Charged Fluid Research Articles

Dynamically equivalent Λ CDM equations with underlying Bianchi Type geometry

Solutions have been found for gravity coupled to electromagnetic field and a set of charged and uncharged perfect fluids for Bianchi Types VI(−1), VIII, IX. It has been assumed that the anisotropy is “frozen”, γμν=α(t)2mμν, where γμν and mμν are the spatial metric and some constant matrix respectively. This, according to previous works, results in the existence of a conformal Killing vector field proportional to the fluid velocity of the comoving matter, which guarantees the absence of parallax effects and the independence of the temperature (assuming black body spectrum) from the direction of observation. The electromagnetic field “absorbs” the “frozen” anisotropy and the remaining equations are dynamically equivalent with the equations of Λ CDM. There are solutions with flat, negative and positive effective spatial curvature corresponding to the three FLRW classes. Three equations of state for the charged perfect fluid were studied: non-relativistic w=0, relativistic w=1/3 and dark energy-like w=−1. For the first two cases, maximum values exist for the scale factor, in order for the weak energy conditions to be respected, which depend upon the geometric and charged fluid parameters. A minimum value for the scale factor exists (for the solutions to be valid) in all the cases and Types, indicating the absence of initial spacetime singularity (big bang). This minimum value depends upon the geometric and electromagnetic parameters. The number of essential constants in the final form of each metric is the minimum without loss of generality due to the use of the constant Automorphism's group. A known solution, with the anisotropy absorbed via one free scalar field is reproduced with our method and contains the minimum possible number of parameters.

A charged perfect fluid model with high compactness

A relativistic, static and spherically symmetrical stellar model is presented, constituted by a perfect charged fluid. This represents a generalization to the case of a perfect neutral fluid, whose construction is made through the solution to the Einstein-Maxwell equations proposing a form of gravitational potential $g_{tt}$ and the electric field. The choice of electric field implies that this model supports values of compactness$u=GM/c^2R\leq 0.5337972212$, values higher than the case without electric charge ($u\leq 0.3581350065$), being this feature of relevance to get to represent compact stars. In addition, density and pressure are positive functions, bounded and decreasing monotones, the electric field is a monotonously increasing function as well as satisfying the condition of causality so the model is physically acceptable. In a complementary way, the internal behavior of the hydrostatic functions and their values are obtained taking as a data the corresponding to a star of $1 M_\odot$,for different values of the charge parameter, obtaining an interval for the central density $\rho_c\approx (7.9545,2.7279) 10^{19}$ $ Kg/m^3$ characteristic of compact stars.

Poisson–Boltzmann equation with a random field for charged fluids

The classical Poisson–Boltzmann equation (CPBE), which is a mean field theory by averaging the ion fluctuation, has been widely used to study ion distributions in charged fluids. In this study, we derive a modified Poisson–Boltzmann equation with a random field from the field theory and recover the ion fluctuation through a multiplicative noise added in the CPBE. The Poisson–Boltzmann equation with a random field (RFPBE) captures the effect of the ion fluctuation and gives different ion distributions in the charged fluids compared to the CPBE. To solve the RFPBE, we propose a Monte Carlo method based on the path integral representation. Numerical results show that the effect of the ion fluctuation strengthens the ion diffusion into the domain and intends to distribute the ions in the fluid uniformly. The final ion distribution in the fluid is determined by the competition between the ion fluctuation and the electrostatic forces exerted by the boundaries. The RFPBE is general and feasible for high dimensional systems by taking the advantage of the Monte Carlo method. We use the RFPBE to study a two dimensional system as an example, in which the effect of ion fluctuation is clearly captured.

Charged perfect fluid gravitational collapse in f(R, T) gravity

We explore the problem of charged perfect fluid spherically symmetric gravitational collapse in f(R, T) gravity (R is Ricci scalar and T is the trace of energy–momentum tensor). We have taken the interior boundary of a star as spherically symmetric metric filled with the charged perfect fluid. In order to study charged perfect fluid collapse, we have investigated the exact solutions of the Maxwell–Einstein field equations solutions using the most simplified form for f(R, T) model f(R, T) = R + 2[Formula: see text]T, where [Formula: see text] is model parameter. This study involves the effects of charge as well as coupling parameter on collapse of a star. We studied the nature of trapped surfaces, apparent horizon and singularity structure in detail. It has been found that singularity is formed earlier than the apparent horizons, so the end state of gravitational collapse in this case is black hole.

