Table of contents

Exact chirped elliptic wave solutions are obtained within the framework of coupled cubic nonlinear Helmholtz equations in the presence of non-Kerr nonlinearity like self-steepening and self-frequency shift. It is shown that, for a particular combination of the self-steepening and the self-frequency shift parameters, the associated nontrivial phase gives rise to chirp reversal across the solitary wave profile. But a different combination of non-Kerr terms leads to chirping but no chirp reversal. The effect of nonparaxial parameter on physical quantities such as intensity, speed and pulse width of the elliptic waves is studied too. It is found that the speed of the solitary wave can be tuned by altering the nonparaxial parameter. Stable propagation of these nonparaxial elliptic waves is achieved by an appropriate choice of parameters.

We explore the hypothesis of magnetic monopoles and propose a magnetic field configuration that yields a Coulomb-type potential in the electric quadrupole moment system. This field configuration establishes a forbidden region for the neutral particle, hence, it establishes a cut-off point. We thus analyse the influence of this cut-off point on a Coulomb-type potential by searching for bound-state solutions to the Schrödinger equation.

The hole probability, i.e., the probability that a region is void of particles, is a benchmark of correlations in many-body systems. We compute analytically this probability P(R) for a sphere of radius R in the case of N noninteracting fermions in their ground state in a d-dimensional trapping potential. Using a connection to the Laguerre-Wishart ensembles of random matrices, we show that, for large N and in the bulk of the Fermi gas, P(R) is described by a universal scaling function of k_F R, for which we obtain an exact formula (k_F being the local Fermi wave vector). It exhibits a super-exponential tail $P(R)\propto e^{- \kappa_d (k_F R)^{d+1}}$ where $\kappa_d$ is a universal amplitude, in good agreement with existing numerical simulations. When R is of the order of the radius of the Fermi gas, the hole probability is described by a large deviation form which is not universal and which we compute exactly for the harmonic potential. Similar results also hold in momentum space.

We propose an interacting non-Hermitian model described by a two-mode quadratic Hamiltonian along with an interaction term to locate and analyse the presence of an exceptional point in the system. Each mode is guided by a Swanson-like quadratic Hamiltonian and a suitable choice is made for the interaction term. The parity-time symmetric transformation is adopted in the standard way relevant for a coupled system.

We study a system of N agents, whose wealth grows linearly, under the effect of stochastic resetting and interacting via a tax-like dynamics —all agents donate a part of their wealth, which is, in turn, redistributed equally among all others. This mimics a socio-economic scenario where people have fixed incomes, suffer individual economic setbacks, and pay taxes to the state. The system always reaches a stationary state, which shows a trivial exponential wealth distribution in the absence of tax dynamics. The introduction of the tax dynamics leads to several interesting features in the stationary wealth distribution. In particular, we analytically find that an increase in taxation for a homogeneous system (where all agents are alike) results in a transition from a society where agents are most likely poor to another where rich agents are more common. We also study inhomogeneous systems, where the growth rates of the agents are chosen from a distribution, and the taxation is proportional to the individual growth rates. We find an optimal taxation, which produces a complete economic equality (average wealth is independent of the individual growth rates), beyond which there is a reverse disparity, where agents with low growth rates are more likely to be rich. We consider three income distributions observed in the real world and show that they exhibit the same qualitative features. Our analytical results are in the N → ∞ limit and backed by numerical simulations.

Based on direct numerical simulations with point-like inertial particles, with Stokes numbers St = 0, 0.5, 3, and 6, transported by homogeneous and isotropic turbulent flows, we present in this letter for the first time evidence for the existence of Markov property in Lagrangian turbulence. We show that the Markov property is valid for a finite step size larger than a Stokes-number-dependent Einstein-Markov coherence time scale. This enables the description of multi-scale statistics of Lagrangian particles by Fokker-Planck equations, which can be embedded in an interdisciplinary approach linking the statistical description of turbulence with fluctuation theorems of non-equilibrium stochastic thermodynamics and local flow structures. The formalism allows estimation of the stochastic thermodynamics entropy exchange associated with the particles Lagrangian trajectories. Entropy-consuming trajectories of the particles are related to specific evolution of velocity increments through scales and may be seen as intermittent structures. Statistical features of Lagrangian paths and entropy values are thus fixed by the fluctuation theorems.

This paper deals with vortices in Maxwell-Chern-Simons models with nonminimal coupling. We introduce constraints between the functions that govern the model and find the conditions to minimize the energy. In this direction, a set of first-order equations with novel features are obtained, allowing us to smoothly modify the slope of the function that drives the scalar field in the rotationally symmetric configurations. The results show that, under specific conditions, the solutions may attain an inflection point outside the origin, while the energy density and the electric and magnetic fields get a ringlike profile. We also introduce a procedure to get multiring vortex configurations whose associated solutions engender several inflection points.

We obtain the analytical solutions to the Schrödinger equation for the attractive inverse-square potential in an induced electric dipole moment system under the influence of the harmonic oscillator. We show that bound states can exist when the electric field configuration brings a cut-off point that imposes a forbidden region for the neutral particle. Then, by dealing with s-waves, we obtain the energy eigenvalues in the strong electric field regime and for small values of the angular frequency of the harmonic oscillator. Further, we extend our discussion about the energy eigenvalues beyond the s-waves.

