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2022, 46(12): 1-2.
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2022, (12): 1-10.
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2022, 46(12): 122001. doi: 10.1088/1674-1137/ac89d0
Abstract:
Conceptually, radii are amongst the simplest Poincaré-invariant properties that can be associated with hadrons and light nuclei. Accurate values of these quantities are necessary so that one may judge the character of putative solutions to the strong interaction problem within the Standard Model. However, limiting their ability to serve in this role, recent measurements and new analyses of older data have revealed uncertainties and imprecisions in the radii of the proton, pion, kaon, and deuteron. In the context of radius measurement using electron+hadron elastic scattering, the past decade has shown that reliable extraction requires minimisation of bias associated with practitioner-dependent choices of data fitting functions. Different answers to that challenge have been offered; and this perspective describes the statistical Schlessinger point method (SPM), in unifying applications to proton, pion, kaon, and deuteron radii. Grounded in analytic function theory, independent of assumptions about underlying dynamics, free from practitioner-induced bias, and applicable in the same form to diverse systems and observables, the SPM returns an objective expression of the information contained in any data under consideration. Its robust nature and versatility make it suitable for use in many branches of experiment and theory.
2022, 46(12): 122002. doi: 10.1088/1674-1137/ac87f1
Abstract:
It is well known that when vacuum polarization emerges in quantum electrodynamics, the non-linear interaction between electromagnetic fields should be considered. Moreover, the corresponding field of non-linear electrodynamics can have important effects on black hole physics. In this work, we focus on the relationship between an observable quantity, that is, the shadow radius, and the first-order phase transition of non-linear charged AdS black holes in the framework of Einstein-power-Yang-Mills gravity. The results show that, under a certain condition, there exists a first-order phase transition from the viewpoint of both the shadow radius and horizon radius, which depend on temperature (or pressure). From the viewpoint of the shadow radius, the phase transition temperature is higher than that from the viewpoint of the horizon radius under the same condition. This may be due to the non-linear Yang Mills charge and the gravitational effect. This indicates that the shadow radius can be regarded as a probe to reveal the thermodynamic phase transition information of black holes. The thermal profiles of coexistent large and small black hole phases when the system is undergoing the phase transition are presented for two different values of the non-linear Yang Mills charge parameter: \begin{document}$\gamma=1,\; 1.5$\end{document}. Furthermore, the effects of the non-linear Yang Mills charge parameter on the shadow radius and thermal profile are investigated.
2022, 46(12): 123001. doi: 10.1088/1674-1137/ac8bc9
Abstract:
JUNO is a multi-purpose neutrino observatory under construction in the south of China. This publication presents new sensitivity estimates for the measurement of the \begin{document}$\Delta m^2_{31}$\end{document}, \begin{document}$\Delta m^2_{21}$\end{document}, \begin{document}$\sin^2 \theta_{12}$\end{document}, and \begin{document}$\sin^2 \theta_{13}$\end{document} oscillation parameters using reactor antineutrinos, which is one of the primary physics goals of the experiment. The sensitivities are obtained using the best knowledge available to date on the location and overburden of the experimental site, the nuclear reactors in the surrounding area and beyond, the detector response uncertainties, and the reactor antineutrino spectral shape constraints expected from the TAO satellite detector. It is found that the \begin{document}$\Delta m^2_{21}$\end{document} and \begin{document}$\sin^2 \theta_{12}$\end{document} oscillation parameters will be determined to 0.5% precision or better in six years of data collection. In the same period, the \begin{document}$\Delta m^2_{31}$\end{document} parameter will be determined to about \begin{document}$0.2$\end{document}% precision for each mass ordering hypothesis. The new precision represents approximately an order of magnitude improvement over existing constraints for these three parameters.