Charged anisotropic strange stars in Finslerian geometry

We investigate a simplified model of the strange stars in the framework of Finslerian geometry, composed of charged fluid. It is considered that the fluid consisting of three flavor quarks including a small amount of non-interacting electrons to maintain the chemical equilibrium and assumed that the fluid is compressible by nature. To obtain the simplified form of the charged strange star we have considered constant flag curvature. Based on geometry, we have developed the field equations within the localized charge distribution. We consider that the strange quarks distributed within the stellar system are complied with the MIT bag model type of equation of state (EOS) and the charge distribution within the system follows a power law. We represent the exterior spacetime by the Finslerian Ressiner-Nordström space-time. The maximum anisotropic stress is obtained at the surface of the system. Whether the system is in equilibrium or not, has been examined with respect to the Tolman–Oppenheimer–Volkoff (TOV) equation, Herrera cracking concept, different energy conditions and adiabatic index. We obtain that the total charge is of the order of 10^{20}hbox { C} and the corresponding electric field is of around 10^{22}hbox { V/m}. The central density and central pressure vary inversely with the charge. Varying the free parameter (charge constant) of the model, we find the generalized mass-radius variation of strange stars and determine the maximum limited mass with the corresponding radius. Furthermore, we also considered the variation of mass and radius against central density respectively.

Two-fluid simulations of waves in the solar chromosphere

Solar chromosphere consists of a partially ionized plasma, which makes modeling the solar chromosphere a particularly challenging numerical task. Here we numerically model chromospheric waves using a two-fluid approach with a newly developed numerical code. The code solves two-fluid equations of conservation of mass, momentum, and energy, together with the induction equation for the case of the purely hydrogen plasma with collisional coupling between the charged and neutral fluid components. The implementation of a semi-implicit algorithm allows us to overcome the numerical stability constraints due to the stiff collisional terms. We test the code against analytical solutions of acoustic and Alfvén wave propagation in uniform medium in several regimes of collisional coupling. The results of our simulations are consistent with the analytical estimates, and with other results described in the literature. In the limit of a large collisional frequency, the waves propagate with a common speed of a single fluid. In the other limit of a vanishingly small collisional frequency, the Alfvén waves propagate with an Alfvén speed of the charged fluid only, while the perturbation in neutral fluid is very small. The acoustic waves in these limits propagate with the sound speed corresponding to either the charges or the neutrals, while the perturbation in the other fluid component is negligible. Otherwise, when the collision frequency is similar to the real part of the wave frequency, the interaction between charges and neutrals through momentum-transfer collisions cause alterations of the waves frequencies and damping of the wave amplitudes.

Charging history and fluid evolution for the Carboniferous volcanic reservoirs in the western Chepaizi Uplift of Junggar Basin as determined by fluid inclusions and basin modelling

Fluid inclusions are rich in the Carboniferous volcanic reservoirs in the western Chepaizi Uplift, occurring in liquid, gaseous, and gas–liquid phases. In this study, the fluid inclusions were investigated in terms of petrographic, optical, and microthermometric characteristics, coupled with pressure–volume–temperature–composition (PVTX) simulations. Two periods of hydrothermal activities in the Carboniferous volcanic reservoirs were suggested by the bimodal distributions of Th (homogenization temperatures) of fluid inclusions with 120–140°C and 160–190°C as the main peaks. The early charged fluids were characterized by a low temperature, low salinity, relatively higher density, and low G/L (gas–liquid volumetric ratio) of aqueous inclusions, whilst the late charged fluids featured a high temperature, moderate salinity, moderate density, and high G/L of aqueous inclusions. The oil inclusions hosted in calcite or quartz veins exhibited light yellow and yellowish‐green fluorescence, whereas those in the microcracks cutting or within quartz or calcite veins showed blue‐white fluorescence. The burial and geothermal histories imply an existence of abnormal hydrothermal activity under overpressure and high temperature, which is evidenced by the simulated trapping pressure that is higher than the lithostatic pressure and the measured Th values that are higher than the formation paleo‐temperatures. The Th range is widely and continuously distributed and, in combination with the burial history, indicates that the hydrocarbon accumulation in the research area has been a continuous process since the Paleogene. Combined with the reconstruction of tectonic evolution and hydrocarbon generation and expulsion, two oil‐charging episodes were defined, that is, the Late Oligocene–Early Miocene (23–16 Ma) and the Late Miocene–Holocene (6 Ma–). The western section of the Aika Fault Belt (F2), together with the sheet sandbodies of the Toutunhe Formation (J2t), and the unconformities between Carboniferous–Cretaceous may have served as the migration pathways.

