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R. Radha

Publications and source records attributed to R. Radha.

51 records · Page 3Linked to original sources
arXiv2015

Persistent bright solitons in sign-indefinite coupled nonlinear Schrodinger equations with a time-dependent harmonic trap

We introduce a model based on a system of coupled nonlinear Schrodinger (NLS) equations with opposite signs infront of the kinetic and gradient terms in the two equations. It also includes time-dependent nonlinearity coefficients and a parabolic expulsive potential. By means of a gauge transformation, we demonstrate that, with a special choice of the time dependence of the trap, the system gives rise to persistent solitons. Exact single and two-soliton analytical solutions and their stability are corroborated by numerical simulations. In particular, the exact solutions exhibit inelastic collisions between solitons.

cond-mat.quant-gas↗
arXiv2015

Generalized gauge transformation approach to construct dark solitons of coupled nonlinear Schrodinger type equations

We harness the freedom in the celebrated gauge transformation approach to generate dark solitons of coupled nonlinear Schrödinger (NLS) type equations. The new approach which is purely algebraic could prove to be very useful, particularly in the construction of vector dark solitons in the fields of nonlinear optics, plasma physics and Bose-Einstein condensates. We have employed this algebraic method to coupled Gross- Pitaevskii (GP) and NLS equations and obtained dark solitons.

nlin.SI↗
arXiv2015

An Analytical Window into the World of Ultracold Atoms

We review the recent developments which had taken place in the domain of quasi one dimensional BECs from the viewpoint of integrability. To start with, we consider the dynamics of scalar BECs in a time independent harmonic trap and observe that the scattering length (SL) can be suitably manipulated either to compress the bright solitons to attain peak matter wave density without causing their explosion or to broaden the width of the condensates without diluting them. When the harmonic trap frequency becomes time dependent, we notice that one can stabilize the condensates in the confining domain while the density of the condensates continue to increase in the expulsive region. We also observe that the trap frequency and the temporal SL can be maneuvered to generate matter wave interference patterns indicating the coherent nature of the atoms in the condensates. We also notice that a small repulsive three body interaction when reinforced with attractive binary interaction can extend the region of stability of the condensates in the quasi-one dimensional regime. On the other hand, the investigation of two component BECs in a time dependent harmonic trap suggests that it is possible to switch matter wave energy from one mode to the other confirming the fact that vector BECs are long lived compared to scalar BECs. The Feshbach resonance management of vector BECs indicates that the two component BECs in a time dependent harmonic trap are more stable compared to the condensates in a time independent trap. The introduction of weak time dependent Rabi coupling rapidly compresses the bright solitons which however can be again stabilized through Feshbach resonance or by finetuning the Rabi coupling while the spatial coupling of vector BECs introduces a phase difference between the condensates which subsequently can be exploited to generate interference pattern in the bright or dark solitons.

cond-mat.quant-gas↗
arXiv2013

Spatiotemporal Binary Interaction and Designer quasi particle condensates

We introduce a new integrable model to investigate the dynamics of two component quasi particle condensates with spatio temporal interaction strengths. We derive the associated Lax-pair of the coupled GP equation and construct matter wave solitons. We show that the spatio temporal binary interaction strengths not only facilitate the stabilization of the condensates, but also enables one to fabricate condensates with desirable densities, geometries and properties leading to the so called "designer quasi particle condensates".

cond-mat.quant-gas↗
arXiv2013

Taming Rogue waves in Vector BECs

Using Gauge transformation method, we generate rogue waves for the two component Bose Einstein Condensates (BECs) governed by the symmetric coupled Gross-Pitaevskii (GP) equations and study their dynamics. We also suggest a mechanism to tame the rogue waves either by manipulating the scattering length through Feshbach resonance or the trapping frequency, a new phenomenon not witnessed in the domain of BEC, we believe that these results may have wider ramifications in the management of rogons.

cond-mat.other↗
arXiv2013

Rotation of the Trajectories of Bright soliton and Realignment of Intensity Distribution in the Coupled Nonlinear Schrodinger Equation

We revisit the collisional dynamics of bright solitons in the coupled Nonlinear Schrodinger equation. We observe that apart from the intensity redistribution in the interaction of bright solitons, one also witnesses a rotation of the trajectories of bright solitons . The angle of rotation can be varied by suitably manipulating the Self-Phase Modulation (SPM) or Cross Phase Modulation (XPM) parameters.The rotation of the trajectories of the bright solitons arises due to the excess energy that is injected into the dynamical system through SPM or XPM. This extra energy not only contributes to the rotation of the trajectories, but also to the realignment of intensity distribution between the two modes. We also notice that the angular separation between the bright solitons can also manouvred suitably. The above results which exclude quantum superposition for the field vectors may have wider ramifications in nonlinear optics, Bose-Einstein condensates, Left Handed (LH) and Right Handed (RH) meta materials.

cond-mat.other↗
arXiv2013

Collisionally inhomogeneous Bose-Einstein condensates with binary and three body interactions in a bichromatic optical lattice

