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Feb 10, 2014 at 23:25 vote accept David Roberts
Feb 10, 2014 at 13:11 comment added Jim Humphreys @David: I should have added an online link to Segal's 1968 paper: numdam.org/numdam-bin/fitem?id=PMIHES_1968__34__113_0 (which Serre discusses in the finite group case, in his textbook on finite group representations).
Feb 10, 2014 at 4:23 comment added David Roberts In fact, I just found that Segal proved $R(G)$ is finitely generated for any compact $G$, by using finite generation over $R(U(n))$.
Feb 10, 2014 at 0:56 comment added Qiaochu Yuan @Jim: thanks for the reference! My claim above is Proposition 2.1 in that section, and the more precise information when $G$ is simply connected is Corollary 2.11. In this case $R(G)$ is actually the polynomial ring on $r$ variables where $r$ is the rank.
Feb 10, 2014 at 0:15 comment added Jim Humphreys Note that a good reference for the structure of representation rings is section VI.2 of Springer GTM 98 Representations of Compact Lie Groups by Brocker and tom Dieck. In particular, the ring is finitely generated (hence noetherian) and has more precise properties if $G$ is simply connected, etc.
Feb 9, 2014 at 23:49 history edited Qiaochu Yuan CC BY-SA 3.0
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Feb 9, 2014 at 23:44 history answered Qiaochu Yuan CC BY-SA 3.0