Ansatz Research Articles

Study tsunamis through approximate solution of damped geophysical Korteweg-de Vries equation

<abstract><p>The article studied tsunami waves with consideration of important wave properties such as velocity, width, and collision through finding an approximate solution to the damped geophysical Korteweg-de Vries (dGKdV). The addition of the damping term in the GKdV is a result of studying the nonlinear waves in bounded nonplanar geometry. The properties of the wave in bounded nonplanar geometry are different than the unbounded planar geometry, as many experiments approved. Thus, this work reported for the first time the analytical solution for the dGKdV equation using the Ansatz method. The used method assumed a suitable hypothesis and the initial condition of the GKdV. The GKdV is an integrable equation and the solution can be found by several known methods either analytically or numerically. On the other hand, the dGKdV is a nonintegrable equation and does not have an initial exact solution, and this is the challenge. In this work, the novel Ansatz method proved its ability to reach the approximate solution of dGKdV and presented the effect of the damping term as well as the Coriolis effect term in the amplitude of the wave. The advantage of the Ansatz method was that the obtained solution was in a general solution form depending on the exact solution of GKdV. This means the variety of nonlinear wave structures like solitons, lumps, or cnoidal can be easily investigated by the obtained solution. We realized that the amplitude of a tsunami wave decreases if the Coriolis term or damping term increases, while it increases if wave speed increases.</p></abstract>

Fully quantal description of combined internal conversion and intersystem crossing processes in the smallest Criegee intermediate CH2OO.

A quantal description of nuclear motion using coupled fifteen-state potential energy and spin-orbit coupling surfaces for studying the photodissociation of CH2OO to H2CO(X1A1) + O1D and H2CO(X1A1) + O3P channels is presented. For the evaluation of surfaces, multireference electronic wave functions are employed. For the fully quantal description of the nuclear motion, we diabatize the PESs of the two and four lowest excited singlet and triplet states, respectively, within the three sets of vibronically coupled states, i.e. (B1A', C1A'), (a3A', b3A') and (a3A'', b3A''), employing the diabatization by ansatz method. This yields three different adiabatic-to-diabatic mixing angles, which are used for the diabatization of the spin-orbit coupling surfaces and allow to investigate simultaneously the internal conversion and intersystem crossing processes in CH2OO using a nuclear quantum dynamical approach for the first time. Our calculation predicts the presence of a weak spectral band with irregular and discrete structures, which originates from the role of spin-orbit couplings. This band of the spectrum is mainly located between the minimum energy of the a3A' state and the onset of the B1A' ← X1A' spectral band. Furthermore, sizable SOC between the B1A' and a3A'' states mixes them via intersystem crossing. Due to the vibronic interaction between the a3A'' and a3A' states, the molecule finally relaxes to the a3A' state and is dissociated to H2CO(X1A1) and O3P products.

Contraction of variational principle and optical soliton solutions for two models of nonlinear Schrödinger equation with polynomial law nonlinearity

<abstract><p>Our study analyzes the two models of the nonlinear Schrödinger equation (NLSE) with polynomial law nonlinearity by powerful and comprehensible techniques, such as the variational principle method and the amplitude ansatz method. We will derive the functional integral and the Lagrangian of these equations, which illustrate the system's dynamic. The solutions of these models will be extracted by selecting the trial ansatz functions based on the Jost linear functions, which are continuous at all intervals. We start with the Jost function that has been approximated by a piecewise linear function with a single nontrivial variational parameter in three cases from a region of a rectangular box, then use this trial function to obtain the functional integral and the Lagrangian of the system without any loss. After that, we approximate this trial function by piecewise linear ansatz function in two cases of the two-box potential, then approximate it by quadratic polynomials with two free parameters rather than a piecewise linear ansatz function, and finally, will be approximated by the tanh function. Also, we utilize the amplitude ansatz method to extract the new solitary wave solutions of the proposed equations that contain bright soliton, dark soliton, bright-dark solitary wave solutions, rational dark-bright solutions, and periodic solitary wave solutions. Furthermore, conditions for the stability of the solutions will be submitted. These answers are crucial in applied science and engineering and will be introduced through various graphs such as 2D, 3D, and contour plots.</p></abstract>

Optical dark, singular and bright soliton solutions with dual-mode fourth-order nonlinear Schrödinger equation involving different nonlinearities

This research article investigates the dynamic characteristics of solitary waves within a medium exhibiting weak nonlinearity in dual-mode. Firstly, the three models are converted to dual-mode. The primary focus is to investigate the behavior of solitary waves in a system described by a fourth-order nonlinear Schrödinger (NLS) equation, which incorporates Kerr nonlinearity, weak nonlocality, parabolic law nonlinearity and diffraction. By employing ansatz methods, the study successfully derives various localized waveforms, including bright, dark and singular solitons, based on the governing model. The examination extends to investigating the influence of nonlocality and power coefficients on dynamics of bright, dark and singular solitons. The findings presented in this article represent a crucial advancement in understanding the generation of solitary waves in nonlinear media. As the examined model finds application in various fields such as plasma physics, Bose-Einstein condensates and others, these findings not only enhance our theoretical understanding but also pave the way for potential practical applications and the advancement of innovative technologies.

