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A theoretical investigation on wavefronts evolution governed by the modified Nagumo equation

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Next Research

Next Research 2024年第2期1卷

作者： Nkeh Oma Nfor Désiré Ndjanfang Gaetan Fautso Kuiate Francois Marie Moukam Kakmeni Department of Physics Higher Teacher Training College Bambili The University of Bamenda Bambili PO Box 39 Cameroon Complex Systems and Theoretical Biology Group (CoSTBiG) and Laboratory of Research on Advanced Materials and Nonlinear Science (LaRAMaNS) Department of Physics Faculty of Science University of Buea Buea PO Box 63 Cameroon Department of Mechanical and Industrial Engineering National Higher Polytechnic Institute The University of Bamenda Bambili PO Box 39 Cameroon

A myelinated nerve fiber model with nonlinear membrane capacitance is considered, and the dynamics of the system is shown to be governed by the modified discrete Nagumo equation. Within the discrete limit, we examined saltatory conduction with the possibility of the capacitive feedback parameter influencing propagation failure. The time series solutions and profile of stationary impulses are equally investigated within the continuum limit approximation. This enhances our understanding of wavefronts initiation in the myelinated fiber under uniform and non-uniform excitabilities. We employed the Bilinear Hirota method and obtained wavefront solutions of the modified Nagumo equation. It is observed that an increase in the capacitive feedback parameter favors the narrowing of wavefronts, while its speed is rapidly increased; thereby enhancing excitability and transfer of neuronal information in the whole of the myelinated axon. The influence of capacitive feedback parameter on the stability of the homogeneous states, is equally brought into sharp focus. Results of numerical simulations of the modified discrete Nagumo equation, portrays a clear concordance with the analytical predictions. This is because the speed of the propagating anti-kink increases as the capacitive feedback parameter is gradually stepped up. We hope that future experimental investigations will validate the theoretical predictions highlighted in this study.

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Experimental demonstration of topological bounds in quantum metrology

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arXiv 2022年

作者： Yu, Min Li, Xiangbei Chu, Yaoming Mera, Bruno Nur Ünal, F. Yang, Pengcheng Liu, Yu Goldman, Nathan Cai, Jianming School of Physics Hubei Key Laboratory of Gravitation and Quantum Physics Institute for Quantum Science and Engineering Huazhong University of Science and Technology Wuhan430074 China International Joint Laboratory on Quantum Sensing and Quantum Metrology Huazhong University of Science and Technology Wuhan430074 China Tohoku University Sendai980-8577 Japan TCM Group Cavendish Laboratory University of Cambridge JJ Thomson Avenue CambridgeCB3 0HE United Kingdom Institut für Theoretische Physik and IQST Universität Ulm Albert-Einstein Allee 11 UlmD-89081 Germany Center for Nonlinear Phenomena and Complex Systems Université Libre de Bruxelles CP 231 Campus Plaine BrusselsB-1050 Belgium Shanghai Key Laboratory of Magnetic Resonance East China Normal University Shanghai200062 China

Quantum metrology is deeply connected to quantum geometry, through the fundamental notion of quantum Fisher information. Inspired by advances in topological matter, it was recently suggested that the Berry curvature and Chern numbers of band structures can dictate strict lower bounds on metrological properties, hence establishing a strong connection between topology and quantum metrology. In this work, we provide a first experimental verification of such topological bounds, by performing optimal quantum multi-parameter estimation and achieving the best possible measurement precision. By emulating the band structure of a Chern insulator, we experimentally determine the metrological potential across a topological phase transition, and demonstrate strong enhancement in the topologically non-trivial regime. Our work opens the door to metrological applications empowered by topology, with potential implications for quantum many-body systems. Copyright © 2022, The Authors. All rights reserved.

关键词： Topology

From branched flow to superwires in periodic potentials

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arXiv 2021年

作者： Daza, Alvar Heller, Eric J. Graf, Anton M. Räsänen, Esa Department of Physics Harvard University CambridgeMA02138 United States Nonlinear Dynamics Chaos and Complex Systems Group Departamento de Física Universidad Rey Juan Carlos Móstoles Madrid Tulipán s/n28933 Spain Department of Chemistry and Chemical Biology Harvard University CambridgeMA02138 United States Harvard John A. Paulson School of Engineering and Applied Sciences Harvard CambridgeMA02138 United States Computational Physics Laboratory Tampere University Tampere33720 Finland

We report unexpected classical and quantum dynamics of a wave propagating in a periodic potential in high Brilloiun zones. Branched ow appears at wavelengths shorter than the typical length scale of the ordered periodic structure and for energies above the potential barrier. The strongest branches remain stable indefinitely and may create linear dynamical channels, wherein waves are not confined directly by potential walls as electrons in ordinary wires, but rather indirectly and more subtly by dynamical stability. We term these superwires, since they are associated with a superlattice. Copyright © 2021, The Authors. All rights reserved.

