arXiv subjects

S. Stalin

Publications and source records attributed to S. Stalin.

At least 19 recordsLinked to original sources

arXiv2026

Nondegenerate bright solitons and their interactions in the generalized coupled nonlinear Schroedinger system

It is known that the generalized coupled nonlinear Schroedinger (GCNLS) equations can be reduced to the basic vector nonlinear Schroedinger models through various symmetry reductions. By using such reductions, soliton solutions of several interesting types can be obtained for the GCNLS system. In this paper, we show how the non-degenerate soliton solutions can be derived using one such reduction and analyze the various special features associated with the resulting soliton solutions. We find that the obtained non-degenerate soliton solutions exhibit breathing behavior, characterized by a breathing frequency. We also show that the vector solitons emerging from the reduction undergo elastic collisions with the standard phase shift, similar to the non-degenerate solitons of other coupled nonlinear Schroedinger models. Further, they undergo interesting energysharing collisions when they interact with the already known bright solitons. These collision scenarios are further confirmed by an appropriate asymptotic analysis. We have also analyzed the stability of the obtained vector solitons and found that they are stable against random perturbations. The results presented here enhance the understanding of the nature and dynamics of non-degenerate vector solitons.

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arXiv2025

Linear coupling effect induced beating non-degenerate vector solitons

In this paper, we propose an alternative approach to generate a new class of beating vector solitons. Unlike earlier procedures that use dark-bright or bright-dark soliton solutions to generate beating solitons, the method described here utilizes non-degenerate vector soliton solutions of the Manakov system. It involves linear superposition of such soliton solutions along with an intensity switching mechanism facilitated by cross-coupling between the optical modes. We find that the obtained beating solitons collide elastically with themselves and keep their beating feature unchanged after the collision. We also find that their beating nature can be controlled by allowing them to collide with degenerate beating solitons exhibiting energy-sharing collisions. The results presented in this work will provide new insights into beating solitons in Bose-Einstein condensates, nonlinear optics, and related areas of research.

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arXiv2025

General two-component long-wave short-wave resonance interaction system: Non-degenerate vector solitons and their collision dynamics

In this paper, we demonstrate the emergence of non-degenerate bright solitons and summarize their several interesting features in a completely integrable two-component long-wave-short-wave resonance interaction model with a general form of nonlinearity coefficients. Through the classical Hirota's bilinear method, we obtain a fully non-degenerate $N$-soliton solution in Gram determinant form for this LSRI model. Depending on the choice of velocity conditions, the obtained non-degenerate fundamental soliton is classified into two types, namely ($1,1,1$)- and ($1,1,2$)-non-degenerate one solitons. We then show that the basic ($1,1,1$)-non-degenerate soliton exhibits novel profile structures, including a double-hump, a special flat-top, and a conventional single-hump profile, and ($1,1,2$)-non-degenerate soliton admits two-soliton like oblique collision, a behavior akin to KP line soliton interaction with a short stem structure. A detailed asymptotic analysis is carried out to study the long time behavior of ($1,1,1$)-non-degenerate solitons and it reveals that they undergo both shape-preserving and shape-changing collisions. However, our analysis confirms that the shape changing collision between these solitons become elastic in nature after appropriate shift of time coordinates. Further, we identified that the ($1,1,2$)-non-degenerate solitons also undergo elastic collision. In addition, we have also investigated the formation or suppression of breathing phenomena during collision between a degenerate soliton and a ($1,1,1$)-non-degenerate soliton. For completeness, we also point out the collision scenario between the completely degenerate solitons. The results presented in this paper are broadly applicable to Bose-Einstein condensates, nonlinear optics, plasma physics, and other closely related fields.

