**Astérisque**

Volume: 359;
2014;
146 pp;
Softcover

MSC: Primary 20;
**Print ISBN: 978-2-85629-781-0
Product Code: AST/359**

List Price: $63.00

Individual Member Price: $50.40

# Split Spetses for Primitive Reflection Groups

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*Michel Broué; Gunter Malle; Jean Michel*

A publication of the Société Mathématique de France

Let \(W\) be an exceptional spetsial irreducible
reflection group acting on a complex vector space \(V\),
*i.e.*, a group \(G{_n}\) for
\[n \in 4, 6, 8, 14, 23, 24, 25, 26, 27, 28,
29, 30, 32, 33, 34, 35, 36, 37\] in the Shephard-Todd notation.

The authors describe how to determine some data associated to the corresponding (split) “spets” \(\mathbb{G} =(V,W)\), given complete knowledge of the same data for all proper subspetses (the method is thus inductive).

The data determined here are the set \(\mathrm{Uch}(\mathbb{G})\) of “unipotent characters” of \(\mathbb{G}\) and its repartition into families, as well as the associated set of Frobenius eigenvalues. The determination of the Fourier matrices linking unipotent characters and “unipotent character sheaves” will be given in another paper.

The approach works for all split reflection cosets for primitive irreducible reflection groups. The result is that all the above data exist and are unique (note that the cuspidal unipotent degrees are only determined up to sign).

The authors keep track of the complete list of axioms used. In order to do that, they explain in detail some general axioms of “spetses”, generalizing (and sometimes correcting) along the way.

A publication of the Société Mathématique de France, Marseilles (SMF), distributed by the AMS in the U.S., Canada, and Mexico. Orders from other countries should be sent to the SMF. Members of the SMF receive a 30% discount from list.

#### Readership

Graduate students and research mathematicians interested in complex reflection groups, braid groups, Hecke algebras, finite reductive groups, and spetses.