Papers by Tanvir Hasan Mithun
Maximum power point tracking in photovoltaic power generation system is performed using recently ... more Maximum power point tracking in photovoltaic power generation system is performed using recently reported Plant Reproduction Algorithm (PRA). The first reported PRA is simplified and tailored towards MPPT in PV systems under partial shaded conditions (PSC). The modified algorithm is simple to understand and easy to implement and converges to global power peak quickly. The new algorithm is evaluated through extensive simulation study and results are presented.
S. I. Mistakidis, 2 T. Mithun, P. G. Kevrekidis, H. R. Sadeghpour, and P. Schmelcher 4 Center for... more S. I. Mistakidis, 2 T. Mithun, P. G. Kevrekidis, H. R. Sadeghpour, and P. Schmelcher 4 Center for Optical Quantum Technologies, Department of Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg Germany ITAMP, Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA 02138 USA Department of Mathematics and Statistics, University of Massachusetts, Amherst MA 01003-4515, USA The Hamburg Centre for Ultrafast Imaging, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany (Dated: October 19, 2021)
Physical Review A
We study the statistical mechanics and the dynamical relaxation process of modulationally unstabl... more We study the statistical mechanics and the dynamical relaxation process of modulationally unstable one-dimensional quantum droplets described by a modified Gross-Pitaevskii equation. To determine the classical partition function thereof, we leverage the semi-analytical transfer integral operator (TIO) technique. The latter predicts a distribution of the observed wave function amplitudes and yields two-point correlation functions providing insights into the emergent dynamics involving quantum droplets. We compare the ensuing TIO results with the probability distributions obtained at large times of the modulationally unstable dynamics as well as with the equilibrium properties of a suitably constructed Langevin dynamics. We find that the instability leads to the spontaneous formation of quantum droplets featuring multiple collisions and by which are found to coalesce at large evolution times. Our results from the distinct methodologies are in good agreement aside from the case of low temperatures in the special limit where the droplet widens. In this limit, the distribution acquires a pronounced bimodal character, exhibiting a deviation between the TIO solution and the Langevin dynamics.
Journal of Physics B: Atomic, Molecular and Optical Physics
We obtain general continuous-wave (CW) solutions in the model of a spinor positronium condensate ... more We obtain general continuous-wave (CW) solutions in the model of a spinor positronium condensate in the absence of magnetic field. The CW solutions with both in-phase (n = 0) and out-of-phase (n = 1) spin components exist, with their ranges limited by the total particle density, ρ. In the limit of negligible population exchange between the spin components, the CW solutions are found to be stable or unstable, depending on the particle density of the para positronium. Ortho positronium, in the F = 1 spinor state, forms a ferromagnetic condensate with stable in-phase CW solutions only. Subsequent examination of the modulational instability (MI) is carried out both in the limit case of identical wavenumbers in the spin components, ∆k ≡ k 1 − k −1 = 0, and in the more general case of ∆k = 0 too. The CW solutions with n = 0 and 1 solutions, which are stable in the case of ∆k = 0, are unstable for ∆k = 0, for the natural repulsive sign of the nonlinearities. The total particle density, ρ, in the limit of ∆k = 0 is found to have a significant role for the stability of the condensate, which is determined by the sign of the self-interaction nonlinearity.
Physical Review A, 2016
We study the vortex lattice dynamics in presence of single impurity as well as random impurities ... more We study the vortex lattice dynamics in presence of single impurity as well as random impurities or disorder. We show that in presence of a single impurity the vortex lattice gets distorted and the distortion depends on the position of the single impurity with respect to the positions of the vortices in the impurity free Abrikosov vortex lattice and also the strength of the impurity potential. We then show that a new type of giant hole with hidden vortices inside it can be created in the vortex lattice by a cluster of impurities. In presence of random impurity potential or disorder the vortex lattice melts. We show that the vortex lattice also melts in presence of pseudorandom potential generated by the superposition of two optical lattices. The absence of long-range order in the melted vortex lattice is demonstrated from the structure factor profile and the histogram of the distances between each pair of the vortices.
AIP Conference Proceedings, 2016
We numerically study the vortex lattice dynamics in presence of pseudorandom potential in rotatin... more We numerically study the vortex lattice dynamics in presence of pseudorandom potential in rotating Bose-Einstein condensate. The rotating condensate displays highly ordered triangular vortex lattice. In presence of pseudorandom potential the vortex lattice gets distorted. The histogram of the distances between each pair of the vortices shows how the long-range order of the triangular vortex lattice is destroyed in presence of pseudorandom potential.
AIP Conference Proceedings, 2013
ABSTRACT Using the CQNLS equation as a model, we observe the dynamics of matter waves in a cigar-... more ABSTRACT Using the CQNLS equation as a model, we observe the dynamics of matter waves in a cigar-shaped trapping potential. The dynamics have been found using the exact solution of CQNLS equation. The results show a novel procedure to control the propagation of matter wave using Feshbach resonance techniques, or by controlling the trapping frequencies. Our study also shows the limit of stability of the 1D CQNLS equation in the trapped potential.
Optics Communications, 2014
We study the statistical mechanics and the dynamical relaxation process of modulationally unstabl... more We study the statistical mechanics and the dynamical relaxation process of modulationally unstable one-dimensional quantum droplets described by a modified Gross-Pitaevskii equation. To determine the classical partition function thereof, we leverage the semi-analytical transfer integral operator (TIO) technique. The latter predicts a distribution of the observed wave function amplitudes and yields two-point correlation functions providing insights into the emergent dynamics involving quantum droplets. We compare the ensuing TIO results with the probability distributions obtained at large times of the modulationally unstable dynamics as well as with the equilibrium properties of a suitably constructed Langevin dynamics. We find that the instability leads to the spontaneous formation of quantum droplets featuring multiple collisions and by which are found to coalesce at large evolution times. Our results from the distinct methodologies are in good agreement aside from the case of low ...
