Search

The convergence properties of spectroscopic factors in the \textit{ab initio} no-core shell model are hereby investigated. For this, we consider nuclear energies and spectroscopic factors in $A = 6$ and 7 isotopes, using the chiral forces NNLO$_{\rm opt}$ and N$^3$LO. While low-lying spectrum energy demonstrates remarkable convergence with the increase of model space within the no-core shell model, the spectroscopic factor exhibits no definitive convergence trend and seems independent of the employed nuclear interaction. The use of spectroscopic factors issued from the no-core shell model to calculate cross-sections of knockout reaction might then be questionable. The results are compared with that of the standard shell model and \textit{ab initio} Monte Carlo calculations., Comment: 9 pages, 7 figures

The existence of magic numbers of protons and neutrons in nuclei is essential for understanding nuclear structure and fundamental nuclear forces. Over decades, researchers have conducted theoretical and experimental studies on the new magic number Z(N) = 6, focusing on observables such as radii, binding energy, electromagnetic transition, and nucleon separation energies. We perform the ab initio no-core shell model calculations for the occupation numbers of the lowest single particle states in the ground states of Z(N) = 6 and Z(N) = 8 isotopes (isotones). Our calculations do not support Z(N) = 6 as a magic number over a span of atomic numbers. However, 14C and 14O exhibit the characteristics of double-magic nuclei.

The mirror energy difference (MED) of the mirror state, especially for states bearing the Thomas-Erhman shift, serves as a sensitive probe of isospin symmetry breaking. We employ the Gamow shell model, which includes the inter-nucleon correlation and continuum coupling, to investigate the MED for $sd$-shell nuclei by taking the $^{18}$Ne/$^{18}$O and $^{19}$Na/$^{19}$O as examples. Our GSM provides good descriptions for the excitation energies and MEDs for the $^{18}$Ne/$^{18}$O and $^{19}$Na/$^{19}$O. Moreover, our calculations also reveal that the large MED of the mirror states is caused by the significant occupation of the weakly bound or unbound $s_{1/2}$ waves, giving the radial density distribution of the state in the proton-rich nucleus more extended than that of mirror states in deeply-bound neutron-rich nuclei. Furthermore, our GSM calculation shows that the contribution of Coulomb is different for the low-lying states in proton-rich nuclei, which significantly contributes to MEDs of mirror states. Moreover, the contributions of the nucleon-nucleon interaction are different for the mirror state, especially for the state of proton-rich nuclei bearing the Thomas-Erhman shift, which also contributes to the significant isospin symmetry breaking with large MED., Comment: 6 Pages,6 figures

Halos epitomize the fascinating interplay between weak binding, shell evolution, and deformation effects, especially in nuclei near the drip line. In this Letter, we apply the state-of-the-art \textit{ab initio} valence-space in-medium similarity renormalization group approach to predict potential candidates for one- and two-neutron halo in the intermediate-mass region. Notably, we use spectroscopic factors (SF) and two-nucleon amplitudes (TNA) as criteria for suggesting one- and two-neutron halo candidates, respectively. This approach is not only theoretically sound but also amenable to experimental validation. Our research focuses on Mg, Al, Si, P, and S neutron-drip-line nuclei, offering systematic predictions of neutron halo candidates in terms of separation energies, SF (TNA), and average occupation. The calculation suggests the ground states of $^{40,42,44,46}$Al, $^{41,43,45,47}$Si, $^{46,48}$P, and $^{47,49}$S are promising candidates for one-neutron halos, while $^{40,42,44,46}$Mg, $^{45,47}$Al, $^{46,48}$Si, $^{49}$P, and $^{50}$S may harbor two-neutron halos. In addition, the relative mean-square neutron radius between halo nuclei and \textit{inner core} is calculated for suggested potential neutron halos. Finally, the relations of halo formations and shell evolution are discussed.

