In the hadronic phase, the dominant configuration of quantum chromodynamics (QCD) with two flavors of massless quarks is a gas of massless pions. We calculate the bulk viscosity ($\zeta$) using the Boltzmann equation with the kinetic theory generalized to incorporate the trace anomaly. We find that the dimensionless ratio $\zeta /s$, $s$ being the entropy density, is monotonic increasing below $T=120$ MeV, where chiral perturbation theory is applicable. This, combined with previous results, shows that $\zeta /s$ reaches its maximum near the phase-transition temperature $T_c$, while $\eta /s$, $\eta$ being the shear viscosity, reaches its minimum near $T_c$ in QCD with massless quarks.

Using Grad's method, we calculate the entropy production and derive a formula for the second-order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance, the shear tensor and the shear viscosity to entropy density ratio $\eta /s$ are numerically calculated by an iterative and self-consistent prescription within the second-order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with $\eta /s$ obtained using the Navier-Stokes approximation, the present result is about $20\%$ larger at a QCD coupling ${\alpha }_s~0.3$ (with $\eta /s\approx 0.18$) and is a factor of 2–3 larger at a small coupling ${\alpha }_s~0.01$. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on $\eta /s$, except when employing a small ${\alpha }_s$. On the other hand, we demonstrate that for such small ${\alpha }_s$, the gluon system is far from kinetic and chemical equilibrium, which indicates the break down of second-order hydrodynamics because of the strong nonequilibrium evolution. In addition, for large ${\alpha }_s$ (0.3–0.6), the Israel-Stewart hydrodynamics formally breaks down at large momentum $p_T\gtrsim 3$ GeV but is still a reasonably good approximation.

The production of ω mesons in the $\mathit{pd}\to {}^3\mathrm{He}\omega$ reaction has been studied at two energies near the kinematic threshold, $T_p=1450$ MeV and $T_p=1360$ MeV. The differential cross section was measured as a function of the ω c.m. angle at both energies over the whole angular range. Whereas the results at 1360 MeV are consistent with isotropy, strong rises are observed near both the forward and backward directions at 1450 MeV. Calculations made using a two-step model with an intermediate pion fail to reproduce the shapes of the measured angular distributions and also underestimate the total cross sections.

The three-dimensional wave function for a sharply cut-off Coulomb potential is analytically derived. The asymptotic form of the related scattering amplitude reveals a failure of the standard renormalization factor which is believed to be generally valid for any type of screening.

The experimentally observed $\Delta I=1$ doublet bands in some odd-odd nuclei are analyzed within the orthosymplectic extension of the interacting vector boson model (IVBM). A new, purely collective interpretation of these bands is given on the basis of the obtained boson-fermion dynamical symmetry of the model. It is illustrated by its application to three odd-odd nuclei from the $A~130$ region, namely ${}^{126}\mathrm{Pr}$, ${}^{134}\mathrm{Pr}$, and ${}^{132}\mathrm{La}$. The theoretical predictions for the energy levels of the doublet bands as well as $E2$ and $M1$ transition probabilities between the states of the yrast band in the last two nuclei are compared with experiment and the results of other theoretical approaches. The obtained results reveal the applicability of the orthosymplectic extension of the IVBM.

Statistical model calculation has been carried out for the excitation functions of the ${}^{93}\mathrm{Nb}(p,n){}^{93}\mathrm{Mo}{}^m$, ${}^{93}\mathrm{Nb}(p,\alpha n){}^{89}\mathrm{Zr}$, and ${}^{93}\mathrm{Nb}(p,\mathit{np}+\mathit{pn}){}^{92}\mathrm{Nb}{}^m$ reactions up to a 20-MeV proton energy range using global reaction parameters. The results are compared and discussed with reported measurements. The calculation for the excitation function of the ${}^{93}\mathrm{Nb}(p,n){}^{93}\mathrm{Mo}{}^m$ reaction can only match the measured magnitudes of cross sections if we postulate the existence of two energy levels with spin-parity values of $19/2^{+}$ and $17/2^{-}$ lying immediately above the 2.425 MeV $(21/2^{+})$ isomeric state. The existence of the hypothetical levels has been discussed in the light of reported shell-model calculations.

We investigate the impact of neutron capture rates near the $A=130$ peak on the $r$-process abundance pattern. We show that these capture rates can alter the abundances of individual nuclear species, not only in the region of $A=130$ peak but also throughout the abundance pattern. We discuss in general the nonequilibrium processes that produce these abundance changes and determine which capture rates have the most significant impact.

We investigate the possibility and consequences of phase transitions from an equation of state (EOS) describing nucleons and hyperons interacting via mean fields of $\sigma$, $\omega$, and $\rho$ mesons in the recently improved quark-meson coupling (QMC) model to an EOS describing a Fermi gas of quarks in an MIT bag. The transition to a mixed phase of baryons and deconfined quarks, and subsequently to a pure deconfined quark phase, is described using the method of Glendenning. The overall EOS for the three phases is calculated for various scenarios and used to calculate stellar solutions using the Tolman-Oppenheimer-Volkoff equations. The results are compared with recent experimental data, and the validity of each case is discussed with consequences for determining the species content of the interior of neutron stars.