Exact solution of the quantum integrable model associated with the Motzkin spin chain

The Motzkin spin chain is a spin-1 frustration-free model introduced by Shor & Movassagh. The ground state is constructed by mapping random walks on the upper half of the square lattice to spin configurations. It has unusually large entanglement entropy [quantum fluctuations]. The ground state of the Motzkin chain can be analytically described by the Motzkin paths. There is no analytical description of the excited states. The model is not solvable. We simplify the model by removing one of the local equivalence moves of the Motzkin paths. The system becomes integrable [similar to the XXX spin chain]. We call it free Motzkin chain. From the point of view of quantum integrability, the model is special since its R-matrix does not have crossing unitarity. We solve the periodic free Motzkin chain by generalizing the functional Bethe Ansatz method. We construct a T − Q relation with an additional parameter to formulate the energy spectrum. This new parameter is related to the roots of unity and can be described by the Möbius function in number theory. We observe further patterns of number theory.

The Krylov–Bogoliubov–Mitropolsky method for modeling a forced damped quadratic pendulum oscillator

In the present investigation, a quadratically forced damped pendulum-type equation is solved analytically using several effective and highly accurate approaches. Some different types of pendulum oscillators linked to the forced and damped terms, in addition to the power of the damping term, are analyzed. In the first part, the Krylov–Bogoliubov–Mitropolsky (KBM) technique and the ansatz method are carried out for analyzing the quadratically damped pendulum oscillator. In the second part, the two variants of the KBM technique are implemented for investigating the quadratically forced damped pendulum oscillator. Some symmetric approximations are derived and compared with the fourth-order Runge–Kutta numerical approximation. In addition, the maximum distance error is estimated in the whole study domain for ensuring that all obtained approximations are accurate. The obtained results are illustrated through concrete examples.

Interaction of the DKP particle with the Coulomb-type potential and Aharonov–Bohm potential under the cosmic rainbow gravity

The Duffin–Kemmer–Petiau (DKP) particle with spin 0 interacts with the Aharonov–Bohm (AB) magnetic vector potential and scalar Coulomb-type potential in the cosmic string space–times under the framework of rainbow gravity (RG). By using Bethe–Ansatz method, we obtain the energy eigenvalue and approximate solution to the wave function of the DKP particle with spin 0. We select two sets of rainbow functions and analyze their influence on the energy eigenvalue and wave functions. We find that the energy eigenvalue is determined by the parameters of the rainbow function. It further shows that the rainbow function affects the properties of the space–time where the DKP particle located, and also affects the distribution probability of DKP particles in the space.

Isomorphic shut form valuation for quantum field theory and biological population models

Abstract The fundamental objective of this work is focused to achieve a class of advanced and impressive exact estimations to the Zoomeron equation and the time-fraction biological population model through contrivance by a couple of important and magnificent techniques, namely, the modified extended tanh-function method which depend on the balance theory and the Ricatti–Bernoulli sub-ODE method which is independent of the balancing principle. The suggested model is one of the major concerns for studying population distribution dynamics as well as the quantum field theory which is an important discipline for the description of interactions between light and electrons. The two suggested reliable, effective techniques are considered famous among ths ansatz methods that have various visions to realize the exact solutions to the non linear partial differential equation that reduce the volume of calculations examined before and usually give good results. It is solicited for this contrivance finding new exact solutions for two models in terms of some variable. The models are significant in quantum field theory, description of interactions between light and electron, quantum electrodynamics, demographic model, important to bring it into line with the reasonable distribution of wealth, resources, income, etc. The achieved results predict many types of solutions as trigonometric functions, hyperbolic functions, perfect periodic soliton solutions, singular periodic soliton solutions, and other rational solitons solutions. The efficiency of the techniques is demonstrated by the satisfactory results obtained through the derivation of closed-form soliton solutions from the exact solution by assigning definite values to the variables present in it.

