Recent applications of the subtracted second random-phase approximation (SSRPA), based on Skyrme functionals, to the study of Gamow-Teller excitations and beta-decay will be presented. The comparison with the conventional random-phase approximation (RPA) results and experimental data is also discussed. It is found that, the amount of Gamow-Teller strength obtained in SSRPA is much lower than...

Neutrinoless double-beta decay ($0\nu\beta\beta$)is a transition in nuclei where two neutrons simultaneously transform into two protons, accompanied by the emission of only two electrons [1]. This second-order process, if observed, would proof that neutrinos are Majorana particles (their own antiparticles), shed light on the existence of massive neutrinos and explain the predominance of...

**$2\nu \beta \beta$ decay to excited states of heavy nuclei**

In double-beta decay, two neutrons convert into two protons, accompanied by the emission of two electrons. According to the Standard Model (SM), this decay, called two-neutrino double-$\beta$ decay ($2\nu \beta \beta$ decay), involves the emission of two antineutrinos, maintaining an equilibrium between matter and antimatter and...

Precision spectrum shape measurements in nuclear beta decay can be used for testing the Standard Model and physics beyond it with accuracy being competitive with high-energy collider experiments. Such a comparison can be carried out in the framework of effective field theory. The most prominent and poorly known effect in the Standard Model is weak magnetism [1], the higher-order recoil...

Precision measurements involving nuclei are at the cutting edges of nuclear physics and testing the Standard Model (SM) of physics. For instance, precision beta decay measurments have the potential to constrain beyond SM physics at TeV scales. To interpret these experiments, it is crucial to have comparably accurate theoretical predictions of relevant quantities along with an accurate...

Conventional high-resolution techniques for $\beta$-decay spectroscopy utilize high-purity germanium detectors to measure individual $\gamma$ rays emitted after $\beta$ decay. However, these measurements are affected by the Pandemonium systematic error [1], resulting in many high-energy $\gamma$ rays and a significant portion of the $\beta$ strength being missed. The Total Absorption...

The measurement of a permanent electric dipole moment (EDM) in atoms is crucial for understanding the origins of CP-violation. Quadrupole and octupole deformed nuclei exhibit significantly enhanced atomic EDM. However, accurate interpretation of the EDM in such systems requires the characterization of their deformation. While nuclear deformation is indicated in various structure models,...

Deviations from the typical liquid-drop-like saturated density of the nucleus are a focal point in the exploration of nuclear structure. Phenomena of nucleon localisation, such as clustering or bubble structures, provide a distinctive perspective on the macroscopic consequences of nuclear interaction.

We performed a proton-transfer direct reaction to probe the wavefunction of $^{46}$Ar and...

A reliable prediction of electroweak processes involving a nucleus is required to further understand nuclear structure and other related topics, such as nucleosynthesis and particle physics. In the past two decades, the range of applicability of nuclear ab initio calculations has been rapidly extending and reaching mass number of 200 systems. Yet, the reproduction of magnetic dipole moment,...

In April 2022, AGATA, the European Ge-array at the forefront of gamma detection technology [1,2] was installed at LNL. Based on the new concept of gamma-ray tracking, it can identify the gamma interaction points (pulse shape analysis) and reconstruct via software the trajectories of the individual photons (gamma-ray tracking). Shortly thereafter a physics campaign has started using stable...

The correlation between the charge radii differences in mirror nuclei pairs and the neutron skin thickness has been studied with the so-called finite-range effective interaction over a wide mass region. The so far precisely measured charge radii differences data within their experimental uncertainty ranges in $^{34}$Ar-$^{34}$S, $^{36}$Ca-$^{36}$S, $^{38}$Ca-$^{38}$Ar and $^{54}$Ni-$^{54}$Fe...

The understanding of the renormalization mechanisms of electroweak currents is nowadays a cornerstone of the nuclear structure research. It is motivated by the need of calculating reliable nuclear matrix elements for the neutrinoless double-$\beta$ decay. Our approach to the problem is the realistic nuclear shell model. It provides a consistent framework to derive effective Hamiltonians and...

The rapid neutron capture process, or r process, is responsible for the production of half of the elements between iron and uranium found in nature. During the r-process nucleosynthesis, several thousands of neutron-rich nuclei are synthesized in few seconds, powering an electromagnetic transient known as kilonova. Since most of such exotic nuclei have never been experimentally observed due to...

Solving the quantum many-body problem involves non-trivial challenges arising from the exponential growth of the Hilbert space dimension, which restricts the applicability of numerically exact techniques to relatively small systems. I will discuss how variational Monte Carlo methods, based on artificial neural networks, can provide a systematically improvable solution to the quantum many-body...