Ab initio calculations have achieved remarkable success in nuclear structure studies. Numerous works highlight the pivotal role of three-body forces in nuclear ab initio calculations. Concurrently, efforts have been made to replicate these calculations using only realistic nucleon-nucleon (NN) interactions. A novel local chiral next-to-next-to-next-to-leading order (N3LO) NN interaction, distinct due to its weaker tensor force, has recently been established. This paper applies this local NN interaction in ab initio frameworks to calculate the low-lying spectra of p-shell light nuclei, particularly 10B, ground-state energies and shell evolution in oxygen isotopes. Results are compared with calculations utilizing nonlocal chiral N3LO NN and chiral NN +3N interactions. The ab initio calculations with the local N N potential accurately describe the spectra of p-shell nuclei, notably the 10B. Additionally, the neutron drip line for oxygen isotopes, with 24O as the drip line nucleus, is accurately reproduced in ab initio calculations with the local NN interaction. Calculations with the local NN interaction also reproduce the subshell closure at N = 14 and 16, albeit with a stronger shell gap compared to experimental data. However, the calculated charge radii based on the local NN interaction are underestimated compared with experimental data, which is similar to results from the nonlocal NN interaction. Consequently, the present ab initio calculations further indicate significant spin-orbit splitting effects with the new local NN potential, suggesting that 3N forces remain an important consideration., Comment: 9 pages, 7 figures

Neutron-rich P, Cl, and K isotopes, particularly those with neutron numbers around $N=28$, have attracted extensive experimental and theoretical interest. We utilize the \textit{ab initio} valence-space in-medium similarity renormalization group approach, based on chiral nucleon-nucleon and three-nucleon forces, to investigate the exotic properties of these isotopes. Systematic calculations of the low-lying spectra are performed. A key finding is the level inversion between $3/2_1^+$ and $1/2_1^+$ states in odd-$A$ isotopes, attributed to the inversion of $\pi 0d_{3/2}$ and $\pi 1s_{1/2}$ single-particle states.\textit{Ab initio} calculations, which incorporate the three-nucleon forces, correlate closely with existing experimental data. Further calculations of effective proton single-particle energies provide deeper insights into the shell evolution for $Z=14$ and $16$ sub-shells. Our results indicate that the three-body force plays important roles in the shell evolution for $Z=14$ and $16$ sub-shells with neutron numbers ranging from 20 to 28. Additionally, systematic \textit{ab initio} calculations are conducted for the low-lying spectra of odd-odd nuclei. The results align with experimental data and provide new insights for future research into these isotopes, up to and beyond the drip line., Comment: 12 pages, 9 figures, 1 table

We provide an investigation of the spectroscopic factor of resonance states in $A =5-8$ nuclei, utilizing the Gamow shell model (GSM). Within the GSM, the configuration mixing is taken into account exactly with the shell model framework, and the continuum coupling is addressed via the complex-energy Berggren ensemble, which treats bound, resonance, and non-resonant continuum single-particle states on an equal footing. As a result, both the configuration mixing and continuum coupling are meticulously considered in the GSM. We first calculate the low-lying states of helium isotopes and isotones with the GSM, and the results are compared with that of \textit{ab initio} no-core shell model (NCSM) calculations. The results indicate that GSM can reproduce the low-lying resonance states more accurately than the no-core shell model. Following this, we delve into the spectroscopic factors of the resonance states as computed through both GSM and NCSM, concurrently conducting systematic calculations of overlap functions pertinent to these resonance states. Finally, the calculated overlap function and spectroscopic factor of $^6$He$(0_1^+)$ $\otimes \nu p_{3/2} \to $ $^7$He$(3/2_1^-)$ with GSM are compared with the results from \textit{ab initio} NCSM, variational Monte Carlo, and Green's function Monte Carlo calculations, as well as avaliable experimental data. The results assert that wave function asymptotes can only be reproduced in GSM, where resonance and continuum coupling are precisely addressed., Comment: 7 pages, 3 figures, 1 table

Although they are part of the lightest nuclei, the hydrogen isotopes are not well understood both experimentally and theoretically. Indeed, besides deuteron and triton, all known hydrogen isotopes are resonances of complex structure. Even more elusive is 7H, which may have been observed experimentally and has been claimed to be a narrow resonance. Nevertheless, even its existence is controversial, and its theoretical study is difficult due to both its unbound character and large number of interacting valence nucleons. It is then the object of this paper to theoretically study the hydrogen isotopes {4-7}H with the Gamow shell model, which is, up to our knowledge, the first direct calculation of unbound resonance hydrogen isotopes up to 7H. As the Gamow shell model includes both continuum coupling and inter-nucleon correlations, useful information can be obtained about poorly known unbound hydrogen isotopes. Our present calculations indicate that {4,6}H ground states are fairly broad resonances, whereas those of {5,7}H are narrow, which is in accordance with current experimental data. The results then suggest that, in particular, {5,7}H should be more heavily studied, as they might well be among the most narrow neutron resonances of the light nuclear chart.