2022, 46(12): 123101. doi: 10.1088/1674-1137/ac878c
Abstract:
Exclusive \begin{document}$\pi^0$\end{document} electroproduction is analyzed within the handbag approach based on Generalized Parton Distribution (GPDs) factorization. We consider the leading-twist contribution together with the transversity effects. It is shown that the transversity GPDs \begin{document}$H_{\rm T}$\end{document} and \begin{document}$\bar E_{\rm T}$\end{document} are essential in the description of the \begin{document}$\pi^0$\end{document} cross section. Predictions for the future Electron-Ion Collider of China (EicC) energy range are provided. It is found that transversity dominance \begin{document}$\sigma_{\rm T}\gg\sigma_{\rm L}$\end{document}, observed at low energies, is valid up to the EicC energy range.
2022, 46(12): 123102. doi: 10.1088/1674-1137/ac8789
Abstract:
A three Higgs-doublet model exhibiting \begin{document}$S_3$\end{document}-symmetry can predict the observed pattern of quark masses and their mixings. However, the same symmetry also introduces potential flavor-changing neutral currents (FCNCs) at the tree level. In this study, we assume that the scalar potential contains appropriate soft \begin{document}$S_3$\end{document}-breaking terms to maintain flexible choices of scalar masses. We identify the parameters in the Yukawa Lagrangian of the quark sector responsible for such FCNCs and constrain them using data from flavor physics observables, such as meson-decays and meson-mixings. We also validate the corresponding model parameter space via renormalization group evaluation.
2022, 46(12): 123103. doi: 10.1088/1674-1137/ac88bd
Abstract:
The perturbative quantum chromodynamics (PQCD) approach based on \begin{document}$k_T$\end{document} factorization has resulted in great achievements in the QCD calculation of hadronic B decays. By regulating the endpoint divergence by the transverse momentum of quarks in the propagators, one can perform the perturbation calculation for various diagrams, including annihilation type diagrams. In this paper, we review the current status of the PQCD factorization calculation of two-body charmless \begin{document}$B\to PP, PV, VV$\end{document}U decays up to next-to-leading order (NLO) QCD corrections. Two new power suppressed terms in the decaying amplitudes are also considered. Using universal input (non-perturbative) parameters, we collect the branching ratios and \begin{document}${C P}$\end{document} asymmetry parameters of all charmless two body B decays, which are calculated in the PQCD approach up to NLO. The results are compared with those of the QCD factorization approach, soft-collinear effective theory approach, and current experimental measurements. For most of the considered B meson decays, the PQCD results for branching ratios agree well with those of other approaches and experimental data. The PQCD predictions for the \begin{document}${C P}$\end{document} asymmetry parameters of many of the decay channels do not agree with those of other approaches but have better agreement with experimental data. The longstanding \begin{document}$K \pi$\end{document} puzzle regarding the pattern of the direct CP asymmetries of penguin-dominated \begin{document}$B \to K \pi$\end{document} decays can be understood after the inclusion of NLO contributions in PQCD. The NLO corrections and power suppressed terms play an important role in color suppressed and pure annihilation type B decay modes. These rare decays are more sensitive to different types of corrections, providing an opportunity to examine the factorization approach with more precise experimental measurements.
2022, 46(12): 123104. doi: 10.1088/1674-1137/ac88bb
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In the framework of the 3-3-1 model with neutral leptons, we investigate lepton-flavor-violating sources based on the Higgs mass spectrum, which has two neutral Higgs identified with the corresponding ones of the two-Higgs-doublet model. We note that at the \begin{document}$13\; {\rm{TeV}}$\end{document} scale of the LHC, the parameter space regions satisfy the experimental limits of \begin{document}$e_i \rightarrow e_j\gamma$\end{document} decays. These regions depend heavily on the mixing of exotic leptons but are predicted to have large \begin{document}$h^0_1\rightarrow \mu \tau$\end{document} signals. We also show that \begin{document}${\rm{Br}}(h^0_1\rightarrow \mu \tau)$\end{document} can reach a value of \begin{document}$10^{-4}$\end{document}.
