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2024-3 Contents
2024, 48(3): 1-2.
Time-reversal asymmetries in $ {\boldsymbol\Lambda_{\boldsymbol b} {\bf\to} {\boldsymbol\Lambda}{\bf (\to}{\boldsymbol p} \boldsymbol\pi^{\bf -}{\bf)}\boldsymbol\ell^{\bf +}\boldsymbol\ell^{\bf -} }$
Chao-Qiang Geng, Chia-Wei Liu, Zheng-Yi Wei
2024, 48(3): 033101. doi: 10.1088/1674-1137/ad13f6
We study the decays of \begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \ell ^+ \ell^- $\end{document} with \begin{document}$ \ell = (e, \mu, \tau) $\end{document}. We examine the full angular distributions with polarized \begin{document}$ \Lambda_b $\end{document}, where the T-odd observables are identified. We discuss the possible effects of new physics (NP) and find that the T-odd observables are sensitive to them as they vanish in the standard model. Special attention is given to the interference of (pseudo)scalar operators with (axial)vector operators in polarized \begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \tau^+ \tau^- $\end{document}, which are studied for the first time. Their effects are proportional to the lepton masses and therefore may evade the constraint from \begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \mu^+ \mu^- $\end{document} at the LHCb naturally. As \begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \tau^+ \tau^- $\end{document} is uncontaminated by the charmonia resonance, it provides a clean background to probe NP. In addition, we show that the experimental central value of \begin{document}$ K_{10} $\end{document} in \begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \mu^+ \mu^- $\end{document} at the LHCb can be explained by the NP case, which couples to the right-handed quarks and leptons. The polarization fraction of \begin{document}$ \Lambda_b $\end{document} at the LHCb is found to be consistent with zero regardless of the NP scenarios.
J/ψ pair hadroproduction at next-to-leading order in nonrelativistic-QCD at ATLAS
Li-Ping Sun
2024, 48(3): 033102. doi: 10.1088/1674-1137/ad1a98
We present a complete study on the \begin{document}$ J/\psi $\end{document} pair hadroproduction at next-to-leading order (NLO) in the nonrelativstic-QCD (NRQCD) framework with the pair of \begin{document}$ c\bar{c} $\end{document} in either \begin{document}$ {}^{3}S_1^{[1]} $\end{document} or \begin{document}$ {}^{1}S_0^{[8]} $\end{document} fock state. We found that the contribution of the \begin{document}$ {}^{1}S_0^{[8]} $\end{document} channel at NLO is essential, and for ATLAS, the NRQCD results can describe the experimental data to a certain extent.
Solving the strong CP problem via a ${ \bar{\boldsymbol\theta} }$-characterized mirror symmetry
Pei-Hong Gu
2024, 48(3): 033103. doi: 10.1088/1674-1137/ad102b
In the standard model QCD Lagrangian, a term of CP violating gluon density is theoretically expected to have a physical coefficient \begin{document}$ \bar{\theta} $\end{document}, which is typically on the order of unity. However, the upper bound on the electric dipole moment of the neutron enforces the value of \begin{document}$ \bar{\theta} $\end{document} to be extremely small. The significant discrepancy between theoretical expectations and experimental results in this context is widely recognized as the strong CP problem. To solve this puzzle in an appealing context of two Higgs doublets, we propose a \begin{document}$ \bar{\theta} $\end{document}-characterized mirror symmetry between two Higgs singlets with respective discrete symmetries. In our scenario, the parameter \begin{document}$ \bar{\theta} $\end{document} can completely disappear from the full Lagrangian after the standard model fermions take a proper phase rotation as well as the Higgs doublets and singlets. Moreover, all of new physics for solving the strong CP problem can be allowed near the TeV scale.