Spectroscopic factors involving well bound nucleons in light nuclei are calculated with standard shell model, no-core shell model and Gamow shell model. Continuum coupling is included exactly in the Gamow shell model, due to the use of the Berggren basis, which contains bound, resonance and scattering states. Conversely, it is absent from standard and no-core shell models, where a basis of harmonic oscillator states is used. As the A - 1 nuclei for which spectroscopic factors are calculated are either weakly bound or unbound, coupling to continuum is prominent, even though the A nuclei are well bound. It is then showed that Gamow shell model can properly reproduce experimental data and is a predictive tool for detailed nuclear structure at drip-line, contrary to standard and no-core shell model.

Isospin-symmetry breaking is responsible for the energy difference of excited states in mirror nuclei. It also influences the coefficient of the isobaric multiplet mass equation. In the present work, we extensively investigate isospin-symmetry breaking in medium mass nuclei within ab initio frameworks. For this, we employ the ab initio valence-space in-medium similarity renormalization group approach, in which charge-symmetry and charge-independence breakings are included in the adopted nuclear force. The mirror energies of sd- and pf- shell nuclei are computed for that matter. The effects of single-particle states on weakly bound and unbound nuclear states, especially those of the s-wave, are discussed. Predictions are also made concerning proton drip-line nuclei bearing large mirror energy difference. Finally, the coefficient of the isobaric multiplet mass equation in T = 1/2 and T = 1 isospin multiplets for A = 18 to A = 76 is calculated.

We investigate the pairing properties of state-of-the-art semilocal coordinate-space and semilocal momentum-space regularized chiral interactions. Specifically, we calculate the pairing gaps in $^3SD_1$ channel of symmetric nuclear matter and in $^1S_0$ and $^3PF_2$ channels of pure neutron matter within the BCS approximation using these chiral interactions. We address the regulator and chiral order dependence of the pairing gaps and compare the pairing properties of the chiral interactions with those of the Argonne v18 (Av18) potential. The effects of the tensor force on the pairing gaps in the $^3SD_1$ and $^3PF_2$ channels are illustrated for both the chiral interactions and the Av18 potential. We evaluate the truncation errors of chiral expansions of the pairing gaps with a Bayesian approach. We find that the pairing gaps converge very well at the higher-order chiral expansions in the $^3SD_1$ and $^1S_0$ channels.

The $^{16}$F nucleus is situated at the proton drip-line and is unbound by proton emission by only about 500 keV. Continuum coupling is then prominent in this nucleus. Added to that, its low-lying spectrum consists of narrow proton resonances as well. It is then a very good candidate to study nuclear structure and reactions at proton drip-line. The low-lying spectrum and scattering proton-proton cross section of $^{16}$F have then been calculated with the coupled-channel Gamow shell model framework for that matter using an effective Hamiltonian. Experimental data are very well reproduced, as well as in its mirror nucleus $^{16}$N. Isospin-symmetry breaking generated by the Coulomb interaction and continuum coupling explicitly appears in our calculations. In particular, the different continuum couplings in $^{16}$F and $^{16}$N involving $s_{1/2}$ partial waves allow to explain the different ordering of low-lying states in their spectrum., Comment: 7 pages, 2 figures, accepted for publication in Phys. Rev. C. (Letters)

