2023 Vol. 47, No. 10

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2023-10 Contents
2023, 47(10): 1-2.
Search for two-neutrino double-beta decay of 136Xe to the ${\bf 0^+_1} $ excited state of 136Ba with the complete EXO-200 dataset
S. Al Kharusi, G. Anton, I. Badhrees, P.S. Barbeau, D. Beck, V. Belov, T. Bhatta, M. Breidenbach, T. Brunner, G.F. Cao, W.R. Cen, C. Chambers, B. Cleveland, M. Coon, A. Craycraft, T. Daniels, L. Darroch, S.J. Daugherty, J. Davis, S. Delaquis, A. Der Mesrobian-Kabakian, R. DeVoe, J. Dilling, A. Dolgolenko, M.J. Dolinski, J. Echevers, W. Fairbank Jr., D. Fairbank, J. Farine, S. Feyzbakhsh, P. Fierlinger, Y.S. Fu, D. Fudenberg, P. Gautam, R. Gornea, G. Gratta, C. Hall, E.V. Hansen, J. Hoessl, P. Hufschmidt, M. Hughes, A. Iverson, A. Jamil, C. Jessiman, M.J. Jewell, A. Johnson, A. Karelin, L.J. Kaufman, T. Koffas, R. Krücken, A. Kuchenkov, K.S. Kumar, Y. Lan, A. Larson, B.G. Lenardo, D.S. Leonard, G.S. Li, S. Li, Z. Li, C. Licciardi, Y.H. Lin, R. MacLellan, T. McElroy, T. Michel, B. Mong, D.C. Moore, K. Murray, O. Njoya, O. Nusair, A. Odian, I. Ostrovskiy, A. Perna, A. Piepke, A. Pocar, F. Retière, A.L. Robinson, P.C. Rowson, J. Runge, S. Schmidt, D. Sinclair, K. Skarpaas, A.K. Soma, V. Stekhanov, M. Tarka, S.
2023, 47(10): 103001. doi: 10.1088/1674-1137/aceee3
A new search for two-neutrino double-beta (2νββ) decay of 136Xe to the \begin{document}$0_1^ + $\end{document} excited state of 136Ba is performed with the full EXO-200 dataset. A deep learning-based convolutional neural network is used to discriminate signal from background events. Signal detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of two. With the addition of the Phase II dataset taken with an upgraded detector, the median 90% confidence level half-life sensitivity of 2νββ decay to the \begin{document}$0_1^ + $\end{document} state of 136Ba is \begin{document}$ 2.9 \times 10^{24} $\end{document} yr using a total 136Xe exposure of 234.1 kg yr. No statistically significant evidence for 2νββ decay to the \begin{document}$0_1^ + $\end{document} state is observed, leading to a lower limit of \begin{document}$ T^{2\nu}_{1/2}(0^+ \rightarrow 0^+_1) > 1.4\times10^{24} $\end{document} yr at 90% confidence level, improved by 70% relative to the current world's best constraint.
