Showing papers in "Pramana in 2012"
TL;DR: In this paper, the authors study static spherically symmetric spacetime to describe compact objects with anisotropic matter distribution, and express the system of Einstein field equations as a new system of differential equations using a coordinate transformation.
Abstract: We study static spherically symmetric spacetime to describe compact objects with anisotropic matter distribution. We express the system of Einstein field equations as a new system of differential equations using a coordinate transformation, and then write the system in another form with polytropic equation of state and obtain two classes of exact models. The models satisfy all major physical features expected in a realistic star. For polytropic index n = 2, we obtain expressions for mass and density which are comparable with the reported experimental observations.
153 citations
CERN1
TL;DR: The current status of indirect searches for dark matter has been reviewed in a schematic way in this paper, where the main relevant experimental results of the recent years have been listed and the excitements and disappointments that their phenomenological interpretations in terms of almost-standard annihilating dark matter have brought along have been discussed.
Abstract: The current status of indirect searches for dark matter has been reviewed in a schematic way here. The main relevant experimental results of the recent years have been listed and the excitements and disappointments that their phenomenological interpretations in terms of almost-standard annihilating dark matter have brought along have been discussed. The main sources of uncertainties that affect this kind of searches are also listed.
88 citations
TL;DR: In this paper, the Lie classical method was used to study the coupled Higgs field equation and Hamiltonian amplitude equation, and the travelling wave solutions were derived by hyperbolic, trigonometric and rational functions.
Abstract: In this paper, coupled Higgs field equation and Hamiltonian amplitude equation are studied using the Lie classical method. Symmetry reductions and exact solutions are reported for Higgs equation and Hamiltonian amplitude equation. We also establish the travelling wave solutions involving parameters of the coupled Higgs equation and Hamiltonian amplitude equation using (G′/G)-expansion method, where G = G(ξ) satisfies a second-order linear ordinary differential equation (ODE). The travelling wave solutions expressed by hyperbolic, trigonometric and the rational functions are obtained.
77 citations
TL;DR: The current status of the India-based Neutrino Observatory (INO) is summarized in this paper, followed by the motivation for building a magnetized iron calorimetric (ICAL) detector.
Abstract: The current status of the India-based Neutrino Observatory (INO) is summarized. The main physics goals are described followed by the motivation for building a magnetized iron calorimetric (ICAL) detector. The charge identification capability of ICAL would make it complementary to large water Cerenkov and other detectors worldwide. The status of the design of the 50 kt magnet, the construction of a prototype ICAL detector, the experience with resistive plate chambers which will be the active elements in ICAL and the status of the associated electronics and data acquisition system are discussed.
70 citations
TL;DR: In this paper, the performance of the optical fiber-based surface plasmon resonance (SPR) sensor with four different metals, gold (Au), silver (Ag), copper (Cu), and aluminium (Al), was analyzed in terms of sensitivity, signal-to-noise (SNR) ratio and quality parameter.
Abstract: The capability of various metals used in optical fibre-based surface plasmon resonance (SPR) sensing is studied theoretically. Four metals, gold (Au), silver (Ag), copper (Cu) and aluminium (Al) are considered for the present study. The performance of the optical fibre-based SPR sensor with four different metals is obtained numerically and compared in detail. The performance of optical fibre-based SPR sensor has been analysed in terms of sensitivity, signal-to-noise (SNR) ratio and quality parameter. It is found that the performance of optical fibre-based SPR sensor with Au metal is better than that of the other three metals. The sensitivity of the optical fibre-based SPR sensor with 50 nm thick and 10 mm long Au metal film of exposed sensing region is 2.373 μm/RIU with good linearity, SNR is 0.724 and quality parameter is 48.281 RIU − 1. The thickness of the metal film and the length of the exposed sensing region of the optical fibre-based SPR sensor for each metal are also optimized.
54 citations
TL;DR: The application of calibration-free laser-induced breakdown spectroscopy for quantitative analysis of materials, illustrated by CF-LIBS applied to a brass sample of known composition, is presented in this article.
