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

The classical problem of water wave scattering by an infinite step in deep water with a free surface is extended here with an ice-cover modelled as a thin uniform elastic plate. The step exists between regions of finite and infinite depths and waves are incident either from the infinite or from the finite depth water region. Each problem is reduced to an integral equation involving the horizontal component of velocity across the cut above the step. The integral equation is solved numerically using the Galerkin approximation in terms of simple polynomial multiplied by an appropriate weight function whose form is dictated by the behaviour of the fluid velocity near the edge of the step. The reflection and transmission coefficients are obtained approximately and their numerical estimates are seen to satisfy the energy identity. These are also depicted graphically against thenon-dimensional frequency parameter for various ice-cover parameters in a number of figures. In the absence of ice-cover, the results for the free surface are recovered. © 2019 S. Ray et al., published by Sciendo 2019.

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International Journal of Applied Mechanics and Engineering

Water Wave Scattering by an Infinite Step in the Presence of an Ice-Cover

The present study is concerned with the reflection and propagation of thermoelastic harmonic plane waves from the stress-free and isothermal surface of a homogeneous, isotropic thermally conducting elastic half-space in the frame of the modified Green–Lindasy (MGL) theory of generalized thermoelasticity with strain rate proposed by Yu et al. (Meccanica 53:2543–2554, 2018). The thermoelastic coupling effect creates two types of coupled longitudinal waves which are dispersive as well as exhibit attenuation. Different from the thermoelastic coupling effect, there also exists one independent vertically shear-type (SV-type) wave. In contrast to the classical Green–Lindsay (GL) and Lord–Shulman (LS) theories of generalized thermoelasticity, the SV-type wave is not only dispersive in nature but also experiences attenuation. Analytical expressions for the amplitude ratios of the reflected thermoelastic waves are determined when a coupled longitudinal wave is made incident on the free surface. The paper concludes with the numerical results on the phase speeds and the amplitude ratios for specific parameter choices. Various graphs have been plotted to analyze the behavior of these quantities. The characteristics of employing the MGL model are discussed by comparing the numerical results obtained for the present model with those obtained in case of the GL and LS models. © 2019, Indian Association for the Cultivation of Science.

Indian Journal of Physics

Modified Greenâ€“Lindsay model on the reflection and propagation of thermoelastic plane waves at an isothermal stress-free surface

In this paper, we obtain approximate bound-state solutions of N-dimensional time-independent fractional Schrödinger equation for the generalised pseudoharmonic potential which has the form V(rα) = a1r2 α+ (a2/ r2 α) + a3. Here α(0&lt;α&lt;1) acts like a fractional parameter for the space variable r. The entire study consists of the Jumarie-type fractional derivative and the elegance of Laplace transform. As a result, we can successfully express the approximate bound-state solution in terms of Mittag–Leffler function and fractionally defined confluent hypergeometric function. Our study may be treated as a generalisation of all previous works carried out on this topic when α= 1 and N arbitrary. We provide numerical result of energy eigenvalues and eigenfunctions for a typical diatomic molecule for different α close to unity. Finally, we try to correlate our work with a Cornell potential model which corresponds to α= 1 / 2 with a3= 0 and predicts the approximate mass spectra of quarkonia. © 2019, Indian Academy of Sciences.

Pramana - Journal of Physics

Higher-dimensional fractional time-independent SchrÃ¶dinger equation via fractional derivative with generalised pseudoharmonic potential

This paper deals with an SIR model with saturated incidence rate affected by inhibitory effect and saturated treatment function. Two control functions have been used, one for vaccinating the susceptible population and other for the treatment control of infected population. We have analysed the existence and stability of equilibrium points and investigated the transcritical and backward bifurcation. The Pontryagin’s maximum principle has been used to characterize the optimal control whose numerical results show the positive impact of two controls mentioned above for controlling the disease. Efficiency analysis is also done to determine the best control strategy among vaccination and treatment. © 2019, Foundation for Scientific Research and Technological Innovation.

Differential Equations and Dynamical Systems

Qualitative Analysis and Optimal Control Strategy of an SIR Model with Saturated Incidence and Treatment

It is well-known that traversable wormholes are valid solutions of the Einstein field equations, but these structures can only be maintained by violating the null energy condition. In this paper, we have obtained such wormhole solutions in an isothermal galactic halo, as well as in a void. We have shown that the null energy condition is violated, with the help of a suitable redshift function obtained from flat galactic rotation curves. © 2019 World Scientific Publishing Company.

