2023 Vol. 47, No. 8

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2023-8 Contents
2023, 47(8): 1-2.
Holographic operator product expansion of loop operators in the ${{ \mathcal N} {\bf{=4}}\sim {\boldsymbol {S O(N)}}} $ super Yang-Mills theory
Hong-Zhe Zhang, Wan-Zhe Feng, Jun-Bao Wu
2023, 47(8): 083101. doi: 10.1088/1674-1137/acd364
In this study, we compute the correlation functions of Wilson(-'t Hooft) loops with chiral primary operators in the \begin{document}$ \mathcal{N}=4 $\end{document} supersymmetric Yang-Mills theory with \begin{document}$S O(N)$\end{document} gauge symmetry, which has a holographic dual description of the Type IIB superstring theory on the \begin{document}$ AdS_{5}\times\mathbf{RP}^{5} $\end{document} background. Specifically, we compute the coefficients of the chiral primary operators in the operator product expansion of Wilson loops in the fundamental representation, Wilson-'t Hooft loops in the symmetric representation, Wilson loops in the anti-fundamental representation, and Wilson loops in the spinor representation. We also compare these results to those of the \begin{document}$\mathcal{N}=4~ S U(N)$\end{document} super Yang-Mills theory.
Charge-changing cross section measurements of 300 MeV/nucleon 28Si on carbon and data analysis
Chang-Jian Wang, Ge Guo, Hooi Jin Ong, Yu-Nan Song, Bao-Hua Sun, Isao Tanihata, Satoru Terashima, Xiu-Lin Wei, Jun-Yao Xu, Xiao-Dong Xu, Ji-Chao Zhang, Yong Zheng, Li-Hua Zhu, Yong Cao, Guang-Wei Fan, Bing-Shui Gao, Jia-Xing Han, Guang-Shuai Li, Chen-Gui Lu, Hao-Tian Qi, Yun Qin, Zhi-Yu Sun, Lu-Ping Wan, Kai-Long Wang, Shi-Tao Wang, Xin-Xu Wang, Mei-Xue Zhang, Wen-Wen Zhang, Xiao-Bin Zhang, Xue-Heng Zhang, Zi-Cheng Zhou
2023, 47(8): 084001. doi: 10.1088/1674-1137/acd366
Charge-changing cross section (\begin{document}$ \sigma_{\text{cc}} $\end{document}) measurements via the transmission method have recently seen significant progress with the aim of determining the charge radii of exotic nuclei. In this work, we report a new \begin{document}$ \sigma_{\text{cc}} $\end{document} measurement of 304(9) MeV/nucleon \begin{document}$ ^{28} $\end{document}Si on carbon at the second Radioactive Ion Beam Line in Lanzhou (RIBLL2) and describe the data analysis procedure in detail. This procedure is essential for evaluating the systematic uncertainty in the transmission method. The determined \begin{document}$ \sigma_{\mathrm{cc}} $\end{document} of 1125(11) mb is found to be consistent with the existing data at similar energies. The present work will serve as a reference for \begin{document}$ \sigma_{\text{cc}} $\end{document} determinations at RIBLL2.
Revisiting band structures in 118Xe nucleus via in-beam γ-ray spectroscopy
A. Pandey, R. Bhushan, A. Rohilla, C. Majumder, H. P. Sharma, S. Chakraborty, R. P. Singh, S. Muralithar, Yashraj, K. Katre, B. Rohila, Subodh, A. Kumar, I. M. Govil, S. Jehangir, N. Rather, G. H. Bhati, A. A. Wani, J. A. Sheikh, S. K. Chamoli
2023, 47(8): 084002. doi: 10.1088/1674-1137/acd83d
The neutron deficient Xe nuclei with A \begin{document}$ \approx $\end{document}120 are predicted to have strong octupole correlation at low spins. In the present study, an attempt was made to improve upon the level scheme and also to examine the signatures of octupole correlation in \begin{document}$ ^{118} $\end{document}Xe via high spin γ-ray spectroscopy. High spin states in \begin{document}$ ^{118} $\end{document}Xe have been populated via the \begin{document}$ ^{93} $\end{document}Nb(\begin{document}$ ^{28} $\end{document}Si, p2n)\begin{document}$ ^{118} $\end{document}Xe fusion-evaporation reaction at a beam energy of 115 MeV provided by the 15 UD pelletron accelerator facility at IUAC, New Delhi. In the experiment, seven new γ-transitions have been found and placed appropriately in the level scheme. A theoretical study using the triaxial projected shell model (TPSM) approach suggests that the first bandcrossing is due to the alignment of two neutrons, and a parallel band tracking the yrast configuration is the γ-band built on the two-quasiparticle state. Enhanced E1 transition rates measured between opposite parity bands involving νh\begin{document}$ _{11/2} $\end{document} and νd\begin{document}$ _{5/2} $\end{document} orbitals having Δj = Δl = 3 indicate the presence of octupole correlation in this nucleus.