2022, 46(12): 123105. doi: 10.1088/1674-1137/ac89d1
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In this study, we investigate quasi-two-body \begin{document}$B_{(s)}\to K^*\gamma\to K\pi\gamma$\end{document} decays in the perturbative QCD approach. Two-meson distribution amplitudes are introduced to describe the final state interactions of the \begin{document}$K\pi$\end{document} pair, which involve time-like form factors and Gegenbauer polynomials. We calculate the CP averaged branching ratios of the \begin{document}$B_{(s)}\to K^*\gamma\to K\pi\gamma$\end{document} decays. Our results are in agreement with newly updated data measured by Belle II. This suggests that it is more appropriate to analyze these quasi-two-body B decays in the three-body framework than the two-body framework. We also predict direct CP asymmetries for the considered decay modes and find that \begin{document}$A_{CP}(B_{u,d}\to K^*\gamma\to K\pi\gamma)$\end{document} is small and less than \begin{document}$1$\end{document}% in magnitude, whereas \begin{document}$A_{CP}(B_{s}\to$\end{document}\begin{document}$K^*\gamma\to K\pi\gamma)$\end{document} is larger and can reach a few percent. Our predictions can be tested in future B meson experiments.
2022, 46(12): 123106. doi: 10.1088/1674-1137/ac8c21
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Motivated by the analogous properties of \begin{document}$Z_c(3900/3885)$\end{document} and \begin{document}$Z_{cs}(3985/4000)$\end{document}, we tentatively assign \begin{document}$Z_c(4020/4025)$\end{document} as the \begin{document}$A{\bar{A}}$\end{document}-type hidden-charm tetraquark state with \begin{document}$J^{PC}=1^{+-}$\end{document}, where A denotes the axialvector diquark states, and explore \begin{document}$A{\bar{A}}$\end{document}-type tetraquark states without strange, with strange, and with hidden-strange via QCD sum rules in a consistent manner. We then explore the hadronic coupling constants in the two-body strong decays of tetraquark states without and with strange via QCD sum rules based on rigorous quark-hadron duality and acquire partial and total decay widths. The present calculations support assigning \begin{document}$Z_c(4020/4025)$\end{document} as the \begin{document}$A{\bar{A}}$\end{document}-type tetraquark state with \begin{document}$J^{PC}=1^{+-}$\end{document}, while the predictions for its strange cousin \begin{document}$Z_{cs}$\end{document} state can be confronted with experimental data in the future.
2022, 46(12): 123107. doi: 10.1088/1674-1137/ac8cd5
Abstract:
The W mass determination at the Tevatron CDF experiment reported a deviation from the SM expectation at the 7σ level. We discuss a few possible interpretations and their collider implications. We perform electroweak global fits under various frameworks and assumptions. We consider three types of electroweak global fits in the effective-field-theory framework: the S-T, S-T-\begin{document}$\delta G_F$\end{document}, and eight-parameter flavor-universal one. We discuss the amounts of tensions between different \begin{document}$m_W$\end{document} measurements reflected in these fits and the corresponding shifts in central values of these parameters. With these electroweak fit pictures in hand, we present a few different classes of models and discuss their compatibility with these results. We find that while explaining the \begin{document}$m_W$\end{document} discrepancy, the single gauge boson extensions face strong LHC direct search constraints unless the \begin{document}$Z'$\end{document} is fermiophobic (leptophobic), which can be realized if extra vector fermions (leptons) mix with the SM fermions (leptons). Vector-like top partners can partially generate the needed shift to the electroweak observables. The compatibility with the top squark is also studied in detail. We find that the non-degenerate top squark soft masses enhance the needed operator coefficients, enabling an allowed explanation compatible with current LHC measurements. Overall, more theoretical and experimental developments are highly in demand to reveal the physics behind this discrepancy.
2022, 46(12): 123108. doi: 10.1088/1674-1137/ac92d8
Abstract:
We study a double covering of modular \begin{document}$A_4$\end{document} flavor symmetry. To this end, we construct lepton models for canonical and radiative seesaw scenarios. Using irreducible doublet representations, heavier Majorana fermion masses are characterized by one free parameter that would differentiate from \begin{document}$A_4$\end{document} symmetry. symmetry. Through χ square numerical analysis, we demonstrate that both scenarios produce some predictions in case of normal hierarchy reproducing neutrino oscillation data. However, no solution satisfies the neutrino oscillation data in case of radiative seesaw of inverted hierarchy.
