## 2022 Vol. 46, No. 6

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2022, 46(6): 061001. doi: 10.1088/1674-1137/ac5a9f
Abstract:
The \begin{document}$\alpha$\end{document}-particle preformation factors of nuclei above doubly magic nuclei \begin{document}$^{100}$\end{document}Sn and \begin{document}$^{208}$\end{document}Pb are investigated within the generalized liquid drop model. The results show that the \begin{document}$\alpha$\end{document}-particle preformation factors of nuclei near self-conjugate doubly magic \begin{document}$^{100}$\end{document}Sn are significantly larger than those of analogous nuclei just above \begin{document}$^{208}$\end{document}Pb, and they will be enhanced as the nuclei move towards the \begin{document}$N = Z$\end{document} line. The proton–neutron correlation energy \begin{document}$E_{p-n}$\end{document} and two protons–two neutrons correlation energy \begin{document}$E_{2p-2n}$\end{document} of nuclei near \begin{document}$^{100}$\end{document}Sn also exhibit a similar situation, indicating that the interactions between protons and neutrons occupying similar single-particle orbitals could enhance the \begin{document}$\alpha$\end{document}-particle preformation factors and result in superallowed \begin{document}$\alpha$\end{document} decay. This also provides evidence of the significant role of the proton–neutron interaction on \begin{document}$\alpha$\end{document}-particle preformation. Also, the linear relationship between \begin{document}$\alpha$\end{document}-particle preformation factors and the product of valence protons and valence neutrons for nuclei around \begin{document}$^{208}$\end{document}Pb is broken in the \begin{document}$^{100}$\end{document}Sn region because the \begin{document}$\alpha$\end{document}-particle preformation factor is enhanced when a nucleus near \begin{document}$^{100}$\end{document}Sn moves towards the \begin{document}$N = Z$\end{document} line. Furthermore, the calculated \begin{document}$\alpha$\end{document} decay half-lives fit well with the experimental data, including the recent observed self-conjugate nuclei \begin{document}$^{104}$\end{document}Te and \begin{document}$^{108}$\end{document}Xe [Phys. Rev. Lett. 121, 182501 (2018)].
2022, 46(6): 063101. doi: 10.1088/1674-1137/ac5318
Abstract:
We perform a detailed study of scalar dark matter with triplet Higgs extensions of the Standard Model in order to explain the cosmic ray electron and positron excesses reported by AMS-02 and DAMPE. A detailed analysis of the AMS-02 positron excess reveals that for different orderings (normal, inverted, and quasi-degenerate) of neutrino mass, the hybrid triplet Higgs portal framework is more favored with respect to the single triplet Higgs portal for TeV scale dark matter. We also show that the resonant peak and continuous excess in DAMPE cosmic ray data can be well explained with the hybrid triplet Higgs portal dark matter when a dark matter sub-halo nearby is taken into account.
2022, 46(6): 063102. doi: 10.1088/1674-1137/ac531a
Abstract:
We study \begin{document}$\bar{Q}Q\bar{q}q$\end{document} and \begin{document}$\bar{Q}qQ\bar{q}$\end{document} states as mixed states in QCD sum rules. By calculating the two-point correlation functions of pure states of their corresponding currents, we review the mass and coupling constant predictions of \begin{document}$J^{PC} = 1^{++}$\end{document}, \begin{document}$1^{--}$\end{document}, and \begin{document}$1^{-+}$\end{document} states. By calculating the two-point mixed correlation functions of \begin{document}$\bar{Q}Q\bar{q}q$\end{document} and \begin{document}$\bar{Q}qQ\bar{q}$\end{document} currents, we estimate the mass and coupling constants of the corresponding "physical state" that couples to both \begin{document}$\bar{Q}Q\bar{q}q$\end{document} and \begin{document}$\bar{Q}qQ\bar{q}$\end{document} currents. Our results suggest that for \begin{document}$1^{++}$\end{document} states, the \begin{document}$\bar{Q}Q\bar{q}q$\end{document} and \begin{document}$\bar{Q}qQ\bar{q}$\end{document} components are more likely to mix, while for \begin{document}$1^{--}$\end{document} and \begin{document}$1^{-+}$\end{document} states, there is less mixing between \begin{document}$\bar{Q}Q\bar{q}q$\end{document} and \begin{document}$\bar{Q}qQ\bar{q}$\end{document}. Our results suggest the Y series of states have more complicated components.