Abstract: The application of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) for quantitative analysis of materials, illustrated by CF-LIBS applied to a brass sample of known composition, is presented in this paper The LIBS plasma is produced by a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a brass sample in air at atmospheric pressure The time-resolved atomic and ionic emission lines of Cu and Zn from the LIBS spectra recorded by an Echelle spectrograph coupled with a gated intensified charge coupled detector are used for the plasma characterization and the quantitative analysis of the sample The time delay where the plasma is optically thin and is also in local thermodynamic equilibrium (LTE), necessary for the elemental analysis of samples from the LIBS spectra, is deduced An algorithm relating the experimentally measured spectral intensity values with the basic physics of the plasma is developed Using the algorithm, the Zn and Cu concentrations in the brass sample are determined The analytical results obtained from the CF-LIBS technique agree well with the certified values of the elements in the sample, with an accuracy error <1%
53 citations
TL;DR: In this article, the applicability of the first integral method to combined KdV-mKdV equation, Pochhammer-Chree equation, and coupled nonlinear evolution equations is shown.
Abstract: In this paper, we show the applicability of the first integral method to combined KdV–mKdV equation, Pochhammer–Chree equation and coupled nonlinear evolution equations. The power of this manageable method is confirmed by applying it for three selected nonlinear evolution equations. This approach can also be applied to other nonlinear differential equations.
51 citations
TL;DR: In this paper, it was shown that in string theory, black hole microstates have no horizons and the evolution of radiation quanta with E∼kT is modified by order unity at the horizon.
Abstract: Many relativists have been long convinced that black hole evaporation leads to information loss or remnants. String theorists have however not been too worried about the issue, largely due to a belief that the Hawking argument for information loss is flawed in its details. A recently derived inequality shows that the Hawking argument for black holes with horizon can in fact be made rigorous. What happens instead is that in string theory, black hole microstates have no horizons. Thus the evolution of radiation quanta with E∼kT is modified by order unity at the horizon, and we resolve the information paradox.
47 citations
TL;DR: In this article, relativistic effects on the linear and nonlinear properties of electron plasma waves are investigated using the one-dimensional quantum hydrodynamic (QHD) model for a two-component electron-ion dense quantum plasma.
Abstract: Relativistic effects on the linear and nonlinear properties of electron plasma waves are investigated using the one-dimensional quantum hydrodynamic (QHD) model for a two-component electron–ion dense quantum plasma. Using standard perturbation technique, a nonlinear Schrodinger equation (NLSE) containing both relativistic and quantum effects has been derived. This equation has been used to discuss the modulational instability of the wave. Through numerical calculations it is shown that relativistic effects significantly change the linear dispersion character of the wave. Unlike quantum effects, relativistic effects are shown to reduce the instability growth rate of electron plasma waves.
46 citations
TL;DR: In this article, the functional variable method was used for exact solutions of the Zakharov-Kuznetsov modified equal width (ZK-MEW), the modified Benjamin-Bona-Mahony (mBBM) and the modified KdV-Kadomtsev-Petviashvili (KdV)-KP) equations.
Abstract: In this paper, we implemented the functional variable method for the exact solutions of the Zakharov–Kuznetsov-modified equal-width (ZK-MEW), the modified Benjamin–Bona–Mahony (mBBM) and the modified KdV–Kadomtsev–Petviashvili (KdV–KP) equations. By using this scheme, we found some exact solutions of the above-mentioned equations. The obtained solutions include solitary wave solutions, periodic wave solutions and combined formal solutions. The functional variable method presents a wider applicability for handling nonlinear wave equations.
44 citations
TL;DR: In this paper, the relationship between the fluorine doping level and the electrical, structural and optical properties of the SnO2:F films were investigated using the Hall effect measurement set-up in van der Pauw configuration, the XRD patterns, UV-vis spectrophotometry and atomic force microscopy (AFM).