2022, 46(12): 123109. doi: 10.1088/1674-1137/ac92da
Abstract:
We conducted a detailed study on the properties of the total decay width of the Higgs decay channel \begin{document}$H\to gg$\end{document} up to \begin{document}$\alpha_s^6$\end{document}-order QCD corrections by using the newly suggested infinite-order scale-setting approach, which is based on both the principle of maximum conformality and intrinsic conformality. This approach is called PMC\begin{document}$_\infty$\end{document}. By using the PMC\begin{document}$_\infty$\end{document} approach, we observed that the conventional renormalization scale ambiguity in perturbative QCD calculation is eliminated, and the residual scale dependence due to unknown higher-order terms can also be highly suppressed. We then obtained an accurate perturbative QCD prediction on the total decay width, e.g., \begin{document}$\Gamma (H \to gg)|_{\rm PMC_\infty} =336.42^{+7.01}_{-6.92}$\end{document} keV, where the errors are squared averages of those from all the mentioned error sources.
2022, 46(12): 123110. doi: 10.1088/1674-1137/ac930b
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We study the dependence of the transverse mass distribution of charged leptons and the missing energy on parton distributions (PDFs) adapted to W boson mass measurements at the CDF and ATLAS experiments. We compare the shape variations of the distribution induced by different PDFs and find that the spread of predictions from different PDF sets can be significantly larger than the PDF uncertainty predicted by a specific PDF set. We suggest analyzing the experimental data using up-to-date PDFs to gain a better understanding of the PDF uncertainties in W boson mass measurements. We also perform a series of Lagrange multiplier scans to identify the constraints on the transverse mass distribution imposed by individual data sets in the CT18 global analysis. In the case of the CDF measurement, the distribution is mostly sensitive to d-quark PDFs in the intermediate x region, which are largely constrained by DIS and Drell-Yan data on deuteron targets and Tevatron lepton charge asymmetry data.
2022, 46(12): 123111. doi: 10.1088/1674-1137/ac8651
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In this study, the magnetic moments of hidden-charm strange pentaquark states with quantum numbers\begin{document}$J^P={\dfrac{1}{2}}^{\pm}$\end{document}, \begin{document}${\dfrac{3}{2}}^{\pm}$\end{document}, \begin{document}${\dfrac{5}{2}}^{\pm}$\end{document}, and \begin{document}${\dfrac{7}{2}}^{+}$\end{document}are calculated in the molecular, diquark-diquark-antiquark, and diquark-triquark models. The numerical results demonstrate that the magnetic moments change for different spin-orbit couplings within the same model and when involving different models with the same angular momentum.
2022, 46(12): 124001. doi: 10.1088/1674-1137/ac878a
Abstract:
The flux-averaged cross-sections \begin{document}$\langle{\sigma(E_{\rm{\gamma max}})}\rangle$\end{document} for the reactions \begin{document}${^{65}{\rm{Cu}}}(\gamma,n)^{64}{\rm{Cu}}$\end{document}, \begin{document}${^{63}{\rm{Cu}}}(\gamma,n)^{62}{\rm{Cu}}$\end{document}, \begin{document}${^{63}{\rm{Cu}}}(\gamma,2n)^{61}{\rm{Cu}}$\end{document} , and \begin{document}${^{63}{\rm{Cu}}}(\gamma,3n)^{60}{\rm{Cu}}$\end{document} have been measured within the bremsstrahlung end-point energy \begin{document}$E_{\rm{\gamma max}}$\end{document} range of 35–94 MeV. The experiments were performed with the electron beam from the NSC KIPT linear accelerator LUE-40 with the use of the activation and off-line γ-ray spectrometric techniques. Theoretical calculation of the flux-average cross-sections \begin{document}$\langle{\sigma(E_{\rm{\gamma max}})}\rangle_{\rm{th}}$\end{document} was conducted using the cross-section \begin{document}$\sigma(E)$\end{document} values from the TALYS1.95 code, run with default options. It is shown that the experimental average cross-sections for the reactions \begin{document}${^{65}{\rm{Cu}}}(\gamma,n)^{64}{\rm{Cu}}$\end{document}, \begin{document}${^{63}{\rm{Cu}}}(\gamma,n)^{62}{\rm{Cu}}$\end{document}, and \begin{document}${^{63}{\rm{Cu}}}(\gamma,2n)^{61}{\rm{Cu}}$\end{document} are systematically higher than the theoretical estimates based on the TALYS1.95 code. The obtained \begin{document}$\langle{\sigma(E_{\rm{\gamma max}})}\rangle$\end{document}values supplement the data of different laboratories for the \begin{document}$(\gamma,n)$\end{document} and \begin{document}$(\gamma,2n)$\end{document} reactions of \begin{document}${^{63}{\rm{Cu}}}$\end{document} and \begin{document}${^{65}{\rm{Cu}}}$\end{document}. For the reaction \begin{document}${^{63}{\rm{Cu}}}(\gamma,3n)^{60}{\rm{Cu}}$\end{document}, the values of \begin{document}$\langle{\sigma(E_{\rm{\gamma max}})}\rangle$\end{document} were measured for the first time.
