物理最新文献

The quantum dynamics of a single particle in a discrete two-dimensional tilted lattice is analyzed from the perspective of the classical-quantum correspondence. Utilizing the fact that tilting the lattice results in oscillatory dynamics, we show how the parameters of the lattice and the initial state of the particle can be tuned so that during evolution the probability distribution does not change its shape, while its center follows the trajectory known in classical mechanics as Lissajous curves.

In this study, we analyze a generalist predator–prey model that includes a strong Allee effect in the prey population. We investigate the positivity and boundedness of solutions, identify ecologically relevant equilibrium points, and determine their stability conditions. Further, we analyze the transcritical, saddle-node, Hopf, Bogdanov-Takens, generalized-Hopf, and cusp bifurcations. Our numerical investigation shows that the model exhibits multiple stable states under similar parametric conditions, driven by bifurcation scenarios linked to the Allee effect. It also underscores the significant role of additional foods for predators in shaping system dynamics, unveiling scenarios ranging from the extinction of predators to their persistence, and the coexistence of both the species. Furthermore, our study delves into the impact of environmental white noise on predator–prey dynamics, introducing stochastic elements. We explore noise-induced transitions between two stable states within the system. Overall, our study highlights the complex dynamics of predator–prey interactions, emphasizing the role of Allee effect and additional food sources.

New experimental data are obtained on cross sections σ₁ and σ₂ of ¹⁹⁷Au(p,n)^197mHg and ¹⁹⁷Au(p,n)^197gHg reactions, respectively, as well as on the isomeric cross-section ratio R = σ₁ / σ₂ for proton energies below 18 MeV. The new data can help to clear up the discrepancies between existing data sets on σ₂ and R from different experiments. The cross-section data sets are compared to the predictions of the nuclear reactions simulation code TALYS (version 1.96), using different combinations of options of several main components of the code, such as the photon strength function, the optical model potential, the nuclear level density and the pre-equilibrium mechanism.

In this paper, we study the relationship between the phase transition and Lyapunov exponents for 4D Hayward anti-de Sitter (AdS) black hole. We consider the motion of massless and massive particles around an unstable circular orbit of the Hayward AdS black hole in the equatorial plane and calculate the corresponding Lyapunov exponents. The phase transition is found to be well described by the multivaled Lyapunov exponents. It is also found that different phases of Hayward AdS black hole coincide with different branches of the Lyapunov exponents. We also study the discontinuous change in the Lyapunov exponents and find that it can serve as an order parameter near the critical point. The critical exponent of change in Lyapunov exponent near the critical point is found to be 1/2.

The shear wavefront propagates in a single direction, influenced by the phase deviation of the missing orthogonal direction in the interference pattern. Furthermore, the restriction of phase sampling points in the shear direction has a certain impact on attaining high spatial resolution in wavefront reconstruction. To attain high-precision wavefront reconstruction, it is necessary to acquire additional sampled data from various orthogonal shear directions. During our investigation, a wavefront reconstruction method was proposed for multi-directional orthogonal lateral shearing interferometry. This method establishes a relationship model that corresponds to multi-directional differential wavefront and differential Zernike polynomials. Using the principle of wavefront reconstruction with differential Zernike polynomials, it allows for the reconstruction of wavefronts from any orthogonal-direction lateral shearing interference patterns. To validate the efficacy of the proposed method, the wavefront reconstruction accuracy of various sets of arbitrarily oriented shearing interferograms was simulated and analyzed. Additionally, the results were compared to those obtained from the average differential wavefront of multiple orthogonal shearing interferograms. The results show that by choosing multiple orthogonal shear directions to improve phase sampling data, wavefront reconstruction can be successfully accomplished using any number of orthogonal lateral shearing interferograms. This effectively reduces the impact of both random and systematic errors on the spatial resolution of the wavefront during the reconstruction process. Ultimately, the accuracy of the proposed method was confirmed through experimental validation. After comparing the repeatability measurement with the results obtained from the ZYGO interferometer, it was discovered that the precision of the relative measurement error in RMS was superior to 0.01λ.

We have developed neutron tomography as a new tool to study the interior of ancient works of art. The present paper details the principles of the method and summarizes also some of the latest results, particularly concerning Mongolian Buddhist statues of the 17./18th century. It is shown that offering deposits made of organic and ceramic materials, even when fully enclosed in a cast metallic statue, can be examined in a non-invasive way. Within certain limits this concerns composition, size, structure and position of the interior deposits. Such studies can contribute to understand the history of ritual practices and their goals. They can also contribute to evaluate whether a statue has been properly cleaned and filled during consecration and is therefore fit for religious service. Such studies can also help to form an opinion of whether a statue is genuine.