We have applied the Gamow shell model to calculate nuclear observables of $^{26-31}$Ne isotopes pertaining to one-neutron halo structure, these nuclei being situated close to neutron drip-line. As both many-body correlations and continuum coupling are taken into account in that approach, halo structure can be analyzed properly. Our calculations provide good descriptions of $^{26-31}$Ne, where asymptotic behavior is crucial for that matter. One-body density, neutron root-mean-square radii of $^{26-31}$Ne, and one-neutron overlap functions of $^{29,31}$Ne have been calculated as well. Our results support the presence of a one-neutron \textit{p}-wave halo in $^{31}$Ne, already pointed out experimentally. A similar situation also occurs in the ground state of $^{29}$Ne, which is mainly a \textit{p}-wave valence neutron coupled to the inner $^{28}$Ne \textit{core}. The $3/2^+$ excited state of $^{29}$Ne, which is dominated by a \textit{d}-wave valence neutron, has also been considered. A larger radius and more extended wave function occur for the ground state of $^{29}$Ne when compared to its $3/2^+$ first excited state. The present results suggest that $^{29}$Ne is a good candidate for one-neutron \textit{p}-wave halo in the medium-mass region., Comment: 7 Pages, 3 Figures

Visual place recognition (VPR) is a key issue for robotics and autonomous systems. For the trade-off between time and performance, most of methods use the coarse-to-fine hierarchical architecture, which consists of retrieving top-N candidates using global features, and re-ranking top-N with local features. However, since the two types of features are usually processed independently, re-ranking may harm global retrieval, termed re-ranking confusion. Moreover, re-ranking is limited by global retrieval. In this paper, we propose a tightly coupled learning (TCL) strategy to train triplet models. Different from original triplet learning (OTL) strategy, it combines global and local descriptors for joint optimization. In addition, a bidirectional search dynamic time warping (BS-DTW) algorithm is also proposed to mine locally spatial information tailored to VPR in re-ranking. The experimental results on public benchmarks show that the models using TCL outperform the models using OTL, and TCL can be used as a general strategy to improve performance for weakly supervised ranking tasks. Further, our lightweight unified model is better than several state-of-the-art methods and has over an order of magnitude of computational efficiency to meet the real-time requirements of robots., Comment: 8 pages, 9 figures

While it is well recognized that both the Galactic interstellar extinction curves and the gas-phase abundances of dust-forming elements exhibit considerable variations from one sight line to another, as yet most of the dust extinction modeling efforts have been directed to the Galactic average extinction curve, which is obtained by averaging over many clouds of different gas and dust properties. Therefore, any details concerning the relationship between the dust properties and the interstellar environments are lost. Here we utilize the wealth of extinction and elemental abundance data obtained by space telescopes and explore the dust properties of a large number of individual sight lines. We model the observed extinction curve of each sight line and derive the abundances of the major dust-forming elements (i.e., C, O, Si, Mg and Fe) required to be tied up in dust (i.e., dust depletion). We then confront the derived dust depletions with the observed gas-phase abundances of these elements and investigate the environmental effects on the dust properties and elemental depletions. It is found that for the majority of the sight lines the interstellar oxygen atoms are fully accommodated by gas and dust and therefore there does not appear to be a "missing oxygen" problem. For those sight lines with an extinction-to-hydrogen column density $A_V/N_H$ $>$ 4.8$\times$10$^{-22}$ mag cm$^2$/H there are shortages of C, Si, Mg and Fe elements for making dust to account for the observed extinction, even if the interstellar C/H, Si/H, Mg/H and Fe/H abundances are assumed to be proto-solar abundances augmented by Galactic chemical evolution., Comment: 48 pages, 26 figures, 3 tables; accepted for publication in The Astrophysical Journal Supplement Series (on 9/27/2021)

The $A=4$ nuclei, i.e., $^4$H, $^4$He and $^4$Li, establish an interesting isospin $T=1$ isobaric system. $^4$H and $^4$Li are unbound broad resonances, whereas $^4$He is deeply bound in its ground state but unbound in all its excited states. The present situation is that experiments so far have not given consistent data on the resonances. Few-body calculations have well studied the scatterings of the $4N$ systems. In the present work, we provide many-body calculations of the broad resonance structures, in an \textit{ab initio} framework with modern realistic interactions. It occurs that, indeed, $^4$H, $^4$Li and excited $^4$He are broad resonances, which is in accordance with experimental observations. The calculations also show that the first $1^-$ excited state almost degenerates with the $2^-$ ground state in the pair of mirror isobars of $^4$H and $^4$Li, which may suggest that the experimental data on energy and width are the mixture of the ground state and the first excited state. The $T = 1$ isospin triplet formed with an excited state of $^4$He and ground states of $^4$H and $^4$Li is studied, focusing on the effect of isospin symmetry breaking., Comment: 7 pages; 3 figures

