arXiv subjects

R. Radha

Publications and source records attributed to R. Radha.

At least 19 recordsLinked to original sources

arXiv2026

Exploring the unknown territory of Dromions of (2+1) dimensional Generalized Nonlinear Schrodinger Equation

In this paper, we travel through an unknown territory of dromions, to unearth and show the new properties/attributes of dromions which have never been brought to the fore since they were first discovered by Boiti etal [1]. These new attributes are brought out by investigating a generalized (2+1) dimensional Nonlinear Schrodinger (NLS) equation by exploiting Truncated Painleve approach. The signatures that can be attributed to dromions include existence of firewall and reflection at the boundary, uneven distribution of energy among different bound states, amplitude dependence on adjacent dromions, etc. We have corroborated the main analytical results with numerical simulations also. We categorically state that these properties are universal and can be extracted in any (2+1) dimensional nonlinear partial differential equation. We do believe that these properties which shed more light on the behaviour of dromions may have wider repercussions in nonlinear optics, Bose-Einstein condensates and plasma physics.

nlin.SI↗

arXiv2026

Stability and dynamics of dark-bright solitons in spin-orbit- and Rabi-coupled binary Bose-Einstein condensates

We investigate the stability and nonlinear dynamics of dark--bright solitons in a one-dimensional binary Bose--Einstein condensate subjected to synthetic spin--orbit and Rabi couplings. In the absence of spin--orbit coupling, we map the coupled Gross--Pitaevskii equations onto the integrable Manakov model to obtain exact dark--bright soliton solutions, providing a rigorous theoretical benchmark. We demonstrate that finite spin--orbit coupling breaks integrability by inducing spin-dependent phase gradients that drive component-wise spatial separation and intrinsic density oscillations. By contrast, coherent Rabi driving enforces phase locking between spin components and supports robust breather-like excitations. Furthermore, we derive analytical continuity relations for mass and spin current densities, mapping the internal spin dynamics onto an internal Josephson-junction framework in which the gauge field acts as a continuous spatial momentum bias. Using imaginary-time propagation together with Bogoliubov--de Gennes analysis, we systematically characterise ground-state phases and excitation spectra for both symmetric and asymmetric interaction regimes in homogeneous and harmonically trapped systems. Real-time simulations further demonstrate that synthetic gauge fields and interaction quenches drive the system far from equilibrium, triggering modulational-instability-induced multi-soliton fragmentation, breathing stripe patterns, and non-equilibrium transport. Our results highlight the interplay of synthetic gauge fields, external confinement, and interaction engineering as powerful tools for controlling the stability and internal dynamics of multicomponent quantum fluids.

cond-mat.quant-gas↗

arXiv2026

Quantum correlation and coherence in a mononuclear nickel-based molecular Magnet

We investigate the behaviors of thermal entanglement, quantum correlation beyond entanglement namely, measurement-induced nonlocality (MIN) and coherence in a nickel radical molecular magnet (Et3NH)[Ni(hfac)2L], whose spin-spin interactions are well described by the Heisenberg model. Using experimentally estimated coupling parameters, we compute the thermal state of the system and analyze the dependence of quantum resources on temperature and magnetic field. The results indicate that the quantum resources of the nickel-radical molecular magnet persist even at room temperature. We show that while negativity (the entanglement measure) rapidly vanishes with increasing temperature and magnetic field, measurement-induced nonlocality and quantum coherence remain comparatively more stable and persist in regions where entanglement is absent. These results highlight the significance of nonclassical correlations beyond entanglement in thermally activated spin systems and suggest that such molecular magnets could serve as viable platforms for quantum information processing in realistic conditions.

quant-ph↗

arXiv2025

Stable Quantum Vortices in Lee-Huang-Yang Dipolar Superfluids

The nucleation and dynamics of vortices in the quasi-two-dimensional rotating dipolar Bose-Einstein condensate are explored by taking into account the Lee-Huang-Yang (LHY) correction to the mean-field (MF) theory. Assuming approximate cancellation of the MF interactions, we focus on the formation of a pure LHY superfluid. The effect of rotational frequency $\Omega $ is investigated numerically by determining the corresponding number of stable vortices in the superfluid, together with the respective energy per particle $E$ and chemical potential $\mu $. The LHY superfluid provides a deep minimum of $E$ and $\mu $, indicating that it is a remarkably robust state of quantum matter. By fixing the LHY interaction strength, an exact single-vortex critical frequency is found, along with the respective chemical potential. A notable feature, observed when creating the LHY superfluid with fewer than five vortices, which is understood as being due to the superfluid's nonlinearity and trapping aspect ratio, is the large frequency ranges admitting the production of two and four vortices, as compared to the small frequency ranges to obtain one and three vortices.

