The European Physical Journal Plus最新文献

Recently, substitutional doping in two-dimensional (2D) materials is demonstrated via chemical vapor deposition (CVD), opening a new strategy for designing and constructing novel ferromagnetic materials. Substitutional doping of Cr doping at possible dopant sites in Zr₂CO₂ monolayer is systematically studied using ab-initio calculations. It is found that Cr prefers Zr-site with suitable bond length and apparent charge transfer to host material, which is also supported by the lowest negative formation energy. In all studied cases, Cr atoms form strong bond to the Zr₂CO₂ crystal, a possible signature magnetization in non-magnetic Zr₂CO₂ monolayer. Ferromagnetic (FM) and anti-ferromagnetic (AFM) coupling calculations disclose that Cr doped at the Zr-site has a FM ground state. Moreover, using the mean-field theory (MFT) and Quantum Monte-Carlo (QMC) simulations, the transition temperature is calculated to be 184.76 K and 411 K, respectively. Our findings predict possible room temperature ferromagnetism in Cr-doped 2D MXene materials for possible spintronics device applications.

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We investigate the microscopic origin of the negative pressure produced by the constant energy density of the vacuum. It is shown that the zero-point photons in the quantum vacuum could generate the pressures of this type in confined spaces for the photon field. We find in particular that an anomalous radiation plays a role in the occurrence of a negative pressure from the quantum vacuum.

This research focuses on the evolution of the universe and observes pulsars using modified gravitational theory. We computed the Einstein field equations for an anisotropic spherical structure with f(R) gravity. Furthermore, our density–pressure relationship is defined using the well-known van der Waals equation of state (VdW EoS). Graphs are used to investigate the behavior of physical parameters, and energy conditions are used to demonstrate the physical continuity of dense stars. Plotting the adiabatic index shows the model’s stability. The resulting figures of physical parameters confirm the model’s practical and conceptual feasibility. Under the effect of f(R) gravity, our work demonstrates regularity, viability and stability, supporting the presence of heavy pulsars such as PSR (J0348+0432), PSR (J0740+6620) and PSR (J0030+0451).

According to the prediction of the classical physics, a macroscopic body moves oscillating between two perfectly reflecting walls with a velocity proportional to its energy. On the contrary, the momentum of the body calculated in the framework of the de Broglie–Bohm interpretation of quantum mechanics is vanishing. This result was considered unsatisfactory by Einstein and other scientists who believed that also for quantum particles, it must be possible to move in an oscillatory way. In order to give an answer to Einstein’s objection, we show that it is possible to obtain a motion of the body using the standard rules of quantum mechanics. We obtain a correction of the Schrödinger equation, and we calculate explicitly the solution for the case of the particle in a box. Finally, we find the expression of the quantum velocity.

In this work we analyze the quantum coherence in a spin-1/2 Ising-XXZ diamond chain with a distorted impurity on a single plaquette. We show that introducing an impurity into the chain can significantly enhance entanglement and quantum correlations compared to the original model without impurity. Due to the flexibility in choosing impurity parameters, the proposed model presented is highly general, which could prove useful for future experimental measurements. Our main goal is to examine the behavior of thermal quantum correlations, specifically focusing on entanglement, quantum coherence, and local quantum Fisher information. In addition, we studied quantum teleportation through a quantum channel composed by a coupled of Heisenberg dimers with distorted impurity in an Ising-XXZ diamond chain, as well as fidelity in teleportation. Our analysis demonstrates that an appropriate choice of parameters can significantly enhance all the measures analyzed. For comparison, we present our results alongside the measurements obtained for the original model, without impurity, studied in previous works.

The role of ¹⁶⁰Tb is crucial in post-detonation analysis, specifically in nuclear forensics. This study investigated the¹⁶⁰ Gd(p,n)¹⁶⁰Tb reaction. The excitation function is assessed through activation analysis for 11 different proton beam energies in the 4 MeV to 18 MeV energy range. The multilayer stack target was irradiated by an external proton beam obtained from the C18/18 cyclotron, which is located at the A.I. Alikhanyan National Science Laboratory (AANL), Yerevan, Armenia. Detailed spectroscopic analysis of the final radioactive materials was carried out using an HPGe detector. The experimentally measured values were compared with theoretical calculations obtained from TALYS 1.96 and EMPIRE 3.2 codes and the MENDL data library. This comparative analysis assessed how well the observed results aligned with theoretical predictions and evaluated the predictive power of each computational model.

