We find that the current radiative energy loss kernels obtained from the opacity expansion dramatically violate the collinear approximation used in their derivation. By keeping only the lowest order in collinearity terms, models based on the opacity expansion have $~50\%$ systematic uncertainty in the calculation of ${\pi }^0$ $R_{\mathit{AA}}$ in the most central RHIC collisions, resulting in a systematic uncertainty of $~200\%$ in the extracted medium density. Surprisingly, the inclusion of a thermal gluon mass of the order of the Debye screening scale affects $R_{\mathit{AA}}$ only at about the $5\%$ level due to nonintuitive coherence effects. For some observables such as $R_{\mathit{AA}}$, the effect of these uncertainties decreases with increasing jet energy; for others, such as the average number of radiated gluons, the effect is energy independent. We note that it is likely that the differences reported in the extracted values of medium parameters such as $\mathrm{q̂}$ by various jet energy loss models will fall within this collinear approximation systematic uncertainty; it is imperative for the quantitative extraction of medium parameters or the possible falsification of the hypothesis of weak coupling between the hard probes and the soft modes of the quark-gluon plasma medium that future radiative energy loss research push beyond the lowest-order collinear approximation.

The properties of low-density neutron matter are important for the understanding of neutron star crusts and the exterior of large neutron-rich nuclei. We examine various properties of dilute neutron matter using quantum Monte Carlo methods, with $s$- and $p$-wave terms in the interaction. Our results provide a smooth evolution of the equation of state and pairing gap from extremely small densities, where analytic expressions are available, up to the strongly interacting regime probed experimentally and described theoretically in cold atomic systems, where $k_F\approx 0.5\hspace{0.5em}{\text{fm}}^{-1}$ and the pairing gap becomes of the order of magnitude of the Fermi energy. We also present results for the momentum distribution and pair distributions, displaying the same evolution from weak to strong coupling. Combined with previous quantum Monte Carlo and other calculations at moderate densities, these results provide strong constraints on the neutron matter equation of state up to saturation densities.

Transport properties of a strongly interacting superfluid mixture of two Fermi liquids are studied. A typical example of such matter is the neutron-proton liquid in the cores of neutron stars. To describe the mixture, the Landau theory of Fermi liquids, generalized to allow for the effects of superfluidity, is employed. The kinetic equation is formulated and the linear response of the system to vector (e.g., electromagnetic) perturbation is analyzed. In particular, the transverse and longitudinal polarization functions for both liquid components are calculated. It is demonstrated that they can be expressed through the Landau parameters of the mixture and polarization functions of noninteracting matter (when the Landau quasiparticle interaction is neglected). These results can be used, for example, for studies of the kinetic coefficients and low-frequency long-wavelength collective modes in superfluid Fermi mixtures.

The $S$ factor and the fusion cross-section values for the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reaction are evaluated in the framework of a simple barrier-penetration model, which takes into account quadrupole and hexadecapole surface deformations of ${}^{12}\mathrm{C}$. The calculated values agree well with corresponding experimental data at off-resonances energies. It is shown that the strong oblate quadrupole deformation of ${}^{12}\mathrm{C}$ induces the increasing of both the $S$ factor and the fusion cross-section values at subbarrier energies. The $S$ factor and the fusion cross section for the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reaction are slightly reduced at low energy due to the influence of the hexadecapole deformation.

Shape invariants within the interacting boson model are used to describe the $\gamma$ deformation of the ground state and $0_2^{+}$ state along the $\beta$-rigid leg of the extended Casten triangle between the symmetry limits SU(3) and $\overline{\mathrm{SU}(3)}$ via the O(6) limit. Similarly to the recently discovered $\beta$-deformation crossing of the ground state with the $0_2^{+}$ state between the symmetry limits U(5) and SU(3), a crossing of those states with respect to the $\gamma$ deformation is observed between SU(3) and $\overline{\mathrm{SU}(3)}$. The newly introduced order parameter $K_3(0_1^{+})-K_3(0_2^{+})$ shows a peaking behavior at O(6), which is a signature of a first-order phase transition and is observed at O(6) for the first time. Comparison with existing data and experimental prospects for measuring this signature are presented and differences and similarities between spherical-deformed and prolate-oblate first-order phase transitions are discussed.

We present the results of a $\gamma \gamma$ angular correlation experiment investigating the nucleus ${}^{196}\mathrm{Hg}$ and compare these with a theoretical description of ${}^{196}\mathrm{Hg}$ within the ${\mathrm{U}}_{\nu }(6/12)\otimes$$U_{\pi }(6/4)$ extended supersymmetry. To populate excited ${}^{196}\mathrm{Hg}$ states, we used the Cologne FN Tandem accelerator inducing the reaction ${}^{194}\mathrm{Pt}$$(\alpha ,2n){}^{196}\mathrm{Hg}$ and analyzed the $\gamma$ decays of levels up to an excitation energy of $2.4$ MeV with the HORUS cube spectrometer. The new results on this mercury isotope allow a comparison between the experimental data and the supersymmetrical predictions and show good agreement. This way we can add ${}^{196}\mathrm{Hg}$ as a fifth supermultiplet member to the so-called magical quartet consisting of ${}^{194,195}\mathrm{Pt}$ and ${}^{195,196}\mathrm{Au}$.