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arXiv2025

Vector soliton molecules and their collisions

In recent times, bound soliton states have often been referred to as soliton molecules in the nonlinear optics literature. The striking analogies between photonic bound states and matter molecular structures in chemistry and physics have intensified studies on optical soliton molecules in both conservative and dissipative systems. In this paper, we demonstrate the existence of vector soliton molecules and their related isomer structures in a conservative optical fiber system by considering the integrable Manakov equation. We show their existence by applying the velocity resonance condition and appropriate choice of temporal separations to the degenerate $N=(\bar{N}+\bar{M})$-soliton solution. Then, we classify the obtained molecular states as either dissociated or synthesized molecular states based on the temporal locations of the constituent solitons. Furthermore, we analyze the collision properties of vector soliton molecules in the present conservative system. The collision scenarios reveal that the soliton molecules undergo intriguing energy-sharing collisions through energy redistribution among the modes. To characterize these collisions, we have carried out an appropriate asymptotic analysis and found that elastic collisions arise as a special case of energy-sharing collisions under specific choices of polarization constants. Finally, we numerically verify the robustness of vector soliton molecules. We believe that the results presented in this paper show potential for soliton molecule-based applications such as optical computation and multi-level encoding for communications.

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arXiv2023

Soliton molecules in Fermi-Pasta-Ulam-Tsingou lattice: Gardner equation approach

We revisit the Fermi-Pasta-Ulam-Tsingou lattice (FPUT) with quadratic and cubic nonlinear interactions in the continuous limit by deducing the Gardner equation. Through the Hirota bilinear method, multi-soliton solutions are obtained for the Gardner equation. Based on these solutions, we show the excitation of an interesting class of table-top soliton molecules in the FPUT lattice through the velocity resonance mechanism. Depending on the condition on the free parameters, we classify them as dissociated and synthetic type molecules. The main feature of the table-top soliton molecules is that they do not exhibit oscillations in the coalescence region. This property ensures that they are distinct from the soliton molecules, having retrieval force, of the nonlinear Schr\"odinger family of systems. Further, to study the stability of the soliton molecule we allow it to interact with a single (or multi) soliton(s). The asymptotic analysis shows that their structures remain constant, though the bond length varies, throughout the collision process. In addition, we consider the FPUT lattice with quadratic nonlinear interaction and FPUT lattice with cubic nonlinearity as sub-cases and point out the nature of the soliton molecules for these cases also systematically. We achieve this based on the interconnections between the solutions of the Gardner, modified K-dV and K-dV equations. Finally, we simulate the FPUT chain corresponding to the Gardner equation numerically and verify the existence of all the soliton structures associated with it. We believe that the present study can be extended to other integrable and non-integrable systems with applications in fluid dynamics, Bose-Einstein condensates, nonlinear optics, and plasma physics.

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arXiv2023

Coupled Nonlinear Schr\"odinger System: Role of Four-Wave Mixing Effect on Nondegenerate Vector Solitons

In this paper, we investigate the role of four-wave mixing effect on the structure of nondegenerate vector solitons and their collision dynamics. For this purpose, we consider the generalized coupled nonlinear Schr\"odinger (GCNLS) system which describes the evolution and nonlinear interaction of the two optical modes. The fundamental as well as higher-order nondegenerate vector soliton solutions are derived through the Hirota bilinear method and their forms are rewritten in a compact way using Gram determinants. Very interestingly, we find that the presence of four-wave mixing effect induces a breathing vector soliton state in both the optical modes. Such breather formation is not possible in the fundamental vector bright solitons of the Manakov system. Then, for both strong and weak four-wave mixing effects, we show that the nondegenerate solitons in the GCNLS system undergo, in general, novel shape changing collisions, in addition to shape preserving collision under suitable choice of wave numbers. Further, we analyze the degenerate soliton collision induced novel shape changing property of nondegenerate vector soliton by deriving the partially nondegenerate two-soliton solution. For completeness, the various collision scenarios related to the pure degenerate bright solitons are indicated. We believe that the results reported in this paper will be useful in nonlinear optics for manipulating light by light through collision.

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arXiv2023

Scalar and vector electromagnetic solitary waves in nonlinear hyperbolic media

In this paper, we investigate the problem of electromagnetic wave propagation in hyperbolic nonlinear media. To address this problem, we consider the scalar hyperbolic nonlinear Schr\"odinger system and its coupled version, namely hyperbolic Manakov type equations. These hyperbolic systems are shown to be non-integrable. Then, we examine the propagation properties of both the scalar and vector electromagnetic solitary waves by deriving their exact analytical forms through the Hirota bilinear method. A detailed analysis shows that the presence of hyperbolic transverse dispersion provides an additional degree of freedom to prevent the formation of singularity in both the scalar and vector solitary wave structures in this hyperbolic nonlinear media. Besides this, we realize that the solitary waves in this media possess fascinating propagation properties which cannot be observed in conventional nonlinear media. We believe that the present study will be very useful in analyzing electromagnetic wave propagation in hyperbolic nonlinear metamaterials.

