Speaker
Description
Nuclear collective excitation such as giant resonances provides valuable information on understanding the structure of finite nuclei and the equation of state for infinite nuclear matter. The quasiparticle random-phase approximation (QRPA) is a suitable theoretical framework for describing collective excitation as a superposition of the two-quasiparticle excitation, but it requires a large-dimensional matrix diagonalization and large computational resources.
The finite-amplitude method (FAM) [1] has been proposed as a solution to the QRPA problem under the presence of a one-body external field. The FAM is an iterative approach that makes it possible to calculate the strength function of giant resonance without additional truncation in the two-quasiparticle model space. Combined with a contour integration technique in the complex-energy plane, discrete low-energy collective states can be obtained [2]. The formulation based on the contour integration enables us to compute various QRPA solutions such as the low-energy collective modes, beta-decay rates, zero-energy pairing rotational modes, sum rules, and the nuclear matrix elements of the double-beta decay. I will review the recent progress and applications of the FAM for various problems including recent extensions for further reduction of the computational cost based on the reduced basis method.
[1] T. Nakatsukasa, T. Inakura, and K. Yabana, Phys. Rev. C 76, 024318 (2007).
[2] N. Hinohara, M. Kortelainen, and W. Nazarewicz, Phys. Rev. C 87, 064309 (2013).
