Narrow Results

The α-condensed state in nuclear systems has been proposed by Tohsaki et al. and given rise to interesting discussions. The Hoyle state of ¹²C has been studied as the most typical example of such an α-condensed state. A new resonant state (E_r = 1.66 MeV, Γ = 1.48 MeV) is predicted as an excited α-condensed state in addition to the second 0⁺ state of the Hoyle state by calculations of the complex scaled 3α model. Based on this result, the breakup strengths of the inversion reaction for sequential (⁸Be + α → ¹²C + γ) and direct (α + α + α → ¹²C + γ) processes are calculated.

We have studied three α states around ⁴⁰Ca based on a microscopic α-cluster model, which has been succeeded experimentally quite recently. This was performed by introducing a Monte Carlo technique for the description of the THSR (Tohsaki Horiuchi Schuck Röpke) wave function, which is called the "virtual THSR" wave function. The three α cluster state around ⁴⁰Ca has an energy below the Coulomb barrier top energy with a spatial extension comparable to the second 0⁺ state of ¹²C.

The famous Hoyle state (0_2⁺ at 7.654 MeV in ¹²C) is identified as being an almost ideal condensate of three α-particles, hold together only by the Coulomb barrier. It, therefore, has a ⁸Be-α structure of low density. Transition probability and inelastic form factor together with position and other physical quantities are correctly reproduced without any adjustable parameter from our two parameter wave function of α-particle condensate type. The possibility of the existence of α-particle condensed states in heavier nα nuclei is also discussed.

The famous Hoyle state (0₂⁺ at 7.654 MeV in ¹²C) is identified as being an almost ideal condensate of three α-particles, hold together only by the Coulomb barrier. It, therefore, has a ⁸Be-α structure of low density. Transition probability and inelastic form factor together with position and other physical quantities are correctly reproduced without any adjustable parameter from our two parameter wave function of α-particle condensate type. The possibility of the existence of α-particle condensed states in heavier nα nuclei is also discussed.

Alternatively to pairing, four-particle correlations may become of importance for the formation of quantum condensates in nuclear matter. With increasing density, four-particle correlations are suppressed because of Pauli blocking. Signatures of α-like clusters are expected to occur in low-density nuclear systems. The famous Hoyle state (0_2⁺ at 7.654 MeV in ¹²C) is identified as being an almost ideal condensate of three α-particles, hold together only by the Coulomb barrier. It, therefore, has a ⁸Be-α structure of low density. Transition probability and inelastic form factor together with position and other physical quantities are correctly reproduced without any adjustable parameter from our two parameter wave function of α-particle condensate type. The possibility of the existence of α-particle condensed states in heavier nα nuclei is also discussed.

We present results for p-shell nuclei based on the ab initio symmetry-adapted no-core shell model that utilizes an SU(3) coupling scheme. Details given for ¹²C are reflective of similar results found for ⁶Li, ⁸B, ⁸Be, and ¹⁶O, all of which exhibit a strong preference for large quadrupole deformations and a narrow set of intrinsic spin values. The outcome suggests that a small subspace of symmetry-adapted configurations can very closely approximate the exact solutions. The symmetry patterns unveiled in these results are, in turn, employed to explore ultra-large model spaces for ¹²C, in particular to study the elusive Hoyle state, as well as for ⁸Be and sd-shell nuclei including Ne and Mg.