%0 Journal Article %T A maximality result for orthogonal quantum groups %A Teodor Banica %A Julien Bichon %A Benoit Collins %A Stephen Curran %J Mathematics %D 2011 %I arXiv %X We prove that the quantum group inclusion $O_n \subset O_n^*$ is "maximal", where $O_n$ is the usual orthogonal group and $O_n^*$ is the half-liberated orthogonal quantum group, in the sense that there is no intermediate compact quantum group $O_n\subset G\subset O_n^*$. In order to prove this result, we use: (1) the isomorphism of projective versions $PO_n^*\simeq PU_n$, (2) some maximality results for classical groups, obtained by using Lie algebras and some matrix tricks, and (3) a short five lemma for cosemisimple Hopf algebras. %U http://arxiv.org/abs/1106.5467v1