*5.4. A Short Summary of This Section*

The present new dripline mechanism [57] involves the monopole–quadrupole interplay and is one of the emerging concepts. It definitely differs from the traditional mechanism of the single-particle origin, where a neutron halo arises at extremes [104,105]. In the new mechanism, the coupling to continuum may be visible if the monopole effect vanishes like heavy F isotopes [57]. As *Z* changes, two dripline mechanisms may appear alternatively, but the present one may be more relevant to heavier nuclei where the deformation develops more. Finally, I would like to point out that the Bethe–Weizäcker mass formula does not include a deformation energy term, at least, explicitly .

#### **6. Prospect**

As this article is a kind of summary, I am afraid that a summary section may be redundant. I state some prospects. First of all, ab initio no-core Monte Carlo shell–model calculations became feasible recently up to 12C and beyond [106], and as an example, we can look into *α* clustering in light nuclei, e.g., the Hoyle state, with correlations produced by nuclear forces [107]. This direction will produce a major outcome from the shell model. This includes clarifications of *α* decay, *α* knockout, etc. Another major frontier is the quest for fission dynamics and superheavy elements, with (almost) full inclusion of the correlations due to nuclear forces.

Although more computer power and further advancements in computational methodology are needed also, the perspectives of the shell model look unlimited, to me. *May the (nuclear) force be with you.*

**Funding:** This work was supported in part by MEXT as "Program for Promoting Researches on the Super computer Fugaku" (Simulation for basic science: from fundamental laws of particles to creation of nuclei) and by JICFuS. This work was supported by JSPS KAKENHI Grant Numbers JP19H05145, JP21H00117.

#### **Data Availability Statement:** Not applicable.

**Acknowledgments:** The author is grateful to A. Gargano and S.M. Lenzi for their interests and for the invitation to this valuable program. He acknowledges T. Abe, Y. Akaishi, B.A. Brown, P. Van Duppen, B. Fornal, R. Fujimoto, A. Gade, H. Grawe, R.V.F. Janssens, M. H.-Jensen, K. Heyde, J. Holt, M. Honma, M. Huyse, Y. Ichikawa, S. Leoni, T. Mizusaki, N. Pietralla, P. Ring, E. Sahin, J. P. Schiffer, A. Schwenk, N. Shimizu, O. Sorlin, Y. Sun, T. Suzuki, K. Takayanagi, T. Togashi, K. Tsukiyama, N. Tsunoda, Y. Tsunoda, Y. Utsuno, S. Yoshida, and H. Ueno for their valuable direct collaborations towards the works presented in this article and thanks many others for their useful comments and help. The comment by Y. Tsunoda on Appendix A is appreciated.

**Conflicts of Interest:** The author declares no conflict of interest.

#### **Appendix A. Note on the Relation between the Present ESPE and the Baranger's ESPE**

This is a short note on the the relation between the present ESPE and Baranger's ESPE [19] discussed in [15]. A possible problem was pointed out by Y. Tsunoda. Although the relevant arguments and results in [15] are basically correct, the following term is found to be added to Equation (43) of [15]: −1/(2*<sup>j</sup>* + <sup>1</sup>)*Vm*(*j*, *<sup>j</sup>*)0|*n*ˆ*<sup>j</sup>* |0, where *<sup>j</sup>* includes the index, proton, or neutron. So, this is the contribution from the interaction between a neutron orbit *j* and the same neutron orbit *j* (or between protons similarly), of which the monopole interaction is known to be weak. In addition, the factor 1/(2*j* + 1) reduces this quantity. Because of all these factors combined, the correction is quite minor. This correction does not change the basic equivalence relation between the two schemes.