We study the impact of collisionally inhomogeneous binary and three body interaction on Bose-Einstein condensates (BECs) of a dilute gas in a bichromatic optical lattice. We observe that the localized matter wave density which decreases after the introduction of repulsive spatially inhomogeneous binary interaction can be sustained by the addition of constant attractive binary strength in equal amounts. If the balance between repulsive spatially inhomogeneous binary interaction and constant attractive interaction is disturbed, the condensates collapse. Reversal of sign of interaction ensures the longevity of BECs. Any imbalance between attractive spatially inhomogeneous interaction and constant repulsive interaction either results in the collapse of BECs or in the occupation of the condensates at multiple sites on either sides. The introduction of a weak three body interaction in phase with the binary interaction increases the extent of instability of BECs. Reversing the sign of spatially inhomogeneous and constant interaction enhances the stability of BECs.

cond-mat.quant-gas↗
arXiv2011

Controlled Split-Recombination of 2D Matter-Wave Solitons in Time-Dependent Trap

We propose a novel approach to manipulate two-dimensional bright matter-wave solitons by tuning the frequency of the trap which is different from Feshbach resonance technique. The exact bright soliton solutions for two-dimensional Gross-Pitaevskii (GP) equation with attractive interaction strength in a time-dependent trap are constructed analytically and its dynamics show no collapse while modulating the trap frequency. The two-soliton dynamics exhibits an interesting splitting and recombination phenomenon which generates interference pattern in the process. This type of behaviour in two-dimensional BECs has wider ramifications and our approach opens new avenues in stabilizing bright solitons in higher dimensional regime. We have also explored the experimental realization of this novel phenomenon.

cond-mat.quant-gas↗
arXiv2009

Collision of Multimode Dromions and a Firewall in the Two Component Long Wave Short Wave Resonance Interaction Equation

In this paper, we investigate the two component long wave short wave resonance interaction (2CLSRI) equation and show that it admits the Painleve property. We then suitably exploit the recently developed truncated Painleve approach to generate exponentially localized solutions for the short wave components $S^{(1)}$ and $S^{(2)}$ while the long wave L admits line soliton only. The exponentially localized solutions driving the short waves $S^{(1)}$ and $S^{(2)}$ in the y direction are endowed with different energies (intensities) and are called "multimode dromions". We also observe that the multimode dromions suffer intramodal inelastic collision while the existence of a firewall across the modes prevents the switching of energy between the modes.

nlin.PS↗
arXiv2007

Holomorphic Sobolev spaces, Hermite ans special Hermite semigroups and a Paley-Wiener theorem for the windowed Fourier transform

The images of Hermite and Laguerre Sobolev spaces under the Hermite and special Hermite semigroups (respectively) are characterised. These are used to characterise the Schwartz class of rapidly decreasing functions. The image of the space of all tempered distributions is also considered and a Paley-Wiener theorem for the windowed Fourier transform is proved.

math.FA↗
arXiv2007

Trilinearization and Localized Coherent Structures and Periodic Solutions for the (2+1) dimensional K-dV and NNV equations

In this paper, using a novel approach involving the truncated Laurent expansion in the Painlevé analysis of the (2+1) dimensional K-dV equation, we have trilinearized the evolution equation and obtained rather general classes of solutions in terms of arbitrary functions. The highlight of this method is that it allows us to construct generalized periodic structures corresponding to different manifolds in terms of Jacobian elliptic functions, and the exponentially decaying dromions turn out to be special cases of these solutions. We have also constructed multi-elliptic function solutions and multi-dromions and analysed their interactions. The analysis is also extended to the case of generalized Nizhnik-Novikov-Veselov (NNV) equation, which is also trilinearized and general class of solutions obtained.

nlin.SI↗
arXiv2006

Periodic and Localized Solutions of the Long Wave-Short Wave Resonance Interaction Equation

In this paper, we investigate the (2+1) dimensional long wave-short wave resonance interaction (LSRI) equation and show that it possess the Painlevé property. We then solve the LSRI equation using Painlevé truncation approach through which we are able to construct solution in terms of three arbitrary functions. Utilizing the arbitrary functions present in the solution, we have generated a wide class of elliptic function periodic wave solutions and exponentially localized solutions such as dromions, multidromions, instantons, multi-instantons and bounded solitary wave solutions.

nlin.SI↗
arXiv2004

Exponentially Localized Solutions of Mel'nikov Equation

The Mel'nikov equation is a (2+1) dimensional nonlinear evolution equation admitting boomeron type solutions. In this paper, after showing that it satisfies the Painlevé property, we obtain exponentially localized dromion type solutions from the bilinearized version which have not been reported so far. We also obtain more general dromion type solutions with spatially varying amplitude as well as induced multi-dromion solutions.

nlin.SI↗
arXiv1999

Explode-decay dromions in the non-isospectral Davey-Stewartson I (DSI) equation

In this letter, we report the existence of a novel type of explode-decay dromions, which are exponentially localized coherent structures whose amplitude varies with time, through Hirota method for a nonisospectral Davey-Stewartson equation I discussed recently by Jiang. Using suitable transformations, we also point out such solutions also exist for the isospectral Davey-Stewartson I equation itself for a careful choice of the potentials.

math.AP↗