arXiv subjects

Ting-Ting Sun

Publications and source records attributed to Ting-Ting Sun.

At least 19 recordsLinked to original sources

arXiv2026

Two-fluid $f$-mode oscillations of dark-matter-admixed neutron stars

We study quadrupolar $f$-mode oscillations of dark-matter-admixed neutron stars (DANSs) in full general relativity (GR). The ordinary component is described by microscopic Brueckner-Hartree-Fock matter matched to the Shen2020 crust, while the dark matter (DM) component is treated as a cold self-interacting fermion fluid coupled to ordinary matter only by gravity. For fixed-DM-fraction sequences we solve the polar two-fluid perturbation equations with an outgoing gravitational-wave (GW) boundary condition, obtaining complex eigenfrequencies rather than only real mode frequencies. The spectrum contains two principal $f$-like sequences. Their local character can be ordinary-matter-led, DM-led, or mixed, and is diagnosed using the component kinetic energies, the displacement overlap, and the cancellation of the matter quadrupole. A main result is that, for intermediate DM fractions, one of the two-fluid branches can become weakly radiating, with damping times enhanced by several orders of magnitude. The same calculation gives the outgoing Zerilli amplitude and the GW damping time, which we use to estimate the GW energy required to reach a prescribed detector threshold. Thus the analysis extends previous two-fluid Cowling studies by retaining metric perturbations and the radiative boundary condition.

gr-qc↗

arXiv2026

Quasiradial oscillations of rotating hybrid neutron stars

We investigate fundamental quasiradial oscillations in slow-rotation approximation of pure and hybrid neutron stars, employing equations of state of nuclear matter from Brueckner-Hartree-Fock theory or the relativistic mean field model, and of quark matter from the Dyson-Schwinger quark model, performing a Gibbs construction for the mixed phase in hybrid stars. Characteristic differences between neutron-star and hybrid-star fundamental quasiradial oscillation frequencies during spin-down are pointed out.

nucl-th↗

arXiv2026

Prolate-oblate shape competition and impact on charge radii in Bk isotopes

The nuclear charge radius provides a fundamental probe of nuclear structure, yet experimental data remain rare in the actinide region. Using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the PC-PK1 functional, we carry out a systematic investigation of prolate-oblate shape competition in odd-$A$ Bk isotopes. Deformation is found to play an important role in the description of charge radii $r_c$ by extending the density distribution. Notably, $r_c$ exhibits a distinct shape dependence: for a given absolute quadrupole deformation $|\beta_2|$, oblate shapes yield larger charge radii than their prolate counterparts in well-deformed nuclei near the mid-shell region, where the empirical formula $r_c(\beta_2) = \left(1 + \frac{5}{4\pi}|\beta_2|^2\right) r_c(0)$ fails to capture the observed behavior. This enhancement is attributed to a central depression (or ``bubble" structure) in the proton density, which microscopically originates from the non-occupation of the spherical $3s_{1/2}$($\Omega=1/2$) orbital in oblate minima. These findings establish a clear microscopic connection between nuclear shape, single-particle occupancy, and nuclear size.

nucl-th↗

arXiv2026

Neutron skin thickness and its volume and surface contributions in berkelium isotopes

Accurate determination of the neutron skin thickness ($\Delta R_{\rm np}$) in finite nuclei is essential for constraining the density dependence of the nuclear symmetry energy. This work presents a systematic investigation of $\Delta R_{\rm np}$ for the transuranium berkelium (Bk) isotopes within the framework of the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). The results indicate an overall increase in neutron skin thickness with $N$, which exhibits antikinks at the shell closures $N = 184, 258$ due to the shell effects. A decomposition of $\Delta R_{\rm np}$ into volume and surface terms, based on two-parameter Fermi (2pF) fits to angle-averaged DRHBc densities, demonstrates that the volume term dominates as much as $60\%$--$70\%$ in most nuclei, consistent with the $65\%$ found in $^{208}$Pb, thereby validating the volume-surface decomposition for deformed nuclei and confirming its correlation with the symmetry energy slope $L$. The surface term prevails only near the proton drip line, where the volume fraction drops below $50\%$ due to the reduced neutron-to-proton ratio. Deformation is found to slightly reduce the central radius $R_c$ but markedly enhance the surface diffuseness $a$, leading to a notable increase in $\Delta R_{\rm np}$, primarily driven by the surface term. Furthermore, we extend the decomposition to a directional analysis by extracting 2pF parameters along the symmetry axis ($\theta=0^\circ$) and perpendicular to it ($\theta=90^\circ$). In prolate deformed nuclei, a strong directional dependence is observed: although the nucleus is elongated along the symmetry axis, $\Delta R_{\rm np}$ is significantly larger in the perpendicular direction. This anisotropy is weak for oblate nuclei around the shell closures.

