We develop a new formalism to treat nuclear many-body systems using bare nucleonnucleon interaction. It has become evident that the tensor interaction plays important role in nuclear many-body systems due to the role of the pion in strongly interacting system. We take the antisymmetrized molecular dynamics (AMD) as a basic framework and add a tensor correlation operator acting on the AMD wave function using the concept of the tensor-optimized shell model (TOSM). We demonstrate a systematical and straightforward formulation utilizing the Gaussian integration and differentiation method and the antisymmetrization technique to calculate all the matrix elements of the many-body Hamiltonian. We can include the three-body interaction naturally and calculate the matrix elements systematically in the progressive order of the tensor correlation operator. We call the new formalism "tensor-optimized antisymmetrized molecular dynamics". (http://creativecommons.org/licenses/by-nc/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.low-momentum shell-model state, which induces high-momentum transfer between nucleons, and provides a large attraction energy. The TOSM was applied to light mass nuclei as He, Li and Be isotopes [6][7][8]. The level orders and spacings come out to be quite good due to the adequate role of the tensor interaction, although the absolute values for the binding energies are not reproduced due to the lack of the three-body interaction [6][7][8]. The saturation property seems satisfied for shell-model states with the use of the bare nucleon-nucleon interaction. The TOSM was able to describe shell-model states and also generate low-lying alpha cluster structures in the spectrum of 8 Be [8]. However, the TOSM could not reproduce sufficient of alpha correlation, and we ought to improve the TOSM for multi-cluster states. The concept of TOSM was also applied to the few-body framework and demonstrated its goodness [9]. However, the few-body framework that uses the relative coordinates has difficulty in handling the antisymmetrization for p-shell nuclei.On the other hand, antisymmetrized molecular dynamics (AMD) was developed by the Kyoto group with great success to describe both the cluster and shell structures simultaneously [10][11][12]. Here, the nuclear dynamics was controlled by an effective interaction, which is obtained from various experimental data. There are several cases where the effective interaction has to be changed for various observables of nuclear structure. A typical case for this change is the ground-state energies of 12 C and 16 O. It is highly desirable to use the bare nucleon-nucleon interaction in the AMD framework for the description of light nuclei, where the structural change between shell and cluster states is essential. For 8 Be, both the shell and alpha structures are observed experimentally and the AMD description should be essential for good description of this nucleus [8].It has become clear from a few-bo...

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Structures of excited states in 14 C are investigated with a method of β-γ constraint antisymmetrized molecular dynamics in combination with the generator coordinate method. Various excited states with the developed 3α-cluster core structures are suggested in positive-and negative-parity states. In the positive-parity states, triaxial deformed and linear-chain structures are found to construct excited bands. Interestingly, 10 Be + α correlation is found in the cluster states above the 10 Be + α threshold energy.In the method of AMD, a basis wave function of an A-nucleon system | is described by a Slater determinant of 0556-2813/2010/82(4)/044301 (13) 044301-1

We present a new picture that the α-linear-chain structure for 12C and 16O has one-dimensional α condensate character. The wave functions of linear-chain states that are described by superposing a large number of Brink wave functions have extremely large overlaps of nearly 100% with single Tohsaki-Horiuchi-Schuck-Röpke wave functions, which were proposed to describe the α condensed "gaslike" states. Although this new picture is different from the conventional idea of the spatial localization of α clusters, the density distributions are shown to have localized α clusters due to the inter-α Pauli repulsion.

We study the tensor-optimized antisymmetrized molecular dynamics (TOAMD) as a successive variational method in many-body systems with strong interaction for nuclei. In TOAMD, the correlation functions for the tensor force and the short-range repulsion and their multiples are operated to the AMD state as the variational wave function. The total wave function is expressed as the sum of all the components and the variational space can be increased successively with the multiple correlation functions to achieve convergence. All the necessary matrix elements of manybody operators, consisting of the multiple correlation functions and the Hamiltonian, are expressed analytically using the Gaussian integral formula. In this paper we show the results of TOAMD with up to the double products of the correlation functions for the s-shell nuclei, 3 H and 4 He, using the nucleon-nucleon interaction AV8 ′ . It is found that the energies and Hamiltonian components of two nuclei converge rapidly with respect to the multiple of correlation functions. This result indicates the efficiency of TOAMD for the power series expansion in terms of the tensor and short-range correlation functions.