2022, 46(6): 063103. doi: 10.1088/1674-1137/ac538c
Abstract:
We explore the possibility that the dark matter relic density is not produced by a thermal mechanism directly, but by the decay of other heavier dark-sector particles which themselves can be produced by the thermal freeze-out mechanism. Using a concrete model with light dark matter from dark sector decay, we study the collider signature of the dark sector particles associated with Higgs production processes. We find that future lepton colliders could be a better place to probe the signature of this kind of light dark matter model than hadron colliders such as LHC. Also, we find that a Higgs factory with center-of-mass energy 250 GeV has a better potential to resolve the signature of this kind of light dark matter model than a Higgs factory with center-of-mass energy 350 GeV.
2022, 46(6): 063104. doi: 10.1088/1674-1137/ac56d0
Abstract:
In this study, the susceptibilities of conserved charges, baryon number, charge number, and strangeness number at zero and low values of chemical potential are presented. Taylor series expansion was used to obtain results for the three-flavor Polyakov quark meson (PQM) model and the Polyakov loop extended chiral quark mean-field (PCQMF) model. Mean-field approximation was used to study quark matter with the inclusion of the isospin chemical potential, as well as the vector interactions. The effects of isospin chemical potential and vector-interactions on phase diagrams were analyzed. A comparative analysis of the two models was completed. Fluctuations of the conserved charges were enhanced in the transition temperature regime and hence provided information about the critical end point (CEP). Susceptibilities of conserved quantities were calculated by using the Taylor series method. Enhancement of fluctuations in the transition temperature neighborhood provided a clear signature of a quantum chromodynamics (QCD) critical-point.
2022, 46(6): 063105. doi: 10.1088/1674-1137/ac57b6
Abstract:
Pion generalized parton distributions are calculated within the framework of the Nambu–Jona-Lasinio model using different regularization schemes, including the proper time regularization scheme, the three-dimensional (3D) momentum cutoff scheme, the four-dimensional momentum cutoff scheme, and the Pauli-Villars regularization scheme. Furthermore, we check the theoretical constraints of pion generalized parton distributions required by the symmetries of quantum chromodynamics in different regularization schemes. The diagrams of pion parton distribution functions are plotted, in addition, we evaluate the Mellin moments of generalized parton distributions, which are related to the electromagnetic and gravitational form factors of pion. Pion generalized parton distributions are continuous but not differential at \begin{document}$x=\pm \,\xi$\end{document}, when considering the effect of the contact contribution term, generalized parton distributions become not continuous at \begin{document}$x=\pm \,\xi$\end{document} in all the four regularization schemes. Generalized parton distributions in impact parameter space are considered, the width distribution of u quark in the pion and the mean-squared \begin{document}$\langle {\boldsymbol{b}}_{\bot}^2\rangle_{\pi}^u$\end{document} are calculated. The light-front transverse-spin distributions are studied when quark polarized in the light-front-transverse \begin{document}$+\,x$\end{document} direction, the transverse-spin density is no longer symmetric around \begin{document}$(b_x=0,b_y=0)$\end{document}, the peaks shift to \begin{document}$(b_x=0,b_y>0)$\end{document}, we compare the average transverse shift \begin{document}$\langle b_{\bot}^y\rangle_1^u$\end{document} and \begin{document}$\langle b_{\bot}^y\rangle_2^u$\end{document} in different regularization schemes. The light-cone energy radius \begin{document}$r_{E,LC}$\end{document} and the light-cone charge radius \begin{document}$r_{c,LC}$\end{document} are also evaluated, we found that in the proper time regularization scheme the values of these quantities were the largest, in the 3D momentum cutoff scheme they were the smallest.