nucl-th↗

arXiv2026

Quarkyonic matter with strangeness in an extended relativistic mean-field model

Quarkyonic matter is expected to play a key role for the transition from hadronic matter to quark matter in compact stars. Within the framework of the relativistic mean-field (RMF) model and equivparticle model with density-dependent quark masses, we construct the ``quark Fermi sea" with a ``baryon Fermi surface" to characterize the properties of the quarkyonic matter. In particular, we develop a comprehensive framework to account for the strangeness degrees of freedom, incorporating $\Lambda$, $\Xi$, and $\Sigma$ hyperons as well as strange quarks in a unified quarkyonic framework. Our calculations indicate that the inevitable emergence of hyperons softens the equations of state, leading to a reduction in the equilibrium sound velocity around $n_{\rm b}\approx 2n_0$, and consequently reducing the masses and radii of neutron stars. When the quark-hadron phase transition is taken into account, the equation of state at high densities exhibits additional softening consistent with current astronomical observational constraints. This softening leads to a maximum equilibrium sound velocity of $v_{eq}^{\rm max} \approx 0.6\,c$, which is close to the ultrarelativistic limit of $0.58\,c$.

nucl-th↗

arXiv2025

Light and heavy $\Lambda$ hyperclusters in nuclear matter with relativistic-mean-field models

In the framework of relativistic-mean-field (RMF) models, we investigate the properties of light and heavy $\Lambda$ hyperclusters emersed in nuclear matter at various densities $n_{\mathrm{gas}}$ and proton fractions $Y_p$. In particular, the (hyper)clusters are fixed by solving the Dirac equations imposing the Dirichlet-Neumann boundary condition, while the nuclear matter take constant densities and is treated with Thomas-Fermi approximation. The binding energies of (hyper)clusters decrease with the density of nuclear matter $n_{\mathrm{gas}}$, which eventually become unbound and melt in the presence of nuclear medium, i.e., Mott transition. For light clusters with proton numbers $N_p < 4$, with the addition of $\Lambda$ hyperons, the binding energies per baryon for $\Lambda$ hyperclusters become smaller and decrease faster with $n_{\mathrm{gas}}$ due to the weaker $N$-$\Lambda$ attraction. For heavy clusters with $N_p \geq 4$, on the contrary, the addition of $\Lambda$ hyperons increases the stability of (hyper)clusters so that the Mott transition density becomes larger as nucleons occupying higher energy states while $\Lambda$ hyperons remain in the $1s_{1/2}$ orbital. The isovector effects on (hyper)clusters in nuclear medium are also identified, where the binding energies for (hyper)clusters with $N_p> N_n$ ($N_p< N_n$) increase (decrease) with $Y_p$. For those predicted by nonlinear relativistic density functionals, light (hyper)clusters are destabilized drastically as $n_{\mathrm{gas}}$ increases, while the binding energies of heavier (hyper)clusters vary smoothly with $n_{\mathrm{gas}}$. The binding energy shifts of various (hyper)clusters due to the impact of nuclear medium are fitted to an analytical formula, which could be employed to examine the evolutions of (hyper)clusters in both heavy-ion collisions and neutron stars.

nucl-th↗

arXiv2025

Constraints on $\Lambda N$ Effective Interactions from Mirror Hypernuclei in a Deformed Relativistic Hartree-Bogoliubov Model

We investigate the ground-state properties of four mirror hypernuclei pairs--$^{10}_\Lambda$Be-$^{10}_\Lambda$B, $^{12}_\Lambda$B-$^{12}_\Lambda$C, $^{16}_\Lambda$N-$^{16}_\Lambda$O, and $^{40}_\Lambda$K-$^{40}_\Lambda$Ca--within the deformed relativistic Hartree-Bogoliubov framework, analyzing their connection to $\Lambda N$ effective interactions. Systematic calculations with eight distinct effective interactions reveal linear correlations between mirror hypernuclei in $\Lambda$ separation energies and charge radii. The charge symmetry breaking effects, quantified through $\Lambda$ separation energy differences, exhibit a positive correlation with the SU(3) flavor symmetry violation. We emphasize that constraints derived from $A=10$ and $A=12$ hypernuclear pairs must explicitly incorporate rotational energy correction effects. Precision measurements of the (near) spherical $A=16$ and $A=40$ mirror systems are proposed as critical benchmarks for refining the isospin part of the hyperon-nucleon interactions.