In most nuclear many-body methods, observables are calculated using many-body wave functions explicitly. The variational two-particle reduced density matrix method is one of the few exceptions to the rule. Ground-state energies of both closed-shell and open-shell nuclear systems can indeed be evaluated by minimizing a constrained linear functional of the two-particle reduced density matrix. However, it has virtually never been used in nuclear theory, because nuclear ground states were found to be well overbound, contrary to those of atoms and molecules. Consequently, we introduced new constraints in the nuclear variational two-particle reduced density matrix method, developed recently for atomic and molecular systems. Our calculations then show that this approach can provide a proper description of nuclear systems where only valence neutrons are included. For the nuclear systems where both neutrons and protons are active, however, the energies obtained with the variational two-particle reduced density matrix method are still overbound. The possible reasons for the noticed discrepancies and solutions to this problem will be discussed., Comment: 14 pages, 9 figures

Proton-rich nuclei possess unique properties in the nuclear chart. Due to the presence of both continuum coupling and Coulomb interaction, phenomena such as halos, Thomas-Ehrman shift, and proton emissions can occur. Experimental data are difficult to be obtained therein, so that theoretical calculations are needed to understand nuclei at drip-lines and guide experimentalists for that matter. In particular, the $^{16}$Ne and $^{18}$Mg isotopes are supposed to be one-proton and/or two-proton emitting nuclei, but associated experimental data are either incomplete or even unavailable. Consequently, we performed Gamow shell model calculations of carbon isotones bearing $A=15\text{-}18$. Isospin-symmetry breaking occurring in carbon isotones and isotopes is also discussed. It is hereby shown that the mixed effects of continuum coupling and Coulomb interaction at drip-lines generate complex patterns in isospin multiplets. Added to that, it is possible to determine the one-proton and two-proton widths of $^{16}$Ne and $^{18}$Mg. Obtained decay patterns are in agreement with those obtained in previous experimental and theoretical works. Moreover, up to the knowledge of authors, this is the first theoretical calculation of binding energy and partial decay widths of $^{18}$Mg in a configuration interaction picture., Comment: 12 pages, 4 figures

A resonant state at $3.21^{+0.12}_{-0.04}$\,MeV, located just above the one-neutron separation threshold, was observed for the first time in $^{12}$Be from the $^{11}$Be\,$(d,p)^{12}$Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^-$, according to the distorted-wave Born approximation (DWBA) and decay-width analysis. Gamow coupled-channel (GCC) and Gamow shell-model (GSM) calculations show the importance of the continuum-coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in $^{12}$Be and in its isotonic nucleus $^{11}$Li are comparably discussed.

The Gamow shell model has shown to efficiently describe weakly bound and unbound nuclear systems, as internucleon correlations and continuum coupling are both taken into account in this model. In the present work, we study neutron-dripline oxygen isotopes. It is hereby demonstrated that the presence of continuum coupling is important for the description of oxygen isotopes at dripline, and especially to assess the eventual bound or unbound character of $^{28}$O. Our results suggest that the ground state of $^{28}$O is weakly unbound and is similar to the narrow resonant $^{26}$O ground state. Predictions of weakly bound and resonance excited states in $^{24\text-26}$O are also provided. The asymptotes of the studied many-body states are analyzed via one-body densities, whereby the different radial properties of well bound, loosely bound, resonance states are clearly depicted., Comment: 8 pages, 4 figures

A kinematically complete quasi-free $(p,pn)$ experiment in inverse kinematics was performed to study the structure of the Borromean nucleus $^{17}$B, which had long been considered to have neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for $1s_{1/2}$ and $0d_{5/2}$ orbitals, and a surprisingly small percentage of 9(2)$\%$ was determined for $1s_{1/2}$. Our finding of such a small $1s_{1/2}$ component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in $^{17}$B. The present work gives the smallest $s$- or $p$-orbital component among known nuclei exhibiting halo features, and implies that the dominant occupation of $s$ or $p$ orbitals is not a prerequisite for the occurrence of neutron halo., Comment: Accepted for publication in Physical Review Letters,8 pages, 4 figures

