[en] The removal of the spurious states associated with the violation of rotational and gauge invariance by mean field approximation from the RPA solutions describing the low-energy spectrum of nuclei is a notoriously difficult task, in particular in a rotating frame. A novel, numerically accurate yet technically simple method to accomplish this aim has been developed based on linear response theory. The results of calculations carried out for the deformed, superfluid, rotating nucleus ¹⁶⁸Yb testify to the power of the technique, the associated solutions respecting the variety of sum rules required to be fulfilled by the RPA solutions because of conservation laws

[en] Isoscalar monopole and quadrupole giant resonances in rotating triaxially deformed nuclei are studied by means of the RPA based on the rotating shell model. The deformation parameters are selfconsistently determined as functions of rotational frequency, and the doubly stretched monopole and quadrupole forces are used as residual interactions. It is found that the properties of these modes-the excitation energies, the splitting and the mixing of the strength-predicted by the harmonic-oscillator potential model are well realized in the realistic calculation. The result indicates that the high frequency rotations affect the properties of these giant resonances mainly through the change of the deformation parameters. (author)

[en] In the meeting I have discussed on the possible mechanisms for the problem of decays out of the superformed rotational bands. One extreme picture is that the decay proceeds through the mixing of the superdeformed state with the compound (normal deformed) states surrounding it. Another is a simple picture such that the decay is governed by the branching ratio to some specific normal deformed states which are connected to the superdeformed states by the electromagnetic transitions. It is shown that the experimentally observed features of the γ-ray intensity can be reproduced by models based on both pictures. The difference of the two pictures and the plausibility of them are discussed. (author)

[en] In this talk, the following two topics related to physics of unstable nuclei are discussed: change of shell structure or magic number in very neutron rich nuclei, and 'phase' transition/coexistence expected in nuclear chart. In the latter topic, the well-known transition between spherical and prolate or oblate shape, the transition to large and/or triaxial deformation, as well as expected existence of exotic shapes like tetrahedral one are examplified. The interesting phenomena in combination with high-frequency rotation are also mentioned. (author)

[en] The importance of the pairing correlation in rapidly rotating nuclei is reviewed by making use of the theoretical method which takes higher order correlations into account. The characteristic difference of the properties of the pairing correlation in the 'static' and 'dynamic' pairing regimes, which are distinguished by the dominance of the mean-field contributions, is emphasized. Through the investigation of the relative energy spectra the concept of the pairing phase transition is re-examined. Interesting phenomena related to the pair transfer reactions are also mentioned briefly. (orig.)

[en] Short communication

[en] We present a result of the RPA calculation in a rotating frame, and suggest that the nature of the γ-vibrational mode in ¹⁶⁴Er is seriously affected by the excitation of aligned two-quasiparticles. (author)

[en] The particle-vibration coupling formalism is generalized to deal with hot, strongly rotating nuclei. In this way the basis to carry out a microscopic description of the structure of compound nuclei has been developed, in particular the calculation of the effective mass of nucleons close to the Fermi energy. As a consequence, it will be possible to provide a realistic estimate of the nuclear level density as a function of rotational frequency and temperature, a quantity which is among the key ingredients needed in the study of the evolution of the cooling of the compound nucleus through nucleon and γ-decay

No abstract available

[en] On the basis of the self-consistently determined diabatic quasiparticle representation, RPA calculations in the rotating frame are performed for the γ-vibrations around the triaxial equilibrium shapes. The doubly stretched quadrupole forces are used as residual interactions. It is found that the negative-signature γ-vibrational modes created on the s-band well retain their collective characters, while the positive-signature modes tend to lose their identities with increasing rotational frequency. (author)