Asutosh College

Kolkata, India

Asutosh College

Kolkata, India
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Rudra P.,Asutosh College | Faizal M.,University of Lethbridge | Ali A.F.,Benha University
Nuclear Physics B | Year: 2016

In this paper, we analyze Vaidya spacetime with an energy dependent metric in Galileon gravity's rainbow. This will be done using the rainbow functions which are motivated from the results obtained in loop quantum gravity approach and noncommutative geometry. We will investigate the Gravitational collapse in this Galileon gravity's rainbow. We will discuss the behavior of singularities formed from the gravitational collapse in this rainbow deformed Galileon gravity. © 2016 The Authors.

Goswami C.,Asutosh College | Mukhopadhyay D.,The Interdisciplinary Center | Poddar B.C.,BE 267
Frontiers of Earth Science | Year: 2012

The impact of neotectonic activity on drainage system has been studied in a large alluvial fan in the eastern Himalayan piedmont area between the Mal River and the Murti River. Two distinct E-Wlineaments passing through this area had been identified by Nakata (1972, 1989) as active faults. The northern lineament manifested as Matiali scarp and the southern one manifested as Chalsa scarp represent the ramp anticlines over two blind faults, probably the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT), respectively. The fan surface is folded into two antiforms with a synform in between. These folds are interpreted as fault propagation folds over the two north dipping blind thrusts. Two lineaments trending NNE-SSW and nearly N-S, respectively, are identified, and parts of present day courses of the Murti and Neora Rivers follow them. These lineaments are named as Murti and Neora lineaments and are interpreted to represent a conjugate set of normal faults. The rivers have changed their courses by the influence of these normal faults along the Murti and Neora lineaments and their profiles show knick points where they cross E-W thrusts. The overall drainage pattern is changed from radial pattern in north of the Matiali scarp to a subparallel one in south due to these conjugate normal faults. The interfluve area between these two rivers is uplifted as a result of vertical movements on the above mentioned faults. Four major terraces and some minor terraces are present along the major river valleys and these are formed due to episodic upliftment of the ground and subsequent down-cutting of the rivers. The uppermost terrace shows a northerly slope north of the Chalsa scarp as a result of folding mentioned above. But rivers on this terrace form incised channels keeping their flow southerly suggesting that they are antecedent to the folding and their downcutting kept pace with the tectonism. © 2011 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Bose P.K.,Jadavpur University | Eriksson P.G.,University of Pretoria | Sarkar S.,Jadavpur University | Wright D.T.,University of Leicester | And 5 more authors.
Marine and Petroleum Geology | Year: 2012

Although the similarities between depositional processes and products as well as the analogous controls on basin-filling and evolution appear to have enjoyed great uniformity throughout the sedimentary rock record, a noticeable distinction exists in the rates and intensities of a broad range of geological processes in the Precambrian epoch. This paper searches for distinctiveness in the Precambrian sedimentary record, both siliciclastic and carbonate, through an extensive, though not exhaustive, review of the relevant literature augmented by new observations. While differences in Precambrian deltaic, aeolian, glacial and possibly also lacustrine deposits and settings appear to have been small, their large-scale development was controlled largely by a combination of temporal and geodynamic influences, essentially of global compass. In this regard the onset of the supercontinent cycle and major perturbations in palaeo-atmospheric composition appear to have been significant. Marine environments provide a poor platform for Precambrian-Phanerozoic comparisons of sedimentation patterns, as those from the former period are preserved almost exclusively in epeiric settings, an environment essentially lacking on modern Earth. For the shallow marine carbonates, biological mediation of chemical sediment deposition changed radically from dominance by microbial biota in the Precambrian to a combination of metazons, protozoans and algae for the skeletal carbonates of the Phanerozoic. Despite it being widely recognized that Precambrian channel systems were braided in all environments (deltaic, tidal, alluvial, fluvial) as a consequence of the lack of vegetation and poor development of soils, the fluvial setting has some enigmatic aspects. Amongst these is evidence for ponding of muddy detritus in apparently sandstone bed-load dominated braided systems, with effects on local palaeoslopes which have resulted in unusual palaeohydraulic parameters for Precambrian fluvial systems. This is perhaps a field of research which holds greater promise when investigating sedimentation patterns prior to the Phanerozoic. © 2010 Elsevier Ltd.

Hens C.R.,CSIR - Central Electrochemical Research Institute | Pal P.,National Institute of Technology Durgapur | Bhowmick S.K.,CSIR - Central Electrochemical Research Institute | Bhowmick S.K.,Asutosh College | And 3 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

We report the existence of diverse routes of transition from amplitude death to oscillation death in three different diffusively coupled systems, which are perturbed by a symmetry breaking repulsive coupling link. For limit-cycle systems the transition is through a pitchfork bifurcation, as has been noted before, but in chaotic systems it can be through a saddle-node or a transcritical bifurcation depending on the nature of the underlying dynamics of the individual systems. The diversity of the routes and their dependence on the complex dynamics of the coupled systems not only broadens our understanding of this important phenomenon but can lead to potentially new practical applications. © 2014 American Physical Society.

