We analyze the properties of the Gogny interaction in homogeneous matter, with special emphasis on the isovector sector. We provide analytical expressions for both the single-particle and the bulk properties of symmetric and asymmetric nuclear matter. We perform an extensive analysis of these properties using eleven parametrizations extracted from the literature. We find that most Gogny interactions have low values for the slope of the symmetry energy, outside the range of empirically extracted values. As a test of extreme isospin dependence, we also study the neutron star mass-radius relations implied by the different Gogny equations of state. Our results call for a more careful fitting procedure of the isovector properties of Gogny functionals.

The scope of the paper is to apply a state-of-the-art beyond mean-field model to the description of the Gamow-Teller response in atomic nuclei. This topic recently attracted considerable renewed interest, due, in particular, to the possibility of performing experiments in unstable nuclei. We study the cases of ${}^{48}\mathrm{Ca},{}^{78}\mathrm{Ni},{}^{132}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$. Our model is based on a fully self-consistent Skyrme Hartree-Fock plus random phase approximation. The same Skyrme interaction is used to calculate the coupling between particles and vibrations, which leads to the mixing of the Gamow-Teller resonance with a set of doorway states and to its fragmentation. We compare our results with available experimental data. The microscopic coupling mechanism is also discussed in some detail.

The heavy-ion fusion reactions with ${}^{16}\mathrm{O}$ bombarding on ${}^{62}\mathrm{Ni},{}^{65}\mathrm{Cu},{}^{74}\mathrm{Ge},{}^{148}\mathrm{Nd},{}^{180}\mathrm{Hf},{}^{186}\mathrm{W},{}^{208}\mathrm{Pb},{}^{238}\mathrm{U}$ are systematically investigated with the improved quantum molecular dynamics model. The fusion cross sections at energies near and above the Coulomb barriers can be reasonably well reproduced by using this semiclassical microscopic transport model with the parameter sets SkP* and IQ3a. The dynamical nucleus-nucleus potentials and the influence of Fermi constraint on the fusion process are also studied simultaneously. In addition to the mean field, the Fermi constraint also plays a key role for the reliable description of the fusion process and for improving the stability of fragments in heavy-ion collisions.

We study here the ternary-fission mass distribution of the ${}^{252}\mathrm{Cf}$ nucleus for a fixed third fragment ${}^{48}\mathrm{Ca}$ using the level-density approach within the framework of statistical theory. For the evaluation of nuclear level densities, the single-particle energies of the finite-range droplet model are used. Our results for temperatures $T=1$ and 2 MeV reproduce qualitatively the experimental expectation of ternary fragmentation of ${}^{132}\mathrm{Sn}+{}^{72}\mathrm{Ni}+{}^{48}\mathrm{Ca}$. In addition, different possible ternary-fission modes are highlighted.

The production cross sections for 110 radioactive nuclides, with mass numbers $22\le A\le 198$, were obtained from the interaction of 4.4 GeV deuteron with a ${}^{197}\mathrm{Au}$ target using the induced-activity method. The deuteron beam was obtained from the Nuclotron of the Laboratory of High Energies (LHE), Joint Institute for Nuclear Research (JINR) at Dubna. Using the charge distribution data, we derived the total mass-yield distribution. The analysis of the mass-yield distribution allowed us to consider the coexistence of different channels in the interaction such as evaporation, fission, and multifragmentation.

Applying a macroscopic reduction procedure to the improved quantum molecular dynamics (ImQMD) model, the energy dependences of the nucleus-nucleus potential, the friction parameter, and the random force characterizing a one-dimensional Langevin-type description of the heavy-ion fusion process are investigated. Systematic calculations with the ImQMD model show that the fluctuation-dissipation relation found in symmetric head-on fusion reactions at energies just above the Coulomb barrier fades out when the incident energy increases. It turns out that this dynamical change with increasing incident energy is caused by a specific behavior of the friction parameter which directly depends on the microscopic dynamical process, i.e., on how the collective energy of the relative motion is transferred into the intrinsic excitation energy. It is shown microscopically that the energy dissipation in the fusion process is governed by two mechanisms: One is caused by the nucleon exchanges between two fusing nuclei, and the other is due to a rearrangement of nucleons in the intrinsic system. The former mechanism monotonically increases the dissipative energy and shows a weak dependence on the incident energy, while the latter depends on both the relative distance between two fusing nuclei and the incident energy. It is shown that the latter mechanism is responsible for the energy dependence of the fusion potential and explains the fading out of the fluctuation-dissipation relation.

The recoil-$\beta$ tagging technique was used to identify transitions associated with the decay of the ${\mathrm{2}}^{+}$ and, tentatively, the ${\mathrm{4}}^{+}$ excited states in ${}^{74}\mathrm{Sr}$. Combining these results with published data for the $A=74$ isobars, triplet energy differences (TEDs) have been extracted, the heaviest case for which these values have been evaluated. State-of-the-art shell-model calculations using the JUN45 interaction and incorporating a $J=0$ isospin nonconserving (INC) interaction with an isotensor strength of 100 keV can reproduce the trend in the TED data, with particularly good agreement for the ${\mathrm{2}}^{+}$ state. This agreement for the TED data taken together with the fact that agreement has also been shown between shell-model calculations with the same strength of INC interaction in the $f_{7/2}$ shell and recently for $A=66$ strongly suggests that such an interaction exists throughout the nuclear chart and cannot have a strong dependence on details of nuclear structure such as which nuclear orbitals are occupied. It also supports the hypothesis that only a $J=0$ component of the INC interaction need be included to explain the observed TEDs.

