}}_{2m},G={\mathrm{Sp}}_{2n}$ over $X$ with $H$ split. Write ${\mathrm{Bun}}_G$ and ${\mathrm{Bun}}_H$ for the stacks of $G$-torsors and $H$-torsors on $X$. The theta-kernel ${\mathrm{Aut}}_{G,H}$ on ${\mathrm{Bun}}_G\times {\mathrm{Bun}}_H$ yields theta-lifting functors $F_G:\mathrm{D}\left({\mathrm{Bun}}_H\right)\to \mathrm{D}\left({\mathrm{Bun}}_G\right)$ and $F_H:\mathrm{D}\left({\mathrm{Bun}}_G\right)\to \mathrm{D}\left({\mathrm{Bun}}_H\right)$ between the corresponding derived categories. We describe the relation of these functors with Hecke operators. In two particular cases these functors realize the geometric Langlands functoriality for the above pair (in the non ramified case)....

Soit $F$ un corps de nombres et soit $E$ une extension cyclique de $F$, de degré $d$. L’induction automorphe associe à une représentation automorphe cuspidale $\tau$ de ${\mathrm{GL}}_m\left({𝔸}_E\right)$ une représentation automorphe $\pi$ de ${\mathrm{GL}}_{md}\left({𝔸}_F\right)$, induite de cuspidale. La représentation $\pi$ est caractérisée par le fait qu’à presque toute place $v$ de $F$, le facteur $L({\pi }_v,s)$ est le produit des facteurs $L({\tau }_w,s)$, $w$ parcourant les places de $E$ au–dessus de $v$. Par la correspondance conjecturale de Langlands, cette opération doit correspondre à l’induction, de $E$ à $F$, des...