2024 Vol. 48, No. 12

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2024- Contents
2024, (12): 1-11.
Abstract:
2024-12 Contents
2024, 48(12): 1-3.
Abstract:
PARTICLES AND FIELDS
Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024
M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H.-R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, G. R. Che, G. Chelkov, C. Chen, C. H. Chen, Chao Chen, G. Chen, H. S. Chen, H. Y. Chen, M. L. Chen, S. J. Chen, S. L. Chen, S. M. Chen, T. Chen, X. R. Chen, X. T. Chen, Y. B. Chen, Y. Q. Chen, Z. J. Chen, Z. Y. Chen, S. K. Choi, G. Cibinetto, F. Cossio, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, C. Q. Deng, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, B. Ding, X. X. Ding, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, M. C. Du, S. X. Du, Y. Y. Duan, Z. H. Duan, P. Egorov, Y. H. Fan, J. Fang, S. S. Fang, W. X. Fang, Y. Fang, Y. Q. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q
2024, 48(12): 123001. doi: 10.1088/1674-1137/ad70a0
Abstract:
We present a measurement of the integrated luminosity of \begin{document}$ e^+e^- $\end{document} collision data collected by the BESIII detector at the BEPCII collider at a center-of-mass energy of \begin{document}$ E_{\rm cm} = 3.773 $\end{document} GeV. The integrated luminosities of the datasets taken from December 2021 to June 2022, from November 2022 to June 2023, and from October 2023 to February 2024 were determined to be \begin{document}$ 4.995 \pm 0.019 $\end{document} fb\begin{document}$ ^{-1} $\end{document}, \begin{document}$ 8.157 \pm 0.031 $\end{document} fb\begin{document}$ ^{-1} $\end{document}, and \begin{document}$ 4.191 \pm 0.016 $\end{document} fb\begin{document}$ ^{-1} $\end{document}, respectively, by analyzing large angle Bhabha scattering events. The uncertainties are dominated by systematic effects, and the statistical uncertainties are negligible. Our results provide essential input for future analyses and precision measurements.
Beauty-charm meson family with coupled channel effects and their strong decays
Wei Hao, Ruilin Zhu
2024, 48(12): 123101. doi: 10.1088/1674-1137/ad75f5
Abstract:
We systematically examined the mass spectra and their two-body hadronic decays of the beauty-charm meson family considering coupled channel effects. Our results can effectively explain the observed \begin{document}$B_c$\end{document} meson spectrum, and the prediction of the mass spectrum for unobserved beauty-charm mesons can be tested in future experiments. Compared with previous studies, we systematically examine the beauty-charm meson family within the coupled channel components. The \begin{document}$1S$\end{document} state in beauty-charm meson family has few percent of coupled channel component, while the \begin{document}$2S$\end{document}, \begin{document}$1P$\end{document}, and \begin{document}$1D$\end{document} states have more than ten percent of coupled channel component. The two-body hadronic decay widths of the \begin{document}$2^3P_2$\end{document} state is as narrow as 3 MeV. The two-body hadronic decay widths of \begin{document}$3^1S_0$\end{document}, \begin{document}$3^3S_1$\end{document}, \begin{document}$2^3D_1$\end{document}, \begin{document}$2D$\end{document}, \begin{document}$2D^\prime$\end{document}, and \begin{document}$2^3D_3$\end{document} are approximately 109, 67, 60, 57, 201, and 76 MeV, respectively. Furthermore, the mixing effects between \begin{document}$B_c(n{}^3L_L)$\end{document} and \begin{document}$B_c(n{}^1L_L)$\end{document} states are discussed.