Two neutron-rich $N=93$ isotones, ${}^{155}\mathrm{Sm}$ and ${}^{153}\mathrm{Nd}$, have been studied by delayed $\gamma$-ray and conversion-electron spectroscopy at the Lohengrin mass spectrometer. A half-life of 2.9(5) $\mu$s has been measured for the $\nu 5/2^{+}$[642] state at 16.5 keV in ${}^{155}\mathrm{Sm}$. The decay of a 1.17(7)-$\mu$s isomer in ${}^{153}\mathrm{Nd}$, at 191.7 keV, has been remeasured and its spin has been reassigned as $(5/2){}^{+}$. This state contains a strong component of the $\nu 5/2^{+}$[642] Nilsson orbital. In addition, a new 1.00(8)-$\mu$s isomeric state at 538.6 keV, with a probable $\nu 11/2^{-}$[505] Nilsson configuration, has been observed in ${}^{155}\mathrm{Sm}$. Triple $\gamma$-ray coincidence data from the spontaneous fission of a ${}^{252}\mathrm{Cf}$ source placed inside the Gammasphere array were used to extend the collective band on top of the $(5/2^{+})$ isomeric state of ${}^{153}\mathrm{Nd}$, and a new band with the same bandhead spin has been observed in ${}^{151}\mathrm{Ce}$. The observation of this new band and an additional new transition in the ground-state band has led us to change the ground-state spin of ${}^{151}\mathrm{Ce}$ to $(3/2^{-})$. Calculations using the quasiparticle-rotor model successfully reproduce the majority of the features of the $\gamma$ decays of these nuclei, including branching ratios and isomeric half-lives. Because this model uses a reflection-symmetric core, we conclude that the polarizing effect of the odd particle is responsible for the dipole moment present in the $\nu 5/2^{+}$[642] states of the three nuclei studied and the $\nu 11/2^{-}$[505] level of ${}^{155}\mathrm{Sm}$.

A candidate of a neutron-halo nucleus, ${}^{31}\mathrm{Ne}$, contains a single neutron in the $\mathit{pf}$ shell. Within the Glauber and eikonal models, we analyze reactions used to study ${}^{31}\mathrm{Ne}$. We show in a ${}^{30}\mathrm{Ne}+n$ model that the magnitudes of the total reaction and above all of the one-neutron removal cross sections of ${}^{31}\mathrm{Ne}$ on ${}^{12}\mathrm{C}$ and ${}^{208}\mathrm{Pb}$ targets strongly depend on the orbital angular momentum of the neutron, thereby providing us with efficient ways to determine both the spin-parity and structure of the ground state of ${}^{31}\mathrm{Ne}$. Besides these inclusive observables, we also calculate energy and parallel-momentum distributions for the breakup of ${}^{31}\mathrm{Ne}$ and show their strong dependence on the orbital of the valence neutron in the bound state of ${}^{31}\mathrm{Ne}$.

The effects of dynamical long-range correlations over a fluid cell-size scale on a relativistic fluid are discussed. It is shown that such correlations among the fluid elements introduced into the hydrodynamical model induce some weak dissipation and viscosity into the fluid. The influence of the long-range correlations on the entropy current is also discussed.

We calculate the kaonic contribution to the shear viscosity of quark matter in the kaon-condensed color-flavor-locked phase (CFL-K0). This contribution comes from a light pseudo-Goldstone boson that arises from the spontaneous breaking of the flavor symmetry by the kaon condensate. The other contribution, from the exactly massless superfluid “phonon,” has been calculated previously. We specialize to a particular form of the interaction Lagrangian, parameterized by a single coupling. We find that if we make reasonable guesses for the values of the parameters of the effective theory, the kaons have a much smaller shear viscosity than the superfluid phonons but also a much shorter mean free path, so they could easily provide the dominant contribution to the shear viscosity of CFL-K0 quark matter in a neutron star in the temperature range $0.01$ to $1$ MeV (${10}^8$ to ${10}^{10}$ K).

Collisions of a very heavy nonfusing nuclear system ${}^{197}\mathrm{Au}$$+$${}^{197}\mathrm{Au}$ were studied at an energy of $15$ MeV/nucleon. An interesting process of violent reseparation of this heavy system into three or four fragments of comparable size was observed. In the case of ternary partitioning, either the projectile-like fragment (PLF) or target-like fragment (TLF) breaks up almost collinearly with the PLF-TLF separation axis. In the case of quaternary reactions, both PLF and TLF were observed breaking up along this direction. By comparison with a dynamical model of deep inelastic collisions it was concluded that the ternary and quaternary reactions occur in semiperipheral collisions, in a range of angular momenta corresponding to about $0.5–0.7$ of the maximum $L$ value for grazing collisions. The time elapsing from the scission of the binary PLF $+$ TLF system to the secondary scission of PLF or TLF was estimated to be of about $70–80$ fm/$c$ for the ternary reactions and $80–100$ fm/$c$ for the quaternary reactions.

