Brazilian Journal of Physics最新文献

Weather forecasting plays a crucial role in supporting strategic decisions across various sectors, including agriculture, renewable energy production, and disaster management. However, the inherently dynamic and chaotic behavior of the atmosphere presents significant challenges to conventional predictive models. On the other hand, introducing quantum computing simulation techniques to the forecasting problems constitutes a promising alternative to overcome these challenges. In this context, this work explores the emerging intersection between quantum machine learning (QML) and climate forecasting. We present a feasibility study of a Quantum Neural Network (QNN) trained on real meteorological data. Despite observed nonlinearities and architectural sensitivities, the QNN employed demonstrated robustness in handling temporal variability and faster convergence in temperature prediction. The findings highlight the potential of quantum models in short- and medium-term climate prediction, while also revealing key challenges and future directions for optimization and broader applicability.

The Jaynes–Cummings (JC) model stands as a fully quantized, fundamental framework for exploring light–matter interactions, a timely reflection on a century of quantum theory. The time-dependent Jaynes–Cummings (TDJC) model introduces temporal variations in certain parameters, which often require the use of numerical methods. However, under the resonance condition, exact solutions can be obtained, offering insight into a variety of physical scenarios. In this work, we study the resonant TDJC model considering different modulations of the atom–field coupling. The model is presented and an analytical solution derived in a didactic way, allowing us to examine how time-dependent couplings affect atomic population inversion and atom–field entanglement. We also consider an atom traversing a partially cooled cavity, which induces periodicity and reveals the combined effects of atomic motion and thermal fluctuations. The Bloch vector is used to analyze the dynamics of the system, including the atomic state purity, and reveals phenomena such as atomic dipole alignment with the field due to the oscillating coupling, as well as atomic population trapping, which arises by increasing the initial mean thermal photon number.

This article presents a theoretical approach for achieving sub-wavelength atomic localization in a four-level tripod-type atomic system. By analyzing the transmission spectrum, we show how the interaction of two orthogonal standing-wave fields with a weak probe field allows precise control over atomic localization. Our results reveal sharply defined one, two and four localized peaks, corresponding to specific atomic positions. We also explore how control fields, probe detuning, and decay rates influence two-dimensional atomic localization. In particular, reducing the decay rates from (0.05gamma) to (0.01gamma) leads to ultra-high precision, with atoms localized to regions as small as (lambda /32 times lambda /32) and a marked increase in localization probability. This enhanced precision arises from the complex interaction between the atom and the standing-wave and probe fields. These findings have important implications for advanced atomic manipulation techniques, such as nano-lithography and laser cooling, where precise control of atomic placement is crucial for improved performance and efficiency.

An analytical investigation of the excitation of the ion Bernstein wave and ion cyclotron wave by ion beam in a plasma with density ripple is reported because the ion beams have the potential to excite the ion Bernstein wave and ion cyclotron wave existing in plasma. The density ripple in plasma with a suitable wave vector results in a significant enhancement in the growth rate of the ion Bernstein wave and the ion cyclotron wave via a Cerenkov interaction. We obtain the maximum growth rate of each mode at the inverse of the Larmor radius. We observe that the growth rate of ion Bernstein and ion cyclotron waves is much affected by the variation in beam cyclotron frequency, ion thermal velocity, and rippled density of plasma for Cerenkov resonance and slow cyclotron interactions. The graphical results show that the growth rate of waves increases with an increase in the density ripple and static magnetic field. This theory of excitation of ion Bernstein and ion cyclotron waves might be relevant in fusion plasma, tokamak plasma, and plasma heating.

In response to the recent Comments [1] on our published paper [2], wherein the authors raise questions on the physical realization of quantum dusty plasma, the present reply provides a detailed justification of the validity and novelty of the study carried in [2].

