物理最新文献

Experimental observation and numerical calculation of the nonlinear absorptivity of Corning^® EAGLE XG^® Glass substrates under ultrafast laser irradiation at high repetition rates are presented in this work. The temperature-dependent material band gap and absorption spectrum are obtained using a quantum mechanics-based computational methodology within density functional theory. The modeling predicts an increase of the multiphoton absorption coefficient and linear thermal absorption at high temperatures due to a reduction of the band gap. The impact of thermally-induced absorption at high substrate temperatures is investigated, which allows for a more accurate prediction of heat accumulation and welding geometry in ultrafast laser welding process.

In this paper, we explore the construction of planar maximally entangled (PME) states from phase states. PME states form a class of n-partite states in which any subset of adjacent particles whose size is less than or equal to half the total number of particles is in a fully entangled state. This property is essential to ensuring the robustness and stability of PME states in various quantum information applications. We introduce phase states for a set of so-called noninteracting n particles and describe their corresponding separable density matrices. These phase states, although individually separable, serve as a starting point for the generation of entangled states when subjected to unitary dynamics. Using this method, we suggest a way to make complex multi-qubit states by watching how unconnected phase states change over time with a certain unitary interaction operator. In addition, we show how to derive PME states from these intricate phase states for two-, three-, four-, and K-qubit systems. This construction method for PME states represents a significant advance over absolutely maximally entangled (AME) states, as it provides a more accessible and versatile resource for quantum information processing. Not only does it enable the creation of a broader class of multipartite entangled states, overcoming the limitations of AME states, notably their restricted availability in low-dimensional systems; for example, in the absence of a four-qubit AME state, it also offers a systematic construction method for any even number of qudits, paving the way for practical applications in key quantum technologies such as teleportation, secret sharing, and error correction, where multipartite entanglement plays a central role in protocol efficiency.

In this work, doping with (hbox {FeX}_{{n}}) (X = C and N; n = 1, 3, and 6) is proposed as an efficient way to modify the electronic and magnetic properties of (hbox {SnS}_{{2}}) monolayer. Pristine monolayer is proven to be a two-dimensional (2D) nonmagnetic semiconductor material with indirect gap value of 1.58(2.37) eV obtained from PBE(HSE06)-based calculations. Doping with single Fe ((hbox {Fe}_{{Sn}}) system) and N ((hbox {N}_{{S}}) system) atoms produces total magnetic moments of 4.00 and 1.00 (mu _{B}), respectively. (hbox {Fe}_{{Sn}}) is a 2D half-metallic material, while the magnetic semiconductor nature is obtained for (hbox {N}_{{S}}) system. In contrast, the substitution of C atom ((hbox {C}_{{S}}) system) causes a band gap reduction of the order of 66.46%, preserving the nonmagnetic nature of (hbox {SnS}_{{2}}) monolayer. Significant magnetism is also induced by doping with (hbox {FeX}_{{n}}) ((hbox {D}_{{FeXn}}) systems) clusters, where Fe and X atoms originate mainly the systems magnetism. In these cases, total magnetic moment depends on the spin coupling insides (hbox {FeC}_{{n}}) clusters, such that values between 0.00 and 8.00 (mu _{B}) are obtained. Interestingly, the feature-rich half-metallicity is found for (hbox {D}_{{FeC3}}), (hbox {D}_{{FeN3}}), and (hbox {D}_{{FeN6}}) systems. Moreover, (hbox {D}_{{FeC}}), (hbox {D}_{{FeN}}), and (hbox {D}_{{FeC6}}) systems are proven to be magnetic semiconductor 2D materials. Bader charge analysis asserts that Fe atom loses charge to transfer to the host monolayer, meanwhile C and N impurities attract charge from the host monolayer. Our study provides insights into the coeffects of Fe and X impurities into (hbox {SnS}_{{2}}) monolayer lattice, which may be useful for further functionalization of this 2D material towards spintronic applications.