Soliton solutions of the space–time fractional nonlocal nonlinear Schrödinger equation

In this paper, the space–time fractional nonlocal nonlinear Schrödinger equations under Jumarie modified Riemann–Liouville derivative is studied. The soliton solutions are formally derived by using the extended tanh method of fractional Riccati subequation and the ansatz method combined with the Hermite–Gaussian function and Mittag-Leffler function. Different types of solutions are obtained and the necessary conditions for the existence of solutions are given. With the help of Maple, we plot figures exhibit that solitons are forming as fractional order λ increasing, and also, we noticed that at different order n of the Hermite–Gaussian function Hn(y), mainly affects the amplitude of soliton. Furthermore, we have discussed the new soliton solutions in the fractional case. It is of great significance to understand complex physical phenomena described by fractional nonlocal nonlinear equations.

Algebraic Bethe Ansatz for the Open XXZ Spin Chain with Non-Diagonal Boundary Terms via $U_{\mathfrak{q}}\mathfrak{sl}_2$ Symmetry

We derive by the traditional algebraic Bethe ansatz method the Bethe equations for the general open XXZ spin chain with non-diagonal boundary terms under the Nepomechie constraint [J. Phys. A 37 (2004), 433-440, arXiv:hep-th/0304092]. The technical difficulties due to the breaking of $\mathsf{U}(1)$ symmetry and the absence of a reference state are overcome by an algebraic construction where the two-boundary Temperley-Lieb Hamiltonian is realised in a new $U_{\mathfrak{q}}\mathfrak{sl}_2$-invariant spin chain involving infinite-dimensional Verma modules on the edges [J. High Energy Phys. 2022 (2022), no. 11, 016, 64 pages, arXiv:2207.12772]. The equivalence of the two Hamiltonians is established by proving Schur-Weyl duality between $U_{\mathfrak{q}}\mathfrak{sl}_2$ and the two-boundary Temperley-Lieb algebra. In this framework, the Nepomechie condition turns out to have a simple algebraic interpretation in terms of quantum group fusion rules.

Analytical Rational Solitons of the Modified Lakshmanan-Porsezian-Daniel Equation

In this paper, the Lakshmanan-Porsezian-Daniel (LPD) equation is studied. New analytical rational solitons to the LPD equation are presented by an ansatz method. Wave solutions of three types, such as parabolic, trigonometric and hyperbolic function solutions have been retrieved. All solutions are plotted in 3D to enhance the understanding of their physical characteristics. These simulations, which represent the behavior of the resulting hyperbolic, parabolic and trigonometric solitons, are provided by choosing different appropriate values of the parameters.

A family of solutions of the time–space fractional longitudinal wave equation

In this article, we have studied a nonlinear time–space fractional longitudinal wave equation in the context of the conformable fractional derivative. Through the soliton ansatz method and a direct integration approach with the symmetry condition, new soliton and solitary wave solutions are derived. Furthermore, the existing conditions of these obtained solutions are also given in this text. These new results add to the existing literature. We believe that they can provide a new window into the understanding of this model.

Multisolitons in the surface gravity waves and internal waves

In this paper, a five-order Korteweg–de Vries (KdV) equation is studied, which is used to describe the nonlinear phenomena in the fluids, especially those of the surface gravity waves and internal waves in the stratified fluids. (a) Via the symbolic calculation, this KdV equation cannot pass the Painlevé test without any constraint conditions. By virtue of the ansatz method, bell-shape and kink soliton solutions of this KdV equation are attained. (b) Via the bilinear method, multisoliton solutions of this KdV equation are obtained under some constraint conditions. Propagation and interaction of the multisoliton are discussed. Soliton interaction is elastic, that is to say, they have no effect on each other’s amplitude and speed except for phase shift. We hope that our results will be useful for experimental studies of surface gravity waves and internal waves since the coefficients of this KdV equation are all expressed in terms of physical constants, depths, and densities of the fluid.

Traveling Wave Solutions and Conservation Laws of a Generalized Chaffee–Infante Equation in (1+3) Dimensions

This paper aims to analyze a generalized Chaffee–Infante equation with power-law nonlinearity in (1+3) dimensions. Ansatz methods are utilized to provide topological and non-topological soliton solutions. Soliton solutions to nonlinear evolution equations have several practical applications, including plasma physics and the diffusion process, which is why they are becoming important. Additionally, it is shown that for certain values of the parameters, the power-law nonlinearity Chaffee–Infante equation allows solitons solutions. The requirements and restrictions for soliton solutions are also mentioned. Conservation laws are derived for the aforementioned equation. In order to comprehend the dynamics of the underlying model, we graphically show the secured findings. Hirota’s perturbation method is included in the multiple exp-function technique that results in multiple wave solutions that contain new general wave frequencies and phase shifts.

