The European Physical Journal D最新文献

The multi-configuration Dirac–Hartree–Fock method implemented in the Grasp2018 package was employed to calculate the magnetic dipole hyperfine interaction constants and electric field gradients of levels in the ground configuration of the neutral bismuth atom. Combining the calculated electric field gradient of the ground state with the measured electric quadrupole hyperfine interaction constant, we extracted the nuclear quadrupole moment for the (^{209})Bi isotope, (textrm{Q}(^{209} {textbf {Bi}}) = -422(22)) mb. A “world average” value of the nuclear quadrupole moment of this isotope, (textrm{Q}(^{209} {textbf {Bi}}) = -420(17)) mb, was deduced from the present result combined with a large sample of other theoretical values obtained with elaborate atomic- and molecular-structure calculations.

The single-center convergent close-coupling (CCC) method is applied to calculate positron scattering from beryllium. A model potential approach is utilized to extract positronium formation, direct ionization, and values between the positronium formation and direct ionization threshold. For this scattering system, we present results for total, electron loss, elastic, momentum transfer, excitation, positronium formation, direct ionization, stopping power, and mean excitation energy from threshold to 5000 eV. A modified independent atom approach is used to calculate total, electron loss, and elastic cross sections for beryllium oxide for energies above 1 eV. For beryllium, good agreement is viewed with past theory for intermediate and high energies. At lower energies, different theoretical models exhibit substantial differences.

The emergence of fractal waveforms in the modified dispersive water wave (MDWW) system, a nonlinear dispersive extension of shallow-water dynamics with recognized analogies in plasma wave theory, is investigated. Through the application of a Riccati-type transformation, the coupled equations are reduced to analytically tractable forms, yielding distinct families of analytic solutions. Subsequently, by imposing auxiliary functional structures involving trigonometric, logarithmic and Jacobi elliptic expressions, these solutions are shown to generate recursive, self-similar waveforms, whose scale-invariant character is established through systematic fractal diagnostics. Successive magnification and voxel and grid-based box-counting computations confirm non-integer fractal dimensions, with robust convergence and statistical validation via relative error, standard error and bootstrap standard deviation. Such consistency across refinement levels establishes stable scaling exponents and rules out numerical artifacts, thereby rigorously demonstrating intrinsic fractal geometry in the MDWW dynamics. From a physical standpoint, such multiscale structures are indicative of how nonlinear dispersive interactions may generate complex spatial organization relevant to turbulent cascades, energy localization and anomalous transport in plasma environments, nonlinear optical media and shallow-water flows. The principal novelty of the work lies in the unified integration of Riccati-based analytic solution construction with quantitative fractal dimension diagnostics and convergence assessment, thereby providing a new analytical–computational framework for probing fine-scale, self-similar behavior in multidimensional dispersive systems of contemporary interest in plasma physics, nonlinear optics, fluid mechanics and wave propagation theory. The results further demonstrate that analytic fractal waveforms can serve as model proxies for structured energy cascades, offering new analytical pathways toward turbulence-inspired modeling and multiscale transport analysis.

Modified dispersive water wave system: fractal dimension and structural evolution

The far-wing photoabsorption and photoemission spectra of the RbAr (D_1) and (D_2) lines provoked by collisions with argon atoms have been determined by adopting a full quantum-mechanical approaches. The calculations have been performed for temperatures ranging from 500 to 3000 K, using two different sets of ab initio potential data points. The effect of temperature and of interatomic potentials on the broadening profiles is then analyzed. The results show that only the free-free transitions are dominant and they revealed the existence of blue satellite features at approximately 740 nm and 750 nm depending on the potential set used. The general shapes of the present simulated spectra are similar to those already measured by many other authors.

We propose a new quantum simulation method for a many-body quantum liquid of identical particles at finite (nonzero) temperature. The new scheme expands the high-temperature density matrix on the overcomplete set of single particles coherent states of John Rider Klauder instead of the usual plane waves as in conventional path integral methods. One is free to tune the elastic constant and/or the mass of the harmonic oscillator subtending the coherent states so as to maximize the computational efficiency of the algorithm. We prove that in the limit of an extremely stiff harmonic oscillator the results for the internal energy tend toward the correct expected values. Moreover, we suggest that a stiff harmonic oscillator could allow the use of larger (imaginary) timesteps. This additional degree of freedom is the characteristic feature of our new algorithm and is not available in more conventional path integral methods.

In this work, we present a comprehensive quantum-mechanical analysis of the spectral properties of the titanium atom, with emphasis on semi-forbidden (intercombination) electronic transitions. The calculations are performed within density-functional theory (DFT) including spin–orbit coupling, and the Kohn–Sham equations are solved numerically by a conjugate-gradient method, yielding high accuracy at moderate computational cost. Oscillator strengths and transition characteristics are obtained within time-dependent DFT using the Casida formalism, which enables a consistent treatment of correlation effects and multiplet structure. Particular attention is paid to the mechanisms of population inversion and to comparisons between theory and experiment. The results validate the proposed approach and demonstrate its potential for applications to complex atomic systems in astrophysics, materials science, and quantum optics.

Four-level system: optical pumping, laser emission, collisions, and spontaneous decays

The choice of basis functions plays a vital role in performing accurate calculations of atomic properties. An alternative to the commonly used Gaussian-type orbitals (GTOs) is the use of B-spline functions, which offer a highly flexible and efficient basis for representing atomic wave functions. The accuracy of an atomic property depends on the quality of the chosen basis functions used to construct single-particle wave functions. This work aims at revisiting the behavior of GTOs and B-spline functions to use them optimally in different atomic calculations so that it can help reduce computational cost. In this context, we analyze the magnetic-dipole hyperfine constants ((A_{fs})) for a number of atomic states in (^{133})Cs. We first analyze results obtained using GTOs and B-splines, which are often used in the literature, followed by redefining them to improve efficiency in the calculation of atomic properties. Our comparative study reveals that an adaptive distribution of GTOs delivers the best results for low- and intermediate-lying states, whereas a kinetically balanced B-spline basis becomes more reliable for high-lying states, especially when a large number of basis functions are employed.

Efficient basis choice improves accuracy and reduces computational cost in atomic property calculations

We investigate whether negative values of Wigner functions purely coming from correlations are sufficient for observing nonlocal correlations. We employ a simple model for superpositions of coherent states and examine how the corresponding Wigner negativity of correlations relates to the violation of a CHSH inequality based on pseudo-spins. We find that a critical amount of this negativity is necessary to violate the inequality, making a nonzero negativity not sufficient for observing nonlocal correlations.