cond-mat.quant-gas↗

arXiv2025

Vortices in Tunable Dipolar Bose-Einstein condensates with Attractive Interactions

We investigate the formation of vortices in quasi-two-dimensional dipolar Bose-Einstein Condensates (BECs) through the interplay between two-body contact and long-ranged dipole-dipole interactions (DDIs), as both interactions can be tuned from repulsive to attractive. By solving the associated Gross-Pitaevskii equation for a rotating system, our initial approach concentrates on stabilizing a collapsing condensate with attractive s-wave two-body interactions by employing sufficiently large repulsive DDIs. Subsequently, the same procedure was applied after reversing the signs of both interactions to evaluate the sensitivity of vortex formation to such an interchange of interactions. As a reference to guide our investigation, valid for generic dipolar atomic species, we have assumed a condensate with the strong dipolar dysprosium isotope, 164Dy. The correlation of the results with other dipolar BEC systems was exemplified by considering rotating BECs with two other isotopes, namely 168Er and 52Cr. For a purely dipolar condensate (with zero contact interactions) under fixed rotation, we demonstrate how the number of visible vortices increases as the DDI becomes more repulsive, accomplished by tuning the orientation of the dipoles through a characteristic angle parameter.

cond-mat.quant-gas↗

arXiv2024

Robust Dynamics of Rogue waves, Breathers and Mixed Bound State Solutions in Spin-Orbit and Rabi Coupled Condensates

In this paper, based on an integrable model governed by four system parameters, namely, spin-orbit coupling and Rabi coupling which are constants while the other two parameters, namely the harmonic trap and scattering lengths which are time dependent, we investigate the spin orbit-Rabi coupled condensates governed by the two coupled Gross-Pitaevskii(GP) equation. Employing Darboux transformation approach with nontrivial seed solution, we generate rogue waves, breathers, mixed rogue-dark-bright and classical dark-bright solitons. While the addition of SOC contributes to rapid oscillations in the amplitude of the rogue waves, Rabi coupling results in the appearance of stripes in the temporal direction. When the transient trap is switched on, these stripes which remain stable within the confining region, begin to overlap exponentially in the expulsive domain and eventually shrink leading to instability. We have shown that the instability arising in the rogue waves in a transient trap can be completely overcome by manipulating the scattering length through Feshbach resonance. In the case of breathers, the Rabi coupling introduces temporal stripes with single and double mode peaks around the origin while under the influence of the transient trap, the breathers get compressed and tilted. On the other hand, the amplitude of breathers which stays constant between a maxima and minima despite oscillating with time undergoes rapid fluctuations in a given spatial domain under the influence of SOC. In the case of classical dark-bright solitons, we see the flipping of dark solitons to attain positive density much similar to bright solitons under the impact of Rabi coupling. One also witnesses a 45 degree shift in the trajectory of dark and bright solitons when the transient trap is switched on. The width of the solitons widen in the confining trap while they shrink in the expulsive domain.

nlin.PS↗

arXiv2024

Exotic Coherent Structures and Their Collisional Dynamics in a (3+1) dimensional Bogoyavlensky-Konopelchenko Equation

In this paper, we analyse the (3+1) dimensional Bogoyavlensky - Konopelchenko equation. Using Painlev\'e Truncation approach, we have constructed solutions in terms of lower dimensional arbitrary functions of space and time. By suitably harnessing the arbitrary functions present in the solution, we have generated physically interesting solutions like periodic solutions, kinks, linear rogue waves, line lumps, dipole lumps and hybrid dromions. It is interesting to note that unlike in (2+1) dimensional nonlinear partial differential equations, the line lumps interact and undergo elastic collision without exchange of energy which is confirmed by the asymptotic analysis. The hybrid dromions are also found to retain their amplitudes during interaction undergoing elastic collision. The highlight of the results is that one also observes the two nonparallel ghost solitons as well whose intersection gives rise to hybrid dromions, a phenomenon not witnessed in (2+1) dimensions.

nlin.SI↗

arXiv2024

Collisional Dynamics of Solitons and Pattern Formation in an Integrable Cross Coupled Nonlinear Schrodinger equation with constant background

