North Guwāhāti, India
North Guwāhāti, India

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Ahanj A.,Khavaran Institute of Higher Education | Ahanj A.,Institute for Research in Fundamental Sciences | Kunkri S.,Mahadevananda Mahavidyalaya | Rai A.,se National Center For Basic Science | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Recently, the principle of nonviolation of information causality has been proposed as one of the foundational properties of nature. We explore the Hardy's nonlocality theorem for two-qubit systems, in the context of generalized probability theory, restricted by the principle of nonviolation of information causality. Applying a sufficient condition for information causality violation, we derive an upper bound on the maximum success probability of Hardy's nonlocality argument. We find that the bound achieved here is higher than that allowed by quantum mechanics but still much less than what the no-signaling condition permits. We also study the Cabello type nonlocality argument (a generalization of Hardy's argument) in this context. © 2010 The American Physical Society.

Gayen P.,Raja Peary Mohan College | Sarker K.K.,Mahadevananda Mahavidyalaya | Sinha C.,Jadavpur University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

Photochromism is dependent on the structure of material and matrix. 1-Alkyl-2-(arylazo)imidazole exists at ambient condition in trans-geometry about NN group. UV light irradiation in toluene solution of the compound has changed their trans structure to cis structure. These two isomers have different absorption spectra. The cis-to-trans isomerization proceeds slowly in visible light irradiation while it is appreciably fast with increasing temperature under thermal process. The rate of trans-to-cis isomerization is increased by 30-70% in presence of neutral (Triton-X-100) and cation (CTAB) micelle while anion micelle (SDS) reduces the same by 34-49%. The quantum yield of the photoisomerization is also increased by 33-84% in presence of neutral and cationic micelle. The activation energy (Ea) of cis→trans thermal isomerization is amplified in presence of Triton-X-100 and CTAB while it is decreased by adding SDS. Thus, the lowering of cis-to-trans thermal process in presence of neutral and cation micelle and increasing in SDS phase is justified. © 2013 Elsevier B.V.

Das S.,Sn Bose National Center For Basic Science | Banik M.,Indian Statistical Institute | Rai A.,Sn Bose National Center For Basic Science | Gazi M.R.,Indian Statistical Institute | Kunkri S.,Mahadevananda Mahavidyalaya
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Recently, Gallego proved that any future information principle aiming at distinguishing between quantum and postquantum correlation must be intrinsically multipartite in nature. We establish similar results by using the device-independent success probability of Hardy's nonlocality argument for tripartite quantum systems. We construct an example of a tripartite Hardy correlation which is postquantum but satisfies not only the all-bipartite information principle but also the guess-your-neighbor's-input (GYNI) inequality. © 2013 American Physical Society.

Saha G.,Jadavpur University | Saha G.,Barrackpore Rastraguru Surendranath College | Datta P.,Jadavpur University | Sarkar K.K.,Mahadevananda Mahavidyalaya | And 3 more authors.
Polyhedron | Year: 2011

[Cu(SRaaiNR′)(PPh3)X] complexes are synthesized by the reaction of CuX (X = Cl, Br, I), triphenylphosphine and 1-alkyl-2-[(o-thioalkyl) phenylazo]imidazole (SRaaiNR′). The single crystal X-ray structure of [Cu(SEtaaiNH)(PPh3)I] (SEtaaiNH = 2-[(o-thioethyl)phenylazo] imidazole) shows a distorted tetrahedral geometry of the copper center with bidentate, N(azo), N(imidazole) chelation of SEtaaiNH and coordination from PPh3 and iodine. These complexes show a trans-to-cis isomerization upon irradiation with UV light. The reverse transformation, cis-to-trans isomerization, is very slow with visible light irradiation and is thermally accessible. The quantum yields (φt→c) of the trans-to-cis isomerization of [Cu(SRaaiNR′)(PPh3)X] are lower than the free ligand values. This is due to the increased mass and rotor volume of the complexes compared to the free ligand data. The rate of isomerization follows the order: [Cu(SRaaiNR′)(PPh3)Cl] < [Cu(SRaaiNR′) (PPh3)Br] < [Cu(SRaaiNR′)(PPh3)I]. The activation energy (Ea) of the cis-to-trans isomerization is calculated by a controlled temperature reaction. DFT computation of representative complexes has been used to determine the composition and energy of the molecular levels. © 2010 Elsevier Ltd. All rights reserved.

Banik M.,Indian Statistical Institute | Gazi M.D.R.,Indian Statistical Institute | Das S.,se National Center for Basic science | Rai A.,se National Center for Basic science | Kunkri S.,Mahadevananda Mahavidyalaya
Journal of Physics A: Mathematical and Theoretical | Year: 2012

Bells theorem teaches us that there are quantum correlations that cannot be simulated by just shared randomness (local hidden variable). There are some recent results which simulate the singlet correlation by using either 1 bit or a binary (no-signaling) correlation which violates Bells inequality maximally. But there is one more possible way to simulate quantum correlation by relaxing the condition of independency of measurement on shared randomness. Recently, Hall showed that the statistics of a singlet state can be generated by sacrificing measurement independence where underlying distribution of hidden variables depends on measurement directions of both parties (Hall 2010 Phys. Rev. Lett. 105 250404). He also proved that for any model of singlet correlation, 86% measurement independence is optimal. In this paper, we show that 59% measurement independence is optimal for simulating the singlet correlation when the underlying distribution of hidden variables depends only on the measurements of one party. We also show that a distribution corresponding to this optimal lack of free will already exists in the literature which first appeared in the context of detection efficiency loophole (Gisin and Gisin 1999 Phys. Lett. A 3237). © 2012 IOP Publishing Ltd.

