The European Physical Journal Plus最新文献

The aim of this paper is to investigate different forms of the M-soliton solutions of the (3+1)-dimensional generalized Calogero–Bogoyavlenskiii–Schiff (gCBS) equation. With the help of Hirota’s bilinear method, the resonant Y-type soliton solution and the M-soliton solutions of the exponential function form of the (3+1)-dimensional gCBS equation are derived. Then, the M-soliton solutions in the Wronskian form are obtained in view of the Wronskian determinant and Plücker relations. Finally, the M-soliton solutions of the Grammian form are given using the Pfaffian formula and Jacobi identity. Meanwhile, some exact solutions and analysis are displayed.

We generalize Pavón’s isotropic horizon thermodynamics to anisotropic Kasner spacetimes by introducing direction-dependent apparent horizons and associated transport coefficients (zeta _i). Analytical expressions for (zeta _i) are derived from the Kasner metric and evaluated across the allowed parameter space. An unbiased numerical sampling of (100,000) Kasner triples reveals that the arithmetic mean of (zeta _i) is ill-defined due to divergences at vanishing exponents ((p_i rightarrow 0)). Using the median as a robust statistic, we establish a characteristic value of (tilde{zeta } approx 0.024), which deviates significantly from the isotropic prediction ((zeta =0.5)). We interpret these divergences as thermodynamic signatures of dimensional reduction, where the horizon temperature vanishes for non-expanding gases. These results highlight the thermodynamic imprint of anisotropy and provide a consistent extension of the isotropic framework to direction-dependent cosmologies.

We investigate the quantum battery capacity of a two-qubit system coupled with an anisotropic XY spin chain with Dzyaloshinskii–Moriya (DM) interaction. Our results show that the battery capacity serves as a sensitive indicator of quantum phase transition, exhibiting a sharp change at the critical point. The DM interaction enhances capacity away from criticality but suppresses it near the transition. Environmental coupling strongly reduces capacity, with even weak coupling causing rapid energy leakage, especially in the thermodynamic limit where decoherence drives capacity to a lower bound. We also reveal a non-monotonic relationship between quantum discord and capacity, which reflects the dynamic interplay between energy storage and quantum correlations. These findings provide insights into optimizing quantum batteries through control of interactions and environmental coupling.

Designing high-performance energetic materials is needed for various applications. For the current study, a machine learning (ML) approach is applied to predict the detonation pressure (DP) of energetic organic compounds. A total of 1000 RDKit and Mordred-based electronic, molecular, topological, and electro-topological descriptors have been designed for ML analysis. For this, various ML regressors, including Extra Trees, Gradient Boosting, Historical Gradient Boosting, and Random Forest regressors, are trained to produce R-Squared (R²) ranging from 0.82 to 0.89. Additionally, a new chemical space of 5000 compounds is proposed with its dimension reduction analysis to reveal a range of DP values having t-SNE components being spanned across − 60 to 60. Furthermore, an analysis of the synthetic accessibility (SA) of the designed compounds reveals that SMILES lengths between 200 and 300 are easier to synthesize. Among them, the top 30 candidates with higher SA are identified to exhibit DPs ranging 27.1–33.9 GPa. The SHapley Additive exPlanations (SHAP) reveal that MolLogP, SlogP_VSA5, and PEOE_VSA9 descriptors are key contributors to model performance. The current results provide a promising strategy to design and synthesize high-performance energetic materials.

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A comprehensive simulation-based analysis is performed to assess the optical absorption characteristics and quantum efficiency (QE) of cadmium telluride/zinc selenide (CdTe/ZnSe) quantum dot (QD) stacks, geared toward their application in ultraviolet (UV) photodetectors. The simulation outcomes clearly bring out the sensitivity of both QD radius and junction height to absorption coefficient and QE. For example, QDs with lower radii and heights contribute toward stronger quantum confinement effects, exploring sharper absorption spectra and higher QE values around 215 and 232 nm. Additionally, from junction depth analysis, there is direct proportionality between depletion width and QE. The simulation study also identified secondary factors of minority diffusion lengths (electron and hole diffusion lengths), most appreciable at larger junction depths. The outcome has effectively verified that QDs with appropriate sizes and junction designs, in addition to optimized carrier transport properties, play crucial roles in exploring superior performance characteristics of deep-UV QD-based photodetectors. The simulation outcome is helpful for exploring design strategies for highly efficient size-engineered QD-based photodetectors.

