The ppK − system, as a prototype for possible quasiboundK nuclei, is investigated using a variational approach. Several versions of energy-dependent effectiveKN interactions derived from chiral SU(3) dynamics are employed as input, together with a realistic NN potential (Av18). Taking into account theoretical uncertainties in the extrapolations below theKN threshold, we find that the antikaonic dibaryon ppK − is not deeply bound. With the driving s-waveKN interaction the resulting total binding energy is B(ppK − ) = 20 ± 3 MeV and the mesonic decay width involvingKN → πY is expected to be in the range 40-70 MeV. Properties of this quasibound ppK − system (such as density distributions of nucleons and antikaon) are discussed. The (1405), as an I = 0 quasibound state ofK and a nucleon, appears to survive in the ppK − cluster. Estimates are given for the influence of p-waveKN interactions and for the width from two-nucleon absorption (KNN → Y N) processes. With inclusion of these effects and dispersive corrections from absorption, the ppK − binding energy is expected to be in the range 20-40 MeV, whereas the total decay width can reach 100 MeV but with large theoretical uncertainties.

In order to study light unstable nuclei systematically, we propose a new method, the antisymmetrized molecular dynamics plus Hartree-Fock ͑AMDϩHF͒ method. This method introduces the concept of the single particle orbits into the usual AMD. Applying the AMDϩHF method to Be isotopes, it is found that the calculated lowest intrinsic states with plus and minus parities have rather good correspondence with the explanation by the two-center shell model. In addition, by active use of the single particle orbits extracted from the AMD wave function, we construct the first excited 0 ϩ state of 10 Be. The obtained state appears in the vicinity of the lowest 1 Ϫ state. This result is consistent with the experimental data. ͓S0556-2813͑97͒04510-X͔

We study the structure of excited states of 10 Be with the method of variation after spin-parity projection in the framework of antisymmetrized molecular dynamics. Present calculations describe many excited states and reproduce the experimental data of E2 and E1 transitions and the new data of the ␤ transition strength successfully. We include systematic discussions on the moleculelike structures of light unstable nuclei and the important role of the valence neutrons based on the results obtained with the framework which is free from such model assumptions as the existence of inert cores and clusters.

The K − pp system is investigated using a variational approach with realistic two-body interactions: the Argonne v18 NN potential and an energy dependentKN effective interaction derived from chiral SU (3) coupled-channel dynamics. Uncertainties in subthreshold extrapolations of theKN interaction are considered. A weakly bound K − pp state is found, with a binding energy B = (19 ± 3) MeV substantially smaller than suggested in previous calculations. The decay width Γ (K − pp → πΣN) is estimated to range between about 40 and 70 MeV.

An extended version of antisymmetrized molecular dynamics was developed to study the structure of p-sd shell hypernuclei. By using an effective N interaction, we investigated the energy curves of 9 Be, 13 C, and 20,21 Ne as a function of nuclear quadrupole deformation. The changes to nuclear deformation caused by particles are discussed. We found that in the p wave enhances nuclear deformation, while that in the s wave reduces it. This effect is most prominent in 13 C. The possibility of parity inversion in 20 Ne is also examined.