Les jeunots en physique nucléaire de basse énergie Some remarks on current theoretical activities:

1. Les jeunots en physique nucléaire de basse énergie Some remarks on current theoretical activities: France vs the rest of the world Thomas Duguet (SPhN)

2. Theory of Nuclei • Goals • Comprehensive and unified description of all nuclei • Low-energy reaction and structure properties • From basic interactions between protons and neutrons • Understand different states of nuclear matter in astrophysics environments • Difficulties • Self-bound, two-component quantum many-fermions system • Complicated interaction from low-energy regime of QCD • Tensor and spin-orbit components • Unnaturally large scattering lengths (2-body virtual and bound states) • NNN unavoidable • Repulsive core and strong tensor at short distances? • Properties of finite and bulk nucleonic matter • Deuteron to SHE nuclei to neutron stars and nuclear (strange) matter • Need to extrapolate to unknown regions • Some trivial facts • No “one size fits all” theory for nuclei • All theoretical approaches need to be linked • Theoretical activity strongly linked to experiment…

3. Selection of advances in the recent years • Ab-initio (NCSM&GFMC) methods allowed for interaction tests • Consistent proof of the role of NNNinteraction in light nuclei • Nuclear interactions: c-EFT provides missing links • Explains hierarchy NN > NNN > NNNN + 2N-3N, N, ,… consistency • Chiral symmetry breaking of QCD encoded => constrains Ninteraction • Renormalization Group provides gentle NN (“Vlowk”)+ NNN • Use relevant degrees of freedom/energy scales for low energy nuclear physics • Many-body problem becomes (mostly) perturbative (HUGE practical implications) • Quantitative microscopic nuclear structure • CI calculations into the fp shell ; sSD608 = 140 keV! • LACM: shape coexistence and fission • Transfermiums as a window on SHE nuclei • First EDF mass tables (SR) and systematics of correlations (MR) in heavy nuclei • Multipole strength S(El)/b-decay from fully self-consistent (deformed!) QRPA • Shell evolution towards drip-lines ; role of tensor force raised • Integration of structure and reaction for light nuclei • Multistep reactions calculations using coupled discretized continuum channels • GSM, CSM and SMEC to incorporate (many-body) continuum in CI • Use of nuclear inputs into reaction models ; e.g. JLM optical model • Astrophysics • Use of consistent nuclear inputs for NS, r-process calculations, supernovae

4. Selection of challenges for the coming years • Bridge between hadrons and nuclei • e.g., lattice QCD with smaller pion masses; match PT with lattice results • NNN interaction • Test NNN (NNNN) from c-EFT at N3LO through NCSM calculations of light nuclei • Role in medium mass nuclei through CC and spectroscopy through CI and EDF • Interplay of phenomenological and non-empirical EDF • Constructed from low-momentum interactions/c-EFT and benchmarked against CC • Predictability (theoretical error bars) and accuracy (new (re)fitting protocols) • Strong focus on spectroscopy • Coherent formulation of SR and MR EDF methods from first principle • Superfluidity • Nature of pairing correlations in finite nuclei • Pairing in asymmetric systems ; e.g. neutron-proton pairing, polarized cold atoms • Shell position/evolution in stable/neutron rich nuclei • Role of tensor, NNN, spin-orbit (matter diffusivity), other? • LACM: coexistence, fusion and fission • Quantitative methods including both diabatic and adiabatic effects • Integration of structure and reaction • Advance GSM/CCSD (interaction) and apply to complex open light nuclei • Extend TDHF(B) (excitations and reactions) ; e.g. neutron skin for heavy ion fusion • Microscopic optical potentials and level densities (inputs from EDF/CI) • Astrophysics • Quantal calc. of NS (inner) crust: compos., clusters shape, pairing prop., transport… • Reliable systematics of Qb, SN, fission, E1 and GT strength… for r-process calc.

5. Some useful experimental data (not exhaustive!!) • Fission • Barriers and life-time • Mass and kinetic energy distributions of fragments • Evaporated neutrons and g’s • Systematic data into the “next major shell” (few mass units) • Mass differences ; e.g. shell evolution and pairing • First 2+, B(E2) and Qs; e.g. deformation and shell evolution • Single-particle energies and spectroscopic factors ; i.e. shell evolution • Pair transfer ; e.g. quantitative information on pairing? • Data at large deformations (low and high J) • Beta-decay and charge-exchange reactions ; e.g. pin down theories for weak rates • Transfermiums • Rotational bands ; i.e. pairing and shell positioning • K-isomers ; i.e. pairing and shell positioning • Neutron radii • Parity violation from e- scattering (208Pb) at JLAB ; i.e. Rn-Rp <=> asym(rsat)/P(rsat/2) • Same in more (neutron-rich) nuclei might be of interest • Neutron star observations • Thermal X-ray emission for cooling • Example 2

6. Young « french » theorists’ activities by methods/subjects

7. Are we well positioned for the next 10/15 years? • Community extremely biased towards EDF methods • Chance to propose a coherent effort • Promising future as experimental facilities move to medium-mass exotic nuclei • Cultural advantage but US and Japan now put strong emphasis on EDF ; e.g. UNEDF • Our expertise suggest to • Push MREDF methods ; e.g. QRPA, GCM/Projection-like methods • Develop further and systematize the use of Time-Dependent EDF methods • Push cross-fertilization between EDF and CI ; e.g. ESNT workshop on April 7-10 • Such a bias carries the danger to miss the big picture • E.g., somewhat true about ab-initio methods and nuclear interactions in the 80/90’s • Could be detrimental as overlap/benchmarks are envisioned ; e.g. with CC • Might need to recruit a few theorists with different expertise • Interplay between structure and reaction ; e.g. GSM • “Hard core” reaction theory ; e.g. issue with extracting spectroscopic factors • Promising ab-initio method for medium mass nuclei: Coupled Cluster

8. Geography • Strong on-going theoretical collaborations • GANIL-IPNO • CENBG-GANIL-IPNL-SPhN • GANIL-SPhN • Future • Projects will naturally follow historical collaborations • But new ones will hopefully arise…