Novel Approximations to the Damped Parametric Driven Pendulum Oscillators

The damped parametric driven nonlinear pendulum equation/oscillator (NPE), also known as the damped disturbed NPE, is examined, along with some associated oscillators for arbitrary angles with the vertical pivot. For analyzing and solving the current pendulum equation, we reduce this equation to the damped Duffing equation (DDE) with variable coefficients. After that, the DDE with variable coefficients is divided into two cases. In the first case, two analytical approximations to the damped undisturbed NPE are obtained. The first approximation is determined using the ansatz method while the second one is derived using He’s frequency formulation. In the second case, i.e., the damped disturbed NPE, three analytical approximations in terms of the trigonometric and Jacobi elliptic functions are derived and discussed using the ansatz method. The semianalytical solutions of the two mentioned cases are graphically compared with the 4th-order Runge–Kutta (RK4) approximations. In addition, the maximum error for all the derived approximations is estimated as compared with the RK4 approximation. The proposed approaches as well as the obtained solutions may greatly help in understanding the mysteries of various nonlinear phenomena that arise in different scientific fields such as fluid mechanics, plasma physics, engineering, and electronic chips.

A fourth-order nonlinear Schrödinger equation involving power law and weak nonlocality: Its solitary waves and modulational instability analysis

The present paper examines the dynamical features of solitary waves in a weakly nonlinear medium. More precisely, the propagation of solitary waves in a system is modeled by a fourth-order nonlinear Schrödinger equation involving diffraction, power law nonlinearity, and weak nonlocality. Several localized waves classified as bright and dark solitons to the governing model are derived using ansatz methods. It is shown how power and nonlocality coefficients affect the dynamics of bright and dark solitons. Furthermore, the modulational instability of continuous waves in the presence of such different effects is studied. The results of the current paper represent a significant advancement in exploring the propagation of solitary waves in a nonlinear medium.

Ansatz and Averaging Methods for Modeling the (Un)Conserved Complex Duffing Oscillators

In this study, both the ansatz and averaging methods are carried out for analyzing the complex Duffing oscillators including the undamped/conserved complex Duffing oscillator (CDO) and the damped/unconserved CDO to obtain some approximate analytical solutions. To analyze the conserved CDO, it is reduced to two decoupled conserved Duffing oscillators. After that, the exact solution of the conserved Duffing oscillator is employed to derive an approximation of the conserved CDO in terms of the Jacobi elliptic function. To analyze the damped CDO, two methodologies are considered. For the first methodology, the damped CDO is reduced to two decoupled damped Duffing oscillators, and the ansatz method is devoted to analyzing the damped Duffing oscillator. Accordingly, an approximation of the damped CDO in terms of trigonometric functions is obtained. In the second methodology, the averaging method is applied directly to the damped CDO to derive an approximation in terms of trigonometric functions. All the obtained solutions are compared with the fourth-order Runge–Kutta (RK4) numerical approximations. This study may help many researchers interested in the field of plasma physics to interpret their laboratory and observations results.

Exact soliton solutions of a (2+1)-dimensional time-modulated nonlinear Schrödinger equation with cubic-quintic nonlinearity

In the present paper, based on the wave ansatz method, exact bright and dark solitons of a (2+1)-dimensional time variable coefficients nonlinear Schrödinger equation with cubic-quintic nonlinearity term are presented. This model can be used to describe the propagation of optical pulse in inhomogeneous media. These obtained solitons exhibit nonautonomous properties due to the amplitude and velocity of them are time-dependent coefficients. At this time, Tangent and Secant function solutions are also reported.

Exact solutions of an extended (3+1)-dimensional nonlinear Schrödinger equation with cubic-quintic nonlinearity term

In this paper, an extended (3+1)-dimensional nonlinear Schrödinger equation with cubic-quintic nonlinearity term is studied. By using the ansatz method, some exact solutions of this equation are obtained, which include solitons solutions, elliptic function solutions, and periodic function solutions. The relations between these solutions and their coefficients are obtained.

Periodic solutions and symmetry reductions of a generalized Chaffee–Infante equation

This paper is devoted to derive periodic solutions of a generalized Chaffee–Infante equation. This will be attained by employing several periodic ansatz methods so as to obtain a variety of exact solutions of distinct physical structures. In addition, other analytical solutions for the aforesaid equation, will be established via the symmetry reduction approach. It will be shown that a generalized Chaffee–Infante equation admits four principal Lie algebra. It will be further shown that the principal Lie algebra admits only one possible extension. The obtained results show that a generalized Chaffee–Infante equation reveals the richness of explicit periodic and traveling wave solutions.