Semileptonic and nonleptonic decays of ${\boldsymbol B^{*}_{\boldsymbol {u,d,s}} }$ in the covariant light-front approach
Si-Yang Wang, You-Ya Yang, Zhi-Jie Sun, Hao Yang, Peng Li, Zhi-Qing Zhang
2024, 48(12): 123102. doi: 10.1088/1674-1137/ad7247
Abstract:
The semileptonic and nonleptonic decays of the b-flavor vector mesons \begin{document}$B^{*}_{u,d,s}$\end{document} and \begin{document}$B_{c}^{*}$\end{document} are investigated within the covariant light-front quark model (CLFQM). By calculating the form factors of the transitions \begin{document}$B_{u, d, s, c}^{*}\to P$\end{document} under the CLFQM, with P denoting a pseudoscalar meson, i.e., \begin{document}$\pi, K, \eta_c(1S,2S), D_{(s)}, B_{(s)}$\end{document}, we predict and discuss several physical observables, including the branching ratios, polarization fractions \begin{document}$f_{L}, f_{\|}$\end{document} , and forward-backward asymmetries \begin{document}$A_{FB}$\end{document}. The total widths of the single-photon radiative decay channels for these b-flavor vector mesons are estimated using their partial widths. In these considered decays, one can find that the semileptonic decays \begin{document}$B_{s}^{*0}\to D_{s}^{-}\ell^{\prime+}{\nu}_{\ell^\prime}$\end{document} and \begin{document}$B_{c}^{*+}\to B_{s}^{0}\ell^{\prime+}{\nu}_{\ell^\prime}, \eta_{c}\ell^{\prime+}{\nu}_{\ell^\prime}$\end{document} , with \begin{document}$\ell^\prime$\end{document} being e or \begin{document}$\tau$\end{document}, and the nonleptonic channels \begin{document}$B_{c}^{*+}\to $\end{document}\begin{document}$ B^0_{s} \pi^{+}, B^0_{s} \rho^{+}$\end{document} have the largest branching ratios, which can reach up to the 10-7 order, and are most likely to be accessible at the future high-luminosity LHCb and Belle-II experiments.
Comprehensive constraints on fermionic dark matter-quark tensor interactions in direct detection experiments
Jin-Han Liang, Yi Liao, Xiao-Dong Ma, Hao-Lin Wang
2024, 48(12): 123103. doi: 10.1088/1674-1137/ad77b3
Abstract:
Effective field theory (EFT) provides a model-independent framework for interpreting the results of dark matter (DM) direct detection experiments. In this study, we demonstrate that the two fermionic DM-quark tensor operators \begin{document}$(\bar{\chi} {\rm{i}}\sigma^{\mu\nu} \gamma^5 \chi) (\bar{q} \sigma_{\mu\nu}q)$\end{document} and \begin{document}$ (\bar{\chi} \sigma^{\mu\nu} \chi) (\bar{q} \sigma_{\mu\nu} q) $\end{document} can contribute to the DM electric and magnetic dipole moments via nonperturbative QCD effects, in addition to the well-studied contact DM-nucleon operators. We then investigate the constraints on these two operators by considering both the contact and dipole contributions using the XENON1T nuclear recoil and Migdal effect data. We also recast other existing bounds on the DM dipole operators, derived from electron and nuclear recoil measurements in various direct detection experiments, as constraints on the two tensor operators. For \begin{document}$m_\chi \lesssim 1\;{\rm{GeV}}$\end{document}, our results significantly extend the reach of constraints on the DM-quark tensor operators to masses as low as \begin{document}$5\;{\rm{MeV}}$\end{document}, with the bound exceeding that obtained by the Migdal effect with only contact interactions by approximately an order of magnitude. In particular, for the operator \begin{document}$(\bar{\chi} \sigma^{\mu\nu}{\rm{i}}\gamma_5 \chi) (\bar{q} \sigma_{\mu\nu}q)$\end{document} with DM mass \begin{document}$m_\chi \gtrsim 10\;{\rm{GeV}}$\end{document}, the latest PandaX constraint on the DM electric dipole moment puts more stringent bounds than the previous direct detection limit. We also briefly discuss the constraints obtained from experiments other than direct detection.