2022, 46(6): 063106. doi: 10.1088/1674-1137/ac57b7
Abstract:
We propose a low-scale Standard Model extension with \begin{document}$T_7\times Z_4 \times Z_3\times Z_2$\end{document} symmetry that can successfully explain observed neutrino oscillation results within the \begin{document}$3 \sigma$\end{document} range. Small neutrino masses are obtained via the linear seesaw mechanism. Normal and inverted neutrino mass orderings are considered with three lepton mixing angles in their experimentally allowed \begin{document}$3\sigma$\end{document} ranges. The model provides a suitable correlation between the solar and reactor neutrino mixing angles, which is consistent with the \begin{document}${\rm{TM}}_2$\end{document} pattern. The prediction for the Dirac phase is \begin{document}$\delta_{\rm CP}\in (295.80, 330.0)^\circ$\end{document} for both normal and inverted orderings, including its experimentally maximum value, while those for the two Majorana phases are \begin{document}$\eta_1\in (349.60, 356.60)^\circ,\, \eta_2=0$\end{document} for normal ordering and \begin{document}$\eta_1\in (3.44, 10.37)^\circ, \, \eta_2=0$\end{document} for inverted ordering. In addition, the predictions for the effective neutrino masses are consistent with the present experimental bounds.
2022, 46(6): 063107. doi: 10.1088/1674-1137/ac581b
Abstract:
The Higgs sector of the standard model can be extended by introducing an \begin{document}$SU(2)_L$\end{document} Higgs triplet Δ to generate tiny neutrino masses in the framework of the type-II seesaw mechanism. In this paper, we study the pair production of the introduced Higgs triplet at future \begin{document}$e^{-}p$\end{document} colliders. The corresponding production cross sections via the vector boson fusion process at the FCC-ep and ILC\begin{document}$\otimes$\end{document}FCC are predicted, where the production of a pair of doubly charged Higgs is found to be dominant and then used to investigate the collider phenomenology of the Higgs triplet. Depending on the size of the Higgs triplet vacuum expectation value, the doubly charged Higgs may decay into a pair of same-sign charged leptons or a pair of same-sign W bosons. To explore the discovery potential of the doubly charged Higgs at future \begin{document}$e^{-}p$\end{document} colliders, we discuss these two decay scenarios in detail and show their detection sensitivity based on the mass of the doubly charged Higgs.
2022, 46(6): 063108. doi: 10.1088/1674-1137/ac5a3a
Abstract:
The recent measurements of \begin{document}$R_{K^+}$\end{document}, \begin{document}$R_{K_S^0}$\end{document}, \begin{document}$R_{K^{*+}}$\end{document}, \begin{document}$B_s\to\mu^+\mu^-$\end{document}, a set of CP-averaged angular observables for the \begin{document}$B^0\to K^{*0}\mu^+\mu^-$\end{document} decay and its isospin partner \begin{document}$B^+\to K^{*+}\mu^+\mu^-$\end{document} by the LHCb Collaboration consistently hint at lepton universality violation in the \begin{document}$b\to s\ell\ell$\end{document} transitions. In this work, we first perform global fits to the \begin{document}$b\to s\ell\ell$\end{document} data and show that five one-dimensional scenarios, i.e, \begin{document}$\delta C_9^{\mu}$\end{document}, \begin{document}$\delta C_{10}^{\mu}$\end{document}, \begin{document}$\delta C_L^{\mu}$\end{document}, \begin{document}$\delta C_9^{\mu}=C_{10}^{\mu\prime}$\end{document}, and \begin{document}$\delta C_9^{\mu}=-C_9^{\mu\prime}$\end{document} can best explain the so-called B anamolies. Furthermore, we explore how these scenarios can be distinguished from each other. For this purpose, we first study the combinations of four angular asymmetries \begin{document}$A_i ~~(i=3,4,5,9)$\end{document} and find that they cannot distinguish the five new physics scenarios. We then show that a newly constructed ratio \begin{document}$R_{S}$\end{document} can uniquely discriminate the five new physics scenarios in proper intervals of \begin{document}$q^2$\end{document} if it can be measured with percent-level precision.
