# Arthur's multiplicity formula for certain inner forms of special orthogonal and symplectic groups

### Olivier Taïbi

École Normale Supérieure de Lyon, France

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## Abstract

Let $\mathbf G$ be a special orthogonal group or an inner form of a symplectic group over a number field $F$ such that there exists a non-empty set $S$ of real places of $F$ at which $\mathbf G$ has discrete series and outside of which $\mathbf G$ is quasi-split. We prove Arthur’s multiplicity formula for automorphic representations of $\mathbf G$ having algebraic regular infinitesimal character at all places in $S$.

## Cite this article

Olivier Taïbi, Arthur's multiplicity formula for certain inner forms of special orthogonal and symplectic groups. J. Eur. Math. Soc. 21 (2018), no. 3, pp. 839–871

DOI 10.4171/JEMS/852