Increase Of Coupling Parameter Research Articles

Violation of Hod’s conjecture and probing it with optical properties of a 5-D black hole in Einstein Gauss–Bonnet Bumblebee theory of gravity

In this work, the quasinormal modes of a 5-D black hole in Einstein Gauss–Bonnet Bumblebee theory of gravity have been investigated with the help of the Padé averaged higher order WKB approximation method and the validity of Hod’s conjecture has been studied. It is found that the presence of Lorentz symmetry breaking due to the Bumblebee field favours Hod’s conjecture. But in the case of the Gauss–Bonnet term, an increase in the coupling parameter increases the chances of violation of Hod’s conjecture. We further investigated the optical properties of the black hole viz., shadow and emission rate. It is found that a black hole with a lower lifetime favours Hod’s conjecture.

Dynamics of Magnetized and Magnetically Charged Particles around Regular Nonminimal Magnetic Black Holes

The present paper is devoted to the study of the event horizon properties of spacetime around a regular nonminimal magnetic black hole (BH), together with dynamics of magnetized and magnetically charged particles in the vicinity of the BH. It is shown that the minimum value of the outer horizon of the extreme charged BH increases with the increase in coupling parameter. It reaches its maximum value of 1.5M when q→∞, while the maximal value of the BH charge decreases and tends toward zero. We also present a detailed analysis of magnetized particles’ motion around a regular nonminimal magnetic black hole. The particle’s innermost circular stable orbits (ISCOs) radius decreases as the magnetic charge and the parameter β increase and the coupling parameter of Yang–Mills field causes a decrease at the values of the magnetic charge near to its maximum. We show that the magnetic charge can mimic the spin of a rotating Kerr black hole up to the value of a=0.7893M, providing the same value for an ISCO of a magnetized particle with the parameter β=10.2 when the coupling parameter is q=0. Moreover, Lyapunov exponents, Keplerian orbits and harmonic oscillations of magnetized particles motion are also discussed.

Efficient Theoretical and Numerical Methods for Solving Free Vibrations and Transient Responses of a Circular Plate Coupled With Fluid Subjected to Impact Loadings

Abstract This paper presents an easy-to-use theoretical method and an efficient numerical method for solving free vibrations and transient responses of a circular plate coupled with fluid subjected to impact loadings and provides insights into various coupling cases with these developed methods. The Kirchhoff plate theory, Mindlin–Reissner plate theory, and the linear velocity potential function are used. The wet mode of the coupled system is described as the superposition of dry modes of the plate, which has been considered in few studies. The natural frequencies and corresponding mode shapes are solved using the orthogonality of dry modes. The transient responses of the plate are then solved using the superposition of the wet modes and the orthogonality of dry modes. To validate the theoretical results, an efficient and flexible finite element method is proposed and verified by comparing with commercial software. The four-node mixed interpolation of the tensorial component quadrilateral plate finite element (MITC4) and the eight-node acoustic pressure element are used to model the plate and the fluid, respectively. The theoretical and numerical methods provide reliable and accurate results. Parametric studies are performed to investigate the influence of geometric sizes, plate material properties, and fluid properties on the natural frequencies of the coupled system. A coupling parameter of fluid–structure interaction is proposed. The nondimensional added virtual mass incremental (NAVMI) factor decreases as the coupling parameter increases. Besides, the influence of fluid on wet modes of the plate decreases with the order.

Numerical simulation and modeling of the die swell for fiber suspension flows

A numerical model is developed to examine the die swell for fiber suspensions, which occurs in 3D printing extrusion processes. More specifically, it focuses on the fiber orientation distribution in a Newtonian suspending fluid and its effects on the shape of the free surface. In a first step, the flow in a 2D axisymmetric capillary die is explored in order to validate the numerical implementation for the fiber orientation model. It is found that the coupling effect flattens the velocity profile but has a small impact on the fiber orientation distribution in the suspension flow. In a second step, the modeling of die swell is considered and result from the literature for the final swelling height is obtained for an uncoupled flow. For fully coupled flows, different values for the coupling parameter and the fiber-fiber interaction coefficient have been tested in order to observe their effects on the free surface shape and on the final fiber orientation distribution. The increase of the fiber coupling parameter increases the die swell ratio when fibers are randomly distributed at the flow inlet, but the opposite behavior, i.e., a decrease of the swelling ratio, is noticed when a perfect fiber alignment condition is imposed at the entrance for low fiber interaction coefficients. The Tanner model, initially developed for viscoelastic fluids, is updated to estimate extrudate swell for fibers suspended in a Newtonian fluid in terms of the coupling parameter and the interaction coefficient. Although this analytical approach used a quadratic closure approximation, it gives qualitative results when compared with the numerical simulations.

Potential Distribution in a Strongly Coupled Dusty Magnetoplasma

The potential distribution around a test charge particle is studied in a strongly coupled dusty magnetoplasma. Special emphasis is given to study the combined influence of the strong interaction between the charged dust grains and the external magnetic field on the potential distribution. It is found that these effects significantly modify the potential profile. For example, an increase in the coupling parameter increases the potential amplitude and then can change the polarity of the response potential. The present results may be useful in laboratories as applications of wave–particle interactions [i.e., inertial confinement fusion (ICF) scheme, particle acceleration, and heavy-ion pumped X-ray lasers], as well as in space plasmas (i.e., dust coagulation in space).

