Journal of the Mathematical Society of Japan

On arithmetic subgroups of a Q-rank 2 form of SU(2,2) and their automorphic cohomology

Takahiro HAYATA and Joachim SCHWERMER

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The cohomology H * ( Γ , E ) of an arithmetic subgroup Γ of a connected reductive algebraic group G defined over Q can be interpreted in terms of the automorphic spectrum of Γ . In this frame there is a sum decomposition of the cohomology into the cuspidal cohomology ( i.e., classes represented by cuspidal automorphic forms for G ) and the so called Eisenstein cohomology. The present paper deals with the case of a quasi split form G of Q -rank two of a unitary group of degree four. We describe in detail the Eisenstein series which give rise to non-trivial cohomology classes and the cuspidal automorphic forms for the Levi components of parabolic Q -subgroups to which these classes are attached. Mainly the generic case will be treated, i.e., we essentially suppose that the coefficient system E is regular.

Article information

J. Math. Soc. Japan, Volume 57, Number 2 (2005), 357-385.

First available in Project Euclid: 14 September 2006

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Mathematical Reviews number (MathSciNet)

Zentralblatt MATH identifier

Primary: 11F75: Cohomology of arithmetic groups
Secondary: 11F70: Representation-theoretic methods; automorphic representations over local and global fields 22E40: Discrete subgroups of Lie groups [See also 20Hxx, 32Nxx]

cohomology of arithmetic subgroups Eisenstein cohomology cuspidal cohomology automorphic representation associate parabolic subgroup minimal coset representatives


HAYATA, Takahiro; SCHWERMER, Joachim. On arithmetic subgroups of a Q-rank 2 form of SU(2,2) and their automorphic cohomology. J. Math. Soc. Japan 57 (2005), no. 2, 357--385. doi:10.2969/jmsj/1158242063.

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