Fully-light vector tetraquark states with explicit P-wave via QCD sum rules
Qi Xin, Zhi-Gang Wang
2024, 48(3): 033104. doi: 10.1088/1674-1137/ad181c
In this study, we apply the QCD sum rules to investigate the vector fully-light tetraquark states with an explicit P-wave between the diquark and antidiquark pairs. We observed that the \begin{document}$ C\gamma_\alpha\otimes\stackrel{\leftrightarrow}{\partial}_\mu\otimes\gamma^\alpha C $\end{document} (or \begin{document}$ C\gamma_\alpha\otimes\stackrel{\leftrightarrow}D_\mu\otimes\gamma^\alpha C $\end{document}) type current with fully-strange quarks couples potentially to a tetraquark state with a mass \begin{document}$ 2.16 \pm 0.14 \,{\rm{GeV}} $\end{document}, which supports assigning \begin{document}$ Y(2175)/\phi(2170) $\end{document} as the diquark-antidiquark type tetraquark state with \begin{document}$J^{PC}=1^{--}$\end{document}. The \begin{document}$ qs\bar{q}\bar{s} $\end{document} and \begin{document}$ ss\bar{s}\bar{s} $\end{document} vector tetraquark states with the structure \begin{document}$ C\gamma_\mu\otimes \stackrel{\leftrightarrow}{\partial}_\alpha \otimes\gamma^\alpha C + C\gamma^\alpha \otimes\stackrel{\leftrightarrow}{\partial}_\alpha \otimes\gamma_\mu $\end{document} (or \begin{document}$ C\gamma_\mu\otimes \stackrel{\leftrightarrow}D_\alpha \otimes\gamma^\alpha C + C\gamma^\alpha \otimes\stackrel{\leftrightarrow}D_\alpha \otimes\gamma_\mu $\end{document}) are consistent with \begin{document}$ X(2200) $\end{document} and \begin{document}$ X(2400) $\end{document}, respectively, which lie in the region from \begin{document}$ 2.20 $\end{document} to \begin{document}$ 2.40\,{\rm{GeV}} $\end{document}. The central values of the masses of the fully-strange vector tetraquark states with an explicit P-wave are approximately \begin{document}$ 2.16-3.13\,{\rm{GeV}} $\end{document} (or \begin{document}$ 2.16-3.16\,{\rm{GeV}} $\end{document}). Predictions for other fully-light vector tetraquark states with and without hidden-strange are also presented.
Influence of low-energy supersymmetric vector-like quirk particles on W mass increment and muon g–2 anomaly
Ping Zhou
2024, 48(3): 033105. doi: 10.1088/1674-1137/ad13f5
In the low energy realization of the quirk assisted Standard Model, the couplings between the exotic particles "quirks" and gauge bosons may contribute to the W mass and muon \begin{document}$ g-2 $\end{document} anomaly reported by FermiLab. We calculate the contributions from supersymmetric quirk particles as an example. By imposing the theoretical constraints, we determined that the CDF II W-boson mass increment strictly constrains the mixing and coupling parameters and the quirk mass \begin{document}$ m_F $\end{document}, while the muon \begin{document}$ g-2 $\end{document} anomaly cannot be solely attributed to the involvement of exotic particles, considering their significantly large masses.
Reconstructing parton distribution function based on maximum entropy method
Sihan Zhang, Xiaobin Wang, Tao Lin, Lei Chang
2024, 48(3): 033106. doi: 10.1088/1674-1137/ad1b3d
A new method based on the maximum entropy principle for reconstructing the parton distribution function (PDF) from moments is proposed. Unlike traditional methods, the new method does not require any artificial assumptions. For the case of moments with errors, we introduce Gaussian functions to soften the constraints of moments. Through a series of tests, the effectiveness and reconstruction efficiency of this new method are evaluated comprehensively, demonstrating that this method is reasonable and can achieve high-quality reconstruction with at least the first six moments as input. Finally, we select a set of lattice quantum chromodynamics (QCD) results regarding moments as input and provide reasonable reconstruction results for the pion.