Choudhary S.K.,Chennai Mathematical Institute | Ghosh S.,Chennai Mathematical Institute | Kar G.,Indian Statistical Institute | Kunkri S.,Mahadevananda Mahavidyalaya | And 2 more authors.
Quantum Information and Computation | Year: 2010

Hardy's non-locality theorem for multiple two-level systems is explored in the context of generalized non-local theory. We find non-local but non-signaling probabilities satisfying Hardy's argument for two two-level and three two-level systems. Maximum probability of success of Hardy's argument is obtained for three two-level systems in quantum theory as well as in a more generalized theory. Interestingly, the maximum in the generalized non-local theory for both the two two-level systems and three two-level systems turns out to be the same. © Rinton Press.

Das K.P.,Mahadevananda Mahavidyalaya | Chattopadhyay J.,Indian Statistical Institute
Mathematical Methods in the Applied Sciences | Year: 2012

An eco-epidemiological model with random environmental disturbance is proposed and analyzed. We assume that the susceptible prey population can acquire infection both from external sources and from internal transmission of the disease. It is also assumed that there is no recovery of the disease, and the consumption of diseased prey has a deleterious effect on the predator population. The conditions for the extinction of the predator and the prey populations are worked out. The most important observation of the present investigation is that oscillatory behavior of the populations observed in deterministic framework undergoes stable coexistence in the stochastic framework. Copyright © 2012 John Wiley & Sons, Ltd.

Das et al. [Effect of disease-selective predation on prey infected by contact and external sources, Biosystems 95(3) (2009) 188-199] proposed an eco-epidemiological model where the prey species is infected through the external source of infection and contact of the species. In this present study we have modified their model by assuming that the predator consumes both the susceptible as well as the infected prey following the modified Holling type-II functional response. Our main focusing points of this study are the role of infection rate (both internal and external), alternative food, and half-saturation constant in the predator-prey dynamics with disease in the prey population. We have shown the local stability of the boundary as well as the interior equilibrium point under certain conditions. We have also worked out the permanence of the system. Our simulation results show that the system enters into limit cycle oscillations from stable position for higher values of the contact rate. But it is also shown that the external infection rate, enrichment of the alternative food of the predator population and the half-saturation constant can prevent limit cycle oscillations and stabilize the system. Thus external disease propagation, enrichment of the alternative food resource, and the half-saturation constant are the key factors for preventing the oscillatory behavior of the species. © 2015 World Scientific Publishing Company.

Das K.,Mahadevananda Mahavidyalaya
Journal of Dynamical and Control Systems | Year: 2015

The effect of parasites and pathogens in the prey population received a lot of attention, but disease in the predator population has been studied comparatively little in literature. In this study, we have considered a predator-prey model with disease in the predator population. Here, we have analyzed the local stability of the model system around the equilibria. We have derived the ecological as well as the disease basic reproduction numbers and analyzed the community structure of the model system by these numbers. Our numerical results reveal that disease introduction in the predator population produces chaotic dynamics. We have observed stable focus, limit cycles, period doubling, and chaos for variation of the force of infection in the predator population. It is also observed that half-saturation constants are responsible for occurrence and control of chaos. It is found that chaos may be prevented by increasing the predation efficiency of the infected predator. © 2015, Springer Science+Business Media New York.

Kooi B.W.,VU University Amsterdam | van Voorn G.A.K.,Wageningen University | Das K.P.,Mahadevananda Mahavidyalaya
Ecological Complexity | Year: 2011

We study the effects of a non-specified infectious disease of the predator on the dynamics a predator-prey system, by evaluating the dynamics of a three-dimensional model. The predator population in this (PSI) model is split into a susceptible and an unrecoverable infected population, while all newborn are susceptible. The incidence rate at which susceptible become infectious is described by a Holling type II functional response giving saturation when the number of susceptibles increases. From a modeling context this three-dimensional model is in the limit case similar to the well-known 3D Rosenzweig-MacArthur (RM) model, with the infected population replacing the top-predator. The RM model is known for the Shil'nikov bifurcation, which is associated to the chaotic behaviour. The effects of the disease are considered to be changes in the parameters that represent relative predation efficiency and mortality rates. A combination of analysis, numerical integration and numerical continuation techniques are used to perform a bifurcation analysis of the model. The positive stationary solution of the disease free, two-dimensional predator-prey system is either a stable equilibrium or a stable limit cycle where the transition occurs at the Hopf bifurcation. For a biologically applicable parameter set, it is found that when the infected individuals feed less fast or less effective than the susceptibles there is bi-stability where the two-dimensional disease free state co-exists with a stable equilibrium for the three-dimensional PSI system. The introduction of a disease can also cause chaos when the infected predator individuals are ecologically not functioning (not feeding and no offspring). However, under small parameter changes first the Shil'nikov bifurcation, and hence the chaotic behaviour, disappears followed by the Hopf bifurcation that marks the existence of limit cycles of the three-dimensional PSI system. As such, an infectious disease has a strongly stabilizing effect on the predator-prey system, similar to the existence of weak links in food webs. © 2010 Elsevier B.V.

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