Abstract: The relationship between the fluorine doping level and the electrical, structural and optical properties of the SnO2:F films are investigated using the Hall effect measurement set-up in van der Pauw configuration, the XRD patterns, UV–vis spectrophotometry and atomic force microscopy (AFM). The X-ray diffraction patterns taken at room temperature show that the films are polycrystalline. The preferred directions of crystal growth in the diffractogram of SnO2:F (FTO) films correspond to the reflections from the (1 1 0), (2 0 0), (2 1 1) and (3 0 1) planes. Thin film thickness and the grain size vary from 280 to 1545 nm and from 17.45 to 33.22 nm, respectively. AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the films are degenerate and exhibit n-type electrical conductivity. The FTO films have a minimum resistivity of 5.29 × 10 − 4 Ω·cm, carrier density of 0.09 × 1020 cm − 3 and mobility of 377.02 cm2/V·s. The sprayed FTO film has the minimum sheet resistance of 5.69 Ω/cm2 and the highest figure-of-merit of 204 × 10 − 4 Ω − 1 at 700 nm. The resistivity attained for the doped film in this study is lower than the values reported for 20 wt.% fluorine-doped tin oxide films prepared from the aqueous solution of SnCl2·2H2O precursor. The highest visible transmittance (700 nm) of the deposited films is 91.8% for 25 wt.% fluorine-doped tin oxide films. The obtained results reveal that the structures and properties of the films are greatly affected by doping levels. These films are useful as conducting layers in electrochromic and photovoltaic devices.
TL;DR: In this paper, the spatial derivative in the proposed Fisher's-type equation is approximated by a sixth-order compact finite difference (CFD6) scheme, and the obtained system of differential equations using a third-order total variation diminishing Runge-Kutta (TVD-RK3) scheme.
Abstract: In this study, we present a new and very accurate numerical method to approximate the Fisher’s-type equations. Firstly, the spatial derivative in the proposed equation is approximated by a sixth-order compact finite difference (CFD6) scheme. Secondly, we solve the obtained system of differential equations using a third-order total variation diminishing Runge–Kutta (TVD-RK3) scheme. Numerical examples are given to illustrate the efficiency of the proposed method.
TL;DR: In this article, the effect of delay on chaos in fractional-order Chen system is investigated and it is observed that inclusion of delay changes chaotic behaviour to limit cycles or stable systems.
Abstract: In the present paper the effect of delay on chaos in fractional-order Chen system is investigated. It is observed that inclusion of delay changes chaotic behaviour to limit cycles or stable systems.
TL;DR: In this article, the (G′/G)-expansion method and its simplified version are used to obtain generalized traveling wave solutions of five nonlinear evolution equations of physical importance, viz. the (2+1)-dimensional Maccari system, the Pochhammer-Chree equation, the Newell-Whitehead equation, Fitzhugh-Nagumo equation and the Burger-Fisher equation.
Abstract: The (G′/G)-expansion method and its simplified version are used to obtain generalized travelling wave solutions of five nonlinear evolution equations (NLEEs) of physical importance, viz. the (2+1)-dimensional Maccari system, the Pochhammer–Chree equation, the Newell–Whitehead equation, the Fitzhugh–Nagumo equation and the Burger–Fisher equation. A variety of special solutions like periodic, kink–antikink solitons, bell-type solitons etc. can easily be derived from the general results. Three-dimensional profile plots of some of the solutions are also drawn.
TL;DR: In this paper, a search for a Higgs boson decaying into two photons in pp collisions at the LHC at a centre-of-mass energy of 7 TeV is presented.
Abstract: A search for a Higgs boson decaying into two photons in pp collisions at the LHC at a centre-of-mass energy of 7 TeV is presented. The analysis is performed on a dataset corresponding to 1.66 fb−1 of data recorded in 2011 by the CMS experiment. Limits are set on the cross-section of a Standard Model Higgs boson decaying into two photons, and on the cross-section of a fermiophobic Higgs boson decaying into two photons.
TL;DR: In this article, the synthesis and characterization of nanosized zinc oxide and its nanofluid in a polyvinyl alcohol (PVA) matrix have been done in the present investigation.