Roles of tensor force and pairing correlation in two-proton radioactivity of halo nuclei
Yan-Zhao Wang, Feng-Zhu Xing, Jian-Po Cui, Yong-Hao Gao, Jian-Zhong Gu
2023, 47(8): 084101. doi: 10.1088/1674-1137/acd680
The tensor force and pairing correlation effects on the two-proton radioactivity of \begin{document}$ ^{18} $\end{document}Mg and \begin{document}$ ^{20} $\end{document}Si with a pronounced two-proton halo are explored in the framework of spherical Skyrme-Hartree-Fock-Bogoliubov theory. It is shown that the halo sizes are enhanced with the increase in the strength of the tensor force and pairing correlation. Furthermore, the increasing halo sizes lead to the enhancement of diproton emission. Then, the tensor force is found to have a small influence on the two-proton decay energies, and the two-proton decay energies calculated with strong surface pairing are smaller than those with weak mixed pairing. Because the two-proton decay energies are relatively large, the predicted order of magnitude of half-lives within the effective liquid drop model is not sensitive to the decay energy variation caused by the tensor force and pairing correlation, which has a value of approximately 10\begin{document}$ ^{-18} $\end{document} s.
Cross sections for inelastic K+ϕ scattering
Yi-Hao Pan, Xiao-Ming Xu
2023, 47(8): 084102. doi: 10.1088/1674-1137/acd9be
In the first Born approximation, we study the reactions \begin{document}$ K\phi\to\pi K $\end{document}, \begin{document}$ \rho K $\end{document}, \begin{document}$ \pi K^* $\end{document}, and \begin{document}$ \rho K^* $\end{document} with quark-antiquark annihilation and creation. Transition amplitudes are derived with the development in the spherical harmonics of the relative-motion wave functions of two initial mesons and two final mesons so that parity is conserved and the total angular momentum of the final mesons equals that of the initial mesons. Unpolarized cross sections are calculated from the transition amplitudes that also contain mesonic quark-antiquark relative-motion wave functions and transition potentials for quark-antiquark annihilation and creation. The notable temperature dependence of the cross sections is shown. The cross sections for \begin{document}$ K\phi\to\rho K $\end{document}, \begin{document}$ K\phi\to\pi K^* $\end{document}, and \begin{document}$ K\phi\to\rho K^* $\end{document} may be of the millibarn scale, whereas the cross section for \begin{document}$ K\phi\to\pi K $\end{document} is small.
Experimental nuclear charge density and theoretical description of the above-barrier light heavy-ion fusion process
I. I. Gontchar, M. V. Chushnyakova
2023, 47(8): 084103. doi: 10.1088/1674-1137/acd682
Theoretical modeling of nucleus-nucleus collisions is often based on the nucleus-nucleus potential. One of the advanced methods for constructing this potential is the semi-microscopical double-folding model with M3Y-Paris NN-forces. Proton and neutron densities are significant components of this model. The correct nucleon density (ND) must reproduce the experimental nuclear charge density (NCD). However, those who deal with modeling the fusion process typically disregard this circumstance. We aim to achieve a good description of both the nuclear charge density and above-barrier fusion cross sections of even-even light nuclei with \begin{document}$ Z=N $\end{document}. We consider several versions of NDs available in literature and construct our own approximation for the ND of the even-even spherical nuclei 12C, 16O, and 40Ca, abbreviated as FE-density (Fermi+exponential). We carefully compare the NCDs resulting from different versions of NDs with the experimental NCDs. After finding the nucleus-nucleus potential using the double-folding model with the density dependent M3Y-Paris NN-forces and FE densities, we evaluate the above-barrier fusion cross sections for five reactions, 12C+12C, 12C+16O, 16O+16O, 16O+40Ca, and 40Ca+40Ca, for which experimental data are available. The cross sections are calculated using two approaches: a) the barrier penetration model and b) the trajectory model with surface friction (TM). To find the transmission coefficients for the TM, the Langevin equations are employed. For all considered reactions, our TM typically reproduces the above-barrier experimental cross sections within 10−15%. The only adjustable parameter of the model, the optimal friction strength \begin{document}$ {K}_{Rm} $\end{document}, is found to be approximately 90 \begin{document}$\mathrm{z}\mathrm{s}\cdot {\mathrm{G}\mathrm{e}\mathrm{V}}^{-1}$\end{document}for the light reactions 12C+12C, 12C+16O, and 16O+16O and approximately 15 \begin{document}$\mathrm{z}\mathrm{s}\cdot {\mathrm{G}\mathrm{e}\mathrm{V}}^{-1}$\end{document}for the heavy reactions 16O+40Ca and 40Ca+40Ca. The latter findings are in reasonable agreement with the systematics found previously. Thus, the FE-recipe allows highly accurate and simultaneous reproduction of both the nuclear charge density and above-barrier fusion cross sections of five reactions involving 12C, 16O, and 40Ca nuclei.
