物理最新文献

Diamond, as an ultra-wide bandgap semiconductor material, exhibits promising properties including strong mechanical stability, fast thermal conductivity, strong radiation resistance and broad-spectrum transmittance. Notably, deep-level defects within the diamond introduce defect-induced energy levels known as color centers. The fluorescence emission from color centers has strong monochromaticity, wavelength stability, and thermal stability, making them great potential for applications in quantum information processing, optical sensing, and biological labeling. Among these, the silicon-vacancy (Siv) color center, characterized by a zero-phonon-line at 738 nm, demonstrates a short excited-state lifetime (1 − 4 ns) and a narrow zero-phonon-line width (≈5 nm) at room temperature, underscoring its superior performance and potential applications. This study investigates the luminescence properties of Siv color centers in silicon-doped single-crystal diamond grown via the microwave plasma chemical vapor deposition (MPCVD) method. Measurements of fluorescence luminescence intensity of Siv color centers were conducted using PL, point-by-point scanning of specific areas to form a mapping image to determine the location of Siv color centers. A strong correlation is established between the distribution of Siv color centers and the surface structural defects existing in the diamond material. The results may support for subsequent research on diamond Siv color-centered single-photon devices such as single-photon detectors, single-photon avalanche diodes.

The magnetocaloric effect(MCE) of the (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy has been investigated by phenomenological model, estimating magnetic entropy change (∆S_M) and heat capacity change. The results indicate that MCE of (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy can be controlled and tuned by several magnetic fields. Furthermore, the study of ∆S_M curves predicts how to expand the temperature range for exploiting (Fe_0.5Cu_0.5)₆₀Zr₄₀ in magnetic refrigeration. ∆S_M reaches a peak of about 0.5 J/Kg K at 112 K with δT_FWHM = 227 K and RCP = 102 J/Kg under 5 T applied field variation. (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy has a potential application for magnetic refrigerants over a wide temperature range, especially its high electrical resistivity leads to decreased eddy current losses, covering a significant range of temperature between 0 K and room temperature. Therefore, these advantages make (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy potentially practical for efficient cooling devices.

In an effort to promote the development of sustainable construction practices, this study explores the utilization of construction waste powders as partial cement replacements in concrete. Specifically, granite and marble waste powders were incorporated at varying replacement ratios up to 9% by cement weight. The influence of these waste materials on the compressive strength and radiation shielding effectiveness of ordinary concrete was evaluated under both ambient and elevated temperature conditions (up to 800 °C). The findings revealed significant enhancements in the mechanical properties. Notably, 9%  cement replacement ratio with waste granite powder (WGP, 9G) yielded the optimal performance for compressive strength, exhibiting increasements of 25.6% and 33.2% at room temperature and 800 °C, respectively. Similarly, a 5% replacement ratio with waste marble powder (WMP, 5M) demonstrated moderate improvements, achieving gains of 10.3% and 18.7% in compressive strength at room temperature and 800 °C, respectively. The samples at optimal replacement ratios of 9% and 5% for granite and marble, respectively, were tested alongside the control sample (CO) to study their effectiveness in attenuating the various types of radiation. The radiation shielding assessment was evaluated against gamma and neutron using the MC Monte Carlo simulation-5 algorithm and Phy-X software. The  gamma ray linear attenuation for concrete mixes ((text{CM})_LAC) order for the CO group was found to be CO < 400CO < 600CO < 800CO. The (text{CM})_LAC order for the G9 group is G9 < 400G9 < 600G9 < 800G9. The (text{CM})_LAC order for the M5 group is M5 < 400M5 < 600M5 < 800M5. The neutron performance (FC) of the CM-concrete samples has values 0.079, 0.075, 0.071, and 0.067 cm⁻¹ for CO, 400CO, 600CO, 800CO samples, 0.094, 0.090, 0.085, and 0.080 cm⁻¹, for G9, 400G9, 600G9, 800G9 samples, and 0.089, 0.083, 0.079, and 0.074 cm⁻¹, for M5, 400M5, 600M5, 800M5 samples, respectively. Thus, the studied CM-concrete samples at room temperature provide the best protection against gamma and fast neutrons. Exposure to high temperatures significantly reduced the gamma and neutron attenuation of concrete samples. However, mixes with optimal granite and marble waste replacements showed enhanced resistance  to this effect compared to the control mix.