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We investigate the effective potential, spatial curvature, and refractive-lensing signatures generated by the antisymmetric dark-state (ADS) configuration introduced in our previous work. Building on insights from analogue-gravity models and analogue-horizon experiments in Bose–Einstein condensates, we formulate a purely quantum, spatial-only (absolute-time) framework in which geometry emerges from the internal coherence of the dark-state wavefunction, (psi _{text {dark}}). In this setting, a single radial metric factor (A(r)equiv g^{(Q)}_{rr}(r)) is determined by the functional structure of (psi _{text {dark}}), without invoking relativistic time warping or classical sources. The resulting geometric contribution to the specific effective potential, (U_Q(r)), is regular and confining, enabling bound trajectories even at vanishing angular momentum. The Ricci scalar–computed on both the two-dimensional polar slice and the three-dimensional spherical geometry–is finite everywhere and tends to zero at large r. We further map A(r) to an effective refractive-index profile to analyse lensing phenomena; the predicted deflections are consistent with geometric confinement. All symbolic derivations, dynamical simulations, and figures are provided in the Supplementary material.

Cloud formation is due to a combination between water uptake and aerosol distribution and characteristics. Globally, the state of the terrestrial atmosphere is influenced by solar activity and galactic cosmic rays through the global electric circuit. This paper investigates the possible link between cloud cover and solar proxies, namely sunspot number (SSN), solar/plasma wind speed (PWS), and the associated interplanetary electric and magnetic fields (IEF, IMF), respectively, for two solar cycles. The seasonal variation on possible links is also investigated. Each solar driver may influence the atmospheric electricity, thus cloud formation and cloud cover. The study uses the first long-term cloud database, as provided by the International Satellite Cloud Climatology Project (ISCCP), since these data had sufficient time for validation and are ready to use as such. Solar proxies were taken from NASA’s OMNIWeb database, from measurements with instruments onboard several spacecraft with geocentric orbits. Cloud types were individually considered, and global distribution of cloud cover was analyzed. The study reveals that the cloud cover response to changes in various solar indicator depends on local conditions, and varies with season. E.g., high clouds cover exhibited anticorrelation with IEF in January on large areas, while low cloud cover was moderately positively correlated with PWS on extended regions in July.

Black hole accretion disks are a fascinating topic in astrophysics, as they play a crucial role in several high-energy situations. This paper investigates the optical appearance of scalar hairy black holes (SHBHs) with asymmetric potential, a numerical solution obtained in Phys. Rev. D 68, 044006 (2003). Since the solution is spherically symmetric and surrounded by a thin accretion disk, we base our analysis on the work of J. P. Lumininet (1979). We discuss the behavior of the effective potential for massive and massless particles, the innermost stable circular orbits (ISCO), and the photon sphere radius for different SHBHs. The study includes the plots of isoradial curves and spectral shifts arising from gravitational and Doppler shifts by considering direct and secondary images. Based on the work of Page and Thorne (1974), we also investigate the intrinsic intensity of radiation emitted by the disk at a given radius, which allows the calculation of the distribution of observed bolometric flux. We use the angular size of the shadow reported by the EHT for Sagittarius A* and M87* to constrain the SHBHs parameters.

This paper proposes a hexa-stable magnetic rolling pendulum electromagnetic energy harvester (HMRP EMEH) for harnessing energy from multidirectional environmental vibrations. A key advantage of the HMRP EMEH is its low damping, which makes it particularly sensitive to low-amplitude excitation. Numerical analysis from the dynamic model illustrates the harvester’s multiple vibrational patterns, which includes the intrawell oscillation, interwell chaotic oscillation, and the full rotational oscillation. Experiments involving sweep frequency excitation enable the harvester to achieve full rotational oscillation at low frequency and then continue to 24.87 Hz for 0.32 g excitation level, with a peak voltage of 4.4 V generated. Under stochastic excitation with proper excitation intensity, the oscillation of the HMRP EMEH could exhibit the chaotic behavior. Additionally, the impedance matching experiment, when subjected to harmonic excitation, yields a peak average power of 2 mW. Furthermore, a mere 5 s of hand-shaking excitation can power a timer to run for 242 s, highlighting the HMRP EMEH’s promising application prospects.

In this paper, we study the polymer black hole solution surrounded by a quintessence field. The influence of quintessence on the polymer black hole is investigated through its thermodynamic properties, such as the Hawking temperature, entropy, and specific heat, which allow us to address the question of thermodynamic stability. We then calculate bounds on the electromagnetic greybody factors and photon emission rates of the black hole, highlighting the interplay between quintessence and quantum gravity effects in determining these phenomena. We also examine the effects of quintessence and quantum gravity on the geodesics and shadows of massless particles around the black hole. Our results are further compared with observational data of both the Sagittarius A* and M87* black holes from the Event Horizon Telescope (EHT) collaboration.