Momentum dependence of $ {\boldsymbol{\rho-\omega}} $ mixing in the pion vector form factor and its effect on ${\boldsymbol{(g-2)_\mu}} $
Yun-Hua Chen, Meng-Ge Qin
2023, 47(10): 103101. doi: 10.1088/1674-1137/ace820
The inclusion of the \begin{document}$\rho-\omega$\end{document} mixing effect is essential for a precise description of the pion electromagnetic form factor in the \begin{document}$e^+e^- \rightarrow\pi^+\pi^-$\end{document} process, which quantifies the two-pion contribution to the anomalous magnetic moment of muon \begin{document}$a_\mu$\end{document}. In this study, we analyze the momentum dependence of \begin{document}$\rho-\omega$\end{document} mixing by considering loop contributions at the next-to-leading order in \begin{document}$1/N_C$\end{document} expansion within the framework of resonance chiral theory. We revisit a previous study [Y. H. Chen, D. L. Yao, and H. Q. Zheng, Commun. Theor. Phys. 69, 1 (2018)] and consider the contribution arising from the kaon mass splitting in the kaon loops and latest experimental data. We perform two types of fits (with momentum-independent or momentum-dependent \begin{document}$\rho-\omega$\end{document} mixing amplitude) to describe \begin{document}$e^+e^-\rightarrow \pi^+\pi^-$\end{document} and \begin{document}$\tau\rightarrow \nu_{\tau}2\pi$\end{document} data within the energy region of 600\begin{document}$-$\end{document}900 MeV and decay width of \begin{document}$\omega \rightarrow \pi^+\pi^-$\end{document}. Furthermore, we compare their results. Our findings indicate that the momentum-independent and momentum-dependent \begin{document}$\rho-\omega$\end{document} mixing schemes provide appropriate descriptions of the data. However, the momentum-dependent scheme exhibits greater self-consistency, considering the reasonable imaginary part of the mixing matrix element \begin{document}$\Pi_{\rho\omega}$\end{document} obtained. Regarding the contribution to the anomalous magnetic moment of the muon, \begin{document}$a_\mu^{\pi\pi}|_{[0.6,0.9]\text{GeV}}$\end{document}, the results obtained from the fits considering the momentum-dependent \begin{document}$\rho-\omega$\end{document} mixing amplitude are in good agreement with those obtained without incorporating the momentum dependence of \begin{document}$\rho-\omega$\end{document} mixing, within the margin of errors. Furthermore, based on the fitted values of the relevant parameters, we observe that the decay width of \begin{document}$\omega \rightarrow \pi^+\pi^-$\end{document}is predominantly influenced by the \begin{document}$\rho-\omega$\end{document} mixing effect.
Exploring muonphilic ALPs at muon colliders
Chih-Ting Lu, Xiaoyi Luo, Xinqi Wei
2023, 47(10): 103102. doi: 10.1088/1674-1137/ace424
Axion-like particles (ALPs) are new particles that extend beyond the standard model (SM) and are extensively investigated. When considering ALPs within an effective field theory framework, their couplings with SM particles can be studied independently. It is a daunting task to search for GeV-scale ALPs coupled to muons in collider experiments because their coupling is proportional to the muon mass. However, a recent study by Altmannshofer, Dror, and Gori (2022) highlighted the importance of a four-point interaction, W-μ-\begin{document}$ \nu_{\mu} $\end{document}-a, as well as interactions from the chiral anomaly, whose couplings are not dependent on the muon mass. These interactions provide a new opportunity to explore muonphilic ALPs (μALPs) at the GeV scale. We explore various μALP production channels at muon colliders with μALPs decaying into a pair of muons. In particular, we find that a pair of neutrinos accompanied by a μALP is the most effective channel to search for μALPs in the electrowek violating (EWV) scenario. In contrast, a photon plus a μALP becomes a better channel to search for μALPs in the electroweak preserving (EWP) scenario because there is no W-μ-\begin{document}$ \nu_{\mu} $\end{document}-a interaction in this situation. Most importantly, we find that the future bounds for μALPs in the EWV scenario are considerably stronger than those in the EWP scenario and the existing bounds for exploring μALPs with \begin{document}$ 1 $\end{document} GeV \begin{document}$ \leq m_a\lesssim M_W $\end{document}.
Custodial symmetry violation in scalar extensions of the standard model
Huayang Song, Xia Wan, Jiang-Hao Yu
2023, 47(10): 103103. doi: 10.1088/1674-1137/ace5a6
The new measurement of the W boson mass from the CDF collaboration shows a significant tension with the standard model prediction, which evidences violation of custodial symmetry in the scalar sector. We study the scalar extensions of the standard model, which can be categorized into two classes, the scalar sector with custodial symmetry (Georgi-Machacek model and its generalizations) and the scalar sector without custodial symmetry, and explore how these extensions fit to electroweak precision data and the new CDF \begin{document}$m_W$\end{document}. The favored oblique parameters originate from either the large mass splitting in the multiplet via the loop contribution or the large vacuum expectation value, which breaks custodial symmetry at the tree level. In particular, we find that \begin{document}$\mathcal{O}(100)$\end{document} GeV new particles are allowed in the scalar extension scenarios.