nucl-th↗

arXiv2025

$f$-mode oscillations of protoneutron stars

We investigate nonradial $f$-mode oscillations of protoneutron stars in full general relativity, employing equations of state described by the Brueckner-Hartree-Fock theory or the relativistic mean field model, while assuming isentropy and fixed lepton fractions for the internal structure. The validity of various universal relations for cold neutron stars involving $f$-mode characteristics and macroscopic properties of the star is confirmed for those isentropic protoneutron stars. Prospects of observations are also discussed. According to simulation results, we then model details of the thermal and trapping profiles in a PNS with the canonical mass. The corresponding $f$-mode frequencies and gravitational-wave strain amplitudes are presented. The validity of the universal relations during the evolution to the formation of a cold neutron star is confirmed.

astro-ph.HE↗

arXiv2025

Charge symmetry breaking in hypernuclei within RMF model

We study the charge symmetry breaking (CSB) effect in the binding energy of mirror hypernuclei in the mass region $A=7\sim 48$ in relativistic mean field (RMF) models introducing $NN$ and $\Lambda N$ interactions. The phenomenological $\Lambda N$ CSB interaction is introduced and the strength parameter is fitted to reproduce the experimental binding energy difference between the mirror hypernuclei $^{12}_\Lambda$B and $^{12}_\Lambda$C. This model is applied to calculate the CSB energy anomaly in mirror hypernuclei with the mass $A=7\sim48$. The model is further applied to predict the binding energy difference of mirror hypernuclei of $A$=40 with the isospin $T=1/2$, $3/2$ and $5/2$ nuclei together with various hyper Ca isotopes and their mirror hypernuclei. Finally the binding energy systematics of $A=$48 hypernuclei are predicted with/without the CSB effect by the PK1 and TM2 energy density functionals (EDFs).

nucl-th↗

arXiv2024

Ground-state properties and structure evolutions of odd-$A$ transuranium Bk isotopes from deformed relativistic Hartree-Bogoliubov theory in continuum

The studies of transuranium nuclei are of vital significance in exploring the existence of the ``island of superheavy nuclei". This work presents the systematic investigations for the ground-state properties and structure evolutions of odd-$A$ transuranium Bk isotopes taking the deformed relativistic Hartree-Bogoliubov theory in continuum~(DRHBc) with PC-PK1 density functional, in comparison with those by spherical relativistic continuum Hartree-Bogoliubov~(RCHB) theory. The DRHBc calculations offer improved descriptions of the binding energies, closely aligning with the experimental data. The incorporation of deformation effects in DRHBc results in enhanced nuclear binding energies and a notable reduction in $\alpha$-decay energies. With the rotational corrections further incorporated, the theoretical deviation by DRHBc from the experimental data is further reduced. Based on the two-neutron gap $\delta_{\rm 2n}$ and the neutron pairing energy $E_{\rm pair}^n$, prominent shell closures at $N=184$ and $258$, as well as potential sub-shell structures at $N=142, 150, 162, 178, 218$, and $230$ are exhibited. A quasi-periodic variation among prolate, oblate, and spherical shapes as well as prolate deformation predominance have been shown in the evolutions of the quadrupole deformation. Possible shape coexistence is predicted in $^{331}$Bk with the oblate and prolate minima in close energies, which is further supported by the triaxial relativistic Hartree-Bogoliubov theory in continuum~(TRHBc) calculations. The neutron, proton, and charge radii predicted by DRHBc reveal pronounced kink structures at $N=184$ and $258$ in their evolutions with neutron number and compared to those by RCHB, deformation effect significantly enhances the radii of open-shell nuclei.

nucl-th↗

arXiv2024

Finite nuclei in an extended Nambu-Jona-Lasinio model

We propose a new theoretical framework to investigate the properties of finite nuclei based on an extended Nambu-Jona-Lasinio (eNJL) model, where the Dirac sea, the spontaneous chiral symmetry breaking, and the quark degrees of freedom are considered by extending the SU(3) NJL model and treating baryons as clusters of quarks. The eNJL model can then be readily adopted to examine the matter states ranging from baryonic matter to quark matter in a unified manner. In this work, by assuming spherically symmetric finite nuclei and neglecting the center-of-mass or rotational corrections, we systematically investigate the properties of finite nuclei based on the eNJL model with additional pairing correlations. It is found that our model generally reproduces the binding energies of the 2495 nuclei ($A>2$) from the 2016 Atomic Mass Evaluation (AME2016) with the root-mean-square deviations $5.38$ MeV. The deviations are mainly attributed to the too large shell gaps at magic numbers $N(Z) =28$, 50, and 82 as well as the spurious shell closures at $N(Z)=34$, 58, and 92. Meanwhile, the obtained charge radii of 906 nuclei are systematically smaller than the experimental values with root-mean-square deviations $0.127$ fm. In our future study, we expect to reduce the uncertainties of our predictions by carefully calibrating the density dependence of coupling constants and considering deformations with microscopic collective corrections from the nucleons in the Fermi sea and quarks in the Dirac sea.