Abstract: The synthesis and characterization of nanosized zinc oxide and its nanofluid in a polyvinyl alcohol (PVA) matrix have been done in the present investigation. Crystalline zinc oxide nanoparticles are synthesized using single-step chemical method while the nanofluids are prepared by the dispersion of nanoparticles in PVA solution using an ultrasonicator. The prepared nanoparticles are characterized using X-ray diffraction, SEM–EDX and UV–visible spectrum. The particle size distribution measurement is carried out by acoustic particle sizer. The ultrasonic velocities are measured in the synthesized nanofluid under different physical conditions using an ultrasonic interferometer. It is found that the degree of crystallinity of nanoparticles depends on the evaporation rate during its synthesis and ultrasonic velocity has non-linear relation with temperature for the present nanofluid.
TL;DR: In this article, a new metric is obtained by solving the field equations and its behavior is typical of a rotating charged source, and the results ensure that the thermodynamic properties in f(R) gravities are qualitatively similar to those of standard General Relativity.
Abstract: In the context of f(R) theories of gravity, we address the problem of finding a rotating charged black hole solution in the case of constant curvature. A new metric is obtained by solving the field equations and we show that its behaviour is typical of a rotating charged source. In addition, we analyse the thermodynamics of the new black hole. The results ensure that the thermodynamical properties in f(R) gravities are qualitatively similar to those of standard General Relativity.
TL;DR: In this paper, a new gate-recessed AlGaN/GaN-based high electron mobility transistor (HEMT) on SiC substrate is proposed and its DC as well as microwave characteristics are discussed for Si3N4 and SiO2 passivation layers using technology computer aided design (TCAD).
Abstract: In this paper, a new gate-recessed AlGaN/GaN-based high electron mobility transistor (HEMT) on SiC substrate is proposed and its DC as well as microwave characteristics are discussed for Si3N4 and SiO2 passivation layers using technology computer aided design (TCAD) The two-dimensional electron gas (2DEG) transport properties are discussed by solving Schrodinger and Poisson equations self-consistently resulting in various subbands having electron eigenvalues From DC characteristics, the saturation drain currents are measured to be 600 mA/mm and 550 mA/mm for Si3N4 and SiO2 passivation layers respectively Apart from DC, small-signal AC analysis has been done using two-port network for various microwave parameters The extrinsic transconductance parameters are measured to be 1317 mS/mm at a gate voltage of Vgs = −035 V and 1146 mS/mm at a gate voltage of Vgs = −04 V for Si3N4 and SiO2 passivation layers respectively The current gain cut-off frequencies (ft) are measured to be 271 GHz and 2397 GHz in unit-gain-point method at a gate voltage of −04 V for Si3N4 and SiO2 passivation layers respectively Similarly, the power gain cut-off frequencies (fmax) are measured to be 41 GHz and 385 GHz in unit-gain-point method at a gate voltage of −01 V for Si3N4 and SiO2 passivation layers respectively Furthermore, the maximum frequency of oscillation or unit power gain (MUG = 1) cut-off frequencies for Si3N4 and SiO2 passivation layers are measured to be 32 GHz and 28 GHz respectively from MUG curves and the unit current gain, ∣ h21 ∣ = 1 cut-off frequencies are measured to be 140 GHz and 75 GHz for Si3N4 and SiO2 passivation layers respectively from the abs ∣ h21 ∣ curves HEMT with Si3N4 passivation layer gives better results than HEMT with SiO2 passivation layer
TL;DR: In this article, the role of space-time geometry in the non-adiabatic collapse of a star dissipating energy in the form of radial heat flow was examined under different initial conditions.
Abstract: We examine the role of space-time geometry in the non-adiabatic collapse of a star dissipating energy in the form of radial heat flow, studying its evolution under different initial conditions. The collapse of a star filled with a homogeneous perfect fluid is compared with that of a star filled with inhomogeneous imperfect fluid under anisotropic pressure. Both the configurations are spherically symmetric. However, in the latter case, the physical space t = constant of the configurations endowed with spheroidal or pseudospheroidal geometry is assumed to be inhomogeneous. It is observed that as long as the collapse is shear-free, its evolution depends only on the mass and size of the star at the onset of collapse.
TL;DR: In this article, the effects of heat transfer in MHD flow of viscoelastic stratified fluid in porous medium on a parallel plate channel inclined at an angle θ were investigated.