In the present work we illustrate that classical but nonlinear systems may possess features remin... more In the present work we illustrate that classical but nonlinear systems may possess features reminiscent of quantum ones, such as memory, upon suitable external perturbation. As our prototypical example, we use the two-dimensional complex Ginzburg-Landau equation in its vortex glass regime. We impose an external drive as a perturbation mimicking a quantum measurement protocol, with a given “measurement rate” (the rate of repetition of the drive) and “mixing rate” (characterized by the intensity of the drive). Using a variety of measures, we find that the system may or may not retain its coherence, statistically retrieving its original glass state, depending on the strength and periodicity of the perturbing field. The corresponding parametric regimes and the associated energy cascade mechanisms involving the dynamics of vortex waveforms and domain boundaries are discussed.
Numerous experimentations are performed in the area of optical character recognition. The overall... more Numerous experimentations are performed in the area of optical character recognition. The overall process of optical character recognition can be assured successful only when there is skew free document input considered at the time of pre-processing. The automatic skew detection and correction of document images is one of the important operation to be focused in this regard, since it increases the chances of obtaining overall accuracy of entire optical character recognition system. In this paper we have devised a skew detection and correction methodology using multiple projection profiles and skew angles. The document is subjected to computation of vertical profiles and difference is black pixel density is used as parameter to identify the tie points of a particular text block and skew angle. The identified text block is then rotated in opposite direction to get a skew eliminated image. The algorithm has given an accuracy of over 90% in many documents experimented..
Physical Review Research
Coherent perfect absorption (CPA), also known as time-reversed laser, is a wave phenomenon result... more Coherent perfect absorption (CPA), also known as time-reversed laser, is a wave phenomenon resulting from the reciprocity of destructive interference of transmitted and reflected waves. In this work we consider quasi one-dimensional lattice networks which posses at least one flat band, and show that CPA and lasing can be induced in both linear and nonlinear regimes of this lattice by fine-tuning non-Hermitian defects (dissipative terms localized within one unit-cell). We show that local dissipations that yield CPA simultaneously yield novel dissipative compact solutions of the lattice, whose growth or decay in time can be fine-tuned via the dissipation parameter. The scheme used to numerically visualize the theoretical findings offers a novel platform for the experimental implementation of these phenomena in optical devices.
EPL (Europhysics Letters)
PACS 03.75.Lm-Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, soli... more PACS 03.75.Lm-Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices, and topological excitations PACS 67.85.Hj-Bose-Einstein condensates in optical potentials Abstract-We simulate a rotating 2D BEC to study the melting of a vortex lattice in the presence of random impurities. Impurities are introduced either through a protocol in which vortex lattice is produced in an impurity potential or first creating the vortex lattice in the absence of random pinning and then cranking up the (co-rotating) impurity potential. We find that for a fixed strength, pinning of vortices at randomly distributed impurities leads to the new states of the vortex lattice. It is unearthed that the vortex lattice follows a two-step melting via loss of positional and orientational order. Also, the comparisons between the states obtained in two protocols show that the vortex lattice states are metastable states when impurities are introduced after the formation of an ordered vortex lattice. We also show that the existence of metastable states depends on the history of how the vortex lattice is created.
Journal of the Optical Society of America B
We study the spatial modulation instability (MI) in a system of coupled surface plasmon polariton... more We study the spatial modulation instability (MI) in a system of coupled surface plasmon polaritons propagating at a dielectric–metal–dielectric interface. One of the dielectric media considered is nonlinear and active, which provides enough gain to compensate for the losses in the metal. It is found that the system is unstable for both focusing or defocusing nonlinearity, with more instability in the focusing case. It is noted that nonlinearity is one of the key parameters for instability, with the real part controlling the maximum MI gain and the imaginary part controlling the MI gain saturation. Gain provided by the active medium is also an important parameter for the development of MI in the system. The generated sidebands are amplified as they propagate along the interfaces. We have noted that the defocusing case requires a large gain threshold to exhibit modulation instability for a symmetric solution.
Physical Review A, 2015
We study modulation instability (MI) of flat states in two-component spin-orbit-coupled (SOC) Bos... more We study modulation instability (MI) of flat states in two-component spin-orbit-coupled (SOC) Bose-Einstein condensates (BECs) in the framework of coupled Gross-Pitaevskii equations for two components of the pseudo-spinor wave function. The analysis is performed for equal densities of the components. Effects of the interaction parameters, Rabi coupling and SOC on the MI are investigated. In particular, the results demonstrates that the SOC strongly alters the commonly known MI (immiscibility) condition, g 2 12 > g1g2, for the binary superfluid with coefficients g1,2 and g12 of the intra-and inter-species repulsive interactions. In fact, the binary BEC is always subject to the MI under the action of the SOC, which implies that ground state of the system is plausibly represented by a striped phase.
We numerically solve the Gross-Pitaeveskii equation to study the Bose-Einstein condensate in the ... more We numerically solve the Gross-Pitaeveskii equation to study the Bose-Einstein condensate in the rotating harmonical tarp and co-rotating optical lattice. The effect of a pinning site or impurity shows that it is able to move the vortex lattice center to either left or right depending on the position of the impurity. Also, it is observed that the impurity at the random positions can destroy the vortex lattice and the resulting disordered lattice has more energy.
Journal of the Optical Society of America B
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Papers by Tanvir Hasan Mithun