The axial charges of the nucleon and the well-established $N^{*}$ resonances are studied within a consistent framework. For the first time the axial charges of the $N^{*}$ resonances are produced for the relativistic constituent quark model. The axial charge of the nucleon is predicted close to experiment, and the ones of $N^{*}(1535)$ and $N^{*}(1650)$, the only cases where such a comparison is possible, agree well with results from quantum chromodynamics on the lattice that have recently become available. The relevance of the magnitudes of the $N^{*}$ axial charges for the low-energy behavior of quantum chromodynamics is discussed.

Relativistic Hartree-Fock-Bogoliubov (RHFB) theory with density-dependent meson-nucleon couplings is presented. The integrodifferential RHFB equations are solved by expanding the different components of the quasiparticle spinors in the complete set of eigensolutions of the Dirac equations with Woods-Saxon potentials. Using the finite-range Gogny force D1S as an effective interaction in the pairing channel, systematic RHFB calculations are performed for Sn isotopes and $N=82$ isotones. It is demonstrated that an appropriate description of both mean field and pairing effects can be obtained within RHFB theory with finite range Gogny pairing forces. Better systematics are also found in the regions from the stable to the neutron-rich side with the inclusion of Fock terms, especially in the presence of $\rho$-tensor couplings.

Medium-spin states of ${}^{70}\mathrm{Ge}$ have been studied via the ${}^{60}\mathrm{Ni}$(${}^{12}\mathrm{C}$,2$p\gamma$)${}^{70}\mathrm{Ge}$ reaction at 45 MeV. The ground-state band and the second $0^{+}$ band have been extended to the ${12}^{+}$ and $8^{+}$ states, respectively. Two negative-parity bands, one of which has a coupled structure and the other has a decoupled structure, have been observed additionally. Although the latter decoupled structure was known up to the (${21}^{-}$) state from a previous experiment, the part of the level scheme up to the ${15}^{-}$ state has been largely modified by the present experiment. Backbendings observed in the positive- and negative-parity yrast bands have been compared with those of the neighboring even Ge isotopes. The experimental level structure has been compared with the shell-model calculations in the model space ($2p_{3/2}$, $1f_{5/2}$, $2p_{1/2}$, $1g_{9/2}$) employing two kinds of effective interactions, one of which is an extended $P+\mathit{QQ}$ interaction with monopole interactions and the other is developed from a renormalized $G$ matrix. Microscopic structures of the observed bands have been discussed with the help of the shell-model calculations.

The evolution of the nuclear shapes along the triaxial landscape is studied in the Pt isotopic chain using the self-consistent Hartree-Fock-Bogoliubov approximation based on the Gogny interaction. In addition to the parametrization D1S, the new incarnations D1N and D1M of this force are also included in our analysis to assess to which extent the predictions are independent of details of the effective interaction. The considered range of neutron numbers $88⩽N⩽126$ includes prolate, triaxial, oblate, and spherical ground-state shapes and serves as a detailed comparison of the predictions obtained with the new sets D1N and D1M against the ones provided by the standard parametrization Gogny-D1S in a region of the nuclear landscape for which experimental and theoretical fingerprints of shape transitions have been found. Structural evolution along the Pt chain is discussed in terms of the deformation dependence of single-particle energies.

The proton-rich nucleus ${}^{33}\mathrm{Ar}$ has been studied by detailed proton and $\gamma$-ray spectroscopy at the low-energy facility of SPIRAL at GANIL. Proton and $\gamma$-ray singles and coincidence measurements allowed to establish a quasicomplete decay scheme of this nucleus. By comparing the proton intensity to different daughter states, tentative spin assignments have been made for some of the states of ${}^{33}\mathrm{Cl}$. The Gamow-Teller strength distribution is deduced and compared to shell-model calculations and a quenching factor is determined. States close to the isobaric analog state are searched for with respect to isospin mixing.

The production cross sections of new neutron-rich ${}^{84,86}\mathrm{Zn}$ and ${}^{90,92}\mathrm{Ge}$ isotopes beyond $N=50$ are estimated for the first time in the multinucleon transfer reactions ${}^{48}\mathrm{Ca}$ $+$ ${}^{238}\mathrm{U}$ and ${}^{48}\mathrm{Ca}$ $+$ ${}^{244}\mathrm{Pu}$. The production of new isotopes in reactions with a ${}^{48}\mathrm{Ca}$ beam is discussed for future experiments.