Transition metal ion doping presents an effective approach to enhance the magnetic properties of BiFeO₃ (BFO). Herein, we explored the impact of dual transition metal ion doping in BFO by preparing BFO and BiFe_0.9Co_xMn_0.1-xO₃ (X = 0, 0.03, 0.05, 0.07, 0.1) samples using a sol-gel method. Comprehensive investigations into the substitution-driven structural, optical and magnetic transformation of Mn, Co co-doped BiFeO₃ have been conducted. The dual ions doping led to the BFO’s structural distortion, which was proved by the Riteveld refinement and Raman spectra. With the addition of dual ions, new energy levels might create additional absorption channels for photons, thereby, increasing photon absorption efficiency and adjusting the bandgap. Analysis of magnetic hysteresis data indicates enhanced magnetism in doped samples. Particularly noteworthy is the coercivity of the BiFe_0.9Co_0.03Mn_0.07O₃ sample, which reaches 14989.6 Oe, compared to the control sample’s coercivity of only 163.9 Oe—almost 100 times greater. This study underscores the efficiency of varying the ratio of double ions in doping samples for enhancing both magnetic and optical properties.

A many-body theory of trions is presented for strongly correlated systems with an analytical expression of trion binding energy being obtained. When there are extra electrons at present, an optical excitation with lower energy may occur besides the exciton peak ((X)), which is usually attributed to the creation of a negatively charged exciton ((X^-)), commonly known as a trion. The energy difference between the (X) and (X^-) peaks was commonly regarded for the trion binding energy ( Delta _{X^-} ), which is later however proposed to be ( Delta _{X^-} + Delta E ) with an energy part ( Delta E ) not accurately known for decades. In this work it is deduced that ( Delta E = U_{ee} - Delta _{qp}(Ntext{+1 }) ) for a confined N-electron system where ( U_{ee} ) is the interaction energy of two electrons and ( Delta _{qp}(Ntext{+1 }) ) is the quasiparticle gap of the system with an extra charge. By using a configuration interaction approach, the newly developed theory is applied to study the correlated trion states in phosphorene nanostructures. The energy part ( Delta E ) is shown to be crucial to obtain the trion binding energies that have the correct dielectric dependence. In the case of ( text{ SiO}_2 ) substrate, our result finds that the binding energy of a negative trion in a rectangular phosphorene nanoflake with 98 atoms is around 63 meV, which agrees well with the recent experimental value of 70 meV.

Rapid and real-time monitoring of the concentrations of metal elements in water is essential for water quality evaluation and freshwater production through water desalination. Here we show the ability of the deep reinforcement learning (DRL) in assisting the filament-induced breakdown spectroscopy (FIBS) technique for high-sensitivity and standoff detection of trace-level metal elements in water. The DRL agent is trained to determine two important intricately-coupled parameters, the pulse duration and the distance between the filament starting point and the water surface, achieving the optimal control of the FIBS intensity at the air–water interface. The limits of detection of DRL-assisted FIBS for Al, Cu and Pb elements in water reach to 230, 850 and 1120 ppb, respectively. With this method, we further perform high-sensitivity analysis of the diffusion properties of multi-salt species during the freezing desalination, and find that the captured possibility of metal ions into the ice body decreases with the increasing freezing time, which exhibits a strong dependence on the metal species. This work opens up possibilities in controlling the nonlinear optical emissions by the high-intensity filament excitation assisted by the cutting-edge artificial intelligence technologies.

The optical and photothermal properties of porous silicon (PS) coated by Poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) polymer have been investigated. The PS layers were formed using electrochemical anodisation method. The deposition of the MEH-PPV polymer on PS and Si surfaces was performed by spin coating process. The MEH-PPV/Si, MEH-PPV/PS, and PS as well as MEH-PPV solution were prepared and compared by photoluminescence (PL) spectroscopy at room temperature. An enhancement of the PL intensity of PS was observed after the deposition of MEH-PPV molecules on its surface. Comparing it with a smooth Si surface, the porous surface plays an important role for the fixation of MEH-PPV molecules thus affecting the PL and the Photo-thermal properties of these structures. The thermal conductivity of MEH-PPV/PS is also increased compared to those of PS and MEH-PPV/Si. The values of the thermal conductivity of MEH-PPV/Si, PS, and MEH-PPV/PS were 0.69, 0.94, and 1.32 W.m^− 1.K^− 1, respectively. The optical and opto-thermal properties are related to the distribution of MEH-PPV molecules which in turn depends on the nature of the substrate surface.