Symmetries in nuclear structure

Abstract

The symmetries of the rotating mean field and their consequences for rotational bands are discussed. Chirality of rotating triaxial nuclei differs from the chirality of molecules and mass-less particles, because the roles of space inversion and time reversal are exchanged. The experimental consequences of chirality and mass regions where it is expected are discussed. Rotational bands of the predicted shapes with tetrahedral symmetry are Δ I = 2 sequences with alternating parity. Breaking of the isospin rotational symmetry by the isovector pair field leads to isorotational bands. The low spin spectra of N = Z nuclei can be explained combining mean-field calculations that take only isovector pairing into account with the concept of isorotational bands. The possible appearance of an isoscalar pair field at high spin would manifest as a pair-rotational band consisting of even-spin states in the even-even and odd-spin states in odd-odd N = Z nuclei.