Three-dimensional magnetohydrodynamic flow of micropolar CNT-based nanofluid through a horizontal rotating channel: OHAM analysis

An examination of simultaneous effects of Hall current and heat radiation on three-dimensional micropolar CNT-based nanofluid flow between two rotating sheets is carried out. The upper sheet is considered to be porous, and the fluid flow is induced due to stretching of the lower sheet. The flow model is presented by a system of nonlinear partial differential equations (PDEs). The leading PDEs are transformed into dimensionless coupled ordinary differential equations by the usual procedure of transformation. The transformed differential equations are solved by the optimal homotopy analysis method in order to analyze the velocity as well as temperature of nanofluid and microrotation of nanotubes. Analysis for physical quantities of interest, viz. skin friction coefficient and Nusselt number, are also carried out for the two kinds of nanotubes, single-wall carbon nanotubes and multiwall carbon nanotubes. It is observed that microrotation of nanotubes increased with the increase in coupling parameter, whereas it slows down with an increase in spin gradient viscosity parameter. An intense magnetic field results in a reduction of skin friction coefficient, whereas an increase in the suction of fluid through upper plate forces a surge in the value of skin friction coefficient.

Hawking Radiation of Reissner-Nordström Black Hole in Electromagnetic Field with Einstein Tensor Corrections

In this paper, we have investigated the absorption probability and Hawking radiation of electromagnetic field while it coupling with Einstein tensor in the background of 4-dimensional Reissner-Nordstrom(RN) black hole spacetime. Our results indicate that the properties of the absorption probability and Hawking radiation depend not only on the coupling parameter, but also on the parity of the electromagnetic field, which is quite different from those of the usual electromagnetic field without coupling in the 4-dimensional spacetime.The absorption probability, power emission spectra and luminosity of Hawking radiation decreases with the increase of coupling parameter α when the coupled electromagnetic field have odd-parity, and increases with the increase of coupling parameter α when the coupled electromagnetic field have even-parity.

MHD flow of carbon in micropolar nanofluid with convective heat transfer in the rotating frame

Abstract This article addresses the MHD flow of micropolar carbon-water nanofluid in the presence of rotating frame. Two types of carbon nanotubes (single and multi-walls) are homogeneously dispersed in the base fluid (water). Convective heat transfer phenomenon is also retained in this study. With the help of the similarity transformation, a mathematical model is developed by transforming the partial differential equation into ordinary differential equation. Further it is then solved analytically by using homotopy analysis method HAM. The impact of emerging parameters, skin friction coefficient and Nusselt number are also discussed in detail. It is observed that temperature profile decreases with the increase in porosity parameter and nanoparticle volume fraction while enhances for higher values of Biot number. Further Micro rotation profile increases with the increase in coupling parameter N 1 and Reynolds number R while decreases with increase in Biot number Bi and volume fraction ϕ .

Non-similarity Solution of Micropolar Fluid Flow over a Truncated Cone with Soret and Viscous Dissipation Effects Using Spectral Quasilinearization Method

This paper is an investigation of viscous dissipation and Soret effects on laminar natural convection flow over a truncated cone immersed in a micropolar fluid with convective boundary condition. For this complex fluid flow problem, the similarity solution does not exist and hence the non-similarity transformations are used to convert the governing fluid flow equations along with associated boundary conditions into a set of non-dimensional form. Due to several advantages of spectral methods over the finite difference and finite element methods, the spectral quasi-linearization method is employed to solve the system of non-similar, coupled, partial differential equations. The numerical results point out that, in the presence and absence of Soret number, the Nusselt number, wall couple stress and Sherwood number decrease, but the temperature, concentration and skin friction increase with an increase of coupling parameter. As the Boit number enhances, the skin friction, Nusselt number and Sherwood number enhance but the wall couple stress reduces in the presence of viscous dissipation parameter.

Role of epoxidation on segmental motion of polyisoprene as studied by broadband dielectric spectroscopy

ABSTRACTIn this article, the broadband dielectric spectroscopy (BDS) is used to investigate the relaxation behavior of polyisoprene (PI) epoxidized to various levels and the special consideration is devoted to the effect of epoxidation degree on segmental relaxation. To associate segmental relaxation with molecular structure, several empirical equations are used to fit experimental data. Furthermore, we want to discuss the origin of the change of segmental relaxation. Thermal measurement reveals that glass transition temperature of epoxidized PI (EPI) increase with the increase of epoxidation degrees. The epoxidation modification increases the breadth of the dielectric dispersion. Oxirane groups as steric interference enhance the cooperativity of segmental relaxation process and retard the relaxation process, which results in the increase of coupling parameter. Specifically, Vogel–Fulcher–Tammann equation shows the relationship between correlation length and temperature. These results further illustrate the effect of epoxidation group on segmental motion of PI. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43879.

