The European Physical Journal B最新文献

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.

The Ising model, originally developed for understanding magnetic phase transitions, has become a cornerstone in the study of collective phenomena across diverse disciplines. In this review, we explore how Ising and Ising-like models have been successfully adapted to sociophysical systems, where binary-state agents mimic human decisions or opinions. By focusing on key areas such as opinion dynamics, financial markets, social segregation, game theory, language evolution, and epidemic spreading, we demonstrate how the models describing these phenomena, inspired by the Ising model, capture essential features of collective behavior, including phase transitions, consensus formation, criticality, and metastability. In particular, we emphasize the role of the dynamical rules of evolution in the different models that often converge back to Ising-like universality. We end by outlining the future directions in sociophysics research, highlighting the continued relevance of the Ising model in the analysis of complex social systems.

This study presents a modified prey–predator model incorporating the Allee effect and Holling-type IV functional response to explore complex dynamics arising from anti-predator behavior, cooperative defense, prey refuge mechanisms, and additional food for the predator. The model is analyzed to explore stability, bifurcation behavior, and population thresholds for the species coexistence. By introducing factors, such as prey refuge and alternative food sources for predator, our study highlights the intricate feedback mechanisms stabilizing population cycles. The simulation results highlight that enhancing prey refuge and incorporating Allee effects can promote prey growth while limiting predator abundance. Additionally, we observe that when the prey growth rate is low, only the predator species can survive. Overall, our findings extend classical results, offering a robust framework for the long-term ecological balance.

The polarization field is the mean dipolar moment of atoms plunged in an external electric field. It characterizes the optical properties of the considered material; light interaction with matter and propagation inside it. This research investigates the dynamics of the polarization field within a ferroelectric substance subjected to a periodically changing electric field. Our analysis deals with the derivation of an equation to describe this behavior. We specifically explore indicators of chaotic behavior, such as the Lyapunov exponent and bifurcation diagram, to demonstrate the emergence of chaos when the electric field’s amplitude varies periodically. Additionally, we identify the parameters responsible for inducing chaos, along with their respective ranges, and examine the phenomenon of multistability within the system. Finally, the linear augmentation method is used to control the multistability in the system under study.