Predictions of nuclear charge radii
Guang-Sheng Li, Cheng Xu, Man Bao
2023, 47(8): 084104. doi: 10.1088/1674-1137/acdb54
In this study, we improve the relations of the charge-radius difference of two isotopes by considering a term that relates to the proton number and the parity of the neutron number. The correction reduces the root-mean-squared deviation to 0.0041 fm for 651 nuclei with a neutron number larger than 20, in comparison with experimental data compiled in the CR2013 database. The improved relations are combined with local relations consisting of the charge radii of four neighboring nuclei. These combinations also prove to be efficient in describing and predicting nuclear charge radii and can reflect the structure evolutions of nuclei. Our predictions of 2467 unknown nuclear charge radii at competitive accuracy, which are calculated using these two types of relations, are tabulated in the Supplemental Material.
Radiative 9Be(n,γ0+1+2+3+4+5)10Be reaction rate in the potential cluster model
S.B. Dubovichenko, B.M. Yeleusheva, N.A. Burkova, A.S. Tkachenko
2023, 47(8): 084105. doi: 10.1088/1674-1137/acdb55
Within the framework of the modified potential cluster model with forbidden states, the total cross-sections of radiative n9Be capture to the ground and five low-lying excited states are calculated at energies from 10−2 eV up to 5 MeV. The thermal cross-section \begin{document}${\sigma _{\rm th}} = 8.35$\end{document}mb is in good agreement with experimental data. We considered five resonances at the excitation energies Ex from 7.371 MeV up to 10.570 MeV corresponding to the following states with \begin{document}${J^\pi }$\end{document}(Ex, MeV): \begin{document}${3^ - }$\end{document}(7.371), \begin{document}${2^ + }$\end{document}(7.542), \begin{document}${3^ + }$\end{document}(9.4), \begin{document}${2^ + }$\end{document}(9.56), and \begin{document}${3^ - }$\end{document}(10.570). The partial and total 9Be(n,γ0+1+2+3+4+5)10Be reaction rates are calculated at temperatures from 0.001 to 10 T9. Contrary to the available data, we propose that the rise in the reaction rate near factor five at T9 >1 is mainly due to the first \begin{document}${3^ - }$\end{document}(ER = 0.559 MeV) resonance. We foresee this contrast as arising from different model approaches.
New insights into the limit of the magnetic monopole flux and the heating source in white dwarfs
Jing-Jing Liu, Dong-Mei Liu, Liang-Huan Hao
2023, 47(8): 084106. doi: 10.1088/1674-1137/acdc8b
Based on the magnetic monopole (MM) catalytic nuclear decay (Rubakov-Callan (RC) effect), we propose five new models to discuss the limit of the MM flux and the heating energy resources of white dwarfs (WDs) based on observations of 13 red giant branch (RGB) stars. We find that the number of MMs captured can reach a maximum value of \begin{document}$ 9.1223\times10^{24} $\end{document} when \begin{document}$ m=10^{17} $\end{document} GeV, \begin{document}$n_{\rm B}=5.99\times10^{31}~\rm{cm^{-3}}$\end{document}, \begin{document}$\phi=7.59\times 10^{-26} \rm{cm^{-2}s^{-1}sr^{-1}}$\end{document}. The good agreement of our calculated luminosities for WDs with observation provides support for our model based on the RC effect by MMs. We obtain a new limit of the MM flux of \begin{document}$\xi=\phi\langle\sigma_m v_{\rm{T}}\rangle_{-28}\leq $\end{document}\begin{document}$ 9.0935\times10^{-13}\rm{cm^{-2}s^{-1}sr^{-1}}$\end{document}, and \begin{document}$ \xi\leq 4.9950\times10^{-13}\rm{cm^{-2}s^{-1}sr^{-1}} $\end{document} at \begin{document}$n_{\rm B}=5.99\times10^{31}\rm{cm^{-3}}$\end{document} when \begin{document}$m=10^{15}\rm{GeV}$\end{document}, \begin{document}$ \beta=9.4868\times10^{-3} $\end{document}, and \begin{document}$ m=10^{17}\rm{GeV}, $\end{document}\begin{document}$ ~\beta=10^{-3} $\end{document}, respectively. Our results show that the RC effect could cause heating that prevents white dwarfs from cooling down into a stellar graveyard. Our results will also provide a new idea for further research on the upper limit of MM flow (note: \begin{document}$n_{\rm B}, \sigma_m, m, \phi, \xi$\end{document} are the baryon number density, reaction cross section, mass, MM flux, and the new limit of the MM flux, respectively, and \begin{document}$ \beta=v_T/c $\end{document} is the ratio of the speed of MMs to that of light).