Nonlinear corrections for the nuclear gluon distribution in eA processes
G.R. Boroun, B. Rezaei, F. Abdi
2024, 48(3): 033107. doi: 10.1088/1674-1137/ad1cdb
An analytical study with respect to the nonlinear corrections for the nuclear gluon distribution function in the next-to-leading order approximation at small x is presented. We consider the nonlinear corrections to the nuclear gluon distribution functions at low values of x and \begin{document}$ Q^{2} $\end{document} using the parametrization \begin{document}$ F_{2}(x,Q^{2}) $\end{document}and the nuclear modification factors obtained from the Khanpour-Soleymaninia-Atashbar-Spiesberger-Guzey model. The CT18 gluon distribution is used for the baseline proton gluon density at \begin{document}$ Q_{0}^{2}=1.69\; {\rm{GeV}}^2 $\end{document}. We discuss the behavior of the gluon densities in the next-to-leading order and the next-to-next-to-leading order approximations at the initial scale \begin{document}$ Q_{0}^{2} $\end{document}, as well as the modifications due to the nonlinear corrections. We find that the QCD nonlinear corrections are more significant for the next-to-leading order accuracy than the next-to-next-to-leading order for light and heavy nuclei. The results of the nonlinear GLR-MQ evolution equation are similar to those obtained with the Rausch-Guzey-Klasen gluon upward and downward evolutions within the uncertainties. The magnitude of the gluon distribution with the nonlinear corrections increases with a decrease in x and an increase in atomic number A.
Elastic scattering of 13C and 14C isotopes on a 208Pb target at energies of approximately five times the Coulomb barriers
Guo Yang, Fang-Fang Duan, Kang Wang, Yan-Yun Yang, Zhi-Yu Sun, Valdir Guimarães, Dan-Yang Pang, Wen-Di Chen, Lei Jin, Shi-Wei Xu, Jun-Bing Ma, Peng Ma, Zhen Bai, Ling-Hao Wang, Quan Liu, Hooi-Jin Ong, Bing-Feng Lv, Song Guo, Mukhi Kumar Raju, Xiu-Hua Wang, Rong-Hua Li, Yu-Hu Zhang, Xiao-Hong Zhou, Zheng-Guo Hu, Hu-Shan Xu
2024, 48(3): 034001. doi: 10.1088/1674-1137/ad1678
The elastic scattering angular distributions of \begin{document}$ ^{13} $\end{document}C at 340 MeV and \begin{document}$ ^{14} $\end{document}C at 294 MeV and 342 MeV on a \begin{document}$ ^{208} $\end{document}Pb target, which correspond to approximately five times the Coulomb barriers, were measured at the Radioactive Ion Beam Line in Lanzhou. The data were analyzed within the optical model and continuum-discretized coupled-channels (CDCC) framework, and the results of both calculations could effectively account for the experimental data. The differential cross sections of elastic scattering revealed no particular suppression at the Coulomb nuclear interference peak angles, suggesting that the breakup coupling effects on the elastic scattering angular distributions were negligibly small in this incident energy region. The contributions from the couplings with inelastic states to the elastic cross sections were of minor importance within the angular range covered by these experiments.
