Structure of hypernuclei in relativistic approaches

We review the relativistic mean-field approach to various aspects of hypernuclei. It was Brockmann and Weise who first applied this approach to hypernuclei. At that time, it had been already observed experimentally that the spin-orbit splittings in hypernuclei are significantly smaller than that in ordinary nuclei. The relativistic approach was suitable for a discussion of spin-orbit splittings in hypernuclei, as the spin-orbit interaction is naturally emerged with the relativistic framework. Since this seminal work, many developments have been done and the relativistic approach has been applied both to the ground state and to excited states of hypernuclei. We summarize those developments in the Chapter. We shall concentrate on $\Lambda$-hypernuclei and do not discuss $\Sigma$ hypernuclei, since the theoretical treatment is rather similar to each other.