Toward a description of the centrality dependence of the charge balance function in the HYDJET++ model
A.S. Chernyshov, G.Kh. Eyyubova, V.L. Korotkikh, I.P. Lokhtin, L.V. Malinina, S.V. Petrushanko, A.M. Snigirev, E.E. Zabrodin
2023, 47(8): 084107. doi: 10.1088/1674-1137/acddd7
Data from the Large Hadron Collider on the charge balance function in Pb+Pb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted within the framework of the HYDJET++ model. This model allows us to qualitatively reproduce the experimentally observed centrality dependence of the balance function widths at relatively low transverse momentum intervals due to the different charge creation mechanisms in soft and hard processes. However, a fully adequate description of the balance function in these intervals implies an essential modification of the model by including exact charge conservation via the canonical rather than the grand canonical ensemble. A procedure is proposed for introducing charge correlations into the thermal model without changing other model parameters. With increasing transverse momenta, the default model results describe the experimental data much better because the contribution of the soft component of the model is significantly reduced in these transverse momentum intervals. In practical terms, there is a transition to a single source of charge correlations, namely, charge correlations in jets in which exact charge conservation holds at each stage.
Echoes of axial gravitational perturbations in stars of uniform density
Kai Lin, Wei-Liang Qian
2023, 47(8): 085101. doi: 10.1088/1674-1137/acd681
This study investigates the echoes in axial gravitational perturbations in compact objects. Accordingly, we propose an alternative scheme of the finite difference method implemented in two coordinate systems, where the initial conditions are placed on the axis of the tortoise coordinate with appropriate boundary conditions that fully respect the causality. The scheme is then employed to study the temporal profiles of the quasinormal oscillations in the Schwarzschild black hole and uniform-density stars. When presented as a two-dimensional evolution profile, the resulting ringdown waveforms in the black hole metric are split into reflected and transmitted waves as the initial perturbations evolve and collide with the peak of the effective potential. Meanwhile, for compact stars, quasinormal oscillations might be characterized by echoes. Consistent with the causality arguments, the phenomenon is produced by the gravitational waves bouncing between the divergent potential at the star's center and the peak of the effective potential. The implications of the present study are also discussed herein.
Onset of chaotic gravitational lensing in non-Kerr rotating black holes with quadrupole mass moment
Wen-Hao Wu, Cheng-Yong Zhang, Cheng-Gang Shao, Wei-Liang Qian
2023, 47(8): 085102. doi: 10.1088/1674-1137/acd83e
In the electromagnetic channel, chaotic gravitational lensing is a peculiar phenomenon in strong gravitational lensing. In this study, we analyze the properties and emergence of chaotic gravitational lensing in the Manko-Novikov black hole spacetime. Aiming to better understand the underlying physics, we elaborate on the boundaries of the accessible region through analyses of the contours of the effective potentials. The latter is associated with the two roots of a quadratic equation. In particular, we explore its interplay with an ergoregion, which leads to specific features of the effective potentials, such as the emergence of a cuspy edge and the formation of a pocket, which serve as static constraints on the geodesics. Additionally, we investigate the properties of the radial and angular accelerations at the turning points in photon trajectories. The accelerations are further examined and may provide kinematic constraints on the geodesics, as argued herein. It is concluded that the onset of the chaotic lensing is significantly related to both constraints; as a result, an arbitrary slight deviation in the incident photon is significantly amplified during evolution through an extensive period, demonstrating the complexity in the highly nonlinear deterministic gravitational system.