2022, 46(6): 064001. doi: 10.1088/1674-1137/ac5600
Abstract:
Using the ground-state mass of 52Ni and two-proton decay energy of 54Zn, the ground-state mass excess of 54Zn is deduced to be –6504(85) keV. This value is about 2 MeV lower than the prediction of the quadratic form of the isobaric multiplet mass equation (IMME). A cubic fit to the existing mass data of the \begin{document}$A=54$\end{document}, \begin{document}$T=3$\end{document} isospin multiplet yields a surprisingly large d coefficient of IMME, i.e., \begin{document}$d=18.6(27)$\end{document}, being \begin{document}$6.9\sigma$\end{document} deviated from zero, and the resultant \begin{document}$|b/c|$\end{document} ratio significantly deviates from the systematics. This phenomenon is analyzed in this study, and we conclude that the breakdown of the quadratic form of IMME could be likely due to the mis-assignment of the \begin{document}$T=3$\end{document} isobaric analog state (IAS) in the \begin{document}$T_z=1$\end{document} nucleus 54Fe or extremely strong isospin mixing.
2022, 46(6): 064002. doi: 10.1088/1674-1137/ac5733
Abstract:
The bremsstrahlung flux-averaged cross-sections \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})}\rangle$\end{document} and the cross-sections per equivalent photon \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} were first measured for the photonuclear multichannel reaction \begin{document}${^{27}{\rm{Al}}}(\gamma,\textit{x})^{22}{\rm{Na}}$\end{document} at end-point bremsstrahlung gamma energies ranging from 35 MeV to 95 MeV. The experiments were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 using the γ-activation technique. The bremsstrahlung quantum flux was calculated with the GEANT4.9.2 program and was also monitored via the \begin{document}$^{100}{\rm{Mo}}(\gamma,{n})^{99}{\rm{Mo}}$\end{document} reaction. The flux-averaged cross-sections were calculated using the partial cross-section \begin{document}$\sigma(E)$\end{document} values computed with the TALYS1.95 code for different level density models. Consideration is given to special features of calculating the cross-sections \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})}\rangle$\end{document} and \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} for the case of the final nucleus \begin{document}$^{22}{\rm{Na}}$\end{document} via several partial channels \begin{document}$\textit{x}$\end{document}: \begin{document}${n}\alpha + {dt} + {npt} + 2{n}{^{3}\text{He}} + {n2d} + {2npd} + {2p3n}$\end{document}.
2022, 46(6): 064101. doi: 10.1088/1674-1137/ac501a
Abstract:
Systematic trends in nuclear charge radii are of great interest due to universal shell effects and odd-even staggering (OES). The modified root mean square (rms) charge radius formula, which phenomenologically accounts for the formation of neutron-proton (np) correlations, is here applied for the first time to the study of odd-Z copper and indium isotopes. Theoretical results obtained by the relativistic mean field (RMF) model with NL3, PK1 and NL3* parameter sets are compared with experimental data. Our results show that both OES and the abrupt changes across \begin{document}$N = 50$\end{document} and 82 shell closures are clearly reproduced in nuclear charge radii. The inverted parabolic-like behaviors of rms charge radii can also be described remarkably well between two neutron magic numbers, namely \begin{document}$N = 28$\end{document} to 50 for copper isotopes and \begin{document}$N = 50$\end{document} to 82 for indium isotopes. This implies that the np-correlations play an indispensable role in quantitatively determining the fine structures of nuclear charge radii along odd-Z isotopic chains. Also, our conclusions have almost no dependence on the effective forces.