*Ab initio* is the expression used to refer to the subset of techniques in nuclear structure that perform calculations from "first principles". While being the most accurate approach in describing atomic nuclei to the date, it is still not used in many fields of nuclear physics due to its high computational cost.

Recently, a method dubbed *Neural Quantum States* was proposed, and there are...

Quantum entanglement offers a unique perspective into the underlying structure of strongly-correlated systems such as atomic nuclei. Using different entanglement metrics on equipartitions of the valence space, we analyze the structure of light and medium-mass berillyum, oxygen, neon and calcium isotopes within the nuclear shell model, and we identify mode-entanglement patterns related to the...

This study presents a simulated quantum computing approach for the investigation into the shell-model energy levels of $^{58}$Ni through the application of the variational eigensolver (VQE) method in combination with a problem-specific ansatz. The primary objective is to achieve a fully accurate low-lying energy spectrum of $^{58}$Ni. In this study, we utilized two distinct shell model spaces:...

There is an increasing interest to develop quantum circuits capable of performing many-body quantum simulation motivated by their scaling advantages against classical devices. We present an analysis of the performance of various *Variational Quantum Eigensolvers* methods for several p-shell nuclei in the shell model framework. In particular, our work is focused on the construction of efficient...

Microscopic approach based on quantum chromodymanics (QCD) is the most challenging ab initio theory for nuclear structure physics. In this respect, QCD sum rule gives a powerful tool, but numerically not highly demanding, to cross a bridge the QCD and hadron spectroscopy such as meson and baryon masses in terms of chiral symmetry breaking due to quark condensation. In nuclear medium, a...

QCD sum rule approach is a powerful tool to implement QCD dynamics into hadron and nuclear many-body physics even for finite density.

We applied the QCD sum rule approach to derive a nuclear charge symmetry breaking (CSB) energy density functional (EDF), which describes the Okamoto-Nolen-Shiffer anomaly successfully.

As the next step, we propose an approach to derive the charge independence...

The formal concept of isospin has been introduced to explain the apparent exchange symmetry between neutrons and protons [1]. However, if the nuclear force were the same for protons and neutrons properties such as masses and excitation energies would depend only on the mass number A. Hence, in the absence of isospin-non-conserving effects, two isobaric analog states would be completely...

The significance of finite temperature effects in nuclear dipole transitions is evident across various applications in nuclear physics and astrophysics [1-4]. To describe temperature effects in electromagnetic transitions, we developed a self-consistent finite temperature relativistic quasiparticle random phase approximation (FT-RQRPA) based on relativistic energy density functional with point...

In this talk, an *ab initio* study of infinite nuclear matter is presented within a recently introduced Green's function approach based on the state-of-the-art algebraic diagrammatic construction (ADC) scheme [1-3].

The goal is, on the one hand, to show the power of the method, that allows to access not only the equation of state (EOS), but also single-particle properties such as the momentum...

The study of single-particle structure in light neutron-rich systems has led to discoveries of dramatic changes which are otherwise gradual near stability, leading to the weakening and appearance of shell closures. For example, the disappearance of N = 20 and emergence of N = 16 [1, 2] as well the emergence of N = 32, 34 in calcium isotopes [3]. Pronounced trends have also been observed in...

Nuclear matter at subsaturation densities is expected to be inhomogeneous, owing to the existence of many-body correlations, which constitutes an essential feature for the construction of a reliable equation of state. A first emergent phenomenon related to this aspect is the fragmentation process, experimentally observed in heavy-ion collisions at intermediate energies as the result of...

The study of reactions involving weakly-bound exotic nuclei is an active field due to advances in radioactive beam facilities. Many of these nuclei can be approximately described by a model consisting of an inert core and one or more valence nucleons. For some of these nuclei, the quadrupole deformation is especially relevant and should be included in the structure models. This is the case of...

We study the shape coexistence in the nucleus $^{28}$Si with the nuclear shell model using numerical diagonalizations complemented with variational calculations based on the projected generator-coordinate method. The calculated electric quadrupole transitions and moments and an analysis of the collective wavefunctions indicate that the standard USDB interaction in the $sd$ shell describes well...

In quantum mechanics the coupling of a particleโs velocity with its own spin is at the origin of the spin-orbit effect that creates many fundamental phenomena in mesoscopic systems. In nuclear physics, a sizeable spin-orbit interaction, that breaks energy levels with the same

orbital momentum (l) but different spin value (s) apart, is responsible for the observed shell structure and generates...