Astrophysical observables for regular black holes with sub-Planckian curvature
Wei Zeng, Yi Ling, Qing-Quan Jiang
2023, 47(8): 085103. doi: 10.1088/1674-1137/acd530
We investigate the photon sphere and marginally stable circular orbit of massive particles over the recently proposed regular black holes with sub-Planckian curvature and a Minkowskian core. We derive the effective potential for geodesic orbits and determine the radius of circular photon orbits, with an analysis of the stability of these orbits. We extend our analysis to the background of a compact massive object (CMO) without a horizon, whose mass is below the lowest bound for the formation of a black hole. For massive particles, marginally stable circular orbits become double-valued in the CMO phase. Through a comparison with Bardeen and Hayward black holes, we also find that the locations of the photon sphere and marginally stable circular orbit in the CMO phase with a Minkowskian core are evidently different from those in the CMO phase with a dS core, which potentially provides a way to distinguish between these two types of black holes by astronomical observation. Finally, we present the observational constraint on the deviation parameter for such regular black holes using observed data from the black hole M87*.
Gravitational waves from cosmic strings associated with pseudo-Nambu-Goldstone dark matter
Ze-Yu Qiu, Zhao-Huan Yu
2023, 47(8): 085104. doi: 10.1088/1674-1137/acd9bf
We study stochastic gravitational waves from cosmic strings generated in an ultraviolet-complete model for pseudo-Nambu-Goldstone dark matter with a hidden \begin{document}${U(1)}$\end{document} gauge symmetry. The dark matter candidate in this model can naturally evade direct detection bounds and easily satisfy other phenomenological constraints. The bound on the dark matter lifetime implies an ultraviolet scale higher than \begin{document}$ 10^9\; \mathrm{GeV} $\end{document}. The spontaneous \begin{document}${U(1)}$\end{document} symmetry breaking at such a high scale would induce cosmic strings with high tension, resulting in a stochastic gravitational wave background with a high energy density. We investigate the constraints from current gravitational wave experiments as well as the future sensitivity. We find that most viable parameter points can be well studied in future gravitational wave experiments.
Inferring redshift and energy distributions of fast radio bursts from the first CHIME/FRB catalog
Li Tang, Hai-Nan Lin, Xin Li
2023, 47(8): 085105. doi: 10.1088/1674-1137/acda1c
We reconstruct the extragalactic dispersion measure – redshift (\begin{document}$ {\rm DM_E}-z $\end{document}) relation from well-localized fast radio bursts (FRBs) using Bayesian inference. Then, the \begin{document}$ {\rm DM_E}-z $\end{document} relation is used to infer the redshift and energy of the first CHIME/FRB catalog. We find that the distributions of the extragalactic dispersion measure and inferred redshift of the non-repeating CHIME/FRBs follow a cut-off power law but with a significant excess at the low-redshift range. We apply a set of criteria to exclude events that are susceptible to the selection effect, but the excess at low redshifts still exists in the remaining FRBs (which we call the gold sample). The cumulative distributions of fluence and energy for both the full sample and the gold sample do not follow the simple power law, but they can be well fitted by the bent power law. The underlying physical implications require further investigation.
A note on the entanglement entropy of primary fermion fields in JT gravity
Chang-Zhong Guo, Wen-Cong Gan, Fu-Wen Shu
2023, 47(8): 085106. doi: 10.1088/1674-1137/acdd60
In this paper we analyze and discuss 2D Jackiw-Teitelboim (JT) gravity coupled to primary fermion fields in asymptotically anti-de Sitter (AdS) spacetimes. We obtain a particular solution of the massless Dirac field outside the extremal black hole horizon and find the solution for the dilaton in JT gravity. As two dimensional JT gravity spacetime is conformally flat, we calculate the two point correlators of primary fermion fields under the Weyl transformations. The primary goal of this work is to present a standard technique, called resolvent, rather than using CFT methods. We redefine the fields in terms of the conformal factor as fermion fields and use the resolvent technique to derive the renormalized entanglement entropy for massless Dirac fields in JT gravity.
Observational insights into the accelerating universe through reconstruction of the deceleration parameter
Devaraja Mallesha Naik, N. S. Kavya, V. Venkatesha
2023, 47(8): 085107. doi: 10.1088/1674-1137/acdc8a
Recent developments in the exploration of the universe suggest that it is in an accelerated phase of expansion. Accordingly, our study aims to probe the current scenario of the universe with the aid of the reconstruction technique. The primary factor that describes cosmic evolution is the deceleration parameter. Here, we provide a physically plausible, newly defined model-independent parametric form of the deceleration parameter. Further, we constrain the free parameters through statistical MCMC analysis for different datasets, including the most recent Pantheon+. With the statistically obtained results, we analyze the dynamics of the model through the phase transition, EoS parameter, and energy conditions. Also, we make use of the tool Om diagnostic to test our model.