2022, 46(6): 064102. doi: 10.1088/1674-1137/ac5236
Abstract:
To study the quenching of single-particle strengths of carbon isotopes, a systematic analysis is performed for 9-12,14-20C, with single neutron knockout reactions on Be/C targets, within an energy range from approximately 43 to 2100 MeV/nucleon, using the Glauber model. Incident energies do not show any obvious effect on the resulting values across this wide energy range. The extracted quenching factors are found to be strongly dependent on the proton-neutron asymmetry, which is consistent with the recent analysis of knockout reactions but is inconsistent with the systematics of transfer and quasi-free knockout reactions.
2022, 46(6): 064103. doi: 10.1088/1674-1137/ac53fa
Abstract:
We extend the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) to go beyond-mean-field framework by performing a two-dimensional collective Hamiltonian. The influences of dynamical correlations on the ground-state properties are examined in different mass regions, picking Se, Nd, and Th isotopic chains as representatives. It is found that the dynamical correlation energies (DCEs) and the rotational correction energies \begin{document}$E_{\mathrm{rot}}$\end{document} in the cranking approximation have an almost equivalent effect on the description of binding energies for most deformed nuclei, and the DCEs can provide a significant improvement for the (near) spherical nuclei close to the neutron shells and thus reduce the rms deviations of \begin{document}$S_{2n}$\end{document} by \begin{document}$\approx$\end{document}17%. Furthermore, it is found that the DCEs are quite sensitive to the pairing correlations; taking \begin{document}$^{148}$\end{document}Nd as an example, a 10% enhancement of pairing strength can raise the DCE by \begin{document}$\approx$\end{document}37%.
2022, 46(6): 064104. doi: 10.1088/1674-1137/ac5513
Abstract:
The magnetic field and density behaviors of various thermodynamic quantities of strange quark matter under compact star conditions are investigated in the framework of the thermodynamically self-consistent quasiparticle model. For individual species, a larger number density \begin{document}$n_i$\end{document} leads to a larger magnetic field strength threshold that aligns all particles parallel or antiparallel to the magnetic field. Accordingly, in contrast to the finite baryon density effect which reduces the spin polarization of magnetized strange quark matter, the magnetic field effect leads to an enhancement of it. We also compute the sound velocity as a function of the baryon density and find the sound velocity shows an obvious oscillation with increasing density. Except for the oscillation, the sound velocity grows with increasing density, similar to the zero-magnetic field case, and approaches the conformal limit \begin{document}$V_s^2=1/3$\end{document} at high densities from below.
2022, 46(6): 064105. doi: 10.1088/1674-1137/ac5587
Abstract:
Controversies exist among experiments and theories on the \begin{document}$S^\star$\end{document} factor of the astrophysical important reaction 12C + 12C for energies below 3 MeV. Only frequentist approaches have been used so far for data analysis, and the confidence levels or theoretical errors are not available from previous theoretical predictions. In this study, the Bayesian method is employed to provide theoretical predictions and its 1σ confidence level based on all the currently available experimental data for the first time. The improved coupled-channels model CCFULL-FEM implemented with the finite element method as well as the Markov chain Monte Carlo approach emcee are adopted to analyze the non-resonant behavior of this reaction. The posterior distribution of the Woods-Saxon potential parameters is investigated. Compared with the widely used frequentist method MIGRAD within the Minuit minimization program, the Bayesian method has a significant advantage for exploring the potential parameter space. When the existing experimental data measured down to subbarrier energies are considered, the potential parameters are constrained to a very narrow range, and the predictions of the \begin{document}$S^\star$\end{document} factor showed no sharp decrease in the low-energy region.
2022, 46(6): 064106. doi: 10.1088/1674-1137/ac5601
Abstract:
The effects of an additional \begin{document}$K^-$\end{document} meson on the ground-state properties of nuclei are investigated within an axially-deformed Skyrme-Hartree-Fock approach combined with a Skyrme-type kaon-nucleon interaction. The \begin{document}$K^-$\end{document} meson increases the binding energies of all nuclei, whereas it affects deformations only for light nuclei without shell closure. The nucleon drip lines are modified due to the strongly attractive \begin{document}$K^-N$\end{document} interaction. This is attributed to the behavior of the highest-occupied nucleon single-particle levels near the drip lines, which is analyzed in detail.
