Speaker
Description
The theoretical description of $\gamma$-ray strength functions ($\gamma$SF) is of special interest in the field of nuclear astrophysics, where some processes - like the radiative neutron capture - are dependent of this quantities, with the dipole modes playing a dominant role. The use of reliable theoretical models to predict $\gamma$SF is a main aim, where the interacting shell model is known to provide precise results for the electromagnetic transitions. However, due to the computational complexity of the exact diagonalization of the model-space, it is restricted to certain regions of the nuclear chart. In a recent study [1], the quasiparticle random-phase approximation (QRPA) has been used to compute M1 strength functions in 25 nuclei from $A=26$ to $A=136$ using shell model calculations as a benchmark, employing identical Hamiltonians and valence spaces. It was concluded that the lack of correlations in the nuclear states and the truncation of the many-body space to two-quasiparticle excitations on top of the mean-field states could be important limitations in the description of dipole M1 strength, while it was suggested that methods like the projected generator coordinate method (PGCM) could produce an improvement caused by the enriched wave functions originated from the breaking and posterior restoration of the symmetries of the system, also giving the possibility to include varied collective degrees of freedom.
In this work, different approaches using the PGCM have been tested to reproduce the M1 transition strength between the different $1^+$ excited states and the $0^+$ ground state of $^{24}$Mg, with the exact diagonalization of the Hamiltonian as a benchmark.
[1] https://doi.org/10.48550/arXiv.2312.11040