Inspired by the five-dimensional Kaluza–Klein theory, we would like to study the dimensional reduction issue of six-dimensional Kaluza–Klein extension in this paper. In particular, we will examine two possible approaches of dimensional reduction from six-dimensional spacetimes to four-dimensional ones. The first one is a direct dimensional reduction, i.e., from six-dimensional spacetimes directly to four-dimensional ones, via a (T^2equiv S^1 times S^1) compactification; while, the second one is an indirect dimensional reduction, i.e., from six-dimensional spacetimes to five-dimensional ones then four-dimensional ones, via two separated (S^1) compactifications. Interestingly, we show that these two approaches lead to different four-dimensional effective actions although using the same six-dimensional metric. It could therefore address an important question of which approach is more reliable than the other.

Ni_0.65Cd_0.35Fe_2-xAl_xO₄ (0 ≤ x ≤ 0.060) disc shape bulk specimen fabricated from the sol–gel synthesized nanocrystalline powders. According to a structural analysis using XRD and Rietveld refinement, single-phase cubic spinel structure confirmed. Crystalline size (40–36) nm calculated using Scherer’s formula. SEM images used to study surface morphology and grain size found decreasing trend from (1.4–1.0) μm. The saturation magnetization (M_s) as well as magnetic moment increased for x = 0.45 and beyond that it decreased with Al content, which phenomenon is attributed due to the reduction of length between tetrahedral (A) sites and octahedral [B] sites of cations. The temperature-dependent magnetization graphs shown sharply declining value of the temperature (i.e., dM/dT maximum) dropping from 582.27 to 578.76 K at the Curie point with Al concentration. The maximum magnetic entropy change (− (Delta S_{M}^{max }) ) derived from the Maxwell relation, is determined to be (0.54–0.72) JKg⁻¹ K⁻¹ as well as to relative cooling power of (43.18–56.97) Jkg⁻¹ with an applied magnetic field of μ₀H = 3 T. UV–visible spectroscopy utilized to explore optical study and found enhancement of absorption properties with Al content.

In the production of silicon solar cells, one of the key stages is the metallization process, where the softening temperature of the glass powder plays a decisive role in the metallization reaction. If the softening temperature is too low, it can lead to excessive erosion of the SiN_x layer. Conversely, if the softening temperature is too high, it may hinder the efficient completion of the metallization process. To address this issue, this study proposes an innovative concept that introduces a melting gradient in the glass binder phase of the electronic paste. Specifically, low-melting-point glass is tightly packed around high-melting-point glass. During the metallization process, the low-melting-point glass melts first, wetting and etching the substrate, while the high-melting-point glass etches the substrate more rapidly and facilitates the formation of silver crystals. The results demonstrate that the optimized mixed glass samples achieve a photovoltaic conversion efficiency improvement of 1.28–2.83% compared to pre-mixed and single glass melts. In particular, the M4 sample of the mixed glass exhibits the shortest melting process and the highest photovoltaic conversion efficiency (22.879%), along with the most significant recrystallization (0.057%). Transmission results indicate a large presence of silver nanoparticles in the glass layer, which can be attributed to the earlier melting of the low-temperature glass that erodes the SiN_x layer. This, in turn, allows the high-temperature glass to react with silver powder and silicon, resulting in the formation of abundant silver crystals. The key to this improvement lies in adjusting the glass's characteristic temperature, wettability, and etching properties, thereby enhancing the overall cell performance. This concept provides a novel approach to the design of conductive pastes, enabling independent tuning of interfacial reactions and thermal properties. It underscores the importance and remarkable performance of mixed glass materials with diverse properties, offering significant potential for various applications.

Providing reliable data on the properties of atomic nuclei and infinite nuclear matter to astrophysical applications remains extremely challenging, especially when treating both properties coherently within the same framework. Methods based on energy density functionals (EDFs) enable manageable calculations of nuclear structure throughout the entire nuclear chart and of the properties of infinite nuclear matter across a wide range of densities and asymmetries. To address these challenges, we present BSkG4, the latest Brussels-Skyrme-on-a-Grid model. It is based on an EDF of the extended Skyrme type with terms that are both momentum and density-dependent, and refines the treatment of (^1S_0) nucleon pairing gaps in asymmetric nuclear matter as inspired by more advanced many-body calculations. The newest model maintains the accuracy of earlier BSkGs for known atomic masses, radii and fission barriers with rms deviations of 0.633 MeV w.r.t. 2457 atomic masses, 0.0246 fm w.r.t. 810 charge radii, and 0.36 MeV w.r.t 45 primary fission barriers of actinides. It also improves some specific pairing-related properties, such as the (^1S_0) pairing gaps in asymmetric nuclear matter, neutron separation energies, (Q_beta ) values, and moments of inertia of finite nuclei. This improvement is particularly relevant for describing the r-process nucleosynthesis as well as various astrophysical phenomena related to the rotational evolution of neutron stars, their oscillations, and their cooling.