关键词： Stability

Modeling of multilevel cell memory with the BaTiO3/Fe nanostructured multiferroic composite material

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Physical Review B 2019年第2期100卷 020404(R)-020404(R)页

作者： Paul André Paglan Jean Pierre Nguenang Pure Physics Laboratory Group of Nonlinear Physics and Complex Systems Department of Physics Faculty of Science University of Douala P.O. Box 24157 Douala Cameroon National Committee for Development of Technologies (NCDT) Ministry of Scientific Research and Innovation P.O. Box 1457 Yaounde Cameroon The Abdus Salam ICTP Strada Costiera 11 I-34151 Trieste Italy

In order to enhance the performance of calculators, multilevel cell (MLC) memories have been proposed as an alternative solution to improve the communication speed between their processors and memories, and also in order to increase the effective storage density of memory devices. In this Rapid Communication, we propose a model of MLC memory based on a multiferroic (MF) composite material. We introduce a one-dimensional trilayer ferromagnetic/ferroelectric/ferromagnetic MF composite material through which we investigate theoretically the dynamics of an electromagnon excitation displaying a soliton structure with an envelope shape. It emerges from this study based on barium titanate (BaTiO3) and iron (Fe) that, for suitable values of the parameters of a single initial polarization excitation, some propagation scenarios display the encoding of the states of a system of two magnetic bits, i.e., the 11, 10, 01, and 00 states. In addition to this result, it is also realized that the system exhibits another scenario for which the signal propagating in the MF material is alternately converted from an electrical signal into a magnetic signal and reversely. Such outcomes suggest, on the one hand, the possibility to model a four-level MLC memory, and on the other hand, the modeling of an electromagnetic oscillator, based on a MF composite material.

关键词： Ferroelectricity Magnetization dynamics Multiferroics Patterns in complex systems

Non-Lagrangian approach for coupled complex Ginzburg-Landau systems with higher order-dispersion

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arXiv 2019年

作者： Djob, Roger Bertin Kenfact-Jiotsa, Aurelien Govindarajan, A. Laboratory of Mechanics Group of Nonlinear Physics and Complex Systems Department of Physics Faculty of Sciences University of Yaounde i P.O. Box 812 Yaounde Cameroon Nonlinear Physics and Complex Systems Group Department of Physics Higher Teacher's Training College University of Yaounde i P.O. Box 47 Yaounde Cameroon Centre for Nonlinear Dynamics School of Physics Bharathidasan University Tiruchirappalli620 024 India

It is known that after a particular distance of evolution in fiber lasers, two (input) asymmetric soliton like pulses emerge as two (output) symmetric pulses having same and constant energy. We report such a compensation technique in dispersionmanaged fiber lasers by means of a semi-analyticalmethod known as collective variable approach (CVA) with including third-order dispersion (TOD). The minimum length of fiber laser, at which the output symmetric pulses are obtained from the input asymmetric ones, is calculated for each and every pulse parameters numerically by employing Runge-Kutta fourth order method. The impacts of intercore linear coupling, asymmetric nature of initial parameters and TOD on the evolution of pulse parameters and on the minimum length are also investigated. It is found that strong intercore linear coupling and asymmetric nature of input pulse parameters result in the reduction of fiber laser length. Also, the role of TOD tends to increase the width of the pulses as well as their energies. Besides, chaotic patterns and bifurcation points on the minimum length of the fiber owing to the impact of TOD are also reported in a nutshell. Copyright © 2019, The Authors. All rights reserved.

关键词： Fiber lasers

Observation of Hermitian and Non-Hermitian Diabolic Points and Exceptional Rings in Parity-Time symmetric ZRC and RLC Dimers

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arXiv 2020年

作者： Tabeu, Stéphane Boris Fotsa-Ngaffo, Fernande Kenfack-Jiotsa, Aurélien Laboratory of Electronics and Signal Processing Department of Electrical and Telecommunication Engineering National Advanced School of Engineering University of Yaoundé I P.O. Box 8390 Yaoundé Cameroon Laboratory of Mechanics Materials and Structures Department of Physics University of Yaoundé I P.O. Box 812 Yaoundé Cameroon Nonlinear Physics and Complex Systems Group Department of Physics Higher Teacher’s Training College University of Yaoundé I P.O. Box 47 Yaoundé Cameroon Institute of Wood Technologies University of Yaoundé I P.O. Box 306 Mbalmayo Cameroon Department of Physics Faculty of Science University of Buea P.O. Box 63 Buea Cameroon Nonlinear Physics and Complex Systems Group Department of Physics Higher Teacher’s Training College University of Yaoundé I P.O. Box 47 Yaoundé Cameroon P.O. Box 105 Yaoundé Cameroon

We present the observation of diabolic points in Hermitian and non-Hermitian electronics dimers. The condition of unbreakable Parity-time symmetry is established for both PT-symmetric ZRC and RLC dimers. We show how appears non-Hermitian degeneracy points in the spectrum and how they are protected against a Hermitian perturbation. When a non-Hermitian perturbation is added in the setup, the non-Hermitian diabolic point (NHDP) turns into a ring of exceptional points as in some Dirac and Weyl semimetals. Some experimental simulations of oscillations around these particular points in LTspice are in perfect accordance with the one predicted analytically and numerically. This work opens a gold road for investigations on topological electrical circuits for robust transport of information at room temperature. Copyright © 2020, The Authors. All rights reserved.