$ {\boldsymbol{B_{(s)} \rightarrow D^{**}_{(s)}}} $ form factors in HQEFT and model independent analysis of relevant semileptonic decays with NP effects
Ya-Bing Zuo, Hong-Yao Jin, Jing-Ying Tian, Jia Yi, Han-Yu Gong, Ting-Ting Pan
2023, 47(10): 103104. doi: 10.1088/1674-1137/ace821
The form factors of \begin{document}$ B_{(s)} $\end{document} decays into P-wave excited charmed mesons (including \begin{document}$ D^*_0(2300) $\end{document}, \begin{document}$ D_1(2430) $\end{document}, \begin{document}$ D_1(2420) $\end{document}, \begin{document}$ D^*_2(2460) $\end{document} and their strange counterparts, denoted generically as \begin{document}$ D^{**}_{(s)} $\end{document}) are systematically calculated via QCD sum rules in the framework of heavy quark effective field theory (HQEFT). We consider contributions up to the next leading order of heavy quark expansion and give all the relevant form factors, including the scalar and tensor ones only relevant for possible new physics effects. The expressions for the form factors in terms of several universal wave functions are derived via heavy quark expansion. These universal functions can be evaluated through QCD sum rules. Then, the numerical results of the form factors are presented. With the form factors given here, a model independent analysis of relevant semileptonic decays \begin{document}$ B_{(s)} \rightarrow D^{**}_{(s)} l \bar{\nu}_l $\end{document} is performed, including the contributions from possible new physics effects. Our predictions for the differential decay widths, branching fractions, and ratios of branching fractions \begin{document}$ R(D^{**}_{(s)}) $\end{document} may be tested in more precise experiments in the future.
Prospects of gluino searches in multi-lepton channels in light of the ongoing LHC RUN-III
Abhi Mukherjee, Saurabh Niyogi, Sujoy Poddar, Jyoti Prasad Saha
2023, 47(10): 103105. doi: 10.1088/1674-1137/ace8f4
This study investigates the prospect of discovering strongly interacting gluinos in different multi-lepton channels with lepton multiplicities greater than or equal to 2 at LHC RUN-III, considering several pMSSM scenarios. The effectiveness of the multivariate analysis (MVA) method with the boosted decision tree (BDT) algorithm is explored to obtain a better significance for different models. Promising results are obtained for the 3-lepton channels, indicating that the use of MVA methods can improve the sensitivity of the search for gluinos at LHC RUN-III. The study probes the multi-lepton signatures arising from gluinos via intermediate eweakinos and sleptons at an early stage of the LHC RUN-III. The heavier eweakinos can give rise to three or four lepton signals, in which the squark hierarchy between the L and R types plays a crucial role. The study considers two sets of benchmark points that satisfy all the collider constraints obtained from the LHC RUN-II data. Moreover, these sets of benchmark points are mostly consistent with WMAP/PLANCK data and the muon (g-2) constraint. The corresponding results from the MVA technique demonstrate that, even for an integrated luminosity of 270 \begin{document}$\rm fb^{-1}$\end{document}, the 5 σ discovery prospect of \begin{document}$3l+ {jets} + {{\not {E_T}}}$\end{document} for \begin{document}$M_{\tilde{g}}=1.8$\end{document} TeV in the wino type model is promising. The study also presents various other models that may emerge at the early stage of LHC RUN-III. Wino type models in the scenario where left squarks are light and right squarks are heavy exhibit the best prospect of discovering gluinos in multi-lepton channels in the LHC RUN-III experiment. The findings of this study provide crucial insights into the potential discovery of gluinos in multi-lepton channels.
Vector-like lepton searches at a muon collider in the context of the 4321 model
Qilong Guo, Leyun Gao, Yajun Mao, Qiang Li
2023, 47(10): 103106. doi: 10.1088/1674-1137/ace5a7
A feasibility study is performed on the search for vector-like leptons (VLLs) at a muon collider in the context of the "4321 model", an ultraviolet-complete model with rich collider phenomenology and the potential to explain several recent existing B physics measurements or anomalies. Pair production and decays of VLLs lead to an interesting final state topology with multi-jets and multi-tau leptons. In this study, we perform a Monte Carlo investigation with various machine learning techniques and examine the projected sensitivity on VLLs over a wide mass range at a TeV-scale muon collider. We find that a 3 TeV muon collider with only \begin{document}$ 10\ \mathrm{fb}^{-1} $\end{document} of data can be sensitive over the mass range of a VLL up to 1450 GeV in the "4321 model."
