The European Physical Journal Special Topics最新文献

The study of oscillator networks is currently the subject of intensive efforts for researchers working in the field of non-linear science. In this article, we are interested in the collective behavior of a star network formed by four mutually coupled Rayleigh–Duffing type oscillators (RDO here after) although each isolated oscillator undergoes a fixed point motion. The coupling considered is non-linear but exploits the intrinsic non-linearity of each of the oscillators so that no non-linear coupling function is necessary as usual. Using analytical techniques, the basic properties of the star system are studied in terms of equilibrium points and their stability, conditions for the appearance of Hopf bifurcations, dissipation and existence of attractors. The direct numerical integration of the mathematical model highlights fascinating phenomena, such as the coexistence of several parallel bifurcation branches, the coexistence of dynamics of the same type or of different types (i.e., regular and chaotic, hidden or self-excited) as well as multi-spiral chaos. These features are uncovered when changing both initial conditions and parameters. The tests carried out in the laboratory using the Arduino module show very good agreement with the results of the theoretical analysis. The study conducted out in this article provides valuable information as a prelude to understanding the behavior of a much more complex network of Rayleigh–Duffing type oscillators and Gunn type microwave oscillators as well.

This article attempts to summarize the effort by the particle physics community in addressing the tedious work of determining the parameter spaces of beyond-the-standard-model (BSM) scenarios, allowed by data. These spaces, typically associated with a large number of dimensions, especially in the presence of nuisance parameters, suffer from the curse of dimensionality and thus render naive sampling of any kind—even the computationally inexpensive ones—ineffective. Over the years, various new sampling (from variations of Markov Chain Monte Carlo (MCMC) to dynamic nested sampling) and machine learning (ML) algorithms have been adopted by the community to alleviate this issue. If not all, we discuss potentially the most important ones among them and the significance of their results, in detail.

In light of recent measurements suggesting potential lepton flavor universality violations in semileptonic decays at collider experiments, this article provides a concise study of tree- and loop-level B-hadron semileptonic decays, (b rightarrow c l nu _l) and (b rightarrow s l^+ l^-). We provide predictions for lepton flavor violating observables, ({mathcal {R}}_{J/psi }) and ({mathcal {R}}_{eta _c}), across the entire (q^2) range. Our study employs the Relativistic Independent Quark Model (RIQM), highlighting a model-dependent approach to these observables. We compare our model’s predictions with existing lattice predictions, demonstrating the strong applicability of the RIQM framework in describing (B_c) decays. Additionally, we reassess global averages for ({mathcal {R}}_{D(D^*)}) and ({mathcal {R}}_{K(K^*)}) in semileptonic transitions. With the upcoming experimental upgrades and the anticipated Run 3 data on (B_c) meson decays, rapid confirmation of these quantities could indicate significant evidence of physics beyond the Standard Model, thereby opening new pathways for understanding the complex flavor dynamics in B meson decays.

The paper deals with theoretical study of effect of interparticle interaction on the complex magnetic susceptibility and the rate of magnetic energy dissipation in a system of single-domain ferromagnetic particles, immobilized in a non-magnetic media. A real prototype of this model can be a biological tissue with embedded magnetic nanoparticles for hyperthermia therapy of tumor (cancer) diseases. Based on mathematically regular methods of statistical physics, we have shown that, depending on frequency of the applied field, the interparticle interaction can either increase or decrease the energy dissipation, and, therefore, the heat production in the system. We hope that the obtained results can help to explain qualitative contradictions between conclusions of various experimental and theoretical studies of influence of the interparticle interactions on the thermal effect in tissues with embedded magnetic particles.

In this work, a new non-fragile based tracking controller design for fractional order systems with non-linear uncertainty, unidentified external disturbances, and time-delay is investigated. A novel structure of a fractional order non-fragile repetitive controller is suggested to obtain the tracking performance for the addressed system. In particular, gain fluctuations are used with an improved two-degrees-of-freedom Smith predictor in the construction of this structure. Using the Lyapunov–Krasovskii stability theory and a continuous amplitude distributed equivalent system, a new set of criteria to determine the asymptotic stability of the associated closed-loop system is proposed in the context of linear matrix inequalities. Within a single framework, disturbance estimation, asymptotic tracking, and time delay compensation are all done using the obtained stability results. The resulting theoretical results are finally confirmed by numerical examples that demonstrate how the specified constraints could lead the system output to precisely match any defined reference signal by balancing for the unidentified exterior disturbance.