We report on the observation of efficient light storage based on recoil-induced resonances and the associated generation of forward four-wave mixing signal. We use a strong coupling beam red-detuned from the closed transition (6S_{1/2}, F=4rightarrow 6P_{3/2}, F^{prime }=5) of cold cesium atom and a two-mode probe beam, whose frequency can be scanned around the coupling beam frequency. First, we demonstrate the coherent phase transfer from one mode component of the probe beam to the corresponding forward generated four-wave mixing beam. We then explore the coherent nature of the stored optical information to retrieve the two-mode probe energy with an efficiency 3.5 fold higher as compared with the total retrieved energy efficiency associated with the case where each mode component of the probe acts separately. Finally, we discuss a possible application of our experimental scheme and observed effects to investigate squeezing and quantum photon correlations.

In this article, we have developed the SIQR type mathematical model including the protected human population and public awareness in the model for the dynamics of an epidemic outbreak. The “level of awareness”, due to awareness campaign, is taken as a separate model variable. Both local (information sharing from local area, relatives) and global awareness (information sharing from social media, Radio, TV, etc.) can increase the level of awareness. We have also included the impact of treatment for recovery from the infection. Also, we have assumed infection transmission as a decreasing function of media awareness. The existence of equilibria of the model and their stability nature have been studied with qualitative theory. The disease-free equilibrium is stable when ({mathcal {R}}_0<1) and unstable when ({mathcal {R}}_0<1). A unique endemic equilibrium exists when ({mathcal {R}}_0>1), and it shows a Hopf bifurcation if the infection rate crosses its critical value. The unstable endemic system becomes stable when the global awareness rate is increased. To obtain crucial insights into disease management strategies, sensitivity analysis is performed to examine the link between model parameters and the basic reproduction number ({mathcal {R}}_{0}). Finally, we formulate an optimal control problem including three control parameters and solved using Pontryagin’s maximum principle. Numerical simulations are executed on the basis of analytical results. The regions of stability of the disease-free equilibrium are identified in different parameter planes. We have determined the optimal profiles of the three control functions to make the disease management process economically viable. This study concluded that the transmission dynamics of the pandemic depend on the rate of infection, the rate of global awareness, and the rate of awareness-based treatments. The proposed awareness-induced mathematical model that includes an optimal control approach is applicable to cost-effectively manage an epidemic outbreak.

Diabetes is a chronic metabolic disorder characterized by elevated blood glucose levels due to insufficient insulin production or ineffective use of insulin. While primarily driven by genetics and lifestyle, viral infections like enteroviruses, cytomegalovirus, hepatitis C, HIV, and COVID-19 have also been linked to triggering both type 1 and type 2 diabetes (T2D), possibly through immune system-induced metabolic changes. In this study, we propose and analyze a nonlinear mathematical model to investigate the effects of awareness campaigns on diabetes prevention and control of viral infection. We assume that individuals who are initially unaware of diabetes risk factors become informed through word-of-mouth communication, and adopt preventive behaviors. The model also includes the impact of social media and television advertisements in raising public awareness. We derive the basic reproduction number ((mathcal {R}_0)) for the system, which serves as a threshold parameter. Our analysis indicates that the system experiences a transcritical bifurcation as (mathcal {R}_0) crosses the unit value, indicating a shift in the stability of equilibria, and the potential for diabetes control. Additionally, we conduct a sensitivity analysis to identify the most influential parameters impacting the number of infected cases. The model is further expanded to incorporate two control strategies aimed at reducing the prevalence of both diabetic and at-risk individuals. Pontryagin’s Maximum principle, along with the forward-backward sweep method, is employed to solve the optimal control problem. Our findings evoke that interventions involving social media and television advertisements are more effective in promoting awareness and reducing the spread of diabetes risk compared to word-of-mouth communication alone.