$\alpha$-decay always has enormous impetuses to the development of physics and chemistry, in particular due to its indispensable role in the research of new elements. Although it has been observed in laboratories for more than a century, it remains a difficult problem to calculate accurately the formation probability $S_\alpha$ microscopically. To this end, we establish a new model, i.e., multistep model, and the corresponding formation probability $S_\alpha$ values of some typical $\alpha$-emitters are calculated without adjustable parameters. The experimental half-lives, in particular their irregular behavior around a shell closure, are remarkably well reproduced by half-life laws combined with these $S_\alpha$. In our strategy, the cluster formation is a gradual process in heavy nuclei, different from the situation that cluster pre-exists in light nuclei. The present study may pave the way to a fully understanding of $\alpha$-decay from the perspective of nuclear structure., Comment: 7 pages, 4 figures

The thermal conductivity and shear viscosity of dense nuclear matter, along with the corresponding shear viscosity timescale of canonical neutron stars (NSs), are investigated, where the effect of Fermi surface depletion (i.e., the $Z$-factor effect) induced by the nucleon-nucleon correlation are taken into account. The factors which are responsible for the transport coefficients, including the equation of state for building the stellar structure, nucleon effective masses, in-medium cross sections, and the $Z$-factor at Fermi surfaces, are all calculated in the framework of the Brueckner theory. The Fermi surface depletion is found to enhance the transport coefficients by several times at high densities, which is more favorable to damping the gravitational-wave-driven $r$-mode instability of NSs. Yet, the onset of the $Z$-factor-quenched neutron triplet superfluidity provides the opposite effects, which can be much more significant than the above mentioned $Z$-factor effect itself. Therefore, different from the previous understanding, the nucleon shear viscosity is still smaller than the lepton one in the superfluid NS matter at low temperatures. Accordingly, the shear viscosity cannot stablize canonical NSs against $r$-mode oscillations even at quite low core temperatures $10^6$ K., Comment: 11 pages, 6 figures

Elements in the interstellar medium (ISM) exist in the form of gas or dust. The interstellar extinction and elemental abundances provide crucial constraints on the composition, size and quantity of interstellar dust. Most of the extinction modeling efforts have assumed the total abundances (both in gas and in dust) of the dust-forming elements---known as the "interstellar abundances", the "interstellar reference abundances", or the "cosmic abundances"---to be solar and the gas-phase abundances to be independent of the interstellar environments. However, it remains unclear if the solar abundances are an appropriate representation of the interstellar abundances. Meanwhile, the gas-phase abundances are known to exhibit appreciable variations with the local interstellar environments. In this work we explore the viability of the abundances of B stars, the solar and protosolar abundances, and the protosolar abundances augmented by Galactic chemical enrichment (GCE) as an appropriate representation of the interstellar abundances by quantitatively examining the extinction and elemental abundances of ten interstellar lines of sight for which both the extinction curves and the gas-phase abundances of all the major dust-forming elements (i.e., C, O, Mg, Si and Fe) have been observationally determined. Instead of assuming a specific dust model and then fitting the observed extinction curves, for each sightline we apply the model-independent Kramers-Kronig relation, which relates the wavelength-integrated extinction to the total dust volume, to place a lower limit on the dust depletion. This, together with the observationally-derived gas-phase abundances, allows us to rule out the B-star, solar, and protosolar abundances as the interstellar reference standard. We conclude that the GCE-augmented protosolar abundances are a viable representation of the interstellar abundances., Comment: 42 pages, 12 figures, 8 tables; accepted for publication in The Astrophysical Journal Supplement Series

We apply the Gamow shell model to study $^{25-31}$F isotopes. As both inter-nucleon correlations and continuum coupling are properly treated therein, the structure shape of $^{31}$F at large distance can be analyzed precisely. For this, one-nucleon densities, root-mean square radii and correlation densities are calculated in neutron-rich fluorine isotopes. It is then suggested that $^{31}$F exhibits a two-neutron halo structure, built from both continuum coupling and nucleon-nucleon correlations., Comment: 5 pages, 3 figures

Nucleon momentum distributions at various densities and isospin-asymmetries for nuclear matter are investigated systematically within the extended Bruecker-Hartree-Fock approach.The shapes of the normalized momentum distributions varying with $k/k_{F}$ are practically identical, while the density and isospin dependent magnitude of the distribution is directly related to the depletion of the Fermi sea. Based on these properties, a parameterized formula is proposed with the parameters calibrated to the calculated result.