2022, 46(6): 064107. doi: 10.1088/1674-1137/ac5b0e
Abstract:
Measuring the kaon structure beyond proton and pion structures is a prominent topic in hadron physics, as it is one way to understand the nature of the Nambu-Goldstone boson of QCD and observe the interplay between the EHM and HB mechanisms for hadron mass generation. In this study, we present a simulation of the leading Λ baryon tagged deep inelastic scattering experiment at EicC (Electron-ion collider in China), which is engaged to unveil the internal structure of kaon via the Sullivan process. According to our simulation results, the suggested experiment will cover the kinematical domain of \begin{document}$0.05\lesssim x_{\rm K} \lesssim 0.85$\end{document} and \begin{document}$Q^2$\end{document} up to 50 GeV\begin{document}$^2$\end{document}, with the acceptable statistical uncertainties. In the relatively low-\begin{document}$Q^2$\end{document} region (\begin{document}$<10$\end{document} GeV\begin{document}$^2$\end{document}), the Monte-Carlo simulation shows a good statistical precision (\begin{document}$<5$\end{document}%) for the measurement of the kaon structure function \begin{document}$F_2^{\rm K}$\end{document}. In the high-\begin{document}$Q^2$\end{document} region (up to 50 GeV\begin{document}$^2$\end{document}), the statistical uncertainty of \begin{document}$F_2^{\rm K}$\end{document} is also acceptable (\begin{document}$<10$\end{document}%) for the data at \begin{document}$x_{\rm K}<0.8$\end{document}. To perform such an experiment at an electron-ion collider, a high-performance zero-degree calorimeter is suggested. The magnitude of the background process and the assumed detector capabilities are also discussed and illustrated in the paper.
2022, 46(6): 064108. doi: 10.1088/1674-1137/ac5b0f
Abstract:
The microscopic mechanisms of the symmetry energy in nuclear matter are investigated in the framework of the relativistic Brueckner-Hartree-Fock (RBHF) model with a high-precision realistic nuclear potential, pvCDBonn A. The kinetic energy and potential contributions to symmetry energy are decomposed. They are explicitly expressed by the nucleon self-energies, which are obtained through projecting the G-matrices from the RBHF model into the terms of Lorentz covariants. The nuclear medium effects on the nucleon self-energy and nucleon-nucleon interaction in symmetry energy are discussed by comparing the results from the RBHF model and those from Hartree-Fock and relativistic Hartree-Fock models. It is found that the nucleon self-energy including the nuclear medium effect on the single-nucleon wave function provides a largely positive contribution to the symmetry energy, while the nuclear medium effect on the nucleon-nucleon interaction, i.e., the effective G-matrices provides a negative contribution. The tensor force plays an essential role in the symmetry energy around the density. The scalar and vector covariant amplitudes of nucleon-nucleon interaction dominate the potential component of the symmetry energy. Furthermore, the isoscalar and isovector terms in the optical potential are extracted from the RBHF model. The isoscalar part is consistent with the results from the analysis of global optical potential, while the isovector one has obvious differences at higher incident energy due to the relativistic effect.
2022, 46(6): 064109. doi: 10.1088/1674-1137/ac5b58
Abstract:
The deformations of multi-\begin{document}${\Lambda}$\end{document} hypernuclei corresponding to even–even core nuclei ranging from \begin{document}$^8$\end{document}Be to \begin{document}$^{40}$\end{document}Ca with 2, 4, 6, and 8 hyperons are studied using the deformed Skyrme–Hartree–Fock approach. It is found that the deformations are reduced when adding 2 or 8 \begin{document}${\Lambda}$\end{document} hyperons, but enhanced when adding 4 or 6 \begin{document}${\Lambda}$\end{document} hyperons. These differences are attributed to the fact that \begin{document}${\Lambda}$\end{document} hyperons are filled gradually into the three deformed \begin{document}$p$\end{document} orbits, of which the [110]1/2\begin{document}$^-$\end{document} orbit is prolately deformed and the degenerate [101]1/2\begin{document}$^-$\end{document} and [101]3/2\begin{document}$^-$\end{document} orbits are oblately deformed.
