New concept of clustering is discussed in $Lambda$ hypernuclei using a new-type microscopic cluster model wave function, which has a structure that constituent clusters are confined in a container, whose size is a variational parameter and which we r
efer to as Hyper-Tohsaki-Horiuchi-Schuck-Ropke (Hyper-THSR) wave function. By using the Hyper-THSR wave function, $2alpha + Lambda$ cluster structure in ${^{9}_Lambda{rm Be}}$ is investigated. We show that full microscopic solutions in the $2alpha + Lambda$ cluster system, which are given as $2alpha + Lambda$ Brink-GCM wave functions, are almost perfectly reproduced by the single configurations of the Hyper-THSR wave function. The squared overlaps between the both wave functions are calculated to be $99.5$%, $99.4$%, and $97.7$% for $J^pi=0^+$, $2^+$, and $4^+$ states, respectively. We also simulate the structural change by adding the $Lambda$ particle, by varying the $Lambda N$ interaction artificially. As the increase of the $Lambda N$ interaction, the $Lambda$ particle gets to move more deeply inside the core and invokes strongly the spatial core shrinkage, and accordingly distinct localized $2alpha$ clusters appear in the nucleonic intrinsic density, though in ${^{8}{rm Be}}$ rather gaslike $2alpha$-cluster structure is shown. The origin of the localization is associated with the strong effect of Pauli principle. We conclude that the container picture of the $2alpha$ and $Lambda$ clusters is essential in understanding the cluster structure in ${^{9}_Lambda{rm Be}}$, in which the very compact spatial localization of clusters is shown in the density distribution.
The 4-alpha condensate state for ^{16}O is discussed with the THSR (Tohsaki-Horiuchi-Schuck-Roepke) wave function which has alpha-particle condensate character. Taking into account a proper treatment of resonances, it is found that the 4-alpha THSR w
ave function yields a fourth 0^+ state in the continuum above the 4-alpha-breakup threshold in addition to the three 0^+ states obtained in a previous analysis. It is shown that this fourth 0^+ ((0_4^+)_{THSR}) state has an analogous structure to the Hoyle state, since it has a very dilute density and a large component of alpha+^{12}C(0_2^+) configuration. Furthermore, single-alpha motions are extracted from the microscopic 16-nucleon wave function, and the condensate fraction and momentum distribution of alpha particles are quantitatively discussed. It is found that for the (0_4^+)_{THSR} state a large alpha-particle occupation probability concentrates on a single-alpha 0S orbit and the alpha-particle momentum distribution has a delta-function-like peak at zero momentum, both indicating that the state has a strong 4-alpha condensate character. It is argued that the (0_4^+)_{THSR} state is the counterpart of the 0_6^+ state which was obtained as the 4-alpha condensate state in the previous 4-alpha OCM (Orthogonality Condition Model) calculation, and therefore is likely to correspond to the 0_6^+ state observed at 15.1 MeV.