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arXiv2022

Bright, dark and breather soliton solutions of the generalized long-wave short-wave resonance interaction system

In this paper, a generalized long-wave short-wave resonance interaction system, which describes the nonlinear interaction between a short-wave and a long-wave in fluid dynamics, plasma physics and nonlinear optics, is considered. Using the Hirota bilinear method, the general $N$-bright and $N$-dark soliton solutions are deduced and their Gram determinant forms are obtained. A special feature of the fundamental bright soliton solution is that, in general, it behaves like the Korteweg-deVries soliton. However, under a special condition, it also behaves akin to the nonlinear Schr\"{o}dinger soliton when it loses the amplitude dependent velocity property. The fundamental dark-soliton solution admits anti-dark, grey, and completely black soliton profiles, in the short-wave component, depending on the choice of wave parameters. On the other hand, a bright soliton like profile always occurs in the long-wave component. The asymptotic analysis shows that both the bright and dark solitons undergo an elastic collision with a finite phase shift. In addition to these, by tuning the phase shift regime, we point out the existence of resonance interactions among the bright solitons. Furthermore, under a special velocity resonance condition, we bring out the various types of bright and dark soliton bound states. Also, by fixing the phase factor and the system parameter $\beta$, corresponding to the interaction between long and short wave components, the different types of profiles associated with the obtained breather solution are demonstrated.

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arXiv2022

Similarity reductions of peakon equations: integrable cubic equations

We consider the scaling similarity solutions of two integrable cubically nonlinear partial differential equations (PDEs) that admit peaked soliton (peakon) solutions, namely the modified Camassa-Holm (mCH) equation and Novikov's equation. By making use of suitable reciprocal transformations, which map the mCH equation and Novikov's equation to a negative mKdV flow and a negative Sawada-Kotera flow, respectively, we show that each of these scaling similarity reductions is related via a hodograph transformation to an equation of Painlev\'e type: for the mCH equation, its reduction is of second order and second degree, while for Novikov's equation the reduction is a particular case of Painlev\'e V. Furthermore, we show that each of these two different Painlev\'e-type equations is related to the particular cases of Painlev\'e III that arise from analogous similarity reductions of the Camassa-Holm and the Degasperis-Procesi equation, respectively. For each of the cubically nonlinear PDEs considered, we also give explicit parametric forms of their periodic travelling wave solutions in terms of elliptic functions. We present some parametric plots of the latter, and, by using explicit algebraic solutions of Painlev\'e III, we do the same for some of the simplest examples of scaling similarity solutions, together with descriptions of their leading order asymptotic behaviour.

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arXiv2021

Dynamics of nondegenerate solitons in long-wave short-wave resonance interaction system

In this paper, we study the dynamics of an interesting class of vector solitons in the long wave-short wave resonance interaction (LSRI) system. The model that we consider here describes the nonlinear interaction of the long-wave and two-short waves and it generically appears in several physical settings. To derive this class of nondegenerate vector soliton solutions we adopt the Hirota bilinear method with the more general form of admissible seed solutions with nonidentical distinct propagation constants. We express the resultant fundamental as well as multi-soliton solutions in a compact way using Gram-determinants. The general fundamental vector soliton solution possesses several interesting properties. For instance, the double-hump or a single-hump profile structure including a special flattop profile form results in when the soliton propagates in all the components with identical velocities. Interestingly, in the case of nonidentical velocities, the soliton number is increased to two in the long-wave (LW) component, while a single-humped soliton propagates in the two short-wave (SW) components. We establish through a detailed analysis that the nondegenerate multi-solitons in contrast to the already known vector solitons (with identical wave numbers) can undergo three types of elastic collision scenarios: (i) shape preserving, (ii) shape altering, and (iii) a novel shape changing collision, depending on the choice of the soliton parameters. In addition, we point out the coexistence of nondegenerate and degenerate solitons simultaneously along with the associated physical consequences. We also indicate the physical realizations of these general vector solitons in nonlinear optics, hydrodynamics, and Bose-Einstein condensates. Our results are generic and they will be useful in these physical systems and other closely related systems including plasma physics.

