The European Physical Journal D最新文献

The effects of gravitational force on the behavior of collisionless shock waves in a nonthermal dusty plasma with fluctuating charge have been examined. The distribution function describing a cold beam of dust grains under the influence of gravitational effects has been reanalyzed, resulting in the derivation of a new density expression. Numerical integration of the Poisson equation, coupled with the dust grain charge equation, reveals that the electrostatic potential associated with DA shock waves forms an asymmetric, oscillatory structure when gravitational effects are considered. Specifically, we have found that due to gravitational effects, the electrostatic potential inherent to the DA shock waves undergoes a jump and increases linearly and the amplitude of each oscillation decreases as the nonthermality of the electrons becomes more important. Furthermore, for medium-sized grains, the interplay between electrostatic potential and gravitational forces results in a shift of the multilayer structure toward higher potential values, along with an increased number of oscillations. This effect becomes even more pronounced for larger grains. The results of our investigation may contribute to a deeper understanding of shock structures in inhomogeneous media obtained in a controlled laboratory environment and may also have practical applications in interpreting similar phenomena in astrophysical contexts.

Because the dust from beryllium (Be) is toxic to humans, ITER has recently decided to replace the first wall material of Be with tungsten boron (B). While there has been much discussion on the electron-impact ionization (EII) cross sections for Be-containing molecules, EII data is still limited for fusion-relevant molecules containing B. We report the EII cross section for the fusion-relevant diatomic molecules BH, BN, BO, BF₃ and WB using the Binary-Encounter-Bethe (BEB) and Deutsch-Märk (DM) methods and evaluate its accuracy based on the available experimental data. The errors between our BEB and DM cross sections for these molecules are within 23%.

The nonlinear dynamics of a quasi-1D BEC loaded in a double-well potential is studied. The beyond-mean-field corrections to the energy in the form of the Lee–Huang–Yang term are taken into account. One-dimensional geometry is considered. The problem is described in the scalar approximation by the extended Gross–Pitaevskii (EGP) equation with the attractive quadratic nonlinearity, due to the Lee–Huang–Yang correction, and the effective cubic mean-field nonlinearity describing the residual intra- and inter-species interactions. To describe tunneling and localization phenomena, a two-mode model was obtained. The frequencies of the Josephson oscillations are found and confirmed by the full numerical simulations of the EGP equation. The parametric resonance in the Josephson oscillations, when the height of the barrier is periodically modulated, is studied. The predictions of the dimer model, including the case of the one-dimensional Lee–Huang–Yang superfluid, have been proven.

We have measured several (2p rightarrow 1s) transition energies in core-excited boron-like ions of sulfur and argon. The measurements are reference-free, with an accuracy of a few parts per million. The x-rays were produced by the plasma of an electron cyclotron resonance ion source and measured with a double-crystal x-ray spectrometer. The precision obtained for the measured (1s 2s^2 2p^2~J - 1s^2 2s^2 2p~J') lines is ({approx 3.8},{hbox {ppm}}) for sulfur and ({approx 2.5},{hbox {ppm}}) for argon. The line energies are compared to relativistic atomic structure calculations performed with the mdfgme multi-configuration Dirac–Fock code. This comparison is used for line identification and tests the theoretical methods, which are in agreement with the experimental data up to (49,hbox {meV}). The theoretical calculations have been extended to B, (hbox {C}^+), (hbox {Si}^{9+}), (hbox {Cr}^{19+}) and (hbox {Fe}^{21+}), which were the only B-like ions where such transitions were measured up to now.

Coherent light has revolutionized scientific research, spanning biology, chemistry and physics. To delve into ultrafast phenomena, the development of high-energy, highly tunable light sources is instrumental. Here, the photoelectric effect is a pivotal tool for dissecting electron correlations and system structures. Particularly, above-threshold ionization (ATI), characterized by the simultaneous absorption of several photons leading to a final electron energy well above the ionization threshold, has been widely explored, both theoretically and experimentally. ATI decouples laser field effects from the structural information carried by photoelectrons, particularly when utilizing ultrashort pulses. In this contribution, we study ATI driven by polarization-crafted (PC) pulses, which offer precise scanning over the electron momentum, through an accurate change of the polarization state. PC pulses enable the manipulation of photoelectron momentum distributions, opening up new avenues for understanding and harnessing coherent light. Our work explores how structured light could allow for a proper understanding of emitted photoelectrons momentum distributions in order to distinguish between light structure effects and target structure effects.

We use the Schur concavity of the von Neumann entropy and introduce a majorization-based entanglement criterion for the states of systems consisting of identical fermions. This criterion is in the form of an inequality between the von Neumann entropies of the total density matrix and the single-particle reduced density matrix which have to be satisfied by the separable states of such systems, and therefore, its violation indicates the entanglement. Our criterion is an improved version of the one introduced by Zander et al. (in Eur. Phys. J. D 66: 14, 2012). To illustrate its utility, we use the criterion to various illustrative instances of the families of mixed states and find that when the single-particle Hilbert spaces are of dimension four, the criterion indicates all the entangled states within the families under consideration.

Discovering hidden physical mechanisms of a system, such as underlying partial differential equations (PDEs), is an intriguing subject that has not yet been fully explored. In particular, how to go beyond the traditional method to obtain the PDEs of complex systems is currently under active debate. In this work, we propose a deep-learning approach to discover the underlying Gross-Pitaevskii equations (GPEs) of one-dimensional Bose–Einstein condensates (BECs). The results show that such method is markedly superior to the traditional method due to advantages of the deep neural network. The former possesses the ability to obtain a parsimonious model with high accuracy and insensitivity to data noise, and can successfully discover the underlying GPEs that BECs should obey directly from the data even in the absence of a knowledge structure. More importantly, we find that such method is able to work well even for data with (15%) noise. Although the cases studied are proof-of-concept, the method provides a promising technique for unveiling hidden novel physical mechanisms in quantum systems from observations.