Charm physics with overlap fermions on 2+1-flavor domain wall fermion configurations
Dong-Hao Li, Ying Chen, Ming Gong, Keh-Fei Liu, Zhaofeng Liu, Ting-Xiao Wang, (χQCD Collaboration)
2024, 48(12): 123104. doi: 10.1088/1674-1137/ad736f
Abstract:
Decay constants of pseudoscalar mesons D, \begin{document}$ D_s $\end{document}, \begin{document}$ \eta_c $\end{document} and vector mesons \begin{document}$ D^* $\end{document}, \begin{document}$ D_s^* $\end{document}, \begin{document}$ J/\psi $\end{document} are determined from the \begin{document}$ N_f=2+1 $\end{document} lattice QCD at a lattice spacing \begin{document}$ a\sim0.08 $\end{document} fm. For vector mesons, the decay constants defined by tensor currents are given in the \begin{document}$ {{\overline{{\rm{MS}}}}} $\end{document} scheme at \begin{document}$ 2 $\end{document} GeV. The calculation is performed on domain wall fermion configurations generated by the RBC-UKQCD collaborations and the overlap fermion action is used for the valence quarks. Comparing the current results with our previous results at a coarser lattice spacing \begin{document}$ a\sim0.11 $\end{document} fm provides a better understanding of the discretization error. We obtain \begin{document}$ f_{D_s^*}^T({{\overline{{\rm{MS}}}}},\text{ 2 GeV})/f_{D_s^*}=0.909(18) $\end{document} with a better precision than our previous result. Combining our \begin{document}$ f_{D_s^*}=277(11) $\end{document} MeV with the total width of \begin{document}$ D_s^* $\end{document} determined in a recent study gives a branching fraction \begin{document}$ 4.26(52)\times10^{-5} $\end{document} for \begin{document}$ D_s^* $\end{document} leptonic decay.
Study of singly anti-charmed pentaquark production in b-factory
Xiao-Hui Hu, Ye Xing
2024, 48(12): 123105. doi: 10.1088/1674-1137/ad77b2
Abstract:
The b-factories, such as BelleII, BarBar, and LHCb, emphasize the increasing importance of exotic hadron research. In this paper, we discuss the possible production of singly anti-charmed pentaquark states \begin{document}$\bar{c}q qqq$\end{document} from B mesons in a b-factory under \begin{document}$S U$\end{document}(3) symmetry analysis. Discussions of both possibilities have been driven by the hypothesis that the pentaquark state considered in this work, known as the lowest lying state \begin{document}$P_{\bar c}$\end{document}, could be bound or unbound. We find the golden channels for the production of the pentaquark ground states, such as \begin{document}$B^0 \to {P}_{\bar{c}sudu}^{(\prime) 0}\Sigma^0$\end{document}. We further estimate the branching ratios for the production of the ground states \begin{document}$P_{\bar c}$\end{document} from B meson decays. Thus, multiple channels are available for experiments, which may remove certain obstacles to the discovery of new pentaquark states.
Operators of quantum theory of Dirac's free field
Ion I. Cotăescu
2024, 48(12): 123106. doi: 10.1088/1674-1137/ad745c
Abstract:
The Pryce (e) spin and position operators of the quantum theory of Dirac's free field were re-defined and studied recently with the help of a new spin symmetry and suitable spectral representations [Eur. Phys. J. C 82, 1073 (2022)]. This approach is generalized here, associating a pair of integral operators acting directly on particle and antiparticle wave spinors in momentum representation to any integral operator in configuration representation, acting on mode spinors. This framework allows an effective quantization procedure, giving a large set of one-particle operators with physical meaning as the spin and orbital parts of the isometry generators, the Pauli-Lubanski and position operators, or other spin-type operators proposed to date. Special attention is paid to the operators that mix the particle and antiparticle sectors whose off-diagonal associated operators have oscillating terms producing Zitterbevegung. The principal operators of this type, including the usual coordinate operator, are derived here for the first time. As an application, it is shown that an apparatus measuring these new observables may prepare and detect one-particle wave packets moving uniformly without Zitterbewegung or spin dynamics, spreading in time normally as any other relativistic or even non-relativistic wave packet.
