The European Physical Journal B最新文献

Synchronization is an important dynamic behavior in coupled oscillator networks, especially in symmetric networks, where the synchronization characteristics of the system are closely related to the symmetry of its coupling topology. This paper investigates a class of structurally symmetric undirected coupled oscillator network models and proposes a new method for identifying synchronization patterns based on the theory of rotating periodic solutions combined with Laplacian matrix eigenvalue analysis. We find that there is a clear correspondence between synchronization types and eigenvalues of the Laplacian matrix, and the corresponding eigenvectors effectively characterize different synchronization modes. In particular, the appearance of repeated eigenvalues in the Laplacian matrix is a necessary condition for the formation of periodic synchronization and synchronous multistability. This study systematically reveals the relationship between the spectral properties of the Laplacian matrix (including the multiplicity of eigenvalues and the structure of their eigenspaces) and synchronization types. The findings provide new theoretical tools for the identification and prediction of synchronization patterns in complex networks and deepen our understanding of the intrinsic relationship between network structure and synchronization types.

Convection in porous media plays a vital role in engineering and natural processes such as geothermal energy recovery, environmental remediation, and microbial transport in bioreactors. This study investigates how gravitational modulation influences bio-convective heat and mass transfer in porous materials saturated with motile microorganisms under reactive flow conditions. The main aim is to develop a comprehensive multiscale model that couples thermal, solutal, microbial, and gravitational processes with chemical reactions. The governing equations are formulated using Darcy–Brinkman and energy transport relations, incorporating activation energy, cross-diffusion effects, and microbial motility. Linear stability analysis is used to determine the critical Rayleigh–Darcy number marking the onset of convection, while weakly nonlinear analysis based on the Ginzburg–Landau equation is employed to capture amplitude evolution and post-onset transport dynamics. The results show that gravitational modulation lowers the critical threshold for instability, thereby promoting earlier onset of convection, while parameters, such as Darcy number, Lewis number, and activation energy, exert a stabilizing influence. Nonlinear analysis reveals that heat and mass transfer rates, represented by the Nusselt and Sherwood numbers, are significantly affected by modulation frequency, amplitude, and microbial activity, leading to either enhancement or suppression of convective transport. Overall, the findings highlight the dual role of gravitational modulation as both a destabilizing factor and a control mechanism, showing that higher modulation frequencies stabilize the system, while larger amplitudes promote earlier convection onset.

This study investigates how gravitational modulation influences bio-convective heat and mass transfer in porous media with motile microorganisms. Using Darcy–Brinkman modeling and linear/nonlinear stability analysis, the critical Rayleigh–Darcy threshold is determined. Linear analysis yields marginal stability curves, while nonlinear theory derives a Ginzburg–Landau amplitude equation. The impacts of microbial activity, chemical reactions, Soret and Dufour effects are revealed through variations in Nusselt and Sherwood numbers.

A set of the metastable at room temperature (RT) (hbox {Au}_{1-x}hbox {Fe}_{x}) alloy films ((0.01le hbox {x}le 0.98)) were fabricated using DC RT magnetron co-sputtering of Au and Fe targets. It was shown that the solid solution of Fe in face-centered cubic (FCC) Au is formed in (hbox {Au}_{1-x}hbox {Fe}_{x}) alloy films for (0.01le hbox {x}le 0.77). At (xapprox 0.80), the transition from the FCC type to body-centered cubic (BCC)-type ordered (hbox {Au}_{1-x}hbox {Fe}_{x}) alloy films takes place. The first-principle calculations of the density of electronic states, the cohesive energies, and element resolved magnetic moments ((m_{Au}) and (m_{Fe})) have been performed for FCC-type ordered structures (hbox {L1}_{2})-(hbox {Au}_{0.75}hbox {Fe}_{0.25}), (hbox {L1}_{0})-(hbox {Au}_{0.50}hbox {Fe}_{0.50}), and (hbox {L1}_{2})-(hbox {Au}_{0.25}hbox {Fe}_{0.75}). The calculations reveal that among these alloys, the (hbox {Au}_{0.25}hbox {Fe}_{0.75}) is the most stable as having the largest cohesive energy. It was also shown that both Au and Fe atoms contribute to the calculated resulting magnetic moment (M_{AuFe}) of (hbox {Au}_{1-x}hbox {Fe}_{x}) alloys but have an opposite compositional dependence on Fe content. The general decrease in calculated magnetic moment of (hbox {Au}_{1-x}hbox {Fe}_{x}) alloys (M_{AuFe}) with a decrease in x nicely agrees with the experimentally determined compositional dependence of magnetic properties of (hbox {Au}_{1-x}hbox {Fe}_{x}) alloy films. Unlike the literature results, the experimentally determined M(x) dependence shows two different parts related to the films with FCC type or BCC type of structure.