In this work, we present a novel approach to transform supervised classifiers into effective unsupervised anomaly detectors. The method we have developed, termed Discriminatory Detection of Distortions (DDD), enhances anomaly detection by training a discriminator model on both original and artificially modified datasets. We conducted a comprehensive evaluation of our models on the Dark Machines Anomaly Score Challenge channels and a search for 4-top quark events, demonstrating the effectiveness of our approach across various final states and beyond the Standard Model scenarios. We compare the performance of the DDD method with the Deep Robust One-Class Classification method (DROCC), which incorporates signals in the training process, and the Deep Support Vector Data Description (DeepSVDD) method, a well-established and well-performing method for anomaly detection. Results show that the effectiveness of each model varies by signal and channel, with DDD proving to be a very effective anomaly detector. We recommend the combined use of DeepSVDD and DDD for purely unsupervised applications, with the addition of flow models for improved performance when resources allow. Findings suggest that network architectures that excel in supervised contexts, such as the particle transformer with standard model interactions, also perform well as unsupervised anomaly detectors. We also show that with these methods, it is likely possible to recognize 4-top quark production as an anomaly without prior knowledge of the process. We argue that the Large Hadron Collider community can transform supervised classifiers into anomaly detectors to uncover potential new physical phenomena in each search.

The Lund jet plane (LJP) is measured for the first time in (tbar{t}) events, using 140 (textrm{fb}^{-1}) of (sqrt{s} = 13) TeV pp collision data collected with the ATLAS detector at the LHC. The LJP is a two-dimensional observable of the sub-structure of hadronic jets that acts as a proxy for the kinematics of parton showers and hadron formation. The observable is constructed from charged particles and is measured for (R=1.0) anti-(k_t) jets with transverse momentum above 350 GeV containing the full decay products of either a top quark or a daughter W boson. The other top quark in the event is identified from its decay into a b-quark, an electron or a muon and a neutrino. The measurement is corrected for detector effects and compared with a range of Monte Carlo predictions sensitive to different aspects of the hadronic decays of the heavy particles. In the W-boson-initiated jets, all the predictions are incompatible with the measurement. In the top quark initiated jets, disagreement with all predictions is observed in smaller subregions of the plane, and with a subset of the predictions across the fiducial plane. The measurement could be used to improve the tuning of Monte Carlo generators, for better modelling of hadronic decays of heavy quarks and bosons, or to improve the performance of jet taggers.

We study the behavior of electromagnetic waves near the interface between two media: a dielectric medium and a conducting medium. Solving this problem within the framework of classical electrodynamics, we obtain results that coincide with the known ones, namely: (1) By comparison of the solution to this problem—when obtained within the framework of classical electrodynamics—with experimental data shows that using the values of electrical conductivity of metals given in physics reference books (the values of the so-called static electrical conductivity), we cannot achieve satisfactory agreement between theory and experiment. (2) We can achieve satisfactory agreement between experimental data and the predictions of classical electrodynamics only if we use values of the so-called optical conductivity that differ by two orders of magnitude from the values of the static conductivity. In addition, we propose a re-evaluation of some well-known facts, namely: (1) According to many literary sources, the permittivity of metals changes by several orders of magnitude depending on frequency and becomes negative at frequencies below the plasma frequency. It turns out that when applying Maxwell’s equations in different frequency ranges, it is necessary to use parameters that differ by two orders of magnitude. (2) At the same time, experimentalists interpret optical experiments by using formulae derived from Maxwell’s equations under the assumption that all parameters are constants. In our opinion, if we interpret experimental data using equations with constant coefficients and as a result we see that the coefficients depend significantly on frequency, we should think about using more complex equations to interpret the experimental data. (3) In this paper, we propose a new approach to interpretation of the experimental data. The novelty is that we use the equations of extended electrodynamics, which are three-dimensional analogues of Kirchhoff’s laws for electrical circuits. We show that extended electrodynamics allows us to describe experimental data using handbook values of conductivity and frequency-independent values of permittivity. Thus, we conclude that extended electrodynamics describes experimental data for metals more accurately than classical electrodynamics.