NUCLEAR PHYSICS
Measurements of the 128Te(n, 2n)127m,gTe reaction cross sections and isomeric cross section ratio of 127m,gTe at the neutron energy of 14 MeV
Junhua Luo, Long He, Liang Zhou, Li Jiang
2024, 48(12): 124001. doi: 10.1088/1674-1137/ad7370
Abstract:
In this study, measurements of the 128Te(n, 2n)127m,gTe reaction cross sections and the computation of the isomeric cross section ratio were performed around the neutron energy of 13−15 MeV. We used a γ-ray spectrometric technique to conduct the measurements. The neutron energy was produced by the 3H(d,n)4He reaction. For the 128Te(n, 2n)127m,gTe reaction, the excited state, ground state, total cross section, and isomeric cross section ratio were determined using the TALYS-1.96 code, a theoretical nuclear model that allows for variations in density options. The initial experimental data, assessed nuclear data, and theoretical calculations based on the TALYS-1.96 algorithm were compared with the measurement results. The new data produced by this study are essential for validating nuclear models and establishing parameters for nuclear reactions.
Scissors vibration and its collective rotation in a microscopic investigation
Fang-Qi Chen
2024, 48(12): 124101. doi: 10.1088/1674-1137/ad6e61
Abstract:
The intrinsic vibrational motion and the rotational behavior of the scissors mode in well deformed nuclei are investigated with an angular-momentum-projected approach, which is interpreted as a generator-coordinate-method with the generator coordinates corresponding to the degrees of freedom of interest. The picture of the intrinsic and rotational motion of the scissors mode is illustrated from the collective wave function within the framework of the generator-coordinate-method. The harmonicity of the scissors vibration is found to arise naturally from the present model but can be disturbed by the Coriolis effect as spin increases. The odd and even spin members of the rotational band based on the scissors mode rotate about different axes perpendicular to each other, leading to the flipping moment of inertia and the consequent splitting behavior that has been suggested previously.
Predicting 28Si projectile fragmentation cross sections with Bayesian neural network method
Ying-Hua Dang, Jun-Sheng Li, Dong-Hai Zhang
2024, 48(12): 124102. doi: 10.1088/1674-1137/ad6c0a
Abstract:
This study utilizes the Bayesian neural network (BNN) method in machine learning to learn and predict the cross-sectional data of 28Si projectile fragmentation for different targets at different energies and to quantify the uncertainty. The detailed modeling process of the BNN is presented, and its prediction results are compared with those of the Cummings, Nilsen, EPAX2, EPAX3, and FRACS models and experimental measurement values. The results reveal that, compared with other models, the BNN method achieves the smallest root-mean-square error (RMSE) and the highest agreement with the experimental values. Only the BNN method and FRACS model show a significant odd-even staggering effect; however, the results of the BNN method are closer to the experimental values. Furthermore, the BNN method is the only model capable of reproducing data features with low cross-section values at Z = 9, and the average ratio of the predicted to experimental values of the BNN is close to 1.0. These results indicate that the BNN method can accurately reproduce and predict the fragment production cross sections of 28Si projectile fragmentation and demonstrate its ability to capture key data characteristics.
Ab initio study of Z(N) = 6 magicity
He Li, H. J. Ong, Dong-Liang Fang, I. A. Mazur, I. J. Shin, A. M. Shirokov, J. P. Vary, Peng Yin, Xing-Bo Zhao, Wei Zuo
2024, 48(12): 124103. doi: 10.1088/1674-1137/ad766e
Abstract:
The existence of magic numbers of protons and neutrons in nuclei is essential for understanding the nuclear structure and fundamental nuclear forces. Over decades, researchers have conducted theoretical and experimental studies on a new magic number, Z(N)=6, focusing on observables such as radii, binding energy, electromagnetic transition, and nucleon separation energies. We performed ab initio no-core shell model calculations for the occupation numbers of the lowest single particle states in the ground states of Z(N)=6 and Z(N)=8 isotopes (isotones). The results of our calculations do not support Z(N)=6 as a magic number over a range of atomic numbers. However, 14C and 14O exhibit the characteristics of double-magic nuclei.