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arXiv2021

Nondegenerate bright solitons in coupled nonlinear Schr\"{o}dinger systems: Recent developments on optical vector solitons

Nonlinear dynamics of an optical pulse or a beam continue to be one of the active areas of research in the field of optical solitons. Especially, in multi-mode fibers or fiber arrays and photorefractive materials, the vector solitons display rich nonlinear phenomena. Due to their fascinating and intriguing novel properties, the theory of optical vector solitons has been developed considerably both from theoretical and experimental points of view leading to soliton based promising potential applications. In the recent past, many types of vector solitons have been identified both in the integrable and non-integrable coupled nonlinear Schr\"{o}dinger (CNLS) equations framework. In this article, we review some of the recent progress in understanding the dynamics of the so called nondegenerate vector bright solitons in nonlinear optics, where the fundamental soliton can have more than one propagation constant. We address this theme by considering the integrable two CNLS family of equations, namely Manakov system, mixed 2-CNLS system, coherently CNLS system, generalized CNLS system and two-component long-wave short-wave resonance interaction (LSRI) system. In these models, we discuss the existence of nondegenerate vector solitons and their associated novel multi-hump geometrical profile nature by deriving their analytical forms through the Hirota bilinear method. Then we reveal the novel collision properties of the nondegenerate solitons in the Manakov system as an example. The asymptotic analysis shows that the nondegenerate solitons, in general, undergo three types of elastic collisions without any energy redistribution among the modes. Further, we show that the energy sharing collision exhibiting vector solitons arises as a special case of the newly reported nondegenerate vector solitons. Finally, we point out the possible further developments in this subject and potential applications.

nlin.PS↗

arXiv2021

Multihumped nondegenerate fundamental bright solitons in $N$-coupled nonlinear Schr\"{o}dinger system

In this letter we report the existence of nondegenerate fundamental bright soliton solution for coupled multi-component nonlinear Schr\"{o}dinger equations of Manakov type. To derive this class of nondegenerate vector soliton solutions, we adopt the Hirota bilinear method with appopriate general class of seed solutions. Very interestingly the obtained nondegenerate fundamental soliton solution of the $N$-coupled nonlinear Schr\"{o}dinger (CNLS) system admits multi-hump natured intensity profiles. We explicitly demonstrate this specific property by considering the nondegenerate soliton solutions for $3$ and $4$-CNLS systems. We also point out the existence of a special class of partially nondegenerate soliton solutions by imposing appropriate restrictions on the wavenumbers in the already obtained completely nondegenerate soliton solution. Such class of soliton solutions can also exhibit multi-hump profile structures. Finally, we present the stability analysis of nondegenerate fundamental soliton of the $3$-CNLS system as an example. The numerical results confirm the stability of triple-humped profile nature against perturbations of 5\% and 10\% white noise. The multi-hump nature of nondegenerate fundamental soliton solution will be usefull in multi-level optical communication applications with enhanced flow of data in multi-mode fibers.

nlin.PS↗

arXiv2020

Nondegenerate Solitons and their Collisions in Manakov System

Recently, we have shown that the Manakov equation can admit a more general class of nondegenerate vector solitons, which can undergo collision without any intensity redistribution in general among the modes, associated with distinct wave numbers, besides the already known energy exchanging solitons corresponding to identical wave numbers. In the present comprehensive paper, we discuss in detail the various special features of the reported nondegenerate vector solitons. To bring out these details, we derive the exact forms of such vector one-, two- and three-soliton solutions through Hirota bilinear method and they are rewritten in more compact forms using Gram determinants. The presence of distinct wave numbers allows the nondegenerate fundamental soliton to admit various profiles such as double-hump, flat-top and single-hump structures. We explain the formation of double-hump structure in the fundamental soliton when the relative velocity of the two modes tends to zero. More critical analysis shows that the nondegenerate fundamental solitons can undergo shape preserving as well as shape altering collisions under appropriate conditions. The shape changing collision occurs between the modes of nondegenerate solitons when the parameters are fixed suitably. Then we observe the coexistence of degenerate and nondegenerate solitons when the wave numbers are restricted appropriately in the obtained two-soliton solution. In such a situation we find the degenerate soliton induces shape changing behavior of nondegenerate soliton during the collision process. By performing suitable asymptotic analysis we analyze the consequences that occur in each of the collision scenario. Finally we point out that the previously known class of energy exchanging vector bright solitons, with identical wave numbers, turns out to be a special case of the newly derived nondegenerate solitons.