The current investigation is the first effort to measure the magnetic characteristics of (CuO, ZnO and CuO-ZnO)/Polyaniline Composites. In this study, the elements of composites such as PANI, CuO and ZnO were synthesized chemically, whereas the composite was synthesized using ex-situ method. Fourier transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and X-ray Diffraction (XRD) were employed to evaluate the as-prepared composites. Magnetic characteristics parameters such as magnetic saturation (Ms), magnetic remanence (Mr), and coercivity (Hc) were effectively determined using VSM data. Ms = 48.79 emu/g, Mr = 14.7 emu/g, and Hc = 0.38Oe are the highest values of all magnetic properties associated with the CuO-ZnO/Polyaniline composite. We observed that ZnO and CuO doping in PANI nanoparticles leads to enhancement in the magnetization that might be suitable for magnetic sensors, data storage, supercapacitors, spintronics devices.

We investigate topological interface states (TISs) in inversion- or mirror-symmetric one-dimensional photonic crystals (PCs) composed of (varvec{n}) dielectric materials, where each unit cell has equal optical thickness ((varvec{lambda /6}) for ternary and (varvec{lambda /8}) for quaternary PCs). Contrary to conventional assumptions that differing outer layers are required for TIS emergence, our results reveal that this is not universally necessary: ternary PCs with identical outer layers and a distinct central material fail to support TISs, while quaternary PCs can exhibit TISs even when the first and last layers are the same, provided that the internal layers differ significantly. This demonstrates that internal structural asymmetry, rather than boundary conditions alone, governs the existence of TISs. Zak phase analysis confirms their topological origin, and we further show that higher refractive index contrast leads to wider bandgaps. These findings establish new design principles for achieving robust and tunable topological states in terahertz photonics and integrated optical applications.

We revisit a family of temperature-dependent van der Waals-type equations of state to improve the estimation of the adiabatic lapse rate in planetary atmospheres. This family of equations of state generalize the classical van der Waals and Berthelot models by introducing a single parameter that modulates the temperature dependence of intermolecular interactions. We analyze their thermodynamic properties, including critical behavior, spinodal and coexistence curves, and entropy. The adiabatic curves are computed by explicitly incorporating the contribution of molecular vibrational and rotational degrees of freedom. Using a generalized expression for the adiabatic lapse rate, we estimate the adiabatic lapse rate in the troposphere of Titan and Venus. Our results show that the van der Waals-type equation of state reproduces the observed lapse rates more accurately than the van der Waals one.

The Peyrard-Bishop-Dauxois (PBD) model is a notable representation of DNA, offering valuable insights due to its helicoidal structure. This configuration brings distant nucleotides into close proximity through hydrogen bonds facilitated by water filaments. This paper focuses on the fifth-order approximation of breather modes and solvent interactions within the helicoidal PBD model. We initiate our study by deriving the discrete nonlinear differential equation governing polynucleotide motion via Hamiltonian formalism. Subsequently, we obtain the linear dispersion law for small-amplitude waves. Utilizing the reductive perturbation method, we then derive the Quintic nonlinear Schrödinger equation (QNLSE), incorporating solvent interaction parameters. A comprehensive modulational instability analysis is conducted, followed by an analytical examination of an exact solution using direct integration. Our findings indicate that solvent interactions significantly influence the amplitude of bright solitons and the breather mode’s pulse.

This study re-examines the influence of quadrupole deformation (beta _2) on optimum fusion orientations and, for the first time in this context, investigates the role of hexadecapole deformation (beta _4) using a microscopic framework. Employing the Skyrme energy density formalism (SEDF) within the semiclassical extended Thomas–Fermi (ETF) approach, we analyse hot-compact and cold-elongated configurations in the fusion of silicon isotopes. While earlier studies based on phenomenological models, such as the Prox77 proximity potential, suggested that optimum orientations depend solely on the sign of (beta _2) and are unaffected by higher-order deformations, our findings show otherwise. We demonstrate that (beta _4) can induce significant deviations, up to 40(^circ), in optimum hot-compact orientations. In contrast, cold-elongated configurations remain unchanged. Moreover, we find that optimum orientations depend on both the sign and the magnitude of (beta _2), particularly when (beta _2) is large. Our results reveal that higher-order multipole deformations are essential for a precise description of orientation-dependent fusion dynamics.