We apply the variational theory for fermions at finite temperature and high density, developed in an earlier paper, to symmetric nuclear matter and pure neutron matter. This extension generalizes to finite temperatures, the many body technique used in the construction of the zero temperature Akmal-Pandharipande-Ravenhall equation of state. We discuss how the formalism can be used for practical calculations of hot dense matter. Neutral pion condensation along with the associated isovector spin longitudinal sum rule is analyzed. The equation of state is calculated for temperatures less than 30 MeV and densities less than three times the saturation density of nuclear matter. The behavior of the nucleon effective mass in medium is also discussed.

The multiplicities, angular correlations, and energy spectra of the neutrons associated with fission were measured for the reactions of ${}^{25,26}\mathrm{Mg}+{}^{232}\mathrm{Th}$ at ${}^{25}\mathrm{Mg}$ and ${}^{26}\mathrm{Mg}$ projectile energies of 132 and 148 MeV, respectively. From these data, we extracted a value of ${\Gamma }_n/{\Gamma }_f$ for the first-chance fission of ${}^{258}\mathrm{No}$ at an excitation energy of 61 MeV. The implications of this result for understanding the survival probabilities of excited heavy nuclei formed in “hot” fusion reactions are discussed.

We explore further the classical quark-gluon plasma using methods from classical liquids. The partition function of an ensemble of $\mathrm{SU}(N_c)$ colored charge spheres is constructed. We analyze it using a cumulant expansion (low density) and a loop expansion (high temperature) after resumming the Debye screening effects. The pertinent free energies are derived in both limits and compared with recent molecular dynamics results.

Calculations of elliptic flow based on two initial state models of $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s}=200$ GeV/n coupled with a hadronic rescattering calculation are presented. The two initial state models used are a thermal model and a partonic model. Results from these calculations are compared with experiments and it is found that both initial state models give satisfactory representations of elliptic flow measurements, provided that the rescattering is started early enough in the collision process. It is also found that the present hadronic model studies do not show the jet suppression observed experimentally.

The linear response of a nonrelativistic superfluid baryon system on an external weak field is investigated while taking into account the Fermi-liquid interactions. We generalize the theory developed by Leggett for a superfluid Fermi-liquid at finite temperature to the case of time-like momentum transfer typical of the problem of neutrino emission from neutron stars. A space-like kinematics is also analyzed for completeness and compared with known results. We use the obtained response functions to derive the neutrino energy losses caused by recombination of broken pairs in the electrically neutral superfluid baryon matter. We find that the dominant neutrino radiation occurs through the axial-vector neutral currents. The emissivity is found to be of the same order as in the BCS approximation, but the details of its temperature dependence are modified by the Fermi-liquid interactions. The role of electromagnetic correlations in the pairing case of protons interacting with the electron background is discussed in the conclusion.

Meson production cross sections in ultraperipheral relativistic heavy ion collisions at the CERN Large Hadron Collider are revisited. The relevance of meson models and of exotic QCD states is discussed. This study includes states that have not been considered before in the literature.

We performed self-consistent Hartree-Fock plus random-phase approximation (HF+RPA) calculations for charge-exchange $1^{+}$ states in ${}^{90}\mathrm{Zr}$ and ${}^{208}\mathrm{Pb}$ by using Skyrme interactions with tensor terms. We employed a parameter set in which the tensor terms are added to the SGII interaction. It is pointed out that Gamow-Teller (GT) states can couple strongly with the spin-quadrupole (SQ) $1^{+}$ states in the high-energy region above $E_x=30$ MeV due to the tensor interactions. As a result of this coupling, more than $10\%$ of the GT strength is shifted to the energy region above 30 MeV, and the main GT peak is moved 2 MeV downward. At the same time, the main SQ $1^{+}$ peak is moved upward by more than 10 MeV due to the tensor correlations. Schematic separable interactions are proposed to elucidate the quenching mechanism induced by the tensor interaction on the GT state.

Incomplete-fusion reactions have been used to study high-spin states in ${}^{171}\mathrm{Tm}$. Gamma rays and conversion electrons were measured using pulsed-beam conditions for enhanced isomer sensitivity. A $K^{\pi }=19/2^{+}$, three-quasiparticle isomer was identified, with a half-life of $1.7(2)$ μs. The faster than expected transition rates from the isomer can be understood as being due to a chance near-degeneracy, with mixing between the isomeric state and the $I^{\pi }=19/2^{+}$ member of the one-quasiparticle rotational band to which it decays. The implied mixing matrix element is $12(2)$ eV.