Fine structure in the $\alpha$ decay of $^{223}$U was observed in the fusion-evaporation reaction $^{187}$Re($^{40}$Ar, p3n) by using fast digital pulse processing technique. Two $\alpha$-decay branches of $^{223}$U feeding the ground state and 244 keV excited state of $^{219}$Th were identified by establishing the decay chain $^{223}$U $\xrightarrow{\alpha_{1}}$ $^{219}$Th $\xrightarrow{\alpha_{2}}$ $^{215}$Ra $\xrightarrow{\alpha_{3}}$ $^{211}$Rn. The $\alpha$-particle energy for the ground-state to ground-state transition of $^{223}$U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62$^{+14}_{-10}$ $\mu$s. Evolution of nuclear structure for $N$ = 131 even-$Z$ isotones from Po to U was discussed in the frameworks of nuclear mass and reduced $\alpha$-decay width, a weakening octupole deformation in the ground state of $^{223}$U relative to its lighter isotones $^{219}$Ra and $^{221}$Th was suggested., Comment: 6 pages, 6 figures

The onset of 1S0 proton spin-singlet pairing in neutron-star matter is studied in the framework of the BCS theory including medium polarization effects. The strong three-body coupling of the diproton pairs with the dense neutron environment and the self-energy effects severely reduce the gap magnitude, so to reshape the scenario of the proton superfluid phase inside the star. The vertex corrections due to the medium polarization are attractive in all isospin-asymmetry range at low density and tend to favor the pairing in that channel. However quantitative estimates of their effect on the energy gap do not give significant changes. Implications of the new scenario on the role of pairing in neutron-star cooling is briefly discussed., Comment: 5 pages, 5 figures

The observations combined with theory of neutron star (NS) cooling play a crucial role in achieving the intriguing information of the stellar interior, such as the equation of state (EOS), composition and superfluidity of dense matter. The traditional NS cooling theory is based on the assumption that the stellar structure does not change with time. The validity of such a static description has not yet been confirmed. We generalize the theory to a dynamic treatment; that is, continuous change of the NS structure (rearrangement of the stellar density distribution with the total baryon number fixed) as the decrease of temperature during the thermal evolution, is taken into account. It is found that the practical thermal energy used for the cooling is slightly lower than that is estimated in static situation, and hence the cooling of NSs is accelerated correspondingly but the effect is rather weak. Therefore, the static treatment is a good approximation in the calculations of NS cooling., Comment: 13 pages, 6 figures

The Wigner Isobaric Multiplet Mass Equation (IMME) is the most fundamental prediction in nuclear physics with the concept of isospin. However, it was deduced based on the Wigner-Eckart theorem with the assumption that all charge-violating interactions can be written as tensors of rank two. In the present work, the charge-symmetry breaking (CSB) and charge-independent breaking (CIB) components of the nucleon-nucleon force, which contribute to the effective interaction in nuclear medium, are established in the framework of Brueckner theory with AV18 and AV14 bare interactions. Because such charge-violating components can no longer be expressed as an irreducible tensor due to density dependence, its matrix element cannot be analytically reduced by the Wigner-Eckart theorem. With an alternative approach, we derive a generalized IMME (GIMME) that modifies the coefficients of the original IMME. As the first application of GIMME, we study the long-standing question for the origin of the Nolen-Schiffer anomaly found in the Coulomb displacement energy of mirror nuclei. We find that the naturally-emerged CSB term in GIMME is largely responsible for explaining the Nolen-Schiffer anomaly., Comment: 7 pages, 3 figures; to be published in Phys. Rev. C