Pairing phase transition in the odd-A nuclei: identification and classification
Yumeng Wang, Yuhang Gao, Lang Liu
2024, 48(12): 124104. doi: 10.1088/1674-1137/ad7011
Abstract:
Research on the pairing phase transition in the odd-A nucleus \begin{document}$ ^{161}\text{Dy} $\end{document} is based on a sophisticated blend of the covariant density functional theory and the shell-model-like approach. It has been observed that variations in thermodynamic quantities at the critical temperature do not exclusively align with pairing phase transitions. The presence of an S-shaped heat capacity curve, often interpreted as an indicator of such transitions, does not offer a definitive confirmation. Additional factors, including the blocking effect, can modify the heat capacity curve and impede the transition process. The pairing phase transition in \begin{document}$ ^{161}\text{Dy} $\end{document}, which occurs approximately from 0.7 to 1.0 MeV, is unequivocally characterized as a first-order transition. Furthermore, the analysis of the impact of varying strengths of pairing correlations on these transitions reveals a nonlinear relationship, thereby adding complexity to the transition dynamics.
Possibility of synthesizing Z = 119 superheavy nuclei with Z > 20 projectiles
Shi Hao Zhu, Tian-Liang Zhao, Xiao Jun Bao
2024, 48(12): 124105. doi: 10.1088/1674-1137/ad86b0
Abstract:
We employ the dinuclear system (DNS) model combined with a statistical model to calculate the evaporation residue cross sections of the reaction systems \begin{document}$ ^{48} $\end{document}Ca + \begin{document}$ ^{243} $\end{document}Am, \begin{document}$ ^{48} $\end{document}Ca + \begin{document}$ ^{248} $\end{document}Cm, and \begin{document}$ ^{48} $\end{document}Ca + \begin{document}$ ^{249} $\end{document}Bk. The theoretical results successfully reproduce the experimental trends in the 3n and 4n evaporation channels of these reaction systems. To synthesize the new element \begin{document}$ Z = 119 $\end{document}, we predict the evaporation residue cross sections for three reaction systems (\begin{document}$ ^{54} $\end{document}Cr + \begin{document}$ ^{243} $\end{document}Am, \begin{document}$ ^{51} $\end{document}V + \begin{document}$ ^{248} $\end{document}Cm, and \begin{document}$ ^{50} $\end{document}Ti + \begin{document}$ ^{249} $\end{document}Bk) to select the most promising projectile-target combinations. We also note that the maximum cross sections predicted by our model and other methods appear to be below the detection limits of current experimental facilities, given the projectile-target combinations feasible under current experimental conditions. Therefore, synthesizing superheavy nuclei with \begin{document}$ Z = 119 $\end{document} will require improvements in beam intensity, detection techniques, and effective separation methods.
PARTICLE AND NUCLEAR ASTROPHYSICS AND COSMOLOGY
FLRW cosmology in metric-affine F(R,Q) gravity
Dinesh Chandra Maurya, K. Yesmakhanova, R. Myrzakulov, G. Nugmanova
2024, 48(12): 125101. doi: 10.1088/1674-1137/ad6e62
Abstract:
We investigated some Friedmann-Lemaître-Robertson-Walker (FLRW) cosmological models in the context of metric-affine \begin{document}$F(R,Q)$\end{document} gravity, as proposed in [arXiv: 1205.5266v6]. Here, R and Q are the curvature and nonmetricity scalars using non-special connections, respectively. We obtained the modified field equations using a flat FLRW metric. We then found a connection between the Hubble constant \begin{document}$H_{0}$\end{document}, density parameter \begin{document}$\Omega_{m0}$\end{document}, and other model parameters in two different situations involving scalars u and w. Next, we used new observational datasets, such as the cosmic chronometer (CC) Hubble and Pantheon SNe Ia datasets, to determine the optimal model parameter values through a Markov chain Monte Carlo (MCMC) analysis. Using these best-fit values of the model parameters, we discussed the results and behavior of the derived models. Further, we discussed the Akaike information criterion (AIC) and Bayesian information criterion (BIC) for the derived models in the context of the Lambda cold dark matter (ΛCDM). We found that the geometrical sector dark equation of state parameter \begin{document}$\omega_{de}$\end{document} behaves just like a dark energy candidate. We also found that both models are transit phase models. Model-I approaches the ΛCDM model in the late-time universe, whereas Model-II approaches quintessence scenarios.