Ground-state mass of 22Al and test of state-of-the-art ab initio calculations
M.Z. Sun, Y. Yu, X.P. Wang, M. Wang, J.G. Li, Y.H. Zhang, K. Blaum, Z.Y. Chen, R.J. Chen, H.Y. Deng, C.Y. Fu, W.W. Ge, W.J. Huang, H.Y. Jiao, H.H. Li, H.F. Li, Y.F. Luo, T. Liao, Yu.A. Litvinov, M. Si, P. Shuai, J.Y. Shi, Q. Wang, Y.M. Xing, X. Xu, H.S. Xu, F.R. Xu, Q. Yuan, T. Yamaguchi, X.L. Yan, J.C. Yang, Y.J. Yuan, X.H. Zhou, X. Zhou, M. Zhang, Q. Zeng
2024, 48(3): 034002. doi: 10.1088/1674-1137/ad1a0a
The ground-state mass excess of the \begin{document}$ T_{z}=-2 $\end{document} drip-line nucleus \begin{document}$ ^{22} $\end{document}Al is measured for the first time as \begin{document}$ 18103(10) $\end{document} keV using the newly-developed Bρ-defined isochronous mass spectrometry method at the cooler storage ring in Lanzhou. The new mass excess value allowed us to determine the excitation energies of the two low-lying \begin{document}$ 1^+ $\end{document} states in \begin{document}$ ^{22} $\end{document}Al with significantly reduced uncertainties of 51 keV. When compared to the analogue states in its mirror nucleus \begin{document}$ ^{22} $\end{document}F, the mirror energy differences of the two \begin{document}$ 1^+ $\end{document} states in the \begin{document}$ ^{22} $\end{document}Al-\begin{document}$ ^{22} $\end{document}F mirror pair are determined to be \begin{document}$ -625(51) $\end{document} keV and \begin{document}$ -330(51) $\end{document} keV. The excitation energies and mirror energy differences are used to test the state-of-the-art ab initio valence-space in-medium similarity renormalization group calculations with four sets of interactions derived from the chiral effective field theory. The mechanism leading to the large mirror energy differences is investigated and attributed to the occupation of the \begin{document}$ \pi s_{1/2} $\end{document} orbital.
Measurement of yields and angular distributions of γ-quanta from the interaction of 14.1 MeV neutrons with oxygen, phosphorus, and sulfur
D. N. Grozdanov, N. A. Fedorov, S. B. Dabylova, Yu. N. Kopatch, I. N. Ruskov, V. R. Skoy, T. Yu. Tretyakova, C. Hramco, P. I. Kharlamov, G. V. Pampushik, P. G. Filonchik, A. V. Andreev
2024, 48(3): 034003. doi: 10.1088/1674-1137/ad147e
A study of the inelastic scattering of neutrons with an energy of \begin{document}$ 14.1 $\end{document} MeV on the nuclei of oxygen, phosphorus, and sulfur was performed at the TANGRA facility at JINR (Dubna). The experiment aimed to refine existing data and obtain new data on the yields and angular distributions of γ-quanta emitted by the studied nuclei due to neutron-induced nuclear reactions using the tagged neutron method. Two types of detector systems were used to register γ-quanta. The γ-ray yields were measured using a high-purity germanium (HPGe) detector. The angular distributions of γ-rays were obtained using a system of 18 scintillation detectors based on bismuth germanite Bi\begin{document}$ _{4} $\end{document}Ge\begin{document}$ _{3} $\end{document}O\begin{document}$ _{12} $\end{document} (BGO) located around the sample. The performed experiments measured the yields of two transitions for the reaction of tagged neutrons with \begin{document}$ ^{16} $\end{document}O, nine transitions for the reaction with \begin{document}$ ^{31} $\end{document}P, and nine transitions for the reaction with \begin{document}$ ^{32} $\end{document}S for the first time. The angular anisotropy of the γ-radiation accompanying the inelastic scattering of neutrons with an energy of \begin{document}$ 14.1 $\end{document} MeV on \begin{document}$ ^{31} $\end{document}P nuclei was also measured for the first time.
What can we learn from recent 2νββ experiments?