Modern Physics Letters A

Possible formation of wormholes from dark matter in an isothermal galactic halo and void

In the present article, we have presented completely new exact, finite and regular class I solutions of Einstein’s field equations i.e. the solutions satisfy the Karmarkar condition. For this purpose needfully we have introduced a completely new suitable grr metric potential to generate the model. We have investigated the various physical aspects for our model such as energy density, pressure, anisotropy, energy conditions, equilibrium, stability, mass, surface and gravitational red-shifts, compactness parameter and their graphical representations. All these physical aspects have ensured that our proposed solutions are well-behaved and hence represent physically acceptable models for anisotropic fluid spheres. The models have satisfied causality and energy conditions. The presented models are also stable by satisfying Bondi condition and Abreu et al. condition, in equilibrium position and static by satisfying TOV equation, Harrison–Zeldovich–Novikov condition, respectively. For the parameters chosen in the paper are matching in modeling Vela X-1, Cen X-3, EXO 1785-248 and LMC X-4. The M–R graph generated from the solutions is matching the ranges of masses and radii for the considered compact stars. This work also estimated the approximate moment of inertia for the mentioned compact stars. © 2019, The Author(s).

European Physical Journal C

Compact star models in class I spacetime

Standard tripartite nonlocality and genuine tripartite nonlocality can be detected by the violations of Mermin inequality and Svetlichny inequality, respectively. Since tripartite quantum nonlocality has novel applications in quantum information and quantum computation, it is important to investigate whether more than three observers can share tripartite nonlocality, simultaneously. In the present study, we answer this question in the affirmative. In particular, we consider a scenario where three spin-12 particles are spatially separated and shared between Alice, Bob and multiple Charlies. Alice performs measurements on the first particle; Bob performs measurements on the second particle, and multiple Charlies perform measurements on the third particle sequentially. In this scenario, we investigate how many Charlies can simultaneously demonstrate standard tripartite nonlocality and genuine tripartite nonlocality with single Alice and single Bob. The interesting result revealed by the present study is that at most six Charlies can simultaneously demonstrate standard tripartite nonlocality with single Alice and single Bob. On the other hand, at most two Charlies can simultaneously demonstrate genuine tripartite nonlocality with single Alice and single Bob. Hence, the present study shows that standard tripartite nonlocality can be simultaneously shared by larger number of Charlies compared to genuine tripartite nonlocality in the aforementioned scenario, which implies that standard tripartite nonlocality is more effective than genuine tripartite nonlocality in the context of simultaneous sharing by multiple observers. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Quantum Information Processing

Sharing of tripartite nonlocality by multiple observers measuring sequentially at one side

The resource theory of quantum coherence originated like entanglement in quantum information theory. However, until now proper classification of quantum states is missing under coherence. In this work we have provided a classification of states under local incoherent operations. We have succeeded in deriving the necessary and sufficient condition for which two pure multipartite states are equivalent under stochastic local incoherent operations and classical communications (SLICC) and local incoherent operations and classical communications (LICC). In particular, we have succeeded in characterizing three-qubit pure states under SLICC. Our result reveals the existence of an infinite number of SLICC inequivalent classes for three-qubit systems. © 2019 American Physical Society.

Physical Review A

Necessary and sufficient condition for the equivalence of two pure multipartite states under stochastic local incoherent operations and classical communications

A theoretical analysis of the dust acoustic and dust ion acoustic wave instabilities in self-gravitating collisional dusty plasma have been presented considering the presence of suprathermal charge particles. The suprathermal charge particles can reduce the dispersion of the dust-acoustic and dust ion acoustic waves, and broaden the wave- number range as well as increase the growth rate. © 2019 Author(s).

GENERAL

AIP Conference Proceedings

Effect of collision on dust acoustic and dust ion acoustic wave instabilities in self-gravitating Lorentzian dusty plasma

The model of star formation has been developed as a result of explosive phenomena in the central region of Our Galaxy. The shock wave generated as a result of such explosion, during its propagation, cools and compresses the ambient medium in a thin layer, which subsequently fragments into molecular clouds. These clouds finally form star clusters or field stars under gravitational collapse. We primarily consider the central region of Our Galaxy under the influence of a magnetic field for modeling such explosive phenomena and derive the minimum Jeans mass for gravitational collapse. It is found that under an inverse variation of temperature with density, a wide range of fragments can be formed. The mass range is enhanced in the presence of a constant as well as varying magnetic field. Under suitable physical conditions a burst of star formation is possible. It is also found that rotation of such fragmented clouds of the order of few km s−1 kpc−1, might lead to a stable structure. © 2019, Institute of Astronomy and Rozhen NAO. All rights reserved.