物理最新文献

The mechanism of antiproton–nucleus annihilation at rest is not fully understood, despite substantial previous experimental and theoretical work. In this study we used slow extracted antiprotons from the ASACUSA apparatus at CERN to measure the charged particle multiplicities and their energy deposits from antiproton annihilations at rest on three different nuclei: carbon, molybdenum and gold. The results are compared with predictions from different models in the simulation tools Geant4 and FLUKA. A model that accounts for all the observed features is still missing, as well as measurements at low energies, to validate such models.

This study aimed to investigate the physical, optical, dielectric properties as well as gamma-ray shielding capacity of borosilicate glass samples with chemical formula 70B₂O₃–5SiO₂–10Li₂O–5Bi₂O₃–10ZnO–XEr₂O₃ with X = 0.0 (Er-0.0) to 1.2 (Er-1.2) mol% which prepared by the melt quenching technique method. Densities (D_s) of Er-X samples increased from 2.95 to 3.12 g/cm³, whereas the molar volume (V_m) declined from 30.68 to 30.50 cm³/mol as Er₂O₃ content increased from 0.0 to 1.2 mol%. The oxygen packing density (OPD) enhanced from 89.64 to 90.33 mol/l, whereas oxygen molar volume (OMV) decreased from 11.16 to 10.95 cm³/mol. The optical band gap decreased from 3.36 to 2.90 eV for direct transition, while decreased from 2.96 to 2.50 eV for indirect transition. Urbach energy (ΔE_u) was enhanced from 0.17 to 0.56 eV. The refractive index (n) was increased from 2.40 to 2.54. The dielectric constant regularly rises with increasing Er₂O₃ content in the glass networks. The mass attenuation coefficient (MAC) followed the trend as (Er-1.2)_MAC > (Er-0.9)_MAC > (Er-0.6)_MAC > (Er-0.3)_MAC > (Er-0.0)_MAC. The Er-1.2 sample possessed the lowest values of half value layer (HVL) and mean free path (MFP). Results showed that suggested Er-X glasses, can be used in optical and radiation shielding applications.

The quantum speed limit (QSL) time of a single qubit coupled to Heisenberg XXZ spin bath is investigated. The time convolutionless (TCL) projection operators technique is followed for investigating the second (TCL2), third (TCL3) and fourth (TCL4) order approximations in QSL time of centrally interacting qubit. The results are discussed up to fourth order of perturbation expansions of the non-Markovian master equation of motion. Behavior of QSL time is studied against temperature, interaction time and coupling strength for second, third and fourth orders of master equation using TCL technique. The behavior of QSL time becomes less perturbative for third and fourth order approximations as compared to second order. It is investigated that QSL time of qubit becomes constant very quickly in the low temperature limit for third and fourth order approximation, which means evolution speed of qubit is less affected for higher orders of approximations. QSL time for third and fourth orders of TCL gives much better results at high temperature and also behave well at short times. It is observed that, as the order of the TCL master equation increases, the accuracy of the approximation improves, but the complexity of the equation also increases due to involvement of more and more interaction terms in the TCL master equation.

Quantum dense coding enables the transmission of two bits of classical information using a single qubit, leveraging the initial maximal entanglement of a Bell state channel. This study investigates this process within a two-qubit anisotropic XY Heisenberg spin chain, influenced by Herring-Flicker coupling and subjected to an external magnetic field. In practical scenarios, the interaction between spins, characterized by the variable coupling strength J, significantly impacts the assessment of these spin systems for quantum computing and communication. Therefore, it is essential to consider the distance between the spins. This article aims to analyze the effects of temperature variations on the quantum communication channel, taking into account Herring-Flicker coupling, which is vital for implementing quantum communication protocols in real-world applications. Our findings suggest that the current channel shows promising potential for the quantum-dense coding protocol.

This study evaluates the viability and stability of anisotropic compact stellar objects by utilizing the Finch–Skea spacetime solutions in f(Q) gravity, where Q is a nonmetricity scalar that incorporates gravitational effects. The physical properties of the compact star EXO 1785-248 are investigated by employing a static spherical metric in the inner region and Schwarzschild spacetime in the outer region. The unknown parameters are determined using observed values of the radius and mass of the studied compact star. The suggested mass and radius values of EXO 1785-248 from existing literature are utilized. Subsequently, calculations are conducted to determine the essential features of the compact star and establish its stability and physical existence. Various aspects are analyzed, including energy density, pressure profiles, gradients, anisotropic factors, energy conditions, sound speeds, Tolman–Oppenheimer–Volkoff forces, equation of state components, mass function, compactification, and redshift, in order to achieve this objective.

Proton radioactivity is an exotic decay mode of proton-rich nuclei far from the (beta )-stability line and shares the similar decay mechanism theory of barrier penetration as (alpha ) decay. In present work, we extend the Hatsukawa formula (Hatsukawa et al. in Phys Rev C 42:674, 1990) for (alpha ) decay to proton radioactivity and propose an empirical formula for evaluating the proton radioactivity half-lives of proton nuclei with Z  >  68. Using this formula, we systematically calculate the proton radioactivity half-lives of 33 spherical proton emitters with the corresponding root-mean-square (rms) deviation being 0.391. It is found that the calculated half-lives can reproduce the experimental data well. Moreover, we extend this formula to predict the proton radioactivity half-lives of 18 spherical proton emitters, whose proton radioactivity is energetically allowed or observed but not yet quantified. For comparison, unified fission model (UFM), Coulomb potential and proximity potential model (CPPM), universal decay law for proton emission (UDLP) and new Geiger-Nuttall law (NG-N) are also used. All the predictions are basically consistent with each other.

A connection between regular black holes and horizonless ultracompact objects was proposed in Carballo-Rubio et al. (JHEP 08:046, 2023, arXiv:2211.05817 [gr-qc]). In this paper, we construct a model of a horizonless compact object, specifically an anisotropic gravastar with continuous pressure, that corresponds to regular black hole spacetime in the appropriate limit. The construction begins by modeling an equation of state that satisfies the anisotropic gravastar conditions and transitions to the de Sitter ((p=-epsilon )) upon horizon formation. The spacetime structure is similar to the Quantum Horizonless Compact Object (QHCO) described in Chen and Yokokura (Phys Rev D 109:104058, 2024, arXiv:2403.09388 [gr-qc]). Within this model, we also generate images of the corresponding objects surrounded by a thin accretion disk. The resulting images reveal that assuming that the emitting matter exists only outside the object, the inner light ring structure closely resembles that of the horizonless configuration of a regular black hole and the QHCO, yet it exhibits a distinct light ring structure compared to the thin-shell gravastar model. However, the opposite occurs when emitting matter is taken into account inside the object.

Chaotic systems are widely used in the field of secure communications due to their initial value sensitivity, long-term unpredictability and other characteristics. In this paper, a Lag Matrix Projection Synchronization (LMPS) scheme based on discrete chaotic system is proposed, which can adapt to a variety of synchronization including lag synchronization, simultaneous synchronization, projection synchronization, inverse synchronization, and complete synchronization. In order to verify the feasibility of the scheme, we also design a new four-dimensional discrete chaotic system, which is fully analyzed by numerical simulation. Simulation results show that the LMPS synchronization scheme can achieve synchronization with an average of only 8 iterations, and the synchronization error is controlled within the range of 10^–10, which reflects the high efficiency and accuracy of the scheme. In addition, we apply it to the field of image encryption, and the security analysis shows that the system performs well in terms of encryption effect, key space size, and resistance to noise attack, and can effectively guarantee the confidentiality and integrity of data.