We investigate the dynamics arising out of the propagation of light pulses with different polarizations through a condensate (referred to as a constant background field) with cross coupling described by a coupled nonlinear Schrodinger equation(NLSE) type equation. We then employ Gauge and Darboux transformation approach to bring out the rich dynamics arising out of the background field and cross coupling. The collisional dynamics of bright solitons is found to be inelastic. The constant background field is found to facilitate the periodic localization of light pulses during propagation. We have also unearthed breathers, bright-bright, bright-dark and dark-bright solitons of the coupled NLSE. While the amplitude of breathers oscillate with time as predicted, their maximum(or minimum) amplitude is found to remain a constant and the addition of cross coupling only contributes to the rapid fluctuations in its amplitude over a period of time. In addition, the reinforcement of cross coupling in the presence of constant wave field facilitates the interference of light pulses leading to interesting pattern formation among bright-bright, bright-dark and dark-bright solitons. The highlight of the results is that one obtains various localized excitations like breathers, bright and dark solitons by simply manipulating the amplitude of the constant wave field.

nlin.SI↗

arXiv2023

Comment on `Painlev\'e Integrability and Multi-wave pattern for (2+1) dimensional Long wave-Short wave Resonance Interaction system'

In the paper by Sivatharani et al [1], the authors make a tall claim about the integrability of a 2 component (2+1) dimensional Long wave Short wave Resonance Interaction (2C(2+1)LSRI) equation with mixed sign which was already claimed to be non integrable and hence known not to satisfy Painlev\'e [2] property which the authors show to pass Painlev\'e test. We have categorically shown how the system does not pass Painlev\'e test and hence non-integrable reinforcing the claim made by Maruno et al [2]. The authors claim to derive the solutions of 2C(2+1)LSRI equation which ironically do not satisfy the equation. To top it all, the authors claim to have generated lumps and dromions which again defy their very own definition.

nlin.SI↗

arXiv2023

Dispersion engineering in spin-orbit coupled spinor $F=1$ condensates driven by negative masses

In this paper, we bring out several potential signatures of negative mass regimes while investigating an expanding spin-orbit (SO) coupled spinor $F=1$ Bose-Einstein condensates by analyzing the dispersion relation of the single-particle quantum system. In SO-coupled spinor condensates, a negative mass parameter generates a wave packet that propagates in the opposite direction of the momentum. We analyze the dynamics of spin waves analytically and present a simple approach to investigate the expansion of spinor condensates. In particular, we examine the dynamics when both masses are negative, which results in the spinor condensates splitting into two counter-propagating self-interfering packets (SIPs). Using numerical simulations of the coupled Gross-Pitaevskii equations, we demonstrate the density expansion and self-interference patterns with and without magnetization for repulsive and attractive interactions with different coupling parameters. The highlight of our investigation is that we are able to unearth several phenomena observed in experiments, such as self-interfering packets, pileup, modulation instability, slow down, self-trapping, and gap solitons. In particular, the gap soliton exists at the gap created by the intersection of two negative masses.

cond-mat.quant-gas↗

arXiv2023

Thermal quantum correlations and Teleportation in a Graphene Sheet

The characterization of quantum resources in dynamical systems is one of the most important problems to be addressed in quantum information theory. In this article, we investigate the behaviors of quantum correlations and teleportation technique in a graphene sheet comprising of disordered electrons in a two-dimensional honeycomb lattice. We use three different measures of quantum correlations such as entanglement, measurement-induced nonlocality and uncertainty-induced nonlocality. We study the ground state properties of the graphene sheet from the perspective of quantum correlations. At thermal equilibrium, we show that the band parameter strengthens the quantum correlations whereas the scattering strength weakens the correlations. Finally, the impact of the system's parameters on the teleportation technique is also expounded.

quant-ph↗

arXiv2022

Quantum correlations in a mixed spin-(1/2,1) Heisenberg dimer

In this article, we consider the heterodinuclear complex [Ni(dpt)(H2O)Cu(pba)].2H2O [pba =1,3-propylenebis(oxamato) and dpt = bis-(3-aminopropyl)amine] realized through the theoretical model of mixed spin-(1/2,1) coupled via Heisenberg interaction. We study the behaviors of thermal quantum correlations of the above material via Measurement-Induced Nonlocality (MIN) based on Hilbert-Schmidt norm and fidelity. We observe that the quantum correlation measures increase with the magnetic field in an unconventional way. The role of system parameters is also brought out at thermal equilibrium. The highlight of the results is that we are able to show the existence of room temperature quantum correlation using fidelity based MIN whereas the entanglement ceases to exist at 141K

quant-ph↗

arXiv2022

Quantum Correlations and Coherence in a Moving Unruh-deWitt Detector

In this paper, we investigate the quantum correlations and coherence of two accelerating Unruh-deWitt detectors coupled to a scalar field in 3 + 1 Minkowski space-time. We show that the entanglement is completely destroyed in the limit of infinite acceleration while the local quantum uncertainty and l1-norm of coherence remain nonzero. In addition, we also highlight the role of Unruh temperature and energy spacing of detectors on quantum correlations for different choices of initial states.

