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RICE UNIVERSITY STUDIES
sentation of G0 over к are “fundamental” in the sense of É. Cartan.
Furthermore, modulo the “duality” or the “triality,” the list of all
admissible representations over к is as follows:
type An (n ≥ 1)
type Bn (« ≥ 2)
type Cn (n ≥ 3)
type Dn (n ≥ 4)
PPi + 4Pn (p + q ≤ n), Pi + P2, P2 + Pn> P2 S
ppl (p ≤ n — 1) in general, and also
Pi + Pn> 2pπ, Pn (n = 2,3),
2Pi + P4, Pi + P4> P4 (« = 4), p5 (n = 5);
ppl (p ≤ n), ρl + p2, ρ2 in general, and also
Рз (n = 3);
PPi (p ≤ n — 2) in general, and also
Pι+ Рз + Pm Pi + Рз (« = 4),
2Pi + p4, Pi + p4, p4 (n = 5),
Pi + Ps> Ps (« = 6);
type E6 p1+ps, 2pl, p1;
type E1 pl (of degree 56);
type F4. 2pι, p1 (of degree 26);
type G2 2p1, p1 (of degree 7).
The numbering of the fundamental representations is the same as in
Chevalley [2] except for F4, where it is reversed. If G is a connected, simply
connected, semisimple group defined over к, we represent к-simple factors
of G as Rκ∣k(Gl), in which G1 are absolutely simple. We pick any rational
representation of G1 defined over K which is equivalent (over Ω) to the one
in the list. This determines a rational representation of -Rκ∕∣c(G1), hence
of G, defined over k. Take the sum of such representations for all ∕<-simple
factors of G. In this manner, we get absolutely admissible representations
of G defined over k. If we apply this consideration to /с-forms of G0 of
type A-D or to a special к-form of G0 of type E6, we will get the represen-
tations that have appeared in the works of Siegel [6], Weil [<8], and Mars
[<3]. We refer to Serre [5] for the concept of к-forms. We observe that,
among the remaining admissible representations for G0, there are essen-
tially two infinite sequences, one for type A and another for type C.