On the microscopic shell-model version of the Bohr-Mottelson collective model
H. G. Ganev
2023, 47(10): 104101. doi: 10.1088/1674-1137/ace67f
The recently proposed microscopic shell-model version of the Bohr-Mottelson (BM) collective model is considered in more detail in the coordinate representation. The latter possesses a clear and transparent physical meaning, which reveals several features of the new version of the collective model missed in the previous formulation. The relationship to the original BM model is considered, along with the relationships between the different limiting submodels of the microscopic version of the BM model, which closely resemble the relationships of the original Wilets-Jean and rotor models. The kinematically correct many-particle wave functions of the microscopic version of the BM model, conserving the experimentally observed integrals of motion, are shown to consist of collective irrotational-flow and intrinsic components \begin{document}$ - $\end{document} in accordance with the original BM unified model. The general BM Hamiltonian is obtained as a contraction limit of the microscopic many-particle nuclear Hamiltonian, or, alternatively, by restricting the latter to the scalar \begin{document}$ O(m) $\end{document} irreducible collective space.
${\boldsymbol{ U_A(1) }}$ symmetry restoration at high baryon density
Jianing Li, Jin Gui, Pengfei Zhuang
2023, 47(10): 104102. doi: 10.1088/1674-1137/ace81d
We study the relation between chiral and \begin{document}$ U_A(1) $\end{document} symmetries in the quark-meson model. Although quarks and mesons are described in mean field approximation, the topological susceptibility characterizing the \begin{document}$ U_A(1) $\end{document} breaking comprises two components: one controlled by the condensate and the other by the meson fluctuation. The \begin{document}$ U_A(1) $\end{document} restoration is governed by the competition of these components. In a hot medium, the condensates melt. However, the fluctuation is enhanced. Therefore, the \begin{document}$ U_A(1) $\end{document} symmetry cannot be solely restored via the temperature effect. Nevertheless, the baryon density reduces the condensates and fluctuation, and thereby, the \begin{document}$ U_A(1) $\end{document} symmetry can only be restored in a dense or dense and hot medium. The strange condensate plays a weak role in the susceptibility, and the chiral and \begin{document}$ U_A(1) $\end{document} symmetry restorations occur almost at the same critical point.
Estimation of radiative capture 13B(n, γ0+1)14B reaction rate in the modified potential cluster model
A.S. Tkachenko, N.A. Burkova, B.M. Yeleusheva, S.B. Dubovichenko
2023, 47(10): 104103. doi: 10.1088/1674-1137/acee55
We discuss current attempts to employ the modified potential cluster model to describe the available experimental data on the 13B(n, γ0+1)14B total cross-sections. The estimated results of the M1 and E1 transitions from the n13B scattering states to the ground and first excited states of 14B are presented. The 1st resonance at Ex = 1. 275 MeV (1+) is revealed in both the cross-section and reaction rate. Within the variation in the asymptotic constant, a thermal cross-section interval of 5.1 – 8.9 mb is proposed. Based on the theoretical total cross-sections at energies of 0.01 eV to 5 MeV, we calculate the reaction rate in the temperature range of 0.01 to 10T9. The ignition T9 values of the 13B(n, γ0+1)14B reaction depending on a neutron number density \begin{document}$ {\bar n_n} $\end{document} of ~ 1022 cm−3 are determined. The radiative neutron capture reaction rates on the boron 10-13B and carbon 12-14С isotopes are compared.
Heavy ion fusion of spherical nuclei
H.C. Manjunatha, N. Sowmya, L. Seenappa, P.S. Damodara Gupta, N. Manjunatha
2023, 47(10): 104104. doi: 10.1088/1674-1137/acea21
We study the experimental and theoretical fusion reactions of compound nuclei synthesized using different projectile-target systems, among which at least one projectile/target nucleus is spherical. The first part of this study analyses the fusion cross sections obtained using different projectile-target combinations in the synthesis of polonium (Po), thorium (Th), and nobelium (No). In the second part of this study, we suggest the fusion reaction to synthesize the superheavy element Z = 122. We select three nuclei, polonium (Po), thorium (Th), and nobelium (No), which are synthesized using various projectile-target combinations. We also investigate fusion reactions such as\begin{document}$^{90}$\end{document}Zr(\begin{document}$^{208}$\end{document}Pb, 2n)\begin{document}$^{296}$\end{document}122 . This study may be a milestone in the synthesis of the superheavy element Z = 122.