Core holes, charge disorder, and transition from metallic to plasma properties in ultrashort pulse irradiation of metals

We study the details of a gradual change in electron properties from those of a nearly-free-electron (NFE) metal to those of a strongly-coupled plasma, in ultrashort pulse energy deposition in solid metal targets. Time scales shorter than those of a target surface layer expansion are considered. Both the case of an optical laser (visible or near infrared wavelengths range) and of a free electron laser (vacuum ultraviolet or X-ray) are treated. The mechanisms responsible for the change in electron behavior are isochoric melting, lattice charge disordering, and electron mean free path reduction. We find that the transition from metal to plasma usually occurs via an intermediate stage of a charge-disordered solid (solid plasma), in which ions are at their lattice sites but the ionization stages of individual ions differ due to ionization from localized bound states. Charge disordered state formation is very rapid (typically, few femtoseconds or few tens of femtoseconds). Pathway to charge-disordered state differs in simple metals and in noble metals. Probabilities are derived for electron impact ionization and 3-body recombination of a bound ionic state in solid-density medium, applicable both in metal and in plasma regime. An evolution of energy coupling between electron and ion subsystems, from metallic electron-phonon (e-ph) to plasma electron-ion (e-i) coupling, is considered. Substantial increase in coupling parameter is expected as a result of charge disorder.

The density distributions of the counterions and the coions confined in two similarly charged plates.

By using the field-theoretic method, we established a unified systematic formulation of a model of counterions and coions confined in two similarly charged plates, and calculated the density distributions of counterions and coions with various coupling parameters by the two methods: Poisson-Boltzmann (PB) approach and the strong coupling (SC) theory, respectively. We also performed Monte Carlo simulations, and obtained the density distributions of counterions and coions with several different coupling parameters. Comparing our theoretical results with those from Monte Carlo simulation, we find that the PB approach is valid when the coupling parameter Xi is smaller than 1, but, as Xi > or = 1, the results by the PB approach deviate from the corresponding Monte Carlo simulation data, and the deviation gets larger with the coupling parameter increasing. This shows that the PB approach is completely invalid when the coupling parameter is equal to 1 or larger than 1. For the latter case, the development trend of the distribution curve calculated by SC theory agrees with that from Monte Carlo simulation as the coupling parameter increases. This demonstrates that the SC theory can give a qualitative available explanation on the density distribution of the counterions in the system in which the coupling parameters are strictly confined.

Decoherence, entanglement, and chaos in the Dicke model

The dynamical properties of quantum entanglement in the Dicke model without rotating-wave approximation are investigated in terms of the reduced-density linear entropy. The characteristic time of decoherence process in the early-time evolution is numerically obtained and it is shown that the characteristic time decreases as the coupling parameter increases. The mean entanglement, which is defined to be averaged over time, is employed to describe the influences of both quantum phase transition and corresponding classical chaos on the behavior of entanglement. For a given energy, initial conditions are taken to be minimum uncertainty wave packets centered at regular and chaotic regions of the classical phase space. It is shown that the entanglement has a distinct change at the quantum phase transition, and that the entanglement for regular initial conditions is smaller than that for chaotic ones in the case of weak coupling, while it fluctuates with small amplitude in strong coupling and for chaotic initial conditions.

Structures in the phase space of a four dimensional symplectic map

We numerically investigate the projections of non periodic orbits in a 4-dimensional (4-D) symplectic map composed of two coupled 2-dimensional (2-D) maps. We describe in detail the structures that are produced in different planes of projection and we find how the morphology of the 4-D orbits is influenced by the features of the 2-D maps as the coupling parameter increases. We give an empirical law that describes this influence.

Structures in coupled map lattices

We report the observation of coherent structures in coupled map lattices. We define the coherent structures as those in which the values of the dynamical variables follow a certain pattern. Larger size coherent structures are observed as the coupling parameter increases. There is also an increase in the number of structures with a given size or lifetime. If noise is added to the system, then there is a considerable increase in the number as well as the size of coherent structures.

Ground State of a Tunneling Particle Coupled to Boson Excitaions in a Double-Well Potential

By using a variation method we study the ground state of a tunneling particle coupled to many bosons in a double-well potential. The boson system is assumed to have dense low-energy excitations, just as taken by Chakravarty and Leggett to discuss the dissipative effect in macroscopic quantum phenomena. We examine reduction of the tunneling matrix and eventual localization of the particle due to boson excitations for arbitrary strengths of tunneling and coupling parameters. Ground state energy is evaluatied. Continuous as well as discontinuous changes from tunneling to localized states are found when the coupling parameter increases. The results are related to the orthogonality of many-particle ground states, as known for many-electron system as Anderson's theorem.

Superconductivity and phonon softening in instable systems

AbstractThe effect of softening of phonon modes on the coupling parameter λ for superconductors with strong electron—phonon interaction is considered by taking into account electron effects. New formulae are derived which relates the increase in coupling parameter with optical phonons λopt for the PdH system and the increase in the parameter λ for A3B‐superconductors with A15‐structure to changes in the density of states at the Fermi level. Using these formulae the role of electron factor N(0) G2 in the increasing of superconductive transition temperature Tc is discussed for the most high temperature superconductors.