In this paper we improve an empirical mass formula constructed by Jänecke and collaborators. This formula is enlightened by the Garvey-Kelson mass relations. The new version of the Jänecke formula reproduces 2275 atomic masses with neutron number $N\ge 10$ and proton number $Z\ge 6$, at an average accuracy of 128 keV, by employing 576 parameters. The predictive power of our formula is exemplified by comparison with predicted results of other mass models.

Relativistic mean field theory is formulated with the Green's function method in coordinate space to investigate the single-particle bound states and resonant states on the same footing. Taking the density of states for free particles as a reference, the energies and widths of single-particle resonant states are extracted from the density of states without any ambiguity. As an example, the energies and widths for single-neutron resonant states in ${}^{120}\mathrm{Sn}$ are compared with those obtained by the scattering phase-shift method, the analytic continuation in the coupling constant approach, the real stabilization method, and the complex scaling method. Excellent agreements with these methods are found for the energies and widths of single-neutron resonant states.

The properties of symmetric nuclear and pure neutron matter are investigated within an extended self-consistent Green's function method that includes the effects of three-body forces. We use the ladder approximation for the study of infinite nuclear matter and incorporate the three-body interaction by means of a density-dependent two-body force. This force is obtained via a correlated average over the third particle, with an in-medium propagator consistent with the many-body calculation we perform. We analyze different prescriptions in the construction of the average and conclude that correlations provide small modifications at the level of the density-dependent force. Microscopic as well as bulk properties are studied, focusing on the changes introduced by the density-dependent two-body force. The total energy of the system is obtained by means of a modified Galitskii-Migdal-Koltun sum rule. Our results validate previously used uncorrelated averages and extend the availability of chirally motivated forces to a larger density regime.

We present details of the derivation of local chiral effective field theory interactions to next-to-next-to-leading order and show results for nucleon-nucleon phase shifts and deuteron properties for these potentials. We then perform systematic auxiliary-field diffusion Monte Carlo calculations for neutron matter based on the developed local chiral potentials at different orders. This includes studies of the effects of the spectral-function regularization and of the local regulators. For all orders, we compare the quantum Monte Carlo results with perturbative many-body calculations and find excellent agreement for low cutoffs.

The mass asymmetry in the fission of ${}^{236}\mathrm{U}$ at low excitation energy is clarified by the analysis of the trajectories obtained by solving the Langevin equations for the shape degrees of freedom. It is demonstrated that the position of the peaks in the mass distribution of fission fragments is determined mainly by the saddle point configuration originating from the shell correction energy. The width of the peaks, on the other hand, results from the shape fluctuations close to the scission point caused by the random force in the Langevin equation. We have found out that the fluctuations between elongated and compact shapes are essential for the fission process. According to our results the fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup, but is accompanied by the fluctuations between elongated and compact shapes. This picture presents a new viewpoint of fission dynamics and the splitting mechanism.

The influence of a two-hadron threshold is studied for the hadron mass scaling with respect to some quantum chromodynamics parameters. A quantum mechanical model is introduced to describe the system with a one-body bare state coupled with a single elastic two-body scattering. The general behavior of the energy of the bound and resonance state near the two-body threshold for a local potential is derived from the expansion of the Jost function around the threshold. It is shown that the same scaling holds for the nonlocal potential induced by the coupling to a bare state. In $p$ or higher partial waves, the scaling law of the stable bound state continues across the threshold describing the real part of the resonance energy. In contrast, the leading contribution of the scaling is forbidden by the nonperturbative dynamics near the $s$-wave threshold. As a consequence, the bound state energy is not continuously connected to the real part of the resonance energy. This universal behavior originates in the vanishing of the field renormalization constant of the zero-energy resonance in the $s$ wave. A proof is given for the vanishing of the field renormalization constant, together with a detailed discussion.

We compute the contribution of phonons to the thermal conductivity in the core of superfluid neutron stars. We use effective field theory techniques to extract the phonon scattering rates, written as a function of the equation of state of the system. We also calculate the phonon dispersion law beyond linear order, which depends on the gap of superfluid neutron matter. With all these ingredients, we solve the Boltzmann equation numerically using a variational approach. We find that the thermal conductivity $\kappa$ is dominated by combined small- and large-angle binary collisions. As in the color-flavor-locked superfluid, we find that our result can be well approximated by $\kappa \propto 1/{\Delta }^6$ at low temperature, where $\Delta$ is the neutron gap, the constant of proportionality depending on the density. We further comment on the possible relevance of electron and superfluid phonon collisions in obtaining the total contribution to the thermal conductivity in the core of superfluid neutron stars.