Excited states in neutron-rich nuclei located south-east of $^{132}$Sn are investigated by shell-model calculations. A new shell-model Hamiltonian is constructed for the present study. The proton-proton and neutron-neutron interactions of the Hamiltonian are obtained through the existing CD-Bonn $G$ matrix results, while the proton-neutron interaction across two major shells is derived from the monopole based universal interaction plus the M3Y spin-orbit force. The present Hamiltonian can reproduce well the experimental data available in this region, including one-neutron separation energies, level energies and the experimental $B(E2)$ values of isomers in $^{134,136,138}$Sn, $^{130}$Cd, and $^{128}$Pd. New isomers are predicted in this region, $e.g.$ in $^{135}$Sn, $^{131}$Cd, $^{129}$Pd, $^{132,134}$In and $^{130}$Ag, in which almost no excited states are known experimentally yet. In the odd-odd $^{132,134}$In and $^{130}$Ag, the predicted very long $E2$ life-times of the low-lying $5^{-}$ states are discussed, demanding more information on the related proton-neutron interaction. The low-lying states of $^{132}$In are discussed in connection with the recently observed $\gamma$ rays. The predicted $19/2^{-}$ isomer in $^{129}$Pd could decay by both electromagnetic transitions and neutron emission with comparable partial life-times, making it a good candidate for neutron radioactivity, a decay mode which is yet to be discovered., Comment: Accepted for publication in Physics Letters B

The quadratic form of the isobaric multiplet mass equation (IMME), which was originally suggested by Wigner and has been generally regarded as valid, is seriously questioned by recent high-precision nuclear mass measurements. The usual resolution to this problem is to add empirically the cubic and quartic $T_z$-terms to characterize the deviations from the IMME, but finding the origin of these terms remains an unsolved difficulty. Based on a strategy beyond the Wigner's first-order perturbation, we derive explicitly the cubic and quartic $T_z$-terms. These terms are shown to be generated by the effective charge-symmetry breaking and charge-independent breaking interactions in nuclear medium combined with the Coulomb polarization effect. Calculations for the $sd$- and lower $fp$-shells explore a systematical emergence of the cubic $T_z$-term, suggesting a general deviation from the original IMME. Intriguingly, the magnitude of the deviation exhibits an oscillation-like behavior with mass number, modulated by the shell effect., Comment: 13 pages, 4 figures

The Fermi surface depletion of beta-stable nuclear matter is calculated to study its effects on several physical properties which determine the neutron star thermal evolution. The neutron and proton Z factors measuring the corresponding Fermi surface depletions, are calculated within the Brueckner-Hartree-Fock approach employing the AV18 two-body force supplemented by a microscopic three body force. Neutrino emissivity, heat capacity and, in particular, neutron 3PF2 superfluidity turn out to be reduced, especially at high baryonic density, to such an extent that the cooling rates of young neutron stars are significantly slowed, Comment: 9 pages, 6 figures, accepted for publication in ApJ

The density and isospin dependences of the nonrelativistic nucleon effective mass ($m^*$) are studied, which is a measure of the nonlocality of the single particle (s.p.) potential. We decouple it further into the so called k-mass ($m^*_k$, i.e., the nonlocality in space) and E-mass ($m^*_E$, i.e., the nonlocality in time). Both masses are determined and compared from the latest versions of the nonrelativistic Brueckner-Hartree Fock (BHF) model and the relativistic Hartree-Fock (RHF) model. The latter are achieved based on the corresponding Schr\"{o}dinger equivalent s.p. potential in a relativistic framework. We demonstrate the origins of different effective masses and discuss also their neutron-proton splitting in the asymmetric matter in different models. We find that the neutron-proton splittings of both the k-mass and the E-mass have the same asymmetry dependences at considered densities, namely $m^*_{k,n} > m^*_{k,p}$ and $m^*_{E,p} > m^*_{E,n}$. However, the resulting splittings of nucleon effective masses could have different asymmetry dependences in the two models, because they could be dominated either by that of the k-mass (then we have $m^*_n > m^*_p$ in the BHF model) or by that of the E-mass (then we have $m^*_p > m^*_n$ in the RHF model)., Comment: 4 pages, 5 figures, 1 table, PHYSICAL REVIEW C (2016) accepted