On diagonal solutions of the reflection equation

We study solutions of the reflection equation associated with the quantum affine algebra $U_{q}(\hat{gl}(N))$ and obtain diagonal K-operators in terms of the Cartan elements of a quotient of $U_{q}(gl(N))$. We also consider intertwining relations for these K-operators and find an augmented q-Onsager algebra like symmetry behind them.
22 pages