The even-even superheavy nuclei with 104 ≤ Z ≤ 126 and N ≤ 258 have been investigated using a microscopic five-dimensional collective Hamiltonian (5DCH) based on constrained triaxial relativistic Hartree-Bogoliubov calculations with the PC-PK1 density functional. The 5DCH approach effectively captures the characteristic of isospin dependence of nuclear binding energies, two-nucleon separation energies, and α -decay energies across isotopic chains and demonstrates consistent accuracy as Z increases, underscoring the model’s predictive power. The collective potentials, average quadrupole deformations, and characteristic collective observables: E ( 2 1 + ) , R 42 , and B ( E 2 ; 2 1 + → 0 1 + ) reveal a shape transition from well-prolate deformation around N = 150 and N = 210 to medium-deformed γ -soft shape around N = 176 and N = 246 , and finally to a spherical shape near N = 184 and N = 258 for the isotopic chains with 104 ≤ Z ≤ 118. Oblate deformations are favored for Z ≥ 120 isotopes around N = 178 . Remarkably, for a substantial range of transitional superheavy nuclei with N ≳ 184 and N ≳ 240, no 0 + states bounded by the fission saddles are predicted within their very shallow potential wells due to quantum shape fluctuations (QSFs). Additionally, sharp variations predicted for two-neutron separation energies S 2 n and α -decay energies Q α at N = 184 and 258 in mean-field calculations are significantly reduced and shifted to N = 182 and 256 in the 5DCH calculations, which is caused by the rapid evolution of the dynamical correlation energies related to QSFs around the nuclear spherical shells.

We have studied the effect of rigorous angular momentum conservation (AMC) in elastic, inelastic, and decay channels on pion production in intermediate-energy heavy-ion collisions based on the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model. We found that the constraint of AMC suppresses the absorption of both Δ resonances and pions, thus considerably enhances pion production and meanwhile reduces the charged pion yield ratio. The AMC effect on the charged pion yield ratio can not be simply compensated by a density-dependent in-medium Δ production cross section. Therefore, incorporating the constraint of AMC is important in obtaining the correct pion multiplicity and charged pion yield ratio by transport simulations, relevant for the extraction of the nuclear symmetry energy at high densities.