Abstract: The paper investigates the effects of heat transfer in MHD flow of viscoelastic stratified fluid in porous medium on a parallel plate channel inclined at an angle θ. A laminar convection flow for incompressible conducting fluid is considered. It is assumed that the plates are kept at different temperatures which decay with time. The partial differential equations governing the flow are solved by perturbation technique. Expressions for the velocity of fluid and particle phases, temperature field, Nusselt number, skin friction and flow flux are obtained within the channel. The effects of various parameters like stratification factor, magnetic field parameter, Prandtl number on temperature field, heat transfer, skin friction, flow flux, velocity for both the fluid and particle phases are displayed through graphs and discussed numerically.
TL;DR: In this article, the authors measured ensemble-averaged dynamic structure factor f(q,t) for WSG and salt-swollen gels (SSG) using static light scattering (SLS) measurements revealed the presence of inhomogeneities in PAAm gels.
Abstract: Swelling kinetics of water-swollen polyacrylamide (PAAm) hydrogels (WSG) was investigated in various concentrations of aqueous NaCl by macroscopic swelling measurements. For lower concentration of NaCl, WSG showed exponential swelling whereas at higher concentration of NaCl it underwent deswelling at short times and exponential swelling at long times. From these studies, collective diffusion coefficient, D, of the polymer network and polymer–solvent interaction parameter, χ, were calculated and found to decrease with increase in [NaCl]. Collective diffusion coefficients measured from dynamic light scattering (DLS) and that obtained from macroscopic swelling measurements are found to agree well. Measured ensemble-averaged dynamic structure factor f(q,t) for WSG and salt-swollen gels (SSG) showed an initial decay followed by a plateau at long times and it can be described by harmonically bound Brownian particle (HBBP) model. Enhanced scattering intensity at low scattering angles using static light scattering (SLS) measurements revealed the presence of inhomogeneities in PAAm gels. The reasons for increased scattering intensity of SSG over WSG gel and the linear decrease of D with increase in NaCl concentration are explained.
TL;DR: In this article, the authors studied the Klein-Gordon-Zakharov equation with power-law nonlinearity and obtained the solutions for this equation by the travelling wave hypothesis method, (G′/G) method and the mapping method.
Abstract: This paper studies the Klein–Gordon–Zakharov equation with power-law nonlinearity. This is a coupled nonlinear evolution equation. The solutions for this equation are obtained by the travelling wave hypothesis method, (G′/G) method and the mapping method.
TL;DR: In this article, the authors study the Indian highway network as a complex network where the junction points are considered as nodes, and the links are formed by an existing connection and explore the topological properties and community structure of the network.
Abstract: In this paper we study the Indian highway network as a complex network where the junction points are considered as nodes, and the links are formed by an existing connection. We explore the topological properties and community structure of the network. We observe that the Indian highway network displays small-world properties and is assortative in nature. We also identify the most important road-junctions (or cities) in the highway network based on the betweenness centrality of the node. This could help in identifying the potential congestion points in the network. Our study is of practical importance and could provide a novel approach to reduce congestion and improve the performance of the highway network.
TL;DR: In this article, function projective synchronizations of identical and non-identical modified finance systems (MFS) and Shimizu-Morioka system (S-MS) are studied via active control technique.
Abstract: In this paper, function projective synchronizations (FPS) of identical and non-identical modified finance systems (MFS) and Shimizu–Morioka system (S-MS) are studied via active control technique. The technique is applied to construct a response system which synchronizes with a given drive system for a desired function relation between identical MFS, identical S-MS and between MFS and S-MS. The results are validated via numerical simulations.
TL;DR: In this article, the effects of two-temperature nonthermal ions on the basic properties of small but finite amplitude nonlinear dust-acoustic waves are examined, and it is found that only compressive solitary waves exist in this system.
Abstract: By using reductive perturbation method, the nonlinear propagation of dust-acoustic waves in a dusty plasma (containing a negatively charged dust fluid, Boltzmann distributed electrons and two-temperature nonthermal ions) is investigated. The effects of two-temperature nonthermal ions on the basic properties of small but finite amplitude nonlinear dust-acoustic waves are examined. It is found that two-temperature nonthermal ions affect the basic properties of the dust-acoustic solitary waves. It is also observed that only compressive solitary waves exist in this system.