Warm inflation triggered by entropies of some recent dark energy models within $ {\boldsymbol{f}\boldsymbol(\boldsymbol{Q}\boldsymbol)} $ gravity
Rabia Saleem, Muhammad Hamza Rasool, M. Israr Aslam, Iqra Shahid
2024, 48(12): 125102. doi: 10.1088/1674-1137/ad654e
Abstract:
This manuscript aims to study cosmic warm inflation (WI) in the framework of \begin{document}$f(Q)$\end{document}- gravity, where Q represents the nonmetricity (NM) scalar. To accomplish this task, we introduce the Tsallis, Renyi, and Barrow holographic dark energy (HDE) entropies into the standard Friedmann equations. Utilizing the slow-roll (SR) approximation, we find exact analytic solutions for the inflaton field, the effective potential necessary to produce inflation, and the scale factor for both low- and high-dissipative regimes. We calculate key parameters, including SR parameters, the number of e-folds, the scalar spectral index and its running, and finally tensor-to-scalar ratio to assess the accuracy of the chosen DE models in light of the published observational data. The allowed ranges of the involved free parameters are found from the limits on inflationary observables imposed by the Planck data. It is concluded that the obtained results are consistent with proposed theoretical predictions up to the \begin{document}$2\sigma$\end{document} confidence level.
Stability analysis of static spherical spacetime in extended symmetric teleparallel gravity
M. Zeeshan Gul, M. Sharif, Adeeba Arooj
2024, 48(12): 125103. doi: 10.1088/1674-1137/ad745b
Abstract:
Our manuscript aims to analyze the viability and stability of anisotropic stellar objects in the modified symmetric teleparallel gravity. A particular model of this extended theory is considered to formulate explicit field equations that govern the interaction between matter and geometry. The configuration of static spherical symmetric structures is examined through the Finch-Skea solution. However, the values of unknown constants in the metric potentials are evaluated by the Darmois junction conditions. For the viability of the proposed stellar objects, physical parameters including density, pressure, anisotropy, mass, energy constraints, compactness function, and redshift are analyzed. Furthermore, the stability of the proposed stellar objects is investigated by the causality condition, Herrera cracking approach, and adiabatic index. Our findings indicate that the proposed stellar objects are viable as well as stable in the presence of correction terms.
Additional observational features of the thin-shell wormhole by considering quantum corrections
Yun-Xian Chen, He-Bin Zheng, Ke-Jian He, Guo-Ping Li, Qing-Quan Jiang
2024, 48(12): 125104. doi: 10.1088/1674-1137/ad78d5
Abstract:
By considering an asymmetric thin-shell wormhole (ATSW) surrounded by an optically and geometrically thin disk, we investigate the luminosity distribution of this ATSW with the spacetime on two sides encoded with the renormalization group improved (RGI) parameters (Ω, γ). Although some light rays are absorbed into the throat in the vicinity of the wormhole, they return through the throat with certain conditions, unlike in the case of black holes. The spacetime on one side of the wormhole can capture the additional photons emitted from the thin disk, resulting in several interesting observable features of the wormhole. The results in this paper show that there are two additional orbit numbers n in the ATSW and six transfer functions, rather than three as in the black hole case. In this case, the ATSW indeed has a more complex observable structure, where some additional light rings arise naturally. For instance, there are two additional photon rings for the emitted Model 1. Moreover, we also find a new wide hump between the first and second additional photon rings in Model 2. The effects of Ω and γ on the observed images are clearly addressed throughout this study, and the influence of Ω is found to be larger. Finally, we conclude that the observations of the RGI-ATSW can help further distinguish it from other ATSWs and black holes when a thin accretion disk exists around it.
