Stellar processes driven by the rise of nuclear collectivity
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Date
2025
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Springer
Abstract
The sudden rise of nuclear collectivity above the pairing gap is revealed in this work as the primary source for the relative increase of the symmetry energy with respect to the ground state, as originally suggested by Donati and collaborators. This finding is uncovered by available data on giant dipole resonances built on excited states and 1h¯ω shell-model calculations of the myriads of products of electric dipole matrix elements that compose the nuclear dipole polarizability of the ground and first-excited states. At the temperatures involved in stellar environments, a larger symmetry energy impacts stellar collapse, the nucleosynthesis of heavy elements and the nuclear equation of state of hot neutron stars. According to the Pauli exclusion principle, the symmetry energy reduces the binding energy of nuclei with a larger number of neutrons N than protons Z. It is commonly given by the term −asym (A)(N − Z)2/A in the Bethe–Weizsäcker semi-empirical mass formula [1,2], where asym (A) is the symmetry energy parameter and A = N +Z the atomic mass number. Analog parametrizations of the symmetry energy can be found in the literature [3–6]. In a seminal work, Donati and collaborators [7] calculated a relative increase of the symmetry energy of approximately 2.5 MeV or 8% for mediummass nuclei in the temperature interval T = 0 − 1 MeV.
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Keywords
Symmetry Energy, Nuclear Dipole Polarizability, Electric Dipole Matrix, Stellar Environments, Nucleosynthesis
Citation
Orce, J.N., 2025. Stellar processes driven by the rise of nuclear collectivity. The European Physical Journal A, 61(10), p.228.