The correlations of the crust-core transition density and pressure in neutron stars with the slope of the symmetry energy and the neutron skin thickness are investigated, using different families of relativistic mean-field parametrizations with constant couplings and nonlinear terms mixing the $\sigma -$, $\omega -$, and $\rho \text{-meson}$ fields. It is shown that the modification of the density dependence of the symmetry energy, involving the $\sigma$ or the $\omega$ meson, gives rise to different behaviors: the effect of the $\omega$ meson may also be reproduced within nonrelativistic phenomenological models, while the effect of the $\sigma$ meson is essentially relativistic. Depending on the parametrization with $\sigma -\rho$ or $\omega -\rho$ mixing terms, different values of the slope of the symmetry energy at saturation must be considered in order to obtain a neutron matter equation of state compatible with results from chiral effective field theory. This difference leads to different pressures at the crust-core transition density. A linear correlation between the transition density and the symmetry energy slope or the neutron skin thickness of the ${}^{208}\text{Pb}$ nucleus is obtained, only when the $\omega$ meson is used to describe the density dependence of the symmetry energy. A comparison is made between the crust-core transition properties of neutron stars obtained by three different methods, the relativistic random phase approximation (RRPA), the Vlasov equation, and thermodynamical method. It is shown that the RRPA and the Vlasov methods predict similar transition densities for $pne\beta \text{-equilibrium}$ stellar matter.

We present results for the three-cluster breakup in deuteron-deuteron collisions at 130 and 270 MeV deuteron beam energy. The breakup amplitude is calculated using the first term in the Neumann series expansion of the corresponding exact four-nucleon equations. In analogy with nucleon-deuteron breakup where an equivalent approximation is compared with exact calculations, we expect this single-scattering approximation to provide a rough estimation of three-body breakup observables in quasifree configurations. We predict the nucleon-deuteron and deuteron-deuteron three-cluster breakup cross sections to be of a comparable size and thereby question the reliability of the recent experimental data [A. Ramazani-Moghaddam-Arani, Ph.D. thesis, University of Groningen, 2009; A. Ramazani-Moghaddam-Arani et al., EPJ Web Conf. 3, 04012 (2010)], which are smaller by about three orders of magnitude. We also show that an equivalent single-scattering approximation provides a reasonable description of deuteron-deuteron elastic scattering at forward-scattering angles.

The product $P_{\mathrm{CN}}{P}_{\mathrm{surv}}$ of compound nucleus (CN) fusion probability $P_{\mathrm{CN}}$ and survival probability $P_{\mathrm{surv}}$ is calculated to determine the reduced evaporation residue cross section ${\sigma }_{\mathrm{ER}}/{\sigma }_{\mathrm{fusion}}$, denoted ${\sigma }_{\mathrm{ER}}^{\mathrm{reduced}}$, with (total) fusion cross section ${\sigma }_{\mathrm{fusion}}$ given as a sum of CN-formation cross section ${\sigma }_{\mathrm{CN}}$ and non-CN cross section ${\sigma }_{\text{nCN}}$ for each reaction, where ${\sigma }_{\mathrm{CN}}$ is the sum of evaporation residue cross section ${\sigma }_{\mathrm{ER}}$ and fusion-fission cross section ${\sigma }_{\mathrm{ff}}$ and ${\sigma }_{\text{nCN}}$, if not measured, is estimated empirically as the difference between measured and calculated ${\sigma }_{\mathrm{fusion}}$. Our calculations of $P_{\mathrm{CN}}$ and $P_{\mathrm{surv}}$, based on the dynamical cluster-decay model, were successfully made for some 17 “hot” fusion reactions, forming different CN of mass numbers $A_{\mathrm{CN}}\sim 100–300$, with deformations of nuclei up to hexadecapole deformations and “compact” orientations for both coplanar (${\mathrm{\Phi }}_c=0^{\circ }$) and noncoplanar (${\mathrm{\Phi }}_c\ne 0^{\circ }$) configurations, using various different nuclear interaction potentials. Interesting variations of ${\sigma }_{\mathrm{ER}}^{\mathrm{reduced}}$ with CN excitation energy $E^{*}$, fissility parameter $\chi$, CN mass $A_{\mathrm{CN}}$, and Coulomb parameter $Z_1{Z}_2$ show that, independent of entrance channel, different isotopes of CN, and nuclear interaction potentials used, the dominant quantity in the product is $P_{\mathrm{surv}}$, which classifies all the studied CN into three groups of weakly fissioning, radioactive, and strongly fissioning superheavy nuclei, with relative magnitudes of ${\sigma }_{\mathrm{ER}}^{\mathrm{reduced}}\sim 1$, $\sim {10}^{-6}$, and $\sim {10}^{-11}$, which, like for $P_{\mathrm{CN}}$, get further grouped in two dependencies of (i) weakly fissioning and strongly fissioning superheavy nuclei decreasing with increasing $E^{*}$ and (ii) radioactive nuclei increasing with increasing $E^{*}$.