Dong-Liang Fang
2024, 48(3): 034101. doi: 10.1088/1674-1137/ad181b
Recent measurements of the two neutrino double beta decay high precision electron spectra, combined with charge exchange or β-decay experimental data, have revealed severe constraints across current nuclear many body calculations. Our calculations show that the quasi-particle random phase approximation (QRPA) approach can adequately reproduce the measured spectra for the two open shell nuclei, \begin{document}$ ^{82} $\end{document}Se and \begin{document}$ ^{100} $\end{document}Mo. For the closed shell nucleus \begin{document}$ ^{136} $\end{document}Xe, QRPA can also reproduce the spectra with proper treatments. Considering the high-lying state reduction, we also find that the nuclear shell model can also adequately reproduce the spectra and Gamow-Teller transition strength under a unique quenched axial-vector coupling constant \begin{document}$ g_A $\end{document}. For \begin{document}$ ^{136} $\end{document}Xe, we find that flipping the sign for the decay strength causes the spectra to go beyond the so-called high-lying state dominance hypothesis. These results call for future high precision measurements of charge-exchange reactions.
Wobbling motion for a triaxial rotor plus a single quasiparticle
Si-Hua Li, Hua-Ming Dai, Qi-Bo Chen, Xian-Rong Zhou
2024, 48(3): 034102. doi: 10.1088/1674-1137/ad18d2
Wobbling motion in a system comprising a triaxial rotor and a single quasiparticle is studied employing the particle-rotor model. The energy spectra, wobbling frequencies, electromagnetic transition probabilities, g-factors, angular momentum components, spin coherent state maps, and static quadrupole moments are investigated. These investigations were conducted with regard to the Fermi surface transitioning from the lowest \begin{document}$ h_{11/2} $\end{document} orbit to the highest one. As the Fermi surface increases, notable transformations occur in the wobbling mode. Initially, the mode exhibits a transverse revolution around the short axis of the nucleus. However, as the Fermi surface continues to increase, the mode gradually shifts to a longitudinal revolution around the intermediate axis. Eventually, it transitions to a transverse revolution around the long axis. Notably, the stability of the long axis transverse mode diminishes relative to its counterpart along the short axis as the total angular momentum increases at \begin{document}$ \gamma=20^\circ $\end{document}.
α-decay properties of superheavy nuclei with 117 ≤ Z ≤ 120 from the systematics of decay chains and isotopic chains
Tao Wan, Shu-Lin Tang, Yi-Bin Qian
2024, 48(3): 034103. doi: 10.1088/1674-1137/ad1582
Recently, the synthesis of new elements above Z = 118 has been a hot topic in nuclear physics. Meanwhile, the α-decay chain is expected to be the unique tool to identify these heaviest nuclei. We have systematically calculated the α-decay energies and half-lives on the same footing for superheavy nuclei (SHN) within the cluster model along with a slightly modified Woods-Saxon (W.S.) potential as the nuclear potential. Based on the available experimental data, the key radius parameter (R) in the α-core potential is determined via the systematic trend from the α-decay and isotopic chains. The α-decay energy (\begin{document}$Q _{\alpha} $\end{document}) values and half-lives are then obtained simultaneously for those unknown SHN in the range of 117 ≤ Z ≤ 120, during which the decay width is obtained using a new treatment for the asymptotic behavior of the α-core wave function. The theoretical values and experimental data are found to be in excellent agreement for the nuclei \begin{document}$ ^{293,294} $\end{document}117 and \begin{document}$ ^{294} $\end{document}118 regardless of the method used to determine the R parameter. Predicting the α-decay chains for new elements Z = 119 and Z = 120 can be useful in ongoing or forthcoming experiments.
Empirical model for fusion cross sections of Ca-induced reactions
Reddi Rani. L, N. Sowmya, K. N Sridhar, H C. Manjunatha, M. M. Armstrong Arasu
2024, 48(3): 034104. doi: 10.1088/1674-1137/ad1a97
A new empirical formula for the astrophysical S-factor has been suggested as a function of the Coulomb interaction parameter, center of mass energy, and barrier height. About 22 fusion reactions with 40,48Ca as projectiles were considered for different targets, leading to compound nuclei with atomic and mass numbers varying between 40 \begin{document}$ \le Z \le $\end{document}112 and \begin{document}$ 88 \le A \le 278$\end{document}, respectively. The fusion cross-sections have been estimated using the geometric factor, the Gamow-Sommerfield factor, and the empirical formula for the S-factor. This study's findings showed better agreement with those of available experiments when compared to Wong's formula. The present work leads to a smaller standard deviation value than Wong's formula when used to correlate the experimental data of calcium-induced fusion reactions. Wong's formula provides a good approximation of fusion cross-sections when the center of mass energy is below the fusion barrier when compared to above the fusion barrier.