Spin alignment of vector mesons from quark dynamics in a rotating medium
Minghua Wei, Mei Huang
2023, 47(10): 104105. doi: 10.1088/1674-1137/acf036
Vorticities in heavy-ion collisions (HICs) are supposed to induce spin alignment and polarization phenomena of quarks and mesons. In this work, we analyze the spin alignment of vector mesons ϕ and ρ induced by rotation from quark dynamics in the framework of the Nambu-Jona-Lasinio (NJL) model. The rotating angular velocity induces mass splitting of spin components for vector \begin{document}$ \phi,\rho $\end{document} mesons \begin{document}$ M_{\phi,\rho}(\Omega)\simeq M_{\phi,\rho}(\Omega=0)-s_{z}\Omega $\end{document}. This behavior contributes to the spin alignment of vector mesons \begin{document}$ \phi,\rho $\end{document} in an equilibrium medium and naturally explains the negative deviation of \begin{document}$ \rho_{00}-1/3 $\end{document} for vector mesons. Incidentally, the positive deviation of \begin{document}$ \rho_{00}-1/3 $\end{document} under the magnetic field can also be easily understood from quark dynamics.
Reconstruction of baryon number distributions
Chuang Huang, Yang-yang Tan, Rui Wen, Shi Yin, Wei-jie Fu
2023, 47(10): 104106. doi: 10.1088/1674-1137/aceee1
The maximum entropy method (MEM) and Gaussian process (GP) regression, which are both well-suited for the treatment of inverse problems, are used to reconstruct net-baryon number distributions based on a finite number of cumulants of the distribution. Baryon number distributions across the chiral phase transition are reconstructed. It is deduced that with the increase of the order of cumulants, distribution in the long tails, i.e., far away from the central number, would become increasingly important. We also reconstruct the distribution function based on the experimentally measured cumulants at the collision energy \begin{document}$\sqrt{s_{_{NN}}}=7.77$\end{document} GeV. Given the sizable error of the fourth-order cumulant measured in the experiments, the calculation of MEM shows that with the increasing fourth-order cumulant, there is another peak in the distribution function developed in the region of the large baryon number. This unnaturalness observed in the reconstructed distribution function could in turn be used to constrain the cumulants measured in the experiments.
Decomposition of multi-particle azimuthal correlations in Q-cumulant analysis
L. Nađđerđ, J. Milošević, D. Devetak, Fu-Qiang Wang
2023, 47(10): 104107. doi: 10.1088/1674-1137/acee56
The method of Q-cumulants is a powerful tool for studying the fine details of azimuthal anisotropies in high energy nuclear collisions. This paper presents a new method, based on mathematical induction, to evaluate the analytical form of high-order Q-cumulants. The capability of this method is demonstrated via a toy model that uses the elliptic power distribution to simulate the anisotropic emission of particles, quantified in terms of Fourier flow harmonics \begin{document}$ {v_n} $\end{document}. The method can help in studying the large amount of event statistics that can be collected in the future and allow measurements of the very high central moments of the \begin{document}$ {v_2} $\end{document} distribution. This can, in turn, facilitate progress in understanding the initial geometry, the input to the hydrodynamic calculations of medium expansion in high energy nuclear collisions, and the constraints on it.