2022, 46(12): 124101. doi: 10.1088/1674-1137/ac8867
Abstract:
The influence of the neck parameter on the fission dynamics at low excitation energy is studied based on the three-dimensional Langevin approach, in which the nuclear shape is described with the two-center shell model (TCSM) parametrization, and the elongation, mass asymmetry, and fragment deformation are set to be the generalized coordinates of the Langevin equation. We first study the influence of the neck parameter on the scission configuration. We find that there is almost no obvious correlation between the neck parameter \begin{document}$\epsilon$\end{document} and mass asymmetry η at the scission point, indicating that \begin{document}$\epsilon$\end{document} has no evident impact on the fragment mass distribution. The elongation \begin{document}$Z_0/R_0$\end{document} and its correlation with the mass asymmetry η at the scission point are clearly influenced by the neck parameter \begin{document}$\epsilon$\end{document}, which has a strong effect on the total kinetic energy (TKE) distribution of the fragments. The pre-neutron emission fragment mass distributions for 14 MeV n+ \begin{document}$^{233,235,238}$\end{document}U and \begin{document}$^{239}$\end{document}Pu are calculated, and then, based on these results, the post-neutron emission fragment mass distributions are obtained by using the experimental data of prompt neutron emission. The calculated post-neutron emission fragment mass distributions can reproduce the experimental data well. The TKE distributions for 14 MeV n+ \begin{document}$^{235}$\end{document}U fission are calculated for \begin{document}$\epsilon$\end{document}=0.25, 0.35, and 0.45, and the results show that the TKE distribution cannot be described very well for the three cases. However, the trend of the calculated TKE distribution with \begin{document}$\epsilon$\end{document} is just as expected from the scission configuration calculations. The results with \begin{document}$\epsilon$\end{document}=0.35 present a better agreement with the experiment data compared with the other two cases.
2022, 46(12): 124102. doi: 10.1088/1674-1137/ac8a8c
Abstract:
The level structure of the double-magic nucleus 34Si (Z = 14, N = 20) was investigated by evaluating the available data. On the basis of experimental results from the beta-decay and fusion-evaporation reactions, we established the level scheme by assigning spin-parities up to 61+ at 6233 keV. The high energy positions of the excited states are consistent with the magicity at 34Si, such as the 22+ state of the spherical ground band at 4.519 MeV and the 3-, 4-, and 5- states of the one-particle one-hole cross-shell states at approximately 4.5 MeV. This nucleus, for a long time, has attracted much attention because of, on one side, a proton bubble structure in the ground state and, on the other side, a deformation in the second 0+ state, 02+. By a comparison of the constructed level scheme with the shell model calculations, we describe the emerging structures in the ground and second 0+ states and the negative-parity 3- states within the framework of the shell model context. We propose a deformed rotational band with the cascading 62+ − 41+ − 21+ transitions built on the 02+ state.