quant-ph↗

arXiv2022

Systems of Left Translates and Oblique Duals on the Heisenberg Group

In this paper, we characterize the system of left translates $\{L_{(2k,l,m)}g:k,l,m\in\mathbb{Z}\}$, $g\in L^2(\mathbb{H})$, to be a frame sequence or a \emph{Riesz} sequence in terms of the twisted translates of the corresponding function $g^\lambda$. Here, $(\mathbb{H}$ denotes the Heisenberg group and $g^\lambda$ the inverse Fourier transform of $g$ with respect to the central variable. This type of characterization for a \emph{Riesz} sequence allows us to find some concrete examples. We also study the structure of the oblique dual of the system of left translates $\{L_{(2k,l,m)}g:k,l,m\in\mathbb{Z}\}$ on $(\mathbb{H}$. This result is also illustrated with an example.

math.FA↗

arXiv2022

Role of higher-order interactions on the modulational instability of Bose-Einstein condensate trapped in a periodic optical lattice

In this paper, we investigate the impact of higher-order interactions on the modulational instability (MI) of Bose-Einstein Condensates (BECs) immersed in an optical lattice potential. We derive the new variational equations for the time evolution of amplitude, phase of modulational perturbation, and effective potential for the system. Through effective potential techniques, we find that high density attractive and repulsive BECs exhibit new character with direct impact over the MI phenomenon. Results of intensive numerical investigations are presented and their convergence with the above semi analytical approach is brought out.

cond-mat.quant-gas↗

arXiv2022

Stability Window of Trapless Polariton Bose-Einstein condensates

We theoretically explore the possibility of stabilizing the trapless polariton Bose-Einstein condensates (pBECs). Exploiting the variational method, we solve the associated nonlinear, complex Gross-Pitaevskii (cGP) equation and derive the equation of motion for the amplitude and width of the condensate. These variational results described by ordinary differential equations are rewritten to perform a linear stability analysis to generate a stability window in the repulsive domain. A set of coupled nonlinear ordinary differential equations obtained through variational approach are then solved by numerical simulations through the fourth order Runge-Kutta method, which are further supported by split-step Crank-Nicholson method, thereby setting the platform for stable pBECs. In particular, we generate a window containing system parameters in the $g_1-\gamma_{eff}$ space within which the system can admit stable condensates. The highlight of the results is that one observes beating effects in the real time evolution of the condensates with attractive interactions much similar to multicomponent BECs, and their periodicity can be varied by manipulating linear and nonlinear loss/gain terms. For repulsive condensates, one notices the stretching of the density.

cond-mat.quant-gas↗

arXiv2022

Characterizing nonclassical correlations of tensorizing states in a bilocal scenario

In the present paper, we attempt to address the question of "can tensorizing states have quantum advantages?". To answer this question, we exploit the notion of measurement-induced nonlocality (MIN) and advocate a fidelity based nonbilocal measure to capture the nonlocal effects of tensorizing states due to locally invariant von Neumann projective measurements. We show that the properties of the fidelity based nonbilocal measure are retrieved from that of MIN. Analytically, we evaluate the nonbilocal measure for any arbitrary pure state. The upper bounds of the nonbilocal measure based on fidelity are also obtained in terms of eigenvalues of correlation matrix. As an illustration, we have computed the nonbilocality for some popular input states.

quant-ph↗

arXiv2021

Modulational Instabity of Spin-Orbit Coupled Bose-Einstein Condensates in Discrete Media

We address the impact of intra-site spin-orbit (SO) coupling and associated inter-component Rabi coupling on the modulational instability (MI) of plane-wave states in two-component discrete Bose-Einstein condensates (BECs). Conditions for the onset of the MI and the respective instability are found analytically. SO coupling allows us to produce the MI even for a small initial wavenumber (q < {\pi}/2) for miscible states. In particular, SO coupling introduces MI even in the absence of hopping coefficient, a concept which may have wider ramifications in heavy atomic BECs. Our investigations predict that the impact of Rabi coupling is more pronounced compared to the other system parameters. We have also shown how our results of the linear stability analysis can be corroborated numerically. The fact that we have brought out the stability criteria in different domains of system parameters means that our model is tailor made experiments.

cond-mat.quant-gas↗