Unraveling the early universe’s equation of state and primordial black hole production with PTA, BBN, and CMB observations
Qing-Hua Zhu, Zhi-Chao Zhao, Sai Wang, Xin Zhang
2024, 48(12): 125105. doi: 10.1088/1674-1137/ad79d5
Abstract:
Pulsar timing array (PTA) data releases show strong evidence for a stochastic gravitational-wave background in the nanohertz band. When the signal is interpreted by a scenario of scalar-induced gravitational waves (SIGWs), we encounter overproduction of primordial black holes (PBHs). We wonder if varying the equation of state (EoS) of the early Universe can resolve this issue and thereby lead to a consistent interpretation of the PTA data. Analyzing a data combination of PTA, big-bang nucleosynthesis, and cosmic microwave background, we find that an epoch with EoS \begin{document}$w\sim{\cal{O}}(10^{-2})$\end{document} between the end of inflation and the onset of radiation domination can significantly suppress the production of PBHs, leading to alleviation of the PBH-overproduction issue. With the inferred interval \begin{document}$w=0.44_{-0.40}^{+0.52}$\end{document} at 95% confidence level, our scenario can interpret the PTA data just as well as the conventional scenario of SIGWs produced during the radiation domination.
The thermodynamic stability and phase structure of the Einstein-Euler-Heisenberg-AdS black holes
Yinan Zhao, Hongbo Cheng
2024, 48(12): 125106. doi: 10.1088/1674-1137/ad79d4
Abstract:
In both the canonical ensemble and grand canonical ensemble, the thermodynamic stability and phase structure of Einstein-Euler-Heisenberg-AdS black holes are studied. We derive the Hawking temperature, Helmholtz free energy, Gibbs potential, entropy and heat capacity of the black holes. We compute the minimum temperature to find that a phase transition may happen at the lowest point. The entropy-temperature diagram consists of two parts. The upper part belonging to the large black holes under the influence from the electromagnetic self-interactions keeps the positive heat capacity, leading the huge compact objects to survive. The lower curves corresponding to small black holes show that the heat capacity of the tiny black holes is negative, which means that the nonlinear-effect-corrected smaller sources will evaporate. The further discussions show that the nonlinear effect modifies the thermodynamic quantities, but the corrections limited by the nonlinear factor μ with allowed values can not change the properties and the phase structure fundamentally and thoroughly. We argue that the influence from self-interaction can not make the Einstein-Euler-Heisenberg-AdS black holes to split under the second law of thermodynamics.
Rapid identification of time-frequency domain gravitational wave signals from binary black holes using deep learning
Yu-Xin Wang, Shang-Jie Jin, Tian-Yang Sun, Jing-Fei Zhang, Xin Zhang
2024, 48(12): 125107. doi: 10.1088/1674-1137/ad73ac
Abstract:
Recent developments in deep learning techniques have provided alternative and complementary approaches to the traditional matched-filtering methods for identifying gravitational wave (GW) signals. The rapid and accurate identification of GW signals is crucial to the advancement of GW physics and multi-messenger astronomy, particularly considering the upcoming fourth and fifth observing runs of LIGO-Virgo-KAGRA. In this study, we used the 2D U-Net algorithm to identify time-frequency domain GW signals from stellar-mass binary black hole (BBH) mergers. We simulated BBH mergers with component masses ranging from 7 to 50 \begin{document}$ M_{\odot}$\end{document} and accounted for the LIGO detector noise. We found that the GW events in the first and second observation runs could all be clearly and rapidly identified. For the third observing run, approximately 80% of the GW events could be identified. In contrast to traditional convolutional neural networks, the U-Net algorithm can output time-frequency domain signal images corresponding to probabilities, providing a more intuitive analysis. In conclusion, the U-Net algorithm can rapidly identify the time-frequency domain GW signals from BBH mergers.