关键词： Topology

Boundary Zonal Flow in Rotating Turbulent Rayleigh-Bénard Convection

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Physical Review Letters 2020年第8期124卷 084505-084505页

作者： Xuan Zhang Dennis P. M. van Gils Susanne Horn Marcel Wedi Lukas Zwirner Guenter Ahlers Robert E. Ecke Stephan Weiss Eberhard Bodenschatz Olga Shishkina Max Planck Institute for Dynamics and Self-Organization 37077 Göttingen Germany Physics of Fluids Group J.M. Burgers Center for Fluid Dynamics University of Twente P.O. Box 217 7500 AE Enschede Netherlands Department of Earth Planetary and Space Sciences University of California Los Angeles California 90095 USA Centre for Fluid and Complex Systems Coventry University Coventry CV1 5FB United Kingdom Department of Physics University of California Santa Barbara California 93106 USA Center for Nonlinear Studies Los Alamos National Laboratory Los Alamos New Mexico 87545 USA Max Planck—University of Twente Center for Complex Fluid Dynamics Institute for the Dynamics of Complex Systems Georg-August-University Göttingen 37073 Göttingen Germany Laboratory of Atomic and Solid-State Physics and Sibley School of Mechanical and Aerospace Engineering Cornell University Ithaca New York 14853 USA

For rapidly rotating turbulent Rayleigh–Bénard convection in a slender cylindrical cell, experiments and direct numerical simulations reveal a boundary zonal flow (BZF) that replaces the classical large-scale circulation. The BZF is located near the vertical side wall and enables enhanced heat transport there. Although the azimuthal velocity of the BZF is cyclonic (in the rotating frame), the temperature is an anticyclonic traveling wave of mode one, whose signature is a bimodal temperature distribution near the radial boundary. The BZF width is found to scale like Ra1/4Ek2/3 where the Ekman number Ek decreases with increasing rotation rate.

关键词： Rayleigh-Bénard convection Structure & turbulence of boundary layers

Experimental observation of real spectra in Parity-Time symmetric ZRC dimers with positive and negative frequencies

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arXiv 2020年

作者： Tabeu, Stéphane Boris Fotsa-Ngaffo, Fernande Tagouegni, Senghor Shouno, Kazuhiro Kenfack-Jiotsa, Aurélien Laboratory of Mechanics Materials and Structures Department of Physics Faculty of Science University of Yaounde I P.O. Box 812 Yaounde Cameroon Nonlinear Physics and Complex Systems Group Department of Physics Higher Teacher’s Training College University of Yaounde I P.O. Box 47 Yaounde Cameroon Laboratory of Electronics and Signal Processing Department of Electrical and Telecommunication Engineering National Advanced School of Engineering University of Yaounde I P.O. Box 8390 Yaounde Cameroon Institute of Wood technologies University of Yaounde I P.O. Box 306 Mbalmayo Cameroon Graduate School of Systems and Information Engineering University of Tsukuba Ibaraki305-8573 Japan P.O. Box 105 Yaounde Cameroon

We present in this work the first experimental observation of oscillations in Parity-Time symmetric ZRC dimers. The system obtained is of first order ordinary differential equation due to the use of imaginary resistors. The coupled cells must share the same type of frequency: positive or negative. We observed the real and imaginary parts of the voltage across the components of a ZRC cell. Exceptional points are well identified. This work may be very useful in the generation of new type of oscillators. It can also be used in the design of new optoelectronic devices for major applications in the transport of information and the mimics of two-level systems for quantum computing. Copyright © 2020, The Authors. All rights reserved.

关键词： Resistors

Breathing pulses in the damped-soliton model for nerves

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Physical Review E 2018年第1期97卷 012211-012211页

作者： G. Fongang Achu F. M. Moukam Kakmeni A. M. Dikande Complex Systems and Theoretical Biology Group (CoSTBiG) Laboratory of Research on Advanced Materials and Nonlinear Science (LaRAMaNS) Department of Physics Faculty of Science University of Buea P.O. Box 63 Buea Cameroon

Unlike the Hodgkin-Huxley picture in which the nerve impulse results from ion exchanges across the cell membrane through ion-gate channels, in the so-called soliton model the impulse is seen as an electromechanical process related to thermodynamical phenomena accompanying the generation of the action potential. In this work, account is taken of the effects of damping on the nerve impulse propagation, within the framework of the soliton model. Applying the reductive perturbation expansion on the resulting KdV-Burgers equation, a damped nonlinear Schrödinger equation is derived and shown to admit breathing-type solitary wave solutions. Under specific constraints, these breathing pulse solitons become self-trapped structures in which the damping is balanced by nonlinearity such that the pulse amplitude remains unchanged even in the presence of damping.

关键词： Action potential propagation Biomechanics Neural encoding Neural information Neuronal dynamics Pattern formation Self-organization