A pioneering study of Gamow-Teller (GT) and Fermi matrix elements (MEs) using no-core-configuration-interaction formalism rooted in multireference density functional theory is presented. After a successful test performed for ${}^6\mathrm{He}\to {}^6\mathrm{Li}\beta$ decay, the model is applied to compute MEs in the $sd$- and $pf$-shell $T=1/2$ mirror nuclei. The calculated GT MEs and the isospin-symmetry-breaking corrections to the Fermi branch are found to be in very good agreement with shell-model predictions in spite of fundamental differences between these models concerning model space, treatment of correlations, or inclusion of a core. This result indirectly supports the two-body-current-based scenarios behind the quenching of the axial-vector coupling constant.

The formation mechanism of fragments with strangeness in collisions of antiprotons on nuclei has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport model. Production of strange particles in the antiproton-induced nuclear reactions is modeled within the LQMD model, in which all possible reaction channels such as elastic scattering, annihilation, charge exchange, and inelastic scattering in antibaryon-baryon, baryon-baryon, and meson-baryon collisions have been included. A coalescence approach is developed for constructing hyperfragments in phase space. The hyperfragments are formed within the narrower rapidities. It has the advantage of producing heavier hyperfragments and hypernuclides with strangeness $s=-2$ (double-$\mathrm{\Lambda }$ fragments) and $s=1$ ($\overline{\mathrm{\Lambda }}$ fragments) in antiproton-induced reactions.

The spectral characteristics of the $L^{\pi }=0^{+}$ excited states in the interacting boson model are systematically investigated. It is found that various types of excited-state quantum phase transitions may widely occur in the model as functions of the excitation energy, which indicates that the phase diagram of the interacting boson model can be dynamically extended along the direction of the excitation energy. It has also been justified that the $d$-boson occupation probability $\rho \left(E\right)$ is qualified to be taken as the effective order parameter to identify these excited-state quantum phase transitions. In addition, the underlying relation between the excite-state quantum phase transition and the chaotic dynamics is also stated.

The levels in ${}^{129}\mathrm{Sn}$ populated from the ${\beta }^{-}$ decay of ${}^{129}\mathrm{In}$ isomers were investigated at the ISOLDE facility of CERN using the newly commissioned ISOLDE Decay Station (IDS). The lowest $1/2^{+}$ state and the $3/2^{+}$ ground state in ${}^{129}\mathrm{Sn}$ are expected to have configurations dominated by the neutron $s_{1/2}$ ($l=0$) and $d_{3/2}$ ($l=2$) single-particle states, respectively. Consequently, these states should be connected by a somewhat slow $l$-forbidden $M1$ transition. Using fast-timing spectroscopy we have measured the half-life of the $1/2^{+}$ 315.3-keV state, $T_{1/2}=$ 19(10) ps, which corresponds to a moderately fast $M1$ transition. Shell-model calculations using the CD-Bonn effective interaction, with standard effective charges and $g$ factors, predict a 4-ns half-life for this level. We can reconcile the shell-model calculations to the measured $T_{1/2}$ value by the renormalization of the $M1$ effective operator for neutron holes.

A systematic investigation of octupole-deformed nuclei is presented for even-even systems with $Z\le 106$ located between the two-proton and two-neutron driplines. For this study we use five most-up-to-date covariant energy density functionals of different types, with a nonlinear meson coupling, with density-dependent meson couplings, and with density-dependent zero-range interactions. Pairing correlations are treated within relativistic Hartree-Bogoliubov theory based on an effective separable particle-particle interaction of finite range. This allows us to assess theoretical uncertainties within the present covariant models for the prediction of physical observables relevant for octupole-deformed nuclei. In addition, a detailed comparison with the predictions of nonrelativistic models is performed. A new region of octupole deformation, centered around $Z\sim 98,N\sim 196$ is predicted for the first time. In terms of its size in the $(Z,N)$ plane and the impact of octupole deformation on binding energies this region is similar to the best known region of octupole-deformed nuclei centered at $Z\sim 90,N\sim 136$. For the later island of octupole-deformed nuclei, the calculations suggest substantial increase of its size as compared with available experimental data.