This paper investigates the interaction of an ultra-short, high-intensity laser with a near-critical density hydrogen target, offering valuable insights into how laser intensity, plasma density, and target thickness influence the generation of high-energy proton beams. We report that optimizing target parameters at a fixed laser intensity results in a significantly greater increase in proton energy compared to simply increasing the laser intensity from (6 times 10^{20}) to (6 times 10^{21} mathrm{W/cm}^2). Specifically, simulation results show that the maximum proton energy rises from 45 to 94 MeV with optimized target parameters, whereas it only increases from 45 to 68 MeV with higher laser intensity on a near-critical density target of thickness 100 nm. By carefully selecting the laser and target parameters, we successfully exploit the Directed Coulomb Explosion (DCE) mechanism for ion acceleration, where both Radiation Pressure Acceleration (RPA) and Coulomb Explosion (CE) contribute to achieving such high proton energies. The optimal density and thickness are found to satisfy the condition for DCE proposed by Brantov et al. (IEEE Trans Plasma Sci 44:364–368, 2015) and the energy obtained matches with the theoretically predicted energy for DCE (Bulanov et al. in Phys. Rev. E-Stat. Nonlinear Soft Matter Phys. 78: 026412, 2008). Protons with energies around 100 MeV hold significant potential for practical applications, including cancer therapy, fusion energy, and other advanced technologies.

In this work, the solid-state reaction strategy be present used headed for synthesize nanoparticle samples of Ce_(2-(x+y+z) Gd_xCu_yDy_zO₂, at various concentrations of x, y, and z = 0.01, 0.03, 0.05. XRD analysis verified with cubic structure of both undoped and doped samples. Crystallite sizes ranged from 19.01 to 35.56 nm, while lattice parameters increased from 5.478 to 5.832 Å. The surface morphology (SEM) was primarily spherical and agglomerated at 500 nm. The elemental analysis (EDS) revealed the predicted stoichiometric atomic ratio (Dy-Cu-Gd). According to the results of optical studies, the optical band gap of the powders increases from 2.749 to 3.185 eV as the concentration increases. Photoluminescence investigations reveal blue, green, yellow, and ultraviolet emissions at different intensities in the emission spectrum. The magnetic parameters of the nanoparticle samples revealed paramagnetic features, the magnetic moment of Ce_(2-(x+y+z) Gd_xCu_yDy_zO₂ nanoparticles ranged from 0.0047 to 0.0785 emu/g.

Understanding the role of pressure anisotropy and dissipation is crucial for modelling compact objects’ internal structure and observable properties. In this work, we reinterpret local pressure anisotropy in relativistic stellar structures as an additional contribution to the energy density. This perspective enables the formulation of anisotropic equations of state for self-gravitating systems by incorporating anisotropy as a fundamental component. We demonstrate that this approach yields more realistic stellar models that satisfy key physical constraints, including mass-radius relationships and stability conditions. Our results are compared with observational data, particularly the inferred compactness of pulsars PSR J0740+6620 and PSR J0030+0451, showing that both anisotropic and isotropic models can describe these objects. Additionally, we examine the influence of dissipation – such as temperature gradients – on radial pressure, demonstrating that it can be modelled similarly to anisotropy. This interpretation allows the transformation of dissipative anisotropic models into equivalent non-dissipative isotropic configurations.