Lead silicate glasses have been widely used in various applications, including radiation shielding, due to their high density and effective atomic number. However, the addition of certain oxides to the glass composition can significantly enhance their radiation shielding properties. In this study, we investigate the effect of incorporating antimony and alumina oxides on the photon attenuation and shielding properties of lead silicate glasses. It is found that the HVL values of the APSSS1 sample started from 0.00239 cm at photon energy of 0.015 MeV and increased with increasing energy to a maximum value of 4.223 cm at 6 MeV photon energy then decreased to 3.767 cm at energy of 15 MeV. Moreover, the shielding ability of the studied samples are compared with commercial glassy materials. The results of the study showed that the addition of antimony and alumina oxides significantly improved the radiation shielding properties of the lead silicate glasses.

The 2nd law of thermodynamics is derived from the principle of least action, positing that the quantum of action is the indivisible and indestructible basic building block of everything. On their least-time paths to balance, the quanta move from the system to its surroundings, or vice versa, so that the kinetic, potential, and dissipated energy tally. When re-expressed in logarithmic terms, this current toward more probable states with decreasing free energy equates to the principle of increasing entropy, the 2nd law of thermodynamics, including path-independent dynamic and path dependent geometric phase shifts. Despite being exact, the equation of evolution to entropy maximum, equivalent to free energy minimum, cannot be solved because evolution, consuming its own driving forces, becomes path dependent. Thus, the future remains open within free energy bounds. As discussed, the entropy derived from the statistical physics of open quantum systems sums states distinguishable in energy; whereas, Boltzmann’s entropy enumerates microstates indistinguishable in energy. Consequently, the statistical physics of open systems differs from that of closed systems: The irreversible evolution in the state space toward thermodynamic balance contrasts with the steady-state revolution in phase space between conceivable configurations. This concrete comprehension explains, among other things, that increasing disorder is not a law of nature itself but a consequence of the law to attain balance with incoherent surroundings in the least time.

Soft x-ray multi-element optical system with two-dimension field light source is widely used for synchrotron radiation, microscope, etc., and optimization design method of this kind of optical systems with large aperture imaging is studied in this paper. Since aberration analysis method is the basis for studying it, and thus, we firstly derived fifth-order aberration expressions of soft x-ray multi-element optical system with two-dimension field light source; secondly, the aberration modification expressions due to aperture-ray coordinates with second-order accuracy are obtained, and the extrinsic aberration calculation expressions are derived by the reverse optical path; then, aberration expressions derived in the above are validated and have a satisfactory calculation accuracy. In addition, evaluation function expression of imaging performance of this kind of optical systems is established, and then applying self-adaptive variation probability genetic optimization algorithm to solve it to obtain the structure parameters of optical system. Finally, they are applied to optimize the aberration of a soft x-ray multi-element optical system with two-dimension field light source, and comparing and analyzing the imaging results before and after aberration optimization; these results verify the effectiveness of the optimization method discussed in this paper.

This study explores the relationship between the Schwarzschild metric and alternative metrics used to describe the gravitational field of a black hole in free space. While it is well-established that an infinite number of coordinate systems can be employed in general relativity, we demonstrate that the black hole solution is unique when expressed in a physically meaningful (proper) coordinate system. Notably, this coordinate system differs from the Schwarzschild metric due to the distinction between the true physical distance R and the Schwarzschild coordinate distance r. Consequently, the event horizon, commonly associated with the Schwarzschild solution, is shown to be a coordinate artefact of the chosen covariant metric tensor rather than a coordinate-invariant physical feature. As a result, no boundary prevents outgoing photons from escaping the black hole’s vicinity. This finding challenges the mainstream interpretation but remains fully consistent with general relativity. Moreover, it is supported by numerical modelling of light rays near a black hole. By reconsidering the existence of event horizons, this work offers potential resolutions to long-standing issues in black hole formation theories and the emission of electromagnetic and gravitational waves from black holes.

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