Beyond the Unified Model

Abstract

The key elements of the Unified Model are reviewed. The microscopic derivation of the Bohr Hamiltonian by means of adiabatic time-dependent mean field theory is presented. By checking against experimental data the limitations of the Unified Model are delineated. The description of the strong coupling between the rotational and intrinsic degrees of freedom in framework of the rotating mean field is presented from a conceptual point of view. The classification of rotational bands as configurations of rotating quasiparticles is introduced. The occurrence of uniform rotation about an axis that differs from the principle axes of the nuclear density distribution is discussed. The physics behind this tilted-axis rotation, unknown in molecular physics, is explained on a basic level. The new symmetries of the rotating mean field that arise from the various orientations of the angular momentum vector with respect to the triaxial nuclear density distribution and their manifestation by the level sequence of rotational bands are discussed. Resulting phenomena, as transverse wobbling, rotational chirality, magnetic rotation and band termination are discussed. Using the concept of spontaneous symmetry breaking the microscopic underpinning of the rotational degrees is refined. † BCS is the acronym of Bardeen, Cooper and Schrieffer, who invented it for describing superconductivity in metals [21]. † "yrast": Swedish "most dizzy". These are the states with the highest angular momentum for given energy, which are the lowest states for given angular momentum . Sometimes the state above the yrast state is referred to as " yrare": Swedish "more dizzy". † We adopt the definition of the D-functions and phase conventions used by Bohr and Mottelson [6] and Rowe [9]. † The sign of q 2 is taken according to the "Lund convention" which is opposite to the "Copenhagen convention" of the Bohr Hamiltonian of Ref.[6]. This unfortunate inconsistency persist in the literature and between section 2 and the following as well.

Chirality of Nd135 reexamined: Evidence for multiple chiral doublet bands

“…Recent reviews of both the experimental and theoretical investigation of the chiral bands can be found in Refs. [3][4][5][6][7]. The first chiral bands were observed in odd-odd nuclei at low spins, where the shape can be γsoft and the competition with other collective modes is important.…”

Reexamining nuclear chiral geometry from the orientation of the angular momentum

“…For recent reviews, see Refs. [2][3][4][5][6][7][8]. With the prediction [9] and confirmation [10] of multiple chiral doublets (Mχ D) in a single nucleus, the investigation of chirality continues to be one of the hottest topics in nuclear physics [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Decoherence of collective motion in warm nuclei

“…With increasing deformation, the LEMAR spike changes from incoherent thermal-like radiation to partially coherent rotational radiation. The ratio B(M1)/B(E2) ∼ 6(µ/eb) 2 is characteristic for magnetic rotation [1][2][3]. As shown in Fig.…”