The non-thermal effects on the low-frequency ion-acoustic Trivelpiece-Gould (TG) wave are examined in a Lorentzian weakly ionized dusty plasma waveguide such as the Hanyang University Diverter Plasma Simulator-2 (DiPS-2). By using the normal mode analysis and the separation of variables, the dispersion relation and the damping modes are obtained for the low-frequency ion-acoustic TG wave in a Lorentzian weakly ionized dusty plasma waveguide. With typical conditions of DiPS-2 such as plasma density $n_{e}\cong n_{i}<10^{11}~{\rm cm}^{-3}$, ion-neutral collision frequency $\nu_{in}\approx 20~{\rm kHz}$, electron temperature $T_{e}\cong 1\text{--}10\ \text{eV}$, and ion temperature $T_{i}\cong 0.1~{\rm eV}$, the following is found: 1) the magnitude of the damping rates of the low-frequency ion-acoustic TG wave in Lorentzian plasmas are always greater than those in Maxwellian plasmas; 2) the ion-acoustic TG wave for the first harmonic mode can also be existed for the shortest period of time; 3) the ion-acoustic TG wave in a smaller waveguide can be existed for a wide range of the wave number; and 4) the non-thermal character of a Lorentzian plasma enhances the anti-symmetric behavior of the damping rate for the ion-acoustic TG wave.

The osmate pyrochlore Cd₂Os₂O₇ supports an antiferromagnet insulator ground state with an all-in/all-out (AIAO) spin ordering at low temperature. Above 225 K, Cd₂Os₂O₇ becomes a paramagnetic metal whereas the mechanism of this metal-to-insulator transition (MIT) remains elusive. In this letter, we use cryogenic near-field technique operating at terahertz frequencies to study the evolution of low-energy response across the MIT. We observed a systematic variation of the magnitude of nano-THz signal across the transition, consistent with the trend in the direct-current conductivity. Conducting domain walls that dominate the nano-scale landscape of the conductivity of a closely related AIAO system Nd₂Ir₂O₇ are not apparent in Cd₂Os₂O₇.

Interaction between isovalent centers is of great interest in device physics. We discovered a quantum oscillatory interaction based on the first principles calculations of two identical isovalent centers in C/Ge/Sn co-doped Si. The interaction is explained by Green's function's analysis and the linear combination of atomic orbitals (LCAO) method. One point defect interacts with another by a product between the defect potentials and the summation term that characterizes the metallization process of the host lattice. The trend of the oscillation is an intrinsic property of the host. The interaction mechanism is further verified by the calculations of the isovalent pairs with different elements. Our works shed light on the precise control of defects in semiconductors.

Two improved kinetic Monte Carlo (kMC) models for investigations of the magnetic properties of finite-size atomic chains are presented. These models take into account the possible noncollinearity of magnetic moments. The spontaneous remagnetization of ferromagnetic Co chains on the Pt(997) surface and antiferromagnetic Fe chains on the $\text{Cu}_2\text{N/Cu(001)}$ surface is investigated in the framework of our models. The results are compared with the results of the simple kMC model. It is also shown that a single domain-wall approximation can be successfully used to estimate the reversal time of the magnetization. Therefore, the improved kMC models can be used for analytical calculations as well as for computer simulations.

Although temperature-dependent self-assembly kinetics is usually described by approaches which assume that the macromolecular aggregates have a definite shape, sometimes that assumption might be inappropriate, as in the case of several colloidal and biopolymeric systems. Here we consider a simple model for particle aggregation which displays a first-order phase transition in order to illustrate a rate theory based on microcanonical thermostatistics that allows one to obtain a shape-free description of its thermally induced self-assembly kinetics. Stochastic simulations are performed to validate our approach and demonstrate how the equilibrium thermostatistics properties of the system can be related to the temperature-dependent rate constants. As a model-independent kinetic approach, it may provide experimentalists with a reliable method to extract information about free-energy profiles and microcanonical entropies from kinetic data.

We study the effects of the interplay between diversity and noise in a 3D network of FitzHugh-Nagumo elements, with topology and dimensions chosen to model a pancreatic β-cell cluster, as an example of an excitable cell network. Our results show that diversity and noise are non-equivalent sources of disorder that have different effects on the network dynamics: their synchronization mechanisms may act independently of one another or synergistically, depending on the mean value of the diversity distribution compared to the intrinsic oscillatory range of the network elements.

Single- and two-qubit nonadiabatic noncyclic geometric quantum computation (NNGQC) have been put forward in theory (Liu B.-J. et al., Phys. Rev. Res.2 (2020) 043130). The features of single-qubit NNGQC have been experimentally verified and the experimental technical route of the two-qubit case has been discussed in detail (Zhang J. W. et al., Phys. Rev. Lett.127 (2021) 030502). The multiple-qubit quantum logic gate is critical for quantum computation. Although combining a series of single- and two-qubit NNGQC gates can form universal operations and create arbitrary multiple-qubit gates, the created multiple-qubit gate often consumes more quantum resource and requires longer evolution time, which makes it more fragile to systematic error and decoherence. In this article, we propose a scheme to directly construct the multiple-qubit NNGQC gates in Rydberg atoms. The numerical results show that the proposed quantum gates have high fidelity and are robust to systemic error and decoherence. Our scheme may be applied in the future quantum computation and many-body quantum science studies.