Nuclear Theory

Magnetic field effect on pion superfluid phase transition is investigated in frame of a Pauli-Villars regularized NJL model. Instead of directly dealing with charged pion condensate, we apply the Goldstone's theorem (massless Goldstone boson π + ) to determine the onset of pion superfluid phase, and obtain the phase diagram in magnetic field, temperature, isospin and baryon chemical potential space. At weak magnetic field, it is analytically proved that the critical isospin chemical potential of pion superfluid phase transition is equal to the mass of π + meson in magnetic field. The pion superfluid phase is retarded to higher isospin chemical potential, and can survive at higher temperature and higher baryon chemical potential under external magnetic field.

The hadron-quark/gluon duality formulated in terms of a topology change at a density $n\gsim 2n_0$ n 0 ??.16 fm ?? is found to describe the core of massive compact stars in terms of quasiparticles of fractional baryon charges, behaving neither like pure baryons nor like deconfined quarks. This can be considered as the Cheshire-Cat mechanism~\cite{CC} for the hadron-quark continuity arrived at bottom-up from skyrmions that is equivalent to the "MIT-bag"-to-skyrmion continuity arrived at top-down from quarks/gluons. Hidden symmetries, both local gauge and pseudo-conformal (or broken scale), emerge and give rise both to the long-standing "effective g ??A ?? " in nuclear Gamow-Teller transitions at $\lsim n_0$ and to the pseudo-conformal sound velocity v 2 pcs / c 2 ??/3 at $\gsim 3n_0$. It is suggested that what has been referred to, since a long time, as "quenched g A " in light nuclei reflects what leads to the dilaton-limit g DL A =1 at near the (putative) infrared fixed point of scale invariance. These properties are confronted with the recent observations in Gamow-Teller transitions and in astrophysical observations.

Lanthanide element signatures are key to understanding many astrophysical observables, from merger kilonova light curves to stellar and solar abundances. To learn about the lanthanide element synthesis that enriched our solar system, we apply the statistical method of Markov Chain Monte Carlo to examine the nuclear masses capable of forming the r -process rare-earth abundance peak. We describe the physical constraints we implement with this statistical approach and demonstrate the use of the parallel chains method to explore the multidimensional parameter space. We apply our procedure to three moderately neutron-rich astrophysical outflows with distinct types of r -process dynamics. We show that the mass solutions found are dependent on outflow conditions and are related to the r -process path. We describe in detail the mechanism behind peak formation in each case. We then compare our mass predictions for neutron-rich neodymium and samarium isotopes to the latest experimental data from the CPT at CARIBU. We find our mass predictions given outflows that undergo an extended (n,\gamma )\rightleftarrows (\gamma ,n) equilibrium to be those most compatible with both observational solar abundances and neutron-rich mass measurements.

Phases of nuclear matter are crucial in the determination of physical properties of neutron stars~(NS). In the core of NS, the density and pressure become so large that the nuclear matter possibly undergoes phase transition into a deconfined phase, consisting of quarks and gluons and their colour bound states. Even though the quark-gluon plasma has been observed in ultra-relativistic heavy-ion collisions\cite{Gyulassy, Andronic}, it is still unclear whether exotic quark matter exists inside neutron stars. Recent results from the combination of various perturbative theoretical calculations with astronomical observations\cite{Demorest, Antoniadis} shows that (exotic) quark matter could exist inside the cores of neutron stars above 2.0 solar masses ( M ⊙ )\cite{Annala:2019puf}. We revisit the holographic model in Ref.\cite{bch, bhp} and implement the equation of states~(EoS) of multiquark nuclear matter to interpolate the pQCD EoS in the high-density region with the nuclear EoS known at low densities. For sufficiently large energy density scale~( ϵ s ) of the model, it is found that multiquark phase is thermodynamically prefered than the stiff nuclear matter above the transition points. The NS with holographic multiquark core at the maximum mass could have masses in the range 1.96−2.23 (1.70−2.17) M ⊙ and radii 14.3−11.8 (14.5−11.5) km for ϵ s =26 (28) GeV/fm 3 respectively.

The observables in a single-channel 2 -body scattering problem remain invariant once the amplitude is multiplied by an overall energy- and angle-dependent phase. This invariance is known as the continuum ambiguity. Also, mostly in truncated partial wave analyses (TPWAs), discrete ambiguities originating from complex conjugation of roots are known to occur. In this note, it is shown that the general continuum ambiguity mixes partial waves and that for scalar particles, discrete ambiguities are just a subset of continuum ambiguities with a specific phase. A numerical method is outlined briefly, which can determine the relevant connecting phases.