Neutron star core-crust transition and the crustal moment of inertia in the nonlinear relativistic Hartree approximation
Niu Li, Si-Na Wei, Rong-Yao Yang, Jing Ye, Wei-Zhou Jiang
2024, 48(3): 034105. doi: 10.1088/1674-1137/ad18d3
We investigate the effects of the σ meson mass (\begin{document}$ m_\sigma $\end{document}), symmetry energy, and slope of the symmetry energy on the neutron star core-crust transition density and the crustal moment of inertia (\begin{document}$ \Delta I/I $\end{document}) in the nonlinear relativistic Hartree approach (RHA), which includes vacuum polarization. Although the core-crust transition density (\begin{document}$ \rho_{t} $\end{document}), pressure (\begin{document}$ P_{t} $\end{document}), and neutron star radius (R), which are all dependent on the symmetry energy, contribute to determining \begin{document}$ \Delta I/I $\end{document}, we find that changing only the slope of symmetry energy within a reasonable range is not sufficient to reach \begin{document}$\Delta I/I\geq7$\end{document}% to achieve the large glitches of the Vela pulsar. However, since all three factors (\begin{document}$ \rho_{t} $\end{document}, \begin{document}$ P_{t} $\end{document}, and R) increase with the increase in \begin{document}$ m_\sigma $\end{document} through scalar vacuum polarization, adjusting \begin{document}$ m_\sigma $\end{document} can easily achieve \begin{document}$\Delta I/I\geq7$\end{document}%.
Complexity growth in a holographic QCD model
Wen-Bin Chang, De-fu Hou
2024, 48(3): 034106. doi: 10.1088/1674-1137/ad1b3e
In this study, we utilize the complexity-action duality to study the evolution of complexity in a holographic QCD model at finite temperature and chemical potential. By inserting a fundamental string as a probe, we investigated the properties of complexity growth in this Einstein-Maxwell-scalar gravity system, which is affected by the string velocity, chemical potential, and temperature. Our results show that the complexity growth is maximized when the probe string is stationary, and it decreases as the velocity of the string increases. When the string approaches relativistic velocities, the complexity growth always increases monotonically with respect to the chemical potential. Furthermore, we find that the complexity growth can be used to identify phase transitions and crossovers in the model.
Impact of the Brink-Axel hypothesis on unique first-forbidden β-transitions for r-process nuclei
Fakeha Farooq, Jameel-Un Nabi, Ramoona Shehzadi
2024, 48(3): 034107. doi: 10.1088/1674-1137/ad1925
Key nuclear inputs for the astrophysical r-process simulations are the weak interaction rates. Consequently, the accuracy of these inputs directly affects the reliability of nucleosynthesis modeling. The majority of the stellar rates, used in simulation studies are calculated by invoking the Brink-Axel (BA) hypothesis. The BA hypothesis assumes that the strength functions of all parent excited states are the same as for the ground state, only shifted in energies. However, the BA hypothesis has to be tested against microscopically calculated state-by-state rates. In this project, we study the impact of the BA hypothesis on calculated stellar \begin{document}$ \beta^{-} $\end{document}-decay and electron capture rates. Our investigation include both unique first forbidden (U1F) and allowed transitions for 106 neutron-rich trans-iron nuclei ([27, 77] ≤ [Z, A] ≤ [82, 208]). The calculations were performed using the deformed proton-neutron quasiparticle random-phase approximation (pn-QRPA) model with a simple plus quadrupole separable and schematic interaction. Waiting-point and several key r-process nuclei lie within the considered mass region of the nuclear chart. We computed electron capture and \begin{document}$ \beta^{-} $\end{document}-decay rates using two different prescriptions for strength functions. One was based on invoking the BA hypothesis and the other was the state-by-state calculation of strength functions, under stellar density and temperature conditions ([10, 1] ≤ [\begin{document}$\rho{{\rm Y}}_{e}$\end{document}(\begin{document}$\rm g/cm^{3}$\end{document}), T(\begin{document}$ GK $\end{document})] ≤ [1011, 30]). Our results show that the BA hypothesis invoked U1F \begin{document}$ \beta^{-} $\end{document}rates are overestimated by 4–5 orders of magnitude as compared to microscopic rates. For capture rates, more than two orders of magnitude differences were noted when applying the BA hypothesis. It was concluded that the BA hypothesis is not a reliable approximation, especially for \begin{document}$ \beta^{-} $\end{document}-decay forbidden transitions.