We introduce a higher quantum mechanics whose fundamental structure arises from the breakdown of categorical coherence beyond the first order. In our formulation, standard quantum mechanics itself emerges from first-order categorical coherence breakdown, corresponding to the familiar non-commutativity of observables and described geometrically by the Uhlmann gauge connection on the purification bundle. By promoting this to a higher categorical and higher gauge framework, we show that breakdown at higher coherence levels corresponds to the emergence of higher Uhlmann curvatures-geometric obstruction classes whose state-dependent structure induces intrinsic nonlinearities in the quantum equations of motion. We provide a concrete categorical model based on a 2-category of contexts generated by projective-valued measures (PVMs) with coarse-grainings, construct the Uhlmann bundle-gerbe over the manifold of full-rank density operators, and compute its Deligne class. A rigorous transgression functor from the path 2-groupoid of contexts to the holonomy 2-group of the gerbe yields curvature-weighted Magnus/Chen expansions, from which we derive explicit nonlinear correction functionals (mathcal {N}_{j}[rho ]) for æ =2,3. These nonlinear terms are the direct quantum-mechanical analog of interaction terms in gauge field theory, but arise here from multi-way measurement incompatibilities rather than external interactions. We argue that this higher-order geometric structure provides a natural theoretical framework for regimes where standard linear quantum mechanics is insufficient-particularly in quantum chemistry, multi-electron strongly correlated systems, and nonadiabatic dynamics at conical intersections. Applications are discussed for catalytic processes, chaotic electron dynamics, and materials with strong electron correlation, where our theory predicts experimentally testable deviations from linear quantum predictions.

Usage of nano-sensors to detect quality of food is an emerging field. A recent experiment on reduced graphene oxide (r-GO) inferred that polymerization of r-GO is necessary to discriminate various volatile organic compounds (VOC), the markers for detecting stage of degradation of food products. Motivated by this, using a combination of density functional theory and non-equilibrium Green’s function, we have investigated in detail the capability of monolayer graphene, r-GO and GO as sensors to detect quality of standard food products like vegetable, fruit, and meat. We assess the sensitivity and selectivity of these 2D materials as chemiresistive as well as work function-based sensors. We find that pristine graphene performs poorly while r-GO is able to differentiate between four, out of six VOCs (acetone, dimethylsulfide, ethanol, methanol, methylacetate, toluene), both as chemiresistive and work function-based sensor. GO, on the other hand, performs at par with r-GO as work function-based sensor but is not useful as chemiresistive one. We show that such behavior can be traced back to the changes in the electronic structures of the 2D materials upon adsorption of the VOCs. We infer that the discrepancy between our results and the experiment in the context of the performance of r-GO sensor can be due to the limitations in the experimental method of reducing Graphene.

This paper investigates the presence and stability of nonlinear localized modes within the Gross–Pitaevskii Equation (GPE), considering interactions involving cubic–quintic nonlinearities and varying spin-orbit momentum (SOM). It also explores two distinct types of complex parity-time ((mathcal{P}mathcal{T}))-symmetric potentials, specifically Gaussian harmonic and periodic potentials. The influence of the SOM coefficient on regions of unbroken and broken phases is examined, revealing its modulation effect on the nonlinear stability and power distribution of these modes. Additionally, the interaction dynamics of two spatial solitons are analyzed within the context of the (mathcal{P}mathcal{T})-symmetric Gaussian potential. Notably, it is found that solitons remain stable even when the (mathcal{P}mathcal{T})-symmetry of the underlying nonlinear model is disrupted. The accuracy of the findings is confirmed through comparisons with numerical simulations and exact analytical expressions of the localized modes in one dimension (1D). The numerical simulations also indicate that obtaining the stable solitons of the cubic–quintic GPE with a varying SOM term is most challenging when the considered (mathcal{P}mathcal{T})-symmetric potential is periodic.

We investigate measures of non-Markovianity in open quantum systems governed by Gaussian free fermionic dynamics. Standard indicators of non-Markovian behavior, such as the BLP and LFS measures, are revisited in this context. We show that for Gaussian states, trace-based distances—specifically the Hilbert–Schmidt norm—and second-order Rényi mutual information can be efficiently expressed in terms of two-point correlation functions, enabling practical computation even in systems where the full-density matrix is intractable. Crucially, this framework remains valid even when the density matrix of the system is an average over stochastic Gaussian trajectories, yielding a non-Gaussian state. We present efficient numerical protocols based on this structure and demonstrate their feasibility through a small-scale simulation. Our approach opens a scalable path to quantifying non-Markovianity in interacting or measured fermionic systems, with applications in quantum information and non-equilibrium quantum dynamics.