nucl-th↗

arXiv2024

Density-dependent relativistic mean-field model for $ \Xi^{-} $ hypernuclei

In hypernuclear systems, interactions involving nucleons and hyperons are intricately influenced by the surrounding particles, particularly by the density and the isospin feature of the nuclear medium. In this work, the relativistic mean-field (RMF) theory is adopted to describe the structure of several typical $\Xi^{-}$ hypernuclei. New sets of $\Xi N$ effective interactions, by taking a density-dependent meson-nucleon/hyperon coupling perspective, are developed by fitting experimental data on the $\Xi^{-}$ hyperon $1s$ and $1p$ state separation energy of $^{15}_{\Xi^{-}}$C as well as the $1p$ state separation energy of $^{13}_{\Xi^{-}}$B. The density-dependent behavior of meson-hyperon coupling strengths sensitively affects the description of hyperon single-particle levels. In fact, the density-dependent meson-baryon coupling strengths introduce additional rearrangement contributions to the hyperon self-energy. Correspondingly, detailed forms of density dependence in these coupling strengths and different considerations of meson-baryon coupling channels will impact the hyperon single-particle properties within hypernuclei. Especially with the additional inclusion of the isovector scalar $ \delta $ meson, the significant enhancement of rearrangement terms in the effective interaction DD-ME$\delta$ impacts the shape of the hyperon potential and alters the characteristics of the isovector channel dynamics balance in the effective nuclear force. Relevant research underscores the importance of precisely accounting for in-medium effects in hyperon-nucleon interactions and incorporating a more comprehensive set of meson-exchange degrees of freedom in effective nuclear forces, offering a potential solution for more self-consistently describing the featured hyperon single-particle behavior of various hypernuclei and for reducing uncertainties in theoretical descriptions.

nucl-th↗

arXiv2024

Inner fission barriers of uranium isotopes in the deformed relativistic Hartree-Bogoliubov theory in continuum

The inner fission barriers of the even-even uranium isotopes from the proton to the neutron drip line are studied with the deformed relativistic Hartree-Bogoliubov theory in continuum. A periodic evolution for the ground state shapes is shown with the neutron number, i.e., spherical shapes at shell closures $N=$126, 184, 258, and prolate dominated shapes between them. In analogy to the shape evolution, the inner fission barriers also exhibit a periodic behavior: peaks at the shell closures and valleys in the mid-shells. The triaxial effect to the inner fission barrier is evaluated using the triaxial relativistic mean field calculations plus a simple BCS method for pairing. With the triaxial correction included, good consistency in the inner barrier heights is found with the available empirical data. Besides, the evolution from the proton to the neutron drip line is in accord with the results by the multi-dimensionally constrained relativistic mean field theory. A flat valley in the fission barrier height is predicted around the neutron-rich nucleus $^{318}$U which may play a role of fission recycling in the astrophysical $r$-process nucleosynthesis.

nucl-th↗

arXiv2023

Uniform descriptions of pseudospin symmetries in bound and resonant states

As a continuation of our previous work on the conservation and breaking of the pseudospin symmetry (PSS) in resonant states [Phys. Lett. B 847, 138320 (2023)}], in this work, the PSS in nuclear single-particle bound and resonant states are investigated uniformly within a relativistic framework by exploring the poles of the Green's function in spherical Woods-Saxon potentials. As the potential depths increase from zero to finite depths, the PS partners evolve from resonant states to bound states. In this progress,the PSS is broken gradually with energy, width, and density splittings. Specially, the energy and width splittings for the resonant and bound states are directly determined by the ratio of the pseudo spin-orbit potentials between the PS partners. Obvious threshold effect is observed for the energy splitting at a critical potential depth, with which the PS partners locate between the centrifugal barriers of PS partners. The differences in the density distributions of the lower component between the PS partners are manifested in the phase shift for the resonant states and amplitudes for bound states. Besides, the evolution of the phase shift as the potential depth is consistent with those for the width splitting.

nucl-th↗

arXiv2023

Probing spin and pseudospin symmetries in deformed nuclei by the Green's function method