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arXiv2019

Nondegenerate soliton solutions in certain coupled nonlinear Schr\"{o}dinger systems

In this paper, we report a more general class of nondegenerate soliton solutions, associated with two distinct wave numbers in different modes, for a certain class of physically important integrable two component nonlinear Schr\"{o}dinger type equations through bilinearization procedure. In particular, we consider coupled nonlinear Schr\"{o}dinger (CNLS) equations (both focusing as well as mixed type nonlinearities), coherently coupled nonlinear Schr\"{o}dinger (CCNLS) equations and long-wave-short-wave resonance interaction (LSRI) system. We point out that the obtained general form of soliton solutions exhibit novel profile structures than the previously known degenerate soliton solutions corresponding to identical wave numbers in both the modes. We show that such degenerate soliton solutions can be recovered from the newly derived nondegenerate soliton solutions as limiting cases.

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arXiv2018

Nondegenerate solitons in Manakov system

It is known that Manakov equation which describes wave propagation in two mode optical fibers, photorefractive materials, etc. can admit solitons which allow energy redistribution between the modes on collision that also leads to logical computing. In this paper, we point out that Manakov system can admit more general type of nondegenerate fundamental solitons corresponding to different wave numbers, which undergo collisions without any energy redistribution. The previously known class of solitons which allows energy redistribution among the modes turns out to be a special case corresponding to solitary waves with identical wave numbers in both the modes and travelling with the same velocity. We trace out the reason behind such a possibility and analyze the physical consequences.

nlin.SI↗

arXiv2018

Degenerate soliton solutions and their dynamics in the nonlocal Manakov system: I Symmetry preserving and symmetry breaking solutions

In this paper, we construct degenerate soliton solutions (which preserve $\cal{PT}$-symmetry/break $\cal{PT}$-symmetry) to the nonlocal Manakov system through a nonstandard bilinear procedure. Here by degenerate we mean the solitons that are present in both the modes which propagate with same velocity. The degenerate nonlocal soliton solution is constructed after briefly indicating the form of nondegenerate one-soliton solution. To derive these soliton solutions, we simultaneously solve the nonlocal Manakov equation and a pair of coupled equations that arise from the zero curvature condition. The later consideration yields general soliton solution which agrees with the solutions that are already reported in the literature under certain specific parametric choice. We also discuss the salient features associated with the obtained degenerate soliton solutions.

nlin.SI↗

arXiv2018

Degenerate soliton solutions and their dynamics in the nonlocal Manakov system: II Interactions between solitons

In this paper, by considering the degenerate two bright soliton solutions of the nonlocal Manakov system, we bring out three different types of energy sharing collisions for two different parametric conditions. Among the three, two of them are new which do not exist in the local Manakov equation. By performing an asymptotic analysis to the degenerate two-soliton solution, we explain the changes which occur in the quasi-intensity/quasi-power, phase shift and relative separation distance during the collision process. Remarkably, the intensity redistribution reveals that in the new types of shape changing collisions, the energy difference of soliton in the two modes is not preserved during collision. In contrast to this, in the other shape changing collision, the total energy of soliton in the two modes is conserved during collision. In addition to this, by tuning the imaginary parts of the wave numbers, we observe localized resonant patterns in both the scenarios. We also demonstrate the existence of bound states in the CNNLS equation during the collision process for certain parametric values.

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arXiv2017

A critique on the soliton solutions of $\cal{PT}$-invariant reverse space nonlocal nonlinear Schr\"{o}dinger equation

We point out certain basic misconceptions and incorrect statements given by G\"{u}rses and Pekcan in the recent paper {\bf J. Math. Phys. 59, 051501 (2018)}. We re-emphasize the soliton solution derived by us earlier in {\bf Phys. Lett. A. 381, 2380 (2017)} for the reverse space nonlocal nonlinear Schr\"{o}dinger equation is correct and more general and contains the solutions given by G\"{u}rses and Pekcan as special cases.

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