2022, 46(12): 124103. doi: 10.1088/1674-1137/ac8c23
Abstract:
We calculate the HBT radius \begin{document}$R_{\rm {s}}$\end{document} for \begin{document}$\pi^+$\end{document} with Coulomb interaction using the string melting version of a multiphase transport (AMPT) model. We study the relationship between the single-particle space-momentum angle and the particle sources and discuss HBT radii without single-particle space-momentum correlation. Additionally, we study the Coulomb interaction effect on the numerical connection between the single-particle space-momentum angle distribution and the transverse momentum dependence of \begin{document}$R_{\rm {s}}$\end{document}.
2022, 46(12): 124104. doi: 10.1088/1674-1137/ac92d9
Abstract:
A partial wave scattering matrix for the total effective complex potential of nucleus nucleus collisions is proposed to easily analyze the angular variations of elastic scattering and fusion cross-sections simultaneously with a unique potential. The expectation value of the imaginary part of the potential calculated using the distorted waves from the full potential in the elastic channel accounts for \begin{document}$\sigma_r$\end{document}. This is equated to the sum of the cross-sections due to absorption in different regions of the potential where the imaginary part is actively present. The potential is taken as energy independent and features a weakly absorbing nature, which supports the resonance states in various partial wave trajectories. Therefore, these resonances show oscillatory behavior changes with respect to energy \begin{document}$D(E_{{\rm c.m.}})=\dfrac{{\rm d}^{2}(E_{{\rm c.m.}}\sigma_{{\rm fus}})}{{\rm d}E_{{\rm c.m.}}^{2}}$\end{document}. In this paper, we discuss elastic scattering and fusion cross-sections in conjunction with the results of \begin{document}$D(E_{{\rm c.m.}})$\end{document} for the \begin{document}$\rm ^{16}O+^{92}Zr$\end{document} system.
2022, 46(12): 125101. doi: 10.1088/1674-1137/ac878b
Abstract:
We study the dynamical properties of the thermodynamic phase transition (PT) of a charged AdS black hole (BH) with a global monopole via the Gibbs free energy landscape and reveal the effects of the global monopole on the kinetics of thermodynamic PTs. First, we briefly review the thermodynamics of a charged AdS BH with a global monopole. Then, we introduce the Gibbs free energy landscape to investigate the thermodynamic stability of the BH states. Because of thermal fluctuations, the small black hole (SBH) state can transit to a large black hole (LBH) state, and vice versa. Further, we use the Fokker-Planck equation with the reflecting boundary condition to study the probability evolution of the BH state with and without a global monopole separately. It is found that for both the SBH and LBH states, the global monopole could slow down the evolution of the BH state. In addition, we obtain the relationship between the first passage time and the monopole parameter η. The result shows that as the monopole parameter η increases, the mean first passage time becomes longer for both the SBH and LBH states.
2022, 46(12): 125102. doi: 10.1088/1674-1137/ac87f0
Abstract:
We investigate generalized Jackiw-Teitelboim gravity, coupling the dilaton field with two scalar matter fields. We obtain the equations of motion for the fields and investigate a linear perturbation of the solutions in general. We study two specific situations that allow for analytic solutions with topological behavior and check how the dilaton field, the warp factor and the Ricci scalar behave. In particular, we show how the parameters can be used to modify the structure of the solutions. Moreover, the perturbations are, in general, described by intricate coupled differential equations, but in some specific cases, we can construct the corresponding zero modes analytically.
2022, 46(12): 125103. doi: 10.1088/1674-1137/ac8868
Abstract:
In this study, we investigate the collapsing scenario for the k-essence emergent Vaidya spacetime in the context of massive gravity's rainbow. For this study, we consider that the background metric is Vaidya spacetime in massive gravity's rainbow. We show that the k-essence emergent gravity metric closely resembles the new type of generalized Vaidya massive gravity metric with the rainbow deformations for null fluid collapse, where we consider the k-essence scalar field as a function solely of the advanced or the retarded time. The k-essence emergent Vaidya massive gravity rainbow mass function is also different. This new type k-essence emergent Vaidya massive gravity rainbow metric satisfies the required energy conditions. The existence of a locally naked central singularity and the strength and strongness of the singularities for the rainbow deformations of the k-essence emergent Vaidya massive gravity metric are the interesting outcomes of the present work.
