(Q)RPA-based methods
7-9 July
Recent developments and challenges for (Q)RPA-based methods
Working group at DPhN Orme b703 Room 45
Organizers: S. Péru (CEA DAM, SPN, contact), G.Colò (Università degli studi, INFN Milano), D. Gambacurta (INFN-LNS), E. Litvinova (Western Michigan Univ) and E. Yüksel (Univ. of Surrey)
The theory of nuclear response plays a paramount role for our understanding of nuclear structure itself, but also for applications to particle physics and astrophysics. Multipole responses probe the basic properties of the nuclear Hamiltonian, while isovector excitations provide unique constraints on the nuclear equation of state and the symmetry energy. Moreover, understanding spin–isospin responses is essential to advance our studies of, e.g., double-beta decay and the propagation of neutrinos in the dense matter that characterises compact objects.
The Random Phase Approximation (RPA) is a microscopic approach extensively used for the study of nuclear response. Within the energy density functionals (EDF) framework, it provides a self-consistent description of small amplitude collective excitations around the ground state. When pairing correlations are included through a superfluid description of the ground state, RPA is naturally extended to the quasiparticle RPA (QRPA).
A dedicated discussion among theorists actively involved in the development of advanced RPA-type methods has become timely and necessary. Such an exchange would aim to (i) identify possible synergies between existing methods, (ii) clarify and communicate their respective complementarities and limitations, and (iii) help each other, i.e. benefit from the knowledge and expertise of colleagues to accelerate the range of applicability of the associated tools.
The goals of the project are to:
1. Bring together developers and users of RPA and extended-RPA frameworks to compare their theoretical assumptions, numerical implementations, and domains of applicability.
2. Build bridges and foster collaborations between research groups working with different nuclear interactions and/or models.
3. Discuss which tools need to be developed to study spherical and deformed systems, or closed-shell and open-shell systems, treating deformation and pairing correlations on equal footing.
4. Compare standard diagonalization solutions versus FAM ((finite amplitude method) and iterative techniques.
5. Identify the main advantages and limitations introduced in beyond-RPA methods, such as the Second RPA, particle-vibration coupling, multi-phonon approaches.
6. Extend current approaches to the description of electromagnetic or weak transitions between excited states.
7. Identify the key theoretical extensions and methodological advances needed to address upcoming experimental data and emerging physics questions.
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