Using the stochastic Langevin model coupled with a statistical decay model, we study postsaddle dissipation properties in fission by analyzing the excitation energy at scission ($E_{\mathrm{sc}}^{*}$) measured in fissioning nuclei ${}^{179}\mathrm{Re}$ and ${}^{254,256}\mathrm{Fm}$. The postsaddle dissipation strength ($\beta$) required to fit $E_{\mathrm{sc}}^{*}$ data is found to be larger for ${}^{254,256}\mathrm{Fm}$ than light ${}^{179}\mathrm{Re}$ which has a smaller postsaddle deformation compared to heavy ${}^{254,256}\mathrm{Fm}$, showing a rise of nuclear dissipation strength at a greater deformation. Furthermore, we explore the influence of initial excitation energy of a fissioning system ${}^{246}\mathrm{Cf}$ on the sensitivity of its $E_{\mathrm{sc}}^{*}$ to $\beta$, and find that the sensitivity is significantly enhanced with increasing the initial excitation energy. Our finding suggests that, on the experimental side, to more accurately probe the postsaddle dissipation strength through the measurement of $E_{\mathrm{sc}}^{*}$, it is best to yield those fissioning systems with high energy.

Considering the emission process of $\alpha$ particles in the transition from an isolated quasibound state to a scattering state, a clear expression for the decay width derived in terms of regular Coulomb function, the quasibound state wave function, and the difference of potentials is analyzed. The Schrödinger equation with the effective potential representing the $\alpha$ + nucleus interaction consistent with the potential obtained in the relativistic mean-field approximation is solved exactly for the wave function. Using this exact wave function at resonance and the difference of the above potential from the point charge Coulomb interaction in the expression of decay width stated above, an analytic expression for the decay half-life is derived from the width. By invoking some approximations for different functions in this expression, a closed formula for the logarithm of half-life in terms of characteristic $Q$ value equal to the resonance energy and the mass and charge numbers of the $\alpha$ emitter is obtained. The calculated results of half-life obtained by using the analytic expression of half-life or the closed formula for the logarithm of the half-life are shown to explain the corresponding measured data with values ranging from ${10}^{-6}$ s to ${10}^{22}$ y in the case of large numbers of $\alpha$ emitters that include heavy and superheavy nuclei. The results of the closed formula aligned in a straight line closely explain the rectilinear arrangement of the logarithm values of experimental results for decay half-lives as a function of a quantity that depends on $Q$ values and charge numbers of the emitters. The analytic closed formula with all its terms defined is preferable to the empirical Viola-Seaborg rule of $\alpha$-decay rate.

The even-even nucleus ${}^{26}\mathrm{Mg}$ has been studied through the reaction ${}^{27}\mathrm{Al}(d,{}^3\mathrm{He})$ at 25 MeV beam energy. The spectroscopic factors of the lowest $\left(T=1\right)$ states of ${}^{26}\mathrm{Mg}$ have been extracted using the zero-range distorted wave Born approximation. These spectroscopic factors are compared with those of $T=1$ analog states in ${}^{26}\mathrm{Al}$ and found to be in good agreement.

The nuclear properties of ${}^{48}\mathrm{Cr}$ composite $\alpha$-like nuclei produced at 60 MeV of excitation energy via the ${}^{24}\mathrm{Mg}+{}^{24}\mathrm{Mg}$ reaction were investigated. This excitation energy corresponds to a resonance with a narrow width (170 keV) observed in the elastic and inelastic channels, which was interpreted as a highly deformed state. To gain insight on the deformation of this state exclusive measurements of light charged particles were carried out with $8\pi \mathrm{LP}$ apparatus at Laboratori Nazionali di Legnaro and compared to statistical model predictions. The measured of $\alpha$-particle energy spectra, $\alpha$-evaporation residues, $\alpha \text{−}\alpha$, and $\alpha \text{−}\alpha \text{−}\alpha$ correlations indicate the limitation of the rotating liquid drop model in describing the nuclear shape of the compound nucleus along the decay cascade. To reproduce the full set of experimental data very elongated nuclear shapes had to be considered, with an axis ratio $3:1$ at the resonance angular momentum. This large deformation is consistent with previous findings for $\alpha$-like nuclei and with the predictions of the cranked cluster model.

The case for a dibaryon resonance, appearing in $np$ scattering, has support from a WASA-at-COSY measurement of the polarization quantity $A_y$ over a center-of-mass energy region suggested by structures seen earlier in two-pion production experiments. Here we compare fits with and without an associated pole in order to clarify the impact of these COSY data. We then consider what further $np$ scattering measurements would most clearly distinguish between the pole and non-pole fit results.

