Speaker
Description
Magnetars and the environments of core-collapse supernovae host some of the most extreme magnetic fields in the universe, reaching intensities of $10^{18}$ G. Under these conditions, the fundamental quantum structure of matter is severely altered. In this work, we investigate the ground-state properties of finite nuclei of astrophysical interest, specifically focusing on waiting-point nuclei in r- and rp-process nucleosynthesis. We employ Covariant Density Functional Theory (CDFT) to calculate bulk properties including the total binding energy, the radius, and the deformation ($\beta_2$). To rigorously assess theoretical uncertainties and model dependency, the self-consistent calculations are performed using two distinct effective interactions: the density-dependent DD-ME2 and the non-linear NL3* parameter sets within a constrained relativistic mean-field framework. Our calculations reveal that the breaking of time-reversal symmetry and the destruction of Kramer's degeneracy induce profound structural phase transitions. As the magnetic field strength increases, we observe a spontaneous rearrangement of single-particle energy levels, with critical crossings at the Fermi surface emerging at $B \approx 10^{17}-10^{18}$ G. This microscopic rearrangement forces a macroscopic phase transition, driving transitional nuclei from spherical configurations into oblate or prolate ground states. Concurrently, we observe a substantial increase in the total binding energy of the nuclei, primarily driven by the strong spin-alignment of protons and Landau orbital coupling. Both parameter sets consistently confirm these magnetically induced changes in the bulk properties of the nuclei. These structural modifications are expected to fundamentally alter the dynamics of stellar weak interaction rates governing nucleosynthesis, highlighting the necessity of robust microscopic modeling in astrophysical simulations.