2022, 46(6): 065101. doi: 10.1088/1674-1137/ac5319
Abstract:
The tension between the Hubble constant values obtained from local measurements and cosmic microwave background (CMB) measurements has motivated us to consider the cosmological model beyond ΛCDM. We investigate the cosmology in the large scale Lorentz violation model with a non-vanishing spatial curvature. The degeneracy among spatial curvature, cosmological constant, and cosmological contortion distribution makes the model viable in describing the known observational data. We obtain some constraints on the spatial curvature by comparing the relationship between measured distance modulus and red-shift with the predicted one, the evolution of matter density over time, and the evolution of effective cosmological constant. The implications of the large scale Lorentz violation model with the non-vanishing spatial curvature under these constrains are discussed.
2022, 46(6): 065102. doi: 10.1088/1674-1137/ac56cf
Abstract:
In this study, we investigate the shadow and photon sphere of the black bole in clouds of strings and quintessence with static and infalling spherical accretions. We obtain the geodesics of the photons near a black hole with different impact parameters b to investigate how the string cloud model and quintessence influence the specific intensity by altering the geodesic and the average radial position of photons. In addition, the range of the string cloud parameter a is constrained to ensure that a shadow can be observed. Moreover, the light sources in the accretion follow a normal distribution with an attenuation factor γ, and we adopt a model of the photon emissivity \begin{document}$j(\nu_e)$\end{document} to obtain the specific intensities. Furthermore, the shadow with static spherical accretion is plotted, which demonstrates that the apparent shape of the shadow is a perfect circle, and the value of γ influences the brightness of the photon sphere. Subsequently, we investigate the profile and specific intensity of the shadows with static and infalling spherical accretions, respectively. The interior of the shadows with an infalling spherical accretion will be darker than that with the static spherical accretion, and the specific intensity with both static and infalling spherical accretions gradually converges.
2022, 46(6): 065103. doi: 10.1088/1674-1137/ac588c
Abstract:
In this work, we study the optical properties of a class of magnetically charged rotating black hole spacetimes. The black holes in question are assumed to be immersed in the quintessence field, and subsequently, the resulting black hole shadows are expected to be modified by the presence of dark energy. We investigate the photon region and the black hole shadow, especially their dependence on the relevant physical conditions, such as the quintessence state parameter, angular momentum, and magnetic charge magnitude. The photon regions depend sensitively on the horizon structure and possess intricate features. Moreover, from the viewpoint of a static observer, we explore a few observables, especially those associated with the distortion of the observed black hole shadows.
2022, 46(6): 065104. doi: 10.1088/1674-1137/ac588d
Abstract:
In this study, we determine the influence of the nucleon-nucleon short range correlation (SRC) on static spherically symmetric neutron stars (NSs) from the perspectives of radial and nonradial oscillations for the first time. We revise the equation of state and coupling parameters in the relativistic mean field theory after considering the SRC effect, and select the hyperon coupling parameters as the SU(3) model. For the non-radial oscillations, the SRC effect decreases the \begin{document}$f$\end{document}-mode frequency by \begin{document}$0.2\sim0.3$\end{document} kHz. For the radial oscillations, it decreases the fundamental radial frequency \begin{document}$f_{1}$\end{document} by 0.75 ~ 0.85 kHz. Additionally, we refit the linear relationship between the average density and \begin{document}$f$\end{document}-mode frequency for SRC. Combining the characteristics of the radial and non-radial frequencies, we provide a view of inferring the maximum mass of NSs. Owing to the characteristics of the SRC influence on the radial frequency, we expect that the SRC can be tested by future observation and can also be used as a probe for the structure inside NSs.