(Pseudo)spin symmetries play vital roles in nuclear physics and have been studied extensively in spherical nuclei. In this work, possible spin and pseudospin symmetries in deformed nuclei are examined by solving a coupled-channel Dirac equation with quadruple deformation. The Green's function method is taken which provides a novel way to exactly determine the single-particle levels and properly describe the spacial density distributions. Taking axially-deformed nucleus $^{154}$Dy as an example, the spin doublets with a combination of Nilsson levels $\Lambda\pm 1/2[\mathcal{N},n_z, \Lambda]$ and pseudospin doublets with a combination of $\widetilde{\Lambda}\pm 1/2[\widetilde{\mathcal{N},n_z, \Lambda}]$ are determined. Different behaviors are displayed for the spin and pseudospin doublets. For the spin partners, those with smaller angular momentum $l$ and the third component $\Lambda$ owns better symmetry such as the $1p$ doublet while good pseudospin symmetry appears in partners locating close to the continuum threshold. By examining the single-particle Nilsson levels $\Omega[\mathcal{N},n_z,\Lambda]$ and the energy splittings between the partners, the conservation and breaking of SS and PSS are examined at different deformations. In the prolate side, the Nilsson levels for the spin and pseudospin doublets are almost parallel and the energy splittings are stable against varying deformations. By examining the density distributions, great similarities have been observed in the upper components for the spin doublets while great similarities in the lower component for the pseudospin doublets. Besides, these similarities maintain well at different deformations.

nucl-th↗

arXiv2023

Quarkyonic matter and quarkyonic stars in an extended RMF model

By combining RMF models and equivparticle models with density-dependent quark masses, we construct explicitly ``a quark Fermi Sea'' and ``a baryonic Fermi surface'' to model the quarkyonic phase, where baryons with momentums ranging from zero to Fermi momentums are included. The properties of nuclear matter, quark matter, and quarkyonic matter are then investigated in a unified manner, where quarkyonic matter is more stable and energy minimization is still applicable to obtain the microscopic properties of dense matter. Three different covariant density functionals TW99, PKDD, and DD-ME2 are adopted in our work, where TW99 gives satisfactory predictions for the properties of nuclear matter both in neutron stars and heavy-ion collisions and quarkyonic transition is unfavorable. Nevertheless, if PKDD with larger slope of symmetry energy $L$ or DD-ME2 with larger skewness coefficient $J$ are adopted, the corresponding EOSs are too stiff according to both experimental and astrophysical constraints. The situation is improved if quarkyonic transition takes place, where the EOSs become softer and can accommodate various experimental and astrophysical constraints.

hep-ph↗

arXiv2023

Non-radial oscillations and gravitational wave emission of hybrid neutron stars

We investigate non-radial oscillations of pure and hybrid neutron stars, employing equations of state of nuclear matter from Brueckner-Hartree-Fock theory, and of quark matter from the Dyson-Schwinger quark model, performing a Gibbs construction for the mixed phase in hybrid stars. Characteristic differences between neutron-star and hybrid-star $g_1$-mode oscillation frequencies, damping times, and gravitational wave strains are pointed out. Prospects of observations are also discussed.

nucl-th↗

arXiv2022

Continuum Skyrme Hartree-Fock-Bogoliubov theory with Green's function method for neutron-rich Ca, Ni, Zr, Sn isotopes

The possible exotic nuclear properties in the neutron-rich Ca, Ni, Zr, and Sn isotopes are explored with the continuum Skyrme Hartree-Fock-Bogoliubov theory formulated with the Green's function method. The available experimental two-neutron separation energies $S_{\rm 2n}$ and one-neutron separation energies $S_{\rm n}$ are well reproduced. Much shorter drip lines predicted by $S_{\rm n}$ are obtained compared with those by $S_{\rm 2n}$. The systematic studies of the neutron pairing energies $-E_{\rm pair}$ shown that values of the odd-$A$ nuclei are much smaller in comparison with those of the neighboring even-even nuclei due to the absent contribution of pairing energy by the unpaired odd neutron. By investigating the single-particle structures, the rms radii and the density distributions, the possible halo structures in the neutron-rich Ca, Ni, and Sn isotopes are predicted, in which the sharp increases of rms radii with significant deviations from the traditional $r\varpropto A^{1/3}$ rule and very diffuse spatial distributions in densities are observed. By analyzing the contributions of different partial waves to the total neutron density $ρ_{lj}(r)/ρ(r)$, the orbitals locating around the Fermi surface especially those with low angular momenta are found the main reason causing the extended nuclear density and large rms radii. Finally, the numbers of the neutrons $N_λ$~($N_0$) occupied above the Fermi surface $λ_n$~(in the continuum) are discussed, the behaviors of which are basically consistent with those of pairing energy, supporting the key role of the pairing correlations in the halo phenomena.

nucl-th↗