University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Applied Mathematics

In this paper, we have considered a discrete-time predator–prey model with sigmoid functional response and Allee effect. We have discussed the conditions of existence of the feasible fixed point. The stability criterion of the fixed point carried out algebraically. Analytically we have shown that the system undergoes flip and Neimark–Sacker bifurcations. We also analyzed Neimark–Sacker bifurcation by center manifold theorem taking discretization factor(generation gap) as a bifurcation parameter. Under a parametric condition, all the bifurcation phenomena and chaotic features have been justified numerically. Finally, we use the hybrid control strategy to control flip and Neimark–Sacker bifurcations. © 2020, Springer-Verlag Italia S.r.l., part of Springer Nature.

World University root node

Rendiconti del Circolo Matematico di Palermo

Stability and bifurcation analysis of a discrete prey–predator model with sigmoid functional response and Allee effect

Physical Review E

Erratum: Homoclinic chaos in strongly dissipative strongly coupled complex dusty plasmas [Phys. Rev. E 103, 023205 (2021)]

arXiv preprint arXiv:2111.

Catalytic Transformations in Coherence Theory

Problems of water wave propagation over an infinite step in the presence of a thin vertical barrier of four different geometrical configurations are investigated in this paper. For each configuration of the barrier, the problem is reduced to solving an integral equation or a coupled integral equation of first kind involving horizontal component of velocity below or above the barrier and above the step. The integral equations are solved employing Galerkin approximation in terms of simple polynomials multiplied by appropriate weight functions whose forms are dictated by the edge conditions at the corner of the step and at the submerged end(s) of the barrier. The reflection and transmission coefficients are then computed and depicted graphically against the wave number. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.

Journal of Engineering Mathematics

Water wave propagation over an infinite step in the presence of a thin vertical barrier

The present paper is concerned with a study of water waves generated due to the presence of a line singularity (source) with time harmonic strength as well as impulsive strength through mangrove forests in the presence of a viscoelastic bed. The trunks of mangroves are assumed to be in the upper layer inviscid fluid, while the roots of mangroves are inside the viscoelastic bed. The equation of motion in the viscoelastic region is obtained by coupling the Voigt's model with the equation of motion in the presence of mangroves. The expressions for the potential functions in the two layers are obtained. The forms of the surface and interface waves are depicted graphically for realistic values of kinematic viscosity and shear modulus of elasticity, the line source being submerged in the upper layer. © 2021. All Rights Reserved.

Fulltext

Journal of Applied Fluid Mechanics

Wave Motion through Mangrove Forests in the Presence of a Viscoelastic Bed due to a Line Source

The Lord–Shulman theory of generalized thermoelasticity based on a memory-dependent derivative is employed to study the thermoelastic response in a three-dimensional elastic half-space medium whose free surface is assumed to be traction-free and subjected to a thermal shock. The numerical solutions for the field variables are presented graphically and analyzed for various values of the time delay parameter. The predictions of the new model are discussed and compared with the Lord–Shulman model (without memory-dependent derivative). © 2019, Indian Association for the Cultivation of Science.

Indian Journal of Physics

Three-dimensional thermal shock problem in the frame of memory-dependent generalized thermoelasticity

In ecology, the intra- and inter-specific competition between individuals of mobile species for shared resources is mostly non-local; i.e., competition at any spatial position will not only be dependent on population at that position, but also on population in neighboring regions. Therefore, models that assume competition to be restricted to the individuals at that position only are actually oversimplifying a crucial physical process. For the past three decades, researchers have established the necessity of considering spatial non-locality while modeling ecological systems. Despite this ecological importance, studies incorporating this non-local nature of resource competition in an aquatic ecosystem are surprisingly scarce. To this end, the celebrated Scheffer's tri-trophic minimal model has been considered here as a base model due to its efficacy in describing the pelagic ecosystem with least complexity. It is modified into an integro-reaction-diffusion system to include the effect of non-local competition by introducing a weighted spatial average with a suitable influence function. A detailed analysis shows that the non-locality may have a destabilizing effect on underlying nutrient-plankton-fish dynamics. A local system in a stable equilibrium state can lose its stability through spatial Hopf and Turing bifurcations when strength of a non-local interaction is strong enough, which eventually generates a large range of spatial patterns. The relationship between a non-local interaction and fish predation has been established, which shows that fish predation contributes in damping of plankton oscillations. Overall, results obtained here manifest the significance of non-locality in aquatic ecosystems and its possible contribution to the phenomena of "spatial patchiness." © 2021 Author(s).

Chaos

Effects of non-local competition on plankton-fish dynamics

Two-stream instabilities in an unmagnetized Lorentzian dusty plasma have been investigated using a kinetic theory approach. The occurrence of this instability is discussed in the case of three different plasma wave modes. The first one is the instability of the Langmuir wave driven by streaming suprathermal electrons. The second one is the instability of the dust ion-acoustic wave driven by streaming suprathermal electrons, ions, and dust grains. The last one is concerned with the instability of the dust acoustic wave driven by streaming suprathermal dust grains. Using the Lorentzian kappa velocity distribution function, the real and imaginary frequencies of these waves have been derived analytically. The effect of the suprathermal particle density and the streaming particle density on the real and imaginary frequencies of the waves is examined numerically. © 2021 Author(s).

Physics of Plasmas

Study of two stream instabilities in Lorentzian dusty plasma

Three dimensional (3D) wave group dynamics of ion acoustic wave is studied in electron-positron-ion (EPI) plasmas incorporating the effects of an external uniform magnetic field through the Laedke-Spatschek equation. In the presence of self-interaction (self-focusing effect), the wave group dynamics is shown to be governed by a (3 + 1) nonlinear Schrödinger equation. The derived nonlinear equations are solved analytically and the solutions predict a wide class of nonlinear structures in EPI plasma in the presence of magnetic field. The boundaries of stable and unstable solutions are also specified in parametric space. The results are expected to provide deeper insights into the ionic processes occurring in both astrophysical and laboratory plasmas. © 2021 Author(s).

Three dimensional wave group dynamics of ion acoustic waves in electron-positron-ion plasmas in the presence of an external uniform magnetic field

In this study, we consider a scale-free network of nonidentical Chialvo neurons, coupled through electrical synapses. For sufficiently strong coupling, the system undergoes a transition from completely out of phase synchronized to phase synchronized state. The principal focus of this study is to investigate the effect of the degree of assortativity over the synchronization transition process. It is observed that, depending on assortativity, bistability between two asymptotically stable states allows one to develop a hysteresis loop which transforms the phase transition from second order to first order. An expansion in the area of hysteresis loop is noticeable with increasing degree-degree correlation in the network. Our study also reveals that effective frequencies of nodes simultaneously go through a continuous or sudden transition to the synchronized state with the corresponding phases. Further, we examine the robustness of the results under the effect of network size and average degree, as well as diverse frequency setup. Finally, we investigate the dynamical mechanism in the process of generating explosive synchronization. We observe a significant impact of lower degree nodes behind such phenomena: in a positive assortative network the low degree nodes delay the synchronization transition. © 2021 American Physical Society.