The present PREX-II and CREX experiments are measuring the rms radius of the weak charge density of 208 Pb and 48 Ca. We discuss the feasibility of a new parity violating electron scattering experiment to measure the surface thickness of the weak charge density of a heavy nucleus. Once PREX-II and CREX have constrained weak radii, an additional parity violating measurement at a momentum transfer near 0.76 fm −1 for 208 Pb or 1.28 fm −1 for 48 Ca can determine the surface thickness.

Fission fragments' charge and mass distribution is an important input to applications ranging from basic science to energy production or nuclear non-proliferation. In simulations of nucleosynthesis or calculations of superheavy elements, these quantities must be computed from models, as they are needed in nuclei where no experimental information is available. Until now, standard techniques to estimate these distributions were not capable of accounting for fine-structure effects, such as the odd-even staggering of the charge distributions. In this work, we combine a fully-microscopic collective model of fission dynamics with a recent extension of the particle number projection formalism to provide the highest-fidelity prediction of the primary fission fragment distributions for the neutron-induced fission of 235 U and 239 Pu. We show that particle number projection is an essential ingredient to reproduce odd-even staggering in the charge yields and benchmark the performance of various empirical probability laws that could simulate its effect. This new approach also enables for the first time the realistic determination of two-dimensional isotopic yields within nuclear density functional theory.

A low-energy M1(K=1) spin-scissors resonance (SSR) located just below the ordinary orbital scissors resonance (OSR) was recently predicted in deformed nuclei within the Wigner Function Moments (WFM) approach. We analyze this prediction using fully self-consistent Skyrme Quasiparticle Random Phase Approximation (QRPA) method. The Skyrme forces SkM*, SVbas and SG2 are implemented to explore SSR and OSR in 160,162,164 Dy and 232 Th. The calculations show that isotopes 160,162,164 Dy indeed have at 1.5-2.4 MeV (below OSR) K ? = 1 + states with a large M1(K=1) spin strength. These states are dominated by pp[411??411?�] and nn[521??521?�] spin-flip configurations corresponding to pp[2 d 3/2 ,2 d 5/2 ] and nn[2 f 5/2 ,2 f 7/2 ] structures in the spherical limit. So the predicted SSR is actually reduced to low-orbital (l=2,3) spin-flip states. Moreover, following our analysis and in contradiction with the spin-scissors treatment of WFM, the deformation is not the principle origin of the low-energy spin M1(K=1) states but only a factor affecting their features. In 232 Th, the M1(K=1) spin strength is found very small. The spin and orbital strengths are generally mixed and exhibit the interference: weak destructive in SSR range and strong constructive in OSR range. The two groups of 1 + states observed experimentally at 2.4-4 MeV in 160,162,164 Dy and at 2-4 MeV in 232 Th are rather explained by fragmentation of the orbital strength than by the occurrence of spin-flip states. The best agreement with the experimental data is obtained for the force SG2.

The low-lying cluster states of 6He (a+n+n) and 6Li (a+n+p) are calculated by the real-time evolution method (REM) which generates basis wave functions for the generator coordinate method (GCM) from the equation of motion of Gaussian wave packets. The 0+ state of 6He as well as the 1+, 0+ and 3+ states of 6Li are calculated as a benchmark. We also calculate the root-mean-square (r.m.s.) radii of the point matter, the point proton, and the point neutron of these states, particularly for the study of the halo characters of these two nuclei. It is shown that REM can be one constructive way for generating effective basis wave functions in GCM calculations.

Density-functional theory for superfluid systems is developed in the framework of the functional renormalization group based on the effective action formalism. We introduce the effective action for the particle-number and nonlocal pairing densities and demonstrate that the Hohenberg-Kohn theorem for superfluid systems is established in terms of the effective action. The flow equation for the effective action is then derived, where the flow parameter runs from 0 to 1 , corresponding to the non-interacting and interacting systems. From the flow equation and the variational equation that the equilibrium density satisfies, we obtain the exact expression for the Kohn-Sham potential generalized to including the pairing potentials. The resultant Kohn-Sham potential has a nice feature that it expresses the microscopic formulae of the external, Hartree, pairing, and exchange-correlation terms, separately. It is shown that our Kohn-Sham potential gives the ground-state energy of the Hartree-Fock-Bogoliubov theory by neglecting the correlations. An advantage of our exact formalism lies in the fact that it provides ways to systematically improve the correlation part.