2022, 46(12): 125104. doi: 10.1088/1674-1137/ac8c22
Abstract:
In this study, we consider an open system from the thermodynamic perspective for an adiabatic FRW universe model in which particle creation occurs within the system. In this case, the modified continuity equation is obtained, and then, we make it correspond to the continuity equation of \begin{document}$f(T)$\end{document} gravity. Therefore, we take \begin{document}$f(T)$\end{document} gravity with a viscous fluid in the flat-FRW metric, where T is the torsion scalar. We assume the contents of the universe to be dark matter and dark energy and consider an interaction term between them. An interesting point of this study is that we make the modified continuity equation resulting from particle creation equivalent to the matter continuity equation resulting from \begin{document}$f(T)$\end{document} gravity. The result of this evaluation establishes a relationship between the number of particles and scale factor. In what follows, we write the corresponding cosmological parameters in terms of the number of particles and also reconstruct the number of particles in terms of the redshift parameter. We then parameterize the Hubble parameter derived from power-law cosmology with 51 data points from the Hubble observational parameter data. Next, we plot the corresponding cosmological parameters for dark energy in terms of the redshift to investigate the accelerated expansion of the universe. In addition, by using the sound speed parameter, we discuss the stability and instability analyses of the present model in different eras of the universe. Finally, we plot the density parameter values for dark energy and dark matter in terms of the redshift parameter.
2022, 46(12): 125105. doi: 10.1088/1674-1137/ac8e53
Abstract:
In this work, the microstructure of charged AdS black holes under minimal length effects is investigated. We study the thermodynamics of black holes in the extended phase space, where the cosmological constant is regarded as the thermodynamic pressure. The modified Hawking temperature and phase transition are obtained based on the generalized uncertainty principle (GUP). Then, using thermodynamic geometry, the microstructure of black holes can be determined by the ratio of the GUP parameter to charge. For a small ratio, the black hole exhibits the typical RN-AdS microstructure with van der Waals phase transition and repulsive/attractive interactions. As the ratio increases, the reentrant phase transition is observed, and both the repulsion-attraction coexisted and the attraction dominated black holes are noted. For a large ratio, the black hole behaves like a Schwarzchild-AdS black hole in which neither phase transition nor repulsive interaction are observed. These results suggest that the GUP effect will reduce the repulsive interaction presented by the charged AdS black hole.
2022, 46(12): 125106. doi: 10.1088/1674-1137/ac90af
Abstract:
In this study, we investigate the influence of the angular momentum of a charged particle around non-extremal and extremal Einstein-Maxwell-Dilaton-Axion black holes on the Lyapunov exponent. The angular momentum's ranges and spatial regions where the bound of the exponent is violated are found for certain values of the rotation parameter and dilatonic constant of the black holes. This violation always exists when the rotation parameter is large enough and the rotation direction of the particle is opposite to that of the black holes. The spatial region outside the extremal black hole of the violation is relatively large. In the near-horizon regions of the extremal black holes, the violation depends on the rotation directions of the black holes and particles and not depend on the value of the angular momentum.
2022, 46(12): 125107. doi: 10.1088/1674-1137/ac917f
Abstract:
In this study, we observe that, in the presence of the string cloud parameter a and the quintessence parameter γ, with the equation of state parameter \begin{document}$\omega_q={-2}/{3}$\end{document}, the radius of the shadow of the Schwarzschild black hole increases as compared with that in the pure Schwarzschild black hole case. The existence of both quintessential dark energy and the cloud of strings increases the shadow size; hence, the strength of the gravitational field around the Schwarzschild black hole increases. Using the data collected by the Event Horizon Telescope (EHT) collaboration for M87* and Sgr A*, we obtain upper bounds on the values of a and γ. Further, we see the effects of a and γ on the rate of emission energy for the Schwarzschild black hole. We notice that the rate of emission energy is higher in the presence of clouds of strings and quintessence. Moreover, we study the weak deflection angle using the Gauss-Bonnet theorem. We show the influence of a and γ on the weak deflection angle. We notice that both a and γ increase the deflection angle α.