The correlation between the elliptic flow $v_2$ scaled by the impact parameter $b$ and the shear viscosity $\eta$ as well as the specific viscosity $\eta /s$, defined as the ratio of the shear viscosity to the entropy density $s$, is investigated for the first time in intermediate-energy heavy-ion collisions based on an isospin-dependent quantum molecular dynamic model. The elliptic flow is calculated at balance energies to exclude the geometric influence such as the blocking effect from the spectators. Our study shows that $v_2/b$ decreases almost linearly with increasing $\eta$, consistent with that observed in ultrarelativistic heavy-ion collisions. On the other hand, $v_2/b$ is found to increase with increasing $\eta /s$.

We show that the charge radii of neighboring atomic nuclei, independent of atomic number and charge, follow remarkably very simple relations, despite the fact that atomic nuclei are complex finite many-body systems governed by the laws of quantum mechanics. These relations can be understood within the picture of independent-particle motion and by assuming that neighboring nuclei have similar patterns in the charge density distribution. A root-mean-square (rms) deviation of 0.0078 fm is obtained between the predictions in these relations and the experimental values, i.e., a precision comparable modern experimental techniques. Such high accuracy relations are very useful to check the consistence of the nuclear charge radius surface and moreover to predict unknown nuclear charge radii, while large deviations from experimental data are seen to reveal the appearance of nuclear shape transition or coexsitence.

High-energy $\gamma$-ray spectra measured by our group involving the compound nuclei (CN) ${}^{63}\mathrm{Cu}$ at excitation energy $E^{*}\sim 36$ MeV with average angular momentum $J=12–17\hslash$, ${}^{97}\mathrm{Tc}$ at $E^{*}\sim 29–50\mathrm{MeV}$ with $J=12–14\hslash$, ${}^{113}\mathrm{Sb}$ at $E^{*}=109$ and 121 MeV with $J=49–59$ $\hslash$, and ${}^{201}\mathrm{Tl}$ at $E^{*}=39.5$ and 47.5 MeV with $J=18–24 \hslash$ have been analyzed utilizing the level density prescriptions of (i) Ignatyuk, Smirenkin, and Tishin (IST), (ii) Budtz-Jorgensen and Knitter (BJK), and (iii) Kataria, Ramamurthy, and Kapoor (KRK). These three prescriptions have been tested for the correct statistical model description of high-energy $\gamma$ rays in the light of extracting the giant dipole resonance (GDR) parameters at low excitation energy and spin where shell effects might play an important role, as well as at high excitation energy where shell effects have melted. Interestingly, only the IST level density prescription could explain the high-energy $\gamma$-ray spectra with reasonable GDR parameters for all four nuclei.

Background: In heavy-ion-induced reactions the mechanism leading to the formation of the compound nucleus and the role of quasifission is still not clear.

Purpose: Investigation of the quasifission process of superheavy composite systems with $Z=110\text{−}116$ and comparison with properties of fusion-fission and quasifission of lighter composite systems.

Method: Mass and energy distributions of fissionlike fragments formed in the reactions ${}^{48}\mathrm{Ca}+{}^{232}\mathrm{Th}$, ${}^{238}\mathrm{U}$, ${}^{244}\mathrm{Pu}$, and ${}^{248}\mathrm{Cm}$ at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET at the U-400 cyclotron of the FLNR JINR.

Results: The most probable fragment masses as well as total kinetic energies and their dispersions in dependence on the interaction energies and ion-target combinations have been studied for asymmetric and symmetric fragments formed in the reactions. The capture cross sections were obtained for the reactions ${}^{48}\mathrm{Ca}+{}^{244}\mathrm{Pu}$ and ${}^{248}\mathrm{Cm}$. The lower limits for fission barriers of ${}^{283-286}\mathrm{Cn}$, ${}^{289-292}\mathrm{Fl}$, and ${}^{293-296}\mathrm{Lv}$ compound nuclei were estimated.

Conclusions: Analysis of the properties of symmetric fragments has shown that a significant part of these fragments may be attributed to fusion-fission process for the reactions ${}^{48}\mathrm{Ca}{+}^{238}\mathrm{U}$, ${}^{244}\mathrm{Pu}$, and ${}^{248}\mathrm{Cm}$.

The power spectrum of heavy-ion collisions is investigated by studying initial state fluctuations on top of a smooth hydrodynamic flow. In particular, the stability of the location of the first minimum of the power spectrum and the dependence of the hydrodynamic response $v_n/{\varepsilon }_n$ on $n$ and on $\eta /s$ are discussed. In our study we develop a new Green's function method for the analytic hydrodynamic flow by S. Gubser and make use of a fully nonlinear hydrodynamics code. We find that there will be no well-defined first minimum of the response for $n<10$, due to the fact that all minima in that region are found to be sensitive to the location of the initial perturbations. Also, we find that the often-proposed form of the hydrodynamical response, that $ln(v_n/{\varepsilon }_n)$ depend quadratically on $n$ and linearly on $\eta /s$, should not hold once many events have been averaged.