Bhowmick S.K.,Asutosh College | Ghosh D.,Indian Statistical Institute
International Journal of Modern Physics C | Year: 2016

A method of targeting engineering synchronization states in two identical and mismatch chaotic systems is explained in detail. The method is proposed using linear feedback controller coupling for engineering synchronization such as mixed synchronization, linear and nonlinear generalized synchronization and targeting fixed point. The general form of coupling design to target any desire synchronization state under unidirectional coupling with the help of Lyapunov function stability theory is derived analytically. A scaling factor is introduced in the coupling definition to smooth control without any loss of synchrony. Numerical results are done on two mismatch Lorenz systems and two identical Sprott oscillators. © 2016 World Scientific Publishing Company.

Ranjit C.,Egra S S B College | Rudra P.,Asutosh College
International Journal of Modern Physics D | Year: 2016

The present work is based on the idea of an interacting framework of new holographic dark energy (HDE) with cold dark matter in the background of f(T) gravity. Here, we have considered the flat modified Friedmann universe for f(T) gravity which is filled with new HDE and dark matter. We have derived some cosmological parameters like deceleration parameter, equation of state (EoS) parameter, state-finder parameters, cosmographic parameters, Om parameter and graphically investigated the nature of these parameters for the above mentioned interacting scenario. The results are found to be consistent with the accelerating universe. Also, we have graphically investigated the trajectories in ω-ω′ plane for different values of the interacting parameter and explored the freezing region and thawing region in ω-ω′ plane. Finally, we have analyzed the stability of this model. © 2016 World Scientific Publishing Company.

Ranjit C.,Egra S S B College | Rudra P.,Asutosh College
International Journal of Theoretical Physics | Year: 2016

FRW universe in Horava-Lifshitz (HL) gravity model filled with a combination of dark matter and dark energy in the form of variable modified Chaplygin gas (VMCG) is considered. The permitted values of the VMCG parameters are determined by the recent astrophysical and cosmological observational data. Here we present the Hubble parameter in terms of the observable parameters Ωdm0, Ωvmcg0, H0, redshift z and other parameters like α, A, γ and n. From Stern data set (12 points), we have obtained the bounds of the arbitrary parameters by minimizing the χ2 test. The best-fit values of the parameters are obtained by 66 %, 90 % and 99 % confidence levels. Next due to joint analysis with BAO and CMB observations, we have also obtained the bounds of the parameters (A, γ) by fixing some other parameters α and n. The best fit value of distance modulus μ(z) is obtained for the VMCG model in HL gravity, and it is concluded that our model is perfectly consistent with the union2 sample data. © 2015, Springer Science+Business Media New York.

Rudra P.,Indian Institute of Science | Rudra P.,Asutosh College
European Physical Journal Plus | Year: 2015

In this note we address the well-known cosmic coincidence problem in the framework of the f(R, T) gravity. In order to achieve this, an interaction between dark energy and dark matter is considered. A constraint equation is obtained which filters the f(R, T) models that produce a stationary scenario between dark energy and dark matter. Due to the absence of a universally accepted interaction term introduced by a fundamental theory, the study is conducted over three different forms of chosen interaction terms. As an illustration three widely known models of f(R, T) gravity are taken into consideration and used in the setup designed to study the problem. The study reveals that, the realization of the coincidence scenario is almost impossible for the popular models of f(R, T) gravity, thus proving to be a major setback for these models. © 2015, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg.

Rudra P.,Asutosh College
Astrophysics and Space Science | Year: 2015

It is well known fact that almost all the recent models of universe are plagued by the cosmic coincidence problem. In this assignment we try to probe the role played by torsion in the current scenario of coincidence and devise a set-up for its realization. In order to model the scenario, the energy arising from the torsion component is considered analogous to dark energy. An interaction between dark energy and dark matter is considered, which is by far the best possible tool to realize the coincidence. A set-up is designed and a constraint equation is obtained which screens the models of f(T) gravity that can successfully accommodate the stationary scenario in its framework, from those which cannot. Due to the absence of a universally accepted interaction term introduced by a fundamental theory, the study is conducted over three different forms of chosen interaction terms. As an illustration two widely known models of f(T) gravity are taken into consideration and used in the designed setup. The study reveals that the realization of the coincidence scenario as well as the role played by torsion in the current universe is a model dependent phenomenon. It is found that the first model showed a considerable departure from the stationary scenario. On the contrary the other four models are perfectly consistent with our setup and generated a satisfactory stationary scenario, thus showing their cosmological viability and their superiority over their counterparts. For the third model (exponential model) it was seen that the cosmological coincidence is realized only in the phantom regime. For the fourth (logarithmic model) and the fifth models, we see that the stationary scenario is attained for negative interaction values. This shows that the direction of flow must be from dark energy to dark matter unlike the previous models. Under such circumstances the universe will return from the present energy dominated phase to a matter dominated phase. © 2015, Springer Science+Business Media Dordrecht.

Rudra P.,Asutosh College
Communications in Theoretical Physics | Year: 2016

In this assignment we will present a reconstruction scheme between f(R) gravity with ordinary and entropy corrected (m,n)-type holographic dark energy. The correspondence is established and expressions for the reconstructed f(R) models are determined. To study the evolution of the reconstructed models plots are generated. The stability of the calculated models are also investigated using the squared speed of sound in the background of the reconstructed gravities. © 2016 Chinese Physical Society and IOP Publishing Ltd.

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