Superfluid vortices in the color-flavor-locked (CFL) phase of dense quark matter are known to be energetically disfavored relative to well-separated triplets of so-called semi-superfluid color flux tubes. However, the short-range interaction (metastable versus unstable) has not been established. In this paper we perform numerical calculations using the effective theory of the condensate field, mapping the regions in the parameter space of coupling constants where the vortices are metastable versus unstable. For the case of zero-gauge coupling we analytically identify a candidate for the unstable mode and show that it agrees well with the results of the numerical calculations. We find that in the region of the parameter space that seems likely to correspond to real-world CFL quark matter the vortices are unstable, indicating that if such matter exists in neutron star cores it is very likely to contain semi-superfluid color flux tubes rather than superfluid vortices.

A precise moment of inertia measurement for PSR J0737-3039A in the double pulsar system is expected within the next five years. We present here a new method of mapping the anticipated measurement of the moment of inertia directly into the neutron star structure. We determine the maximum and minimum values possible for the moment of inertia of a neutron star of a given radius based on physical stability arguments, assuming knowledge of the equation of state only at densities below the nuclear saturation density. If the equation of state is trusted up to the nuclear saturation density, we find that a measurement of the moment of inertia will place absolute bounds on the radius of PSR J0737-3039A to within $\pm 1$ km. The resulting combination of moment of inertia, mass, and radius measurements for a single source will allow for new, stringent constraints on the dense-matter equation of state.

Background: In the past few decades quantum phase transitions have been of great interest in nuclear physics. In this context, two-fluid algebraic models are ideal systems to study how the concept of quantum phase transition evolves when moving into more complex systems, but the number of publications along this line has been scarce up to now.

Purpose: We intend to determine the phase diagram of a two-fluid Lipkin model that resembles the nuclear proton-neutron interacting boson model Hamiltonian using both numerical results and analytic tools, i.e., catastrophe theory, and compare the mean-field results with exact diagonalizations for large systems.

Method: The mean-field energy surface of a consistent-$Q$-like two-fluid Lipkin Hamiltonian is studied and compared with exact results coming from a direct diagonalization. The mean-field results are analyzed using the framework of catastrophe theory.

Results: The phase diagram of the model is obtained and the order of the different phase-transition lines and surfaces is determined using a catastrophe theory analysis.

Conclusions: There are two first-order surfaces in the phase diagram, one separating the spherical and the deformed shapes, while the other separates two different deformed phases. A second-order line, where the later surfaces merge, is found. This line finishes in a transition point with a divergence in the second-order derivative of the energy that corresponds to a tricritical point in the language of the Ginzburg-Landau theory for phase transitions.

Extending our earlier work, a new family of three Hartree-Fock-Bogoliubov (HFB) mass models, labeled HFB-30, HFB-31, and HFB-32, is presented, along with their underlying interactions, BSk30, BSk31, and BSk32, respectively. The principle new feature is a purely phenomenological pairing term that depends on the density gradient. This enables us to have a bulk pairing term that is fitted to realistic nuclear-matter calculations in which for the first time the self-energy corrections are included, while the behavior of the nucleon effective masses in asymmetric homogeneous nuclear matter is significantly improved. Furthermore, in the particle-hole channel all the highly realistic constraints of our earlier work are retained. In particular, the unconventional Skyrme forces containing $t_4$ and $t_5$ terms are still constrained to fit realistic equations of state of neutron matter stiff enough to support the massive neutron stars PSR J1614–2230 and PSR J0348+0432. All unphysical long-wavelength spin and spin-isospin instabilities of nuclear matter, including the unphysical transition to a polarized state in neutron-star matter, are eliminated. Our three interactions are characterized by values of the symmetry coefficient $J$ of 30, 31, and 32 MeV, respectively. The best fit to the database of 2353 nuclear masses is found for model HFB-31 $\left(J=31\mathrm{MeV}\right)$ with a model error of 0.561 MeV. This model also fits the charge-radius data with an root-mean-square error of 0.027 fm.

Experimental results are presented for the inclusive reaction ${}^{59}\mathrm{Co}(\vec{p},\alpha )$ at an incident energy of 100 MeV. A theoretical analysis based on a statistical multistep mechanism indicates that the terminal step leading to emission of an $\alpha$ particle can be a pickup or knockout process and that both processes are very prominent. This is a conclusion which is in agreement with an earlier study of the ${}^{93}\mathrm{Nb}(\vec{p},\alpha )$ reaction. This inspires an investigation of the reason why a mixture of knockout and pickup is present at an incident energy of 100 MeV, whereas at both higher and lower incident energies knockout appears to dominate for the target nucleus ${}^{93}\mathrm{Nb}$. It is found that the different dynamics of the two competing reaction mechanisms provide an explanation for the observed phenomenon. It is speculated that for ${}^{59}\mathrm{Co}$ at both lower and higher incident energies the trend is likely to be similar to that of ${}^{93}\mathrm{Nb}$.