Eur. Phys. J. A (2014) 50: 26
https://doi.org/10.1140/epja/i2014-14026-9

Regular Article - Theoretical Physics

Symmetry energy from the nuclear collective motion: constraints from dipole, quadrupole, monopole and spin-dipole resonances

¹ Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, I-20133, Milano, Italy
² INFN, Sezione di Milano, via Celoria 16, I-20133, Milano, Italy
³ Physics Department, University of Notre Dame, 46556, Notre Dame, USA
⁴ Joint Institute for Nuclear Astrophysics, University of Notre Dame, 46556, Notre Dame, Indiana, USA
⁵ Center for Mathematics and Physics, University of Aizu, 965-8560, Fukushima, Japan
⁶ RIKEN Nishina Center, 351-0198, Wako, Japan

^* e-mail: colo@mi.infn.it

Received: 5 September 2013
Revised: 6 December 2013
Accepted: 30 December 2013
Published online: 26 February 2014

Abstract

The experimental and theoretical studies of Giant Resonances, or more generally of the nuclear collective vibrations, are a well-established domain in which sophisticated techniques have been introduced and firm conclusions reached after an effort of several decades. From it, information on the nuclear equation of state can be extracted, albeit not far from usual nuclear densities. In this contribution, which complements other contributions appearing in this topical issue, we survey some of the constraints that have been extracted recently concerning the parameters of the nuclear symmetry energy. Isovector modes, in which neutrons and protons are in opposite phase, are a natural source of information and we illustrate the values of symmetry energy around saturation deduced from isovector dipole and isovector quadrupole states. The isotopic dependence of the isoscalar monopole energy has also been suggested to provide a connection to the symmetry energy: relevant theoretical arguments and experimental results are thoroughly discussed. Finally, we consider the case of the charge-exchange spin-dipole excitations in which the sum rule associated with the total strength gives in principle access to the neutron skin and thus, indirectly, to the symmetry energy.