Study of various ground state decay mechanisms of Actinide nuclei
Chahat Jindal, Nitin Sharma, Manoj K. Sharma
2023, 47(10): 104108. doi: 10.1088/1674-1137/ace9c4
The special property of the actinide mass region is that nuclei belonging to this group are radioactive and undergo different ground state processes, such as alpha decay, cluster radioactivity (CR), heavy particle radioactivity (HPR), and spontaneous fission (SF). In this study, the probable radioactive decay modes of the heavy mass region (Z = 89−102) are studied within the framework of the preformed cluster model (PCM). In the PCM, the radioactive decay modes are explored in terms of the preformation probability (\begin{document}$ P_0 $\end{document}) and penetration probability (P) at the turning point \begin{document}$ R_a $\end{document}, where the penetration of fragments is initiated [R\begin{document}$ _a $\end{document} = R\begin{document}$ _T $\end{document}(touching state) + \begin{document}$ \Delta R $\end{document}(neck length parameter)]. First, the alpha decay half-lives are calculated for light and heavy nuclei, and \begin{document}$ R_a $\end{document} points are obtained by optimizing the neck length parameter. These \begin{document}$ R_a $\end{document} points are further employed to fix the Q-value dependent turning point (\begin{document}$ R_a $\end{document}(Q)). Then, using the (\begin{document}$ R_a $\end{document}(Q)) relation, the decay half-lives are computed, and the calculated results are compared with the available theoretical and experimental data. The isotopical trend of \begin{document}$ P_0 $\end{document} and P is studied with respect to the mass number of the parent and daughter nucleus, respectively. The CR and HPR channels are also explored, and a comparison of calculated data is conducted with the available literature. Comparative analysis of the fragmentation potential and preformation probability is carried out for alpha decay and SF. The mass distribution of the nuclei is studied as a function of fragment mass (A\begin{document}$ _2 $\end{document}) by considering the spherical and hot-compact deformation of the decaying fragments. Finally, the most probable fission fragments are identified using the fragmentation structure, and the corresponding fission fragment total kinetic energy of the identified fragments is calculated and compared with available data, wherever applicable.
Parameter estimation for Einstein-dilaton-Gauss-Bonnet gravity with ringdown signals
Cai-Ying Shao, Yu Hu, Cheng-Gang Shao
2023, 47(10): 105101. doi: 10.1088/1674-1137/ace522
Future space-based gravitational-wave detectors will detect gravitational waves with high sensitivity in the millihertz frequency band, providing more opportunities to test theories of gravity than ground-based detectors. The study of quasinormal modes (QNMs) and their application in gravity theory testing have been an important aspect in the field of gravitational physics. In this study, we investigate the capability of future space-based gravitational wave detectors, such as LISA, TaiJi, and TianQin, to constrain the dimensionless deviating parameter for Einstein-dilaton-Gauss-Bonnet (EdGB) gravity with ringdown signals from the merger of binary black holes. The ringdown signal is modeled by the two strongest QNMs in EdGB gravity. Considering time-delay interferometry, we calculate the signal-to-noise ratio of different space-based detectors for ringdown signals to analyze their capabilities. The Fisher information matrix is employed to analyze the accuracy of parameter estimation, with particular focus on the dimensionless deviating parameter for EdGB gravity. The impact of the parameters of gravitational wave sources on the estimation accuracy of the dimensionless deviating parameter is also studied. We find that the constraint ability of EdGB gravity is limited because the uncertainty of the dimensionless deviating parameter increases with a decrease in the dimensionless deviating parameter. LISA and TaiJi offer more advantages in constraining the dimensionless deviating parameter to a more accurate level for massive black holes, whereas TianQin is more suited to less massive black holes. The Bayesian inference method is used to perform parameter estimation on simulated data, which verifies the reliability of the conclusion.
Thermodynamic quantities and phase transitions of five-dimensional de Sitter hairy spacetime
Xin-Ping Li, Li-Chun Zhang, Yu-Bo Ma, Huai-Fan Li
2023, 47(10): 105102. doi: 10.1088/1674-1137/ace8f5
In this study, we take the mass, electric charge, hair parameter, and cosmological constant of five-dimensional de Sitter hairy spacetime as the state parameters of the thermodynamic system, and when these state parameters satisfy the first law of thermodynamics, the equivalent thermodynamic quantities of spacetime and the Smarr relation of five-dimensional de Sitter hairy spacetime are obtained. Then, we study the thermodynamic characteristics of the spacetime described by these equivalent thermodynamic quantities and find that de Sitter hairy spacetime has a phase transition and critical phenomena similar to those of van de Waals systems or charged AdS black holes. It is shown that the phase transition point of de Sitter hairy spacetime is determined by the ratio of two event horizon positions and the cosmic event horizon position. We discuss the influence of the hair parameter and electric charge on the critical point. We also find that the isochoric heat capacity of the spacetime is not zero, which is consistent with the ordinary thermodynamic system but differs from the isochoric heat capacity of AdS black holes, which is zero. Using the Ehrenfest equations, we prove that the critical phase transition is a second order equilibrium phase transition. Research on the thermodynamic properties of five-dimensional de Sitter hairy spacetime lays a foundation for finding a universal de Sitter spacetime thermodynamic system and studying its thermodynamic properties. Our universe is an asymptotically dS spacetime, and the thermodynamic characteristics of de Sitter hairy spacetime will help us understand the evolution of spacetime and provide a theoretical basis to explore the physical mechanism of the accelerated expansion of the universe.