TL;DR: In this article, the role of cosmological constant in the evolution of the temperature of a collapsing star was investigated by employing causal heat transport equation, and it was shown that the inclusion of the cosmology constant enhances the temperature within the stellar core.
Abstract: We investigate the role played by the cosmological constant during gravitational collapse of a radiating star with vanishing Weyl stresses in the interior. We highlight the role played by the cosmological constant during the latter stages of collapse. The evolution of the temperature of the collapsing body is studied by employing causal heat transport equation. We show that the inclusion of the cosmological constant enhances the temperature within the stellar core.
TL;DR: In this paper, the authors investigated the energy-momentum distributions for homogeneous and anisotropic Bianchi type-IV in B class universe and found that all energy prescriptions are negative and their results agree with Nester et al.
Abstract: In this study we have investigated the energy–momentum distributions for homogeneous and anisotropic Bianchi type-IV in B class Universe. For this purpose, we have used energy–momentum complexes of Einstein, Bergmann–Thomson, Landau–Lifshitz (LL), Papapetrou, Tolman and Moller in general relativity (GR) is also Einstein, Bergmann–Thomson, Landau–Lifshitz and Moller in teleparallel gravity (TG). From the obtained results we have found that Einstein and Bergmann–Thomson distributions are exactly giving the same results in GR and TG but the Landau–Lifshitz, Papapetrou Tolman and Moller energy–momentum distributions do not provide the same results with Einstein and Bergmann–Thomson in GR and TG. Furthermore, Einstein, Bergmann–Thomson and LL results are the same in different gravitation theories and we get that both GR and TG are equivalent theories for these prescriptions. From the obtained solutions, we could say that these are equivalent theories. Also, Moller energy–momentum distributions do not give the same results in GR and TG. However, we have found that all energy prescriptions are negative and our results agree with Nester et al.
TL;DR: In this article, the mesonic wave function was modified by using a short distance scale r0 in analogy with hydrogen atom and estimate the values of masses and decay constants of the open flavour charm mesons D, Ds and Bc within the framework of a QCD potential model.
Abstract: We modify the mesonic wave function by using a short distance scale r0 in analogy with hydrogen atom and estimate the values of masses and decay constants of the open flavour charm mesons D, Ds and Bc within the framework of a QCD potential model. We also calculate leptonic decay widths of these mesons to study branching ratios and lifetime. The results are in good agreement with experimental and other theoretical values.
TL;DR: In this article, a new rotating black hole in three-dimensional anti-de Sitter space using an anisotropic perfect fluid inspired by the noncommutative black hole was found.
Abstract: We find a new rotating black hole in three-dimensional anti-de Sitter space using an anisotropic perfect fluid inspired by the noncommutative black hole. We deduce the thermodynamical quantities of this black hole and compare them with those of a rotating BTZ solution and give corrections to the area law to get the exact nature of the Bekenstein-Hawking entropy.
TL;DR: The results of the multiplicity, flow, fluctuations and Bose-Einstein correlations indicate that the fireball formed in nuclear collisions at the LHC is hotter, lives longer, and expands to a larger size at freeze-out as compared to lower energies as discussed by the authors.
Abstract: On November 8, 2010 the Large Hadron Collider (LHC) at CERN collided the first stable beams of heavy ions (Pb on Pb) at the centre-of-mass energy of 2.76 TeV/nucleon. The LHC worked exceedingly well during its one month of operation with heavy ions, delivering about 10 μb − 1 of data, with peak luminosity reaching to $L_{0} = 2 \times 10^{25}\,{\rm cm}^{-2}\,{\rm s}^{-1}$
towards the end of the run. Three experiments, ALICE, ATLAS and CMS, recorded their first heavy-ion data, which were analysed in a record time. The results of the multiplicity, flow, fluctuations and Bose–Einstein correlations indicate that the fireball formed in nuclear collisions at the LHC is hotter, lives longer, and expands to a larger size at freeze-out as compared to lower energies. We give an overview of these as well as new results on quarkonia and heavy flavour suppression, and jet energy loss.