Chinese Journal of Physics最新文献

Propagating surface plasmon polaritons (SPPs) provide an important platform for the design of various photoelectric devices such as nanometer-scale ultrafast electron sources. Here, a high-brightness nanoscale photoelectron source in a plasmon focusing lens with a nanohole is investigated using time-of-flight photoemission electron microscopy (TOF-PEEM). By exploiting the high spatial resolution of TOF-PEEM, it is found that the photoemission was localized at the nanoscale in both x and y directions. In addition, a large multiphoton photoemission enhancement was achieved and a strong-field effect was observed due to the interplay between the SPP and the nanohole. This paper provides a new idea for the development of the high-brightness nanoscale photoelectron sources and a deep understanding of the interplay between SPP and LSP.

In this article, we utilize the non-relativistic potential model to investigate the mass spectra of exotic fully-heavy tetraquark states $QQ\bar{Q}\bar{Q}$ ($Q\in \{c,b\}$), specifically examining $\left[cc\right]\left[\bar{c}\bar{c}\right]$ and $\left[bb\right]\left[\bar{b}\bar{b}\right]$.We treat these states as diquark–antidiquark bound systems governed by a diquark–antidiquark color Coulomb plus confining linear potential.To determine the masses of the ground state and its radially and orbitally excited states for fully-heavy tetraquark states, we incorporate perturbative spin–spin, spin–orbit and spin–tensor interaction potentials.Our results of masses of $nS$, $nP$ and $nD$ states of fully heavy tetraquark states are compared with both other theoretical predictions and experimental data.Remarkably, our results closely align with theoretical as well as experimental observations.Furthermore, our findings also support the assignment of $J^{PC}$ quantum numbers to the recently observed structures by ATLAS, LHCb and CMS collaborations, including $X\left(6600\right)$, $X\left(6900\right)$ and $X\left(7200\right)$.

An analytical approach has been considered to inspect the flow and heat transfer of immiscible Newtonian and micropolar fluid in a porous medium. This study aims to elucidate the Darcy effect on the model in which isotropic porous regions with different permeability are used. The model of the current problem explains that the flow region is divided into two regions: Newtonian fluid flows in the upper layer, and micropolar fluid flows in the lower layer. Different constant temperatures imposed at boundary walls, heat transfer does not affect the pressure gradient. The governing equations are solved analytically by applying a linear differential equation (LDE). The effect of associated physical parameters such as material parameter, Darcy number, Eckert number, Prandtl number, and viscosity ratio on velocity, micro-rotation, heat transfer, flow rate, heat transfer rate, wall shear stress, and Nusselt number have been inspected. The most significant finding of this research work is that increasing the Darcy number signifies enhanced permeability, resulting in a higher flow rate. The heat transfer rate at the top occurs maximum when the material parameter’s range is minimum while raising the viscosity ratio leads to an increasing heat transfer rate at the bottom. Enhancement in material parameter influences Nusselt number and decreases in nature. The findings of our study are verified with the previously established results. The present work has a setup that is useful in petroleum extraction, transport problems in reservoir rock of an oil field, improving nutrient transport and thermal regulation in tissue engineering, and designing more efficient drug delivery systems and biomedical devices.

Understanding the nature of dark energy in the universe is an actual issue in theoretical astrophysics and cosmology. One way to do it is by probing dark fluids with different equations of states (EoS). In the present work, we consider a Schwarzschild black hole (BH) surrounded by a dark fluid with a Chaplygin-like EoS as a generalized version of the Chaplygin EoS. We first investigate the effects of the dark fluid parameters on the horizon properties of the BH. The effective mass of the spacetime is calculated and analyzed under the dark fluid parameters. The scalar invariants of the BH spacetime are also calculated, and it is shown that the spacetime curvature increases as the dark fluid parameter increases. Next, we studied the circular motion of the test particle around the BH. As standard particle motion investigations, we analyze the effective potential of the particles for circular motion, specific energy, and angular corresponding to circular orbits with zero and nonvanishing values of the dark fluid intensity. In addition, we study the innermost stable circular orbits (ISCO). It is observed that there is an outermost stable circular orbit (OSCO) due to the presence of the dark fluid. It also shows that at a critical value of the dark fluid intensity parameter, ISCO and OSCO take the same radius. We calculate the frequency of Keplerian orbits and radial and vertical oscillations of the particles along stable circular orbits. We also applied orbital data from hotspots observed near Sgr A* to obtain upper and lower values for the EoS parameter. Finally, we investigate quasiperiodic oscillations and obtain the mass-to-EoS parameter relations for GRS J1915-105 and XTE 1550-564.