Physical aspects of ${ \boldsymbol{f}(\boldsymbol R,\boldsymbol G_{\boldsymbol\mu \boldsymbol\nu}\boldsymbol T^{\boldsymbol\mu \boldsymbol\nu})} $ modified gravity theories
Mihai Marciu, Dana Maria Ioan
2023, 47(10): 105103. doi: 10.1088/1674-1137/ace81e
The paper extends basic Einstein–Hilbert action by incorporating an invariant derived from a specific contraction between the Einstein tensor and energy momentum tensor. This represents a non–minimal coupling between the space–time geometry and matter fields. The fundamental Einstein–Hilbert action is extended by considering a generic function \begin{document}$ {f}(R,G_{\mu \nu}T^{\mu \nu}) $\end{document}. This function is subsequently dissected into its primary components: a geometric part reliant on the scalar curvature, and another segment encapsulating the interaction between geometry and matter fields. Distinct cosmological models are formulated at the backdrop of these dynamics, rooted in specific associations between the matter energy-momentum tensor and Einstein tensor. Upon deriving the consequent field equations, the cosmological model's physical implications are explored through a dynamical system analysis applied to diverse coupling functions. This exploration reveals that the current model aligns with various phases in the Universe's evolution, potentially elucidating several late-time historical epochs.
Simulation of high-frequency gravitational wave detection using modulated Gaussian beam
Mingjun Wu, Jin Li, Qingquan Jiang
2023, 47(10): 105104. doi: 10.1088/1674-1137/ace9c3
This paper investigates the feasibility of using a Li-Baker detector based on a modulated Gaussian beam to detect gravitational waves in the GHz band. The first-order perturbation photon fluxes (PPF, signal of the detector) and the background photon fluxes (BPF, main noise of the detector), which vary with time, and the transverse distance are calculated. The results show that their propagation directions and energy densities are much different in some areas. Apart from BPF, we also consider two other important noises: diffraction noise and shot noise. In the simulation, it is found that the diffraction noise and shot noise are both lower than the signal level. Meanwhile, the main noise (BPF) can be eliminated when the receiving screen is located in certain special transverse areas where the BPF direction is opposite to that of PPF. Thus, the signal to noise ratio (SNR) obtained using our detection method can reach up to \begin{document}$320$\end{document} in some transverse areas. These results are beneficial for the design of the Li-Baker detector.
Strong gravitational lensing of rotating regular black holes in non-minimally coupled Einstein-Yang-Mills theory
Ruanjing Zhang, Jiliang Jing, Zhipeng Peng, Qihong Huang
2023, 47(10): 105105. doi: 10.1088/1674-1137/acf489
The strong gravitational lensing of a regular and rotating magnetic black hole in non-minimally coupled Einstein-Yang-Mills theory is studied. We find that, with the increase of any characteristic parameters of this black hole, such as the rotating parameter a, magnetic charge q and EYM parameter λ, the angular image position \begin{document}$\theta_{\infty}$\end{document} and relative magnification \begin{document}$r_m$\end{document} decrease while deflection angle \begin{document}$\alpha(\theta)$\end{document} and image separation s increase. The results will degenerate to that of the Kerr case, RN case with magnetic charge and Schwarzschild case when we take some specific values for the black hole parameters. The results also show that, due to the small influence of magnetic charge and EYM parameters, it is difficult for current astronomical instruments to tell this black hole apart from a General Relativity one.