Consider the automorphism of the algebra $U_q(\widehat{\mathfrak{sl}}_n)$ induced by the obvious diagram automorphism of the extended type A Dynkin diagram. More precisely, if the vertices of the Dynkin diagram are labelled $0,1,\ldots,n-1$, define $\overline{i}$ to be the number which is congruent to $-i$ modulo $n$. Then the diagram map sends the vertex labelled $i$ to the vertex labelled $\overline{i}$, and this induces an involution on the algebra which is given in terms of the Serre generators as $e_i\mapsto e_{\overline{i}}$, $f_i\mapsto f_{\overline{i}}$, $t_i^{\pm 1}\mapsto t_{\overline i}^{\pm 1}$ and $q^d\mapsto q^d$. Call this involution $\sigma$ (it is easy but tedious to check that this is indeed an involution).
Now consider the algebra $U_q(\widehat{\mathfrak{sl}}_n)^\sigma$ of points fixed by the involution $\sigma$. My question is: can this algebra be realised as $U_q(\mathfrak{g})$ for some affine Lie algebra $\mathfrak{g}$? If not, is there a known presentation of the fixed point algebra by generators and relations?