In this paper, we explore the existence of spherically symmetric strange quark configurations coupled with anisotropic fluid setup in the framework of modified Gauss–Bonnet theory. In this regard, we adopt two models such as (i) $f\left(G\right)=\beta G^2$, and (ii) $f\left(G\right)={\delta }_1{G}^x({\delta }_2{G}^y+1)$, and derive the field equations representing a static sphere. We then introduce bag constant in the gravitational equations through the use of MIT bag model, so that the quarks’ interior can be discussed. Further, we work out the modified equations under the use of Tolman IV ansatz to make their solution possible. Junction conditions are also employed to find the constants involved in the considered metric potentials. Afterwards, different values of model parameters and bag constant are taken into account to graphically exploring the resulting solutions. This analysis is done by considering five strange quark objects like Her X-I, LMC X-4, 4U 1820-30, PSR J 1614-2230, and Vela X-I. Certain tests are also applied on the developed models to check their physical feasibility. It is much interesting that this modified gravity under its both considered functional forms yield physically viable and stable results for certain parametric values.

Temperature anisotropies exist in all the solar terrestrial regions and act as a source of free energy that plays a pivotal role for the destabilization of various plasma modes, one of them is the electromagnetic electron whistler-cyclotron instability. In this paper, the kinetic-scale diagnostic of parallel propagating electromagnetic electron whistler-cyclotron instability is numerically investigated in hybrid non-thermal non-extensive non-collisional magnetized plasmas. The dielectric response function (DRF) of right handed circularly polarized whistler instability (WI) is derived by the incorporation of Vlasov–Maxwell model for both super-extensive ($q<1$, $\alpha \ne 0$) and sub-extensive ($q>1$, $\alpha \ne 0$) bi-Cairns–Tsallis distributed plasma (bi-CTDP) systems. The unstable solutions of WI are obtained through the exact numerical analysis of DRF to compute the oscillatory/real frequency and growth rate. The dependence of pertinent parameters, i.e., non-thermality ($q$), non-extensivity ($\alpha$), temperature anisotropy ratio (${\delta }_e$) and ($\alpha ,q$)-dependent plasma beta (${\beta }_{\parallel e}^{\alpha ,q}$), on the destabilization of whistler mode are examined in detail. The prevalence of hybrid non-thermal non-extensive electrons population plays a substantial role in altering the characteristics of whistler-cyclotron instability in bi-CTDP system as compared to other non-thermal/non-equilibrium plasma systems. The nature and characteristics of the instabilities and waves are substantially influenced by the shape of particle velocity distributions, particularly on kinetic scale. The hybrid non-thermal non-extensive character of electrons distribution remarkably support the instability growth. We observed the highest growth rate of WI in super-extensive bi-CTDP in contrast to other non-thermal plasma distributions. A detailed comparison of the present findings with the other models, e.g. bi-Cairns, bi-nonextensive, and bi-Maxwellian plasmas is also unveiled in the present research.

The nuclear ground state properties of ${}^{67-80}$As nuclei have been investigated within the framework of relativistic mean field (RMF) approach. The RMF model with density-dependent (DD-ME2) interaction is utilized for the calculation of potential energy curves and the nuclear ground-state deformation parameters (${\beta }_2$) of selected As isotopes. Later, the $\beta$-decay properties of As isotopes were studied using the proton–neutron quasi particle random phase approximation (pn-QRPA) model. These include Gamow Tellar (GT) strength distributions, log $\mathrm{ft}$ values, $\beta$-decay half-lives, stellar ${\beta }^{\pm }$ decays and stellar electron/positron capture rates. The ${\beta }_2$ values computed from RMF model were employed in the pn-QRPA model as an input parameter for the calculations of $\beta$-decay properties for ${}^{67-80}$As. The calculated log $\mathrm{ft}$ values were in decent agreement with the measured data. The predicted $\beta$-decay half-lives matched the experimental values within a factor of 10. The stellar rates were compared with the shell model results. Only at high temperature and density values, the sum of ${\beta }^{+}$ and electron capture rates had a finite contribution. On the other hand, the sum of ${\beta }^{-}$ and positron capture rates were sizeable only at low density and high temperature values. For all such cases, the pn-QRPA rates were found to be bigger than the shell model rates up to a factor of 33 or more. The findings reported in the current investigation could prove valuable for simulating the late-stage stellar evolution of massive stars.

Traveling wave solutions of fractional partial differential equations have great importance in the literature. The diversity of solutions plays an important role in understanding the physical structure of the model it represents. For this reason, two important differential equations with the fractional order, which have a significant role in applied sciences and can model real-life problems most accurately, have been solved by the generalized $\left(\frac{G^{\prime }}{G}\right)$-expansion method in this study. This method is a generalization of the classical $\left(\frac{G^{\prime }}{G}\right)$-expansion method. With this developed method, the non-linear fractional Schmael Korteweg–De Vries equation and fractional modified Liouville differential equations are discussed to find their exact solutions. In this way, new exact solutions of these equations that were not previously included in the literature have been found. The presented method has been applied to these two equations for the first time, and various new traveling wave solutions have been obtained. Thus, the study goes beyond other studies. To understand the physical behavior of these new exact solutions, three-dimensional graphs have been drawn according to different parameter values.