We present measurements of the energy dependence of event-by-event fluctuations in the $K/\pi$ and $(p+\overline{p})/\pi$ multiplicity ratios in heavy-ion collisions at the CERN SPS. The particle ratio fluctuations were obtained for central $\mathrm{Pb}+\mathrm{Pb}$ collisions at five collision energies, $\sqrt{s_{\mathit{NN}}}$, between 6.3 and 17.3 GeV. After accounting for the effects of finite-number statistics and detector resolution, we extract the strength of nonstatistical fluctuations at each energy. For the $K/\pi$ ratio, larger fluctuations than expected for independent particle production are found at all collision energies. The fluctuations in the $(p+\overline{p})/\pi$ ratio are smaller than expectations from independent particle production, indicating correlated pion and proton production from resonance decays. For both ratios, the deviation from purely statistical fluctuations shows an increase toward lower collision energies. The results are compared to transport model calculations, which fail to describe the energy dependence of the $K/\pi$ ratio fluctuations.

We investigate $\Lambda (1405)$ as a resonance in a coupled-channels baryon-meson ($\Sigma \pi \text{−}N\overline{K}\text{−}\Lambda \eta$) scattering with a ‘bound state embedded in the continuum’ (BSEC). For this purpose, we solve the Lippmann-Schwinger equation including a BSEC with the semirelativistic kinematics in the momentum space. This BSEC is introduced by hand, as a state not originated from a simple baryon-meson system. We assume it comes from the three-quark state. There appears a resonance in the $\Sigma \pi$ scattering below the $N\overline{K}$ threshold without introducing a BSEC when the $N\overline{K}$ channel has a strong attraction, just like the chiral unitary approach. Even if the baryon-meson interaction is weakened by using a lower-momentum cut-off parameter, a resonance also appears around 1405 MeV when a BSEC is introduced. The corresponding peak also has a large width, and the $N\overline{K}$ scattering length is well reproduced. The interaction whose channel dependence is the same as the one originated from the color-magnetic interaction, where no $N\overline{K}$ attraction exists, also gives a broad peak with help of a BSEC. In order to reproduce the observed $N\overline{K}$ scattering length, the calculation including a BSEC seems to be preferable. Our calculation gives an appropriate $N\overline{K}$ scattering length when the BSEC contribution to the resonance is roughly half that of the $N\overline{K}$ channel.

The ${}^{122}\mathrm{Sn}({}^{11}\mathrm{B},4n)$ fusion-evaporation reaction at $E_{\mathrm{lab}}=60$ MeV was used to populate excited states in ${}^{129}\mathrm{Cs}$, and the deexcitations were investigated using in-beam $\gamma$-ray spectroscopic techniques. The level scheme of ${}^{129}\mathrm{Cs}$ is established up to ∼8 MeV excitation energy and 47/2 ħ spin. The observed band structures are interpreted for their configurations in the framework of cranking model calculations and systematic of the neighboring ${}_{55}$Cs isotopes. A negative-parity $\Delta I=1$ coupled band has been assigned the $\pi h_{11/2}\otimes \nu (h_{11/2}){}^2$ configuration as solution of the tilted-axis cranking, which coexists with the $\pi h_{11/2}$ yrast band resulting from the principal-axis cranking. A new band has been identified as a $\gamma$-vibrational band built on the $\pi h_{11/2}$ orbital. A pair of strongly coupled positive-parity bands exhibiting similar features have been assigned different unpaired three-quasiparticle configurations involving the $\pi h_{11/2}\otimes \nu h_{11/2}$ component. The previously identified unfavored signature partners of the $\pi d_{5/2}$ and $\pi g_{7/2}$ bands are reassigned as $\gamma$ vibrations of the core coupled to the $\pi g_{7/2}$ single-particle configuration, and the favored signature of the $\pi d_{5/2}$ band, respectively.

Multi reference calculations along the lines of the generator coordinate method or the restoration of broken symmetries within the nuclear energy density functional (EDF) framework are becoming a standard tool in nuclear structure physics. These calculations rely on the extension of a single-reference energy functional, of the Gogny or the Skyrme types, to nondiagonal energy kernels. There is no rigorous constructive framework for this extension so far. The commonly accepted way proceeds by formal analogy with the expressions obtained when applying the generalized Wick theorem to the nondiagonal matrix element of a Hamilton operator between two product states. It is pointed out that this procedure is ill defined when extended to EDF calculations as the generalized Wick theorem is taken outside of its range of applicability. In particular, such a procedure is responsible for the appearance of spurious divergences and steps in multi reference EDF energies, as was recently observed in calculations restoring particle number or angular momentum. In the present work, we give a formal analysis of the origin of this problem for calculations with and without pairing, i.e., constructing the density matrices from either Slater determinants or quasiparticle vacua. We propose a method to regularize nondiagonal energy kernels such that divergences and steps are removed from multi reference EDF energies. Such a removal is a priori quasiparticle-basis dependent. A special feature of the method we use to proceed to the actual regularization is that it singles out one basis among all possible ones. The regularization method is applicable to calculations based on any symmetry restoration or generator coordinate but is limited to EDFs depending only on integer powers of the normal and anomalous density matrices. Eventually, the method is formally illustrated for particle-number restoration and is specified to configuration mixing calculations based on Slater determinants.