Proton-neutron symplectic model description of 106Cd
H. G. Ganev
2024, 48(3): 034108. doi: 10.1088/1674-1137/ad1d4b
In this study, a microscopic shell-model description of the low-lying collective states in the weakly deformed nucleus \begin{document}$ ^{106} $\end{document}Cd within the recently proposed microscopic version of the Bohr-Mottelson model is provided. A good description of the excitation energies of the lowest ground, γ, and β quasibands is obtained without the adjustable kinetic energy term. Furthermore, γ degrees of freedom are shown to play a crucial role in the description of spectroscopy of this nucleus. A modified \begin{document}$S U(3)$\end{document} preserving high-order interaction is used to produce a γ-unstable type of odd-even staggering, observed experimentally between the states of the quasi-γ band. The current approach enables the characterization of observed intraband and interband quadrupole collectivity. The findings of this study propose an alternative interpretation of the fundamental question regarding the nature of low-energy vibrations, as well as the emergence of deformation and collectivity in weakly deformed atomic nuclei.
Post-Newtonian binary dynamics in the effective field theory of Horndeski gravity
Wen-Hao Wu, Yong Tang
2024, 48(3): 035101. doi: 10.1088/1674-1137/ad1a0c
General relativity has been very successful since its proposal more than a century ago. However, various cosmological observations and theoretical consistency still motivate us to explore extended gravity theories. Horndeski gravity stands out as one attractive theory by introducing only one scalar field. Here we formulate the post-Newtonian effective field theory of Horndeski gravity and investigate the conservative dynamics of inspiral compact binary systems. We calculate the leading effective Lagrangian for a compact binary and obtain the periastron advance per period. In particular, we apply our analytical calculation to two binary systems, PSR B 1534+12 and PSR J0737-3039, and constrain the relevant model parameters. This theoretical framework can also be systematically extended to higher orders.
Quasinormal modes and isospectrality of Bardeen (Anti-) de Sitter black holes
Ying Zhao, Wentao Liu, Chao Zhang, Xiongjun Fang, Jiliang Jing
2024, 48(3): 035102. doi: 10.1088/1674-1137/ad1ed8
Black holes (BHs) exhibiting coordinate singularities but lacking essential singularities throughout the spacetime are referred to as regular black holes (RBHs). The initial formulation of RBHs was presented by Bardeen, who considered the Einstein equation coupled with a nonlinear electromagnetic field. In this study, we investigate the gravitational perturbations, including the axial and polar sectors, of the Bardeen (Anti-) de Sitter black holes. We derive the master equations with source terms for both axial and polar perturbations and subsequently compute the quasinormal modes (QNMs) through numerical methods. For the Bardeen de Sitter black hole, we employ the 6th-order WKB approach. The numerical results reveal that the isospectrality is broken in this case. Conversely, the QNM frequencies are calculated using the HH method for the Bardeen Anti-de Sitter black hole.