Stochastic hydrodynamics and long time tails of an expanding conformal charged fluid

We investigate the impact of hydrodynamic fluctuations on correlation functions in a scale invariant fluid with a conserved $\text{U}(1)$ charge. The kinetic equations for the two-point functions of pressure, momentum, and heat energy densities are derived within the framework of stochastic hydrodynamics. The leading nonanalytic contributions to the energy-momentum tensor as well as the $\text{U}(1)$ current are determined from the solutions to these kinetic equations. In the case of a static homogeneous background we show that the long time tails obtained from hydrokinetic equations reproduce the one-loop results derived from statistical field theory. We use these results to establish bounds on transport coefficients. We generalize the stochastic equation to a background flow undergoing Bjorken expansion. We compute the leading fractional power $\mathcal{O}({(\ensuremath{\tau}T)}^{\ensuremath{-}3/2})$ correction to the $\text{U}(1)$ current and compare with the first-order gradient term.

Dust-Acoustic Shock Waves for Multi-Temperature Electrons and Ions

An investigation has been made on the propagation of dust-acoustic shock waves (DASWs) in an unmagnetized collisionless dusty plasma consisting of two distinct temperature ions (one follows the Maxwell-Boltzmann distribution and the other one follows the nonthermal Cairn’s distribution), two distinct temperature electrons (one follows the nonextensive distribution and the other one follows the superthermal kappa distribution) and a negatively charged viscous dust fluid. The investigation was performed by deriving the nonlinear Burger’s equation through the application of the reductive perturbation method (RPM) and solving the Burger’s equation under steady-state condition. The viscous force is seen to cause dissipation for which DASWs are formed. The fundamental properties of the DASWs are also observed to be strongly modified by the effect of the Maxwellian ions, nonthermal ions, nonextensive electrons, superthermal electrons and viscous dust fluid. The possible implications of this investigation in astrophysical plasma systems, like Saturn’s rings, cometary environments, interstellar and circumstellar media etc., are also briefly addressed.

Theoretical equations of state for a charged fluid.

In this article, we present a molecular thermodynamic study of a system of N particles contained within a volume V and interacting via a hard-core pair potential with an attractive interaction according to the Wolf model for charged systems. This variable-range potential is characterized by three parameters: the repulsive hard-core diameter σ, the energy-well depth ϵ, and the inverse range α; a fourth parameter of the model is a cut-off distance xc that depends on α according to the relation xc = 2/α. Two equations of state (EOSs) are presented and derived from thermodynamic perturbation theory and Monte Carlo (MC) simulation data. The first EOS is given by the standard Zwanzig's high-temperature expansion of the Helmholtz free energy, where the first three perturbation terms a1, a2, and a3 were obtained from MC simulations in the canonical ensemble (NVT) and parameterized as functions of α and the reduced density of particles ρ* = Nσ3/V. The second EOS was obtained from the discrete perturbation theory applied to a discrete representation of the Wolf potential. Results for pressures, internal energies, and isochoric heat capacities are compared to the MC computer simulation data of the Wolf system, including vapor-liquid coexistence curves, for different values of α. Overall, both EOSs give a very good representation of the thermodynamic properties of the Wolf fluid when 0.3 ≤ α ≤ 1.0 and 0.05 ≤ ρ* ≤ 0.8. Since the Yukawa fluid can reproduce information of screened ionic interactions, we discuss the equivalence between the Wolf and Yukawa fluids in the context of equivalent systems in liquid theory.

Electromagnetic field and dark dynamical scalars for spherical systems

This paper studies the effects of inhomogeneous fluid configurations on the evolution of relativistic spheres within the context of electromagnetic field and fourth order gravity. We assume a compact distribution of spherical structure that evolves due to the curvature influences coming from f (R) gravity model and non-ideal matter source. After calculating the corresponding f (R) equations of motion, an explicit formulation among Weyl scalar, dark dynamical scalars and material variables is developed. With f (R) curvature and charged fluid terms, all the non-zero dynamical variables are presented from the orthogonal decomposition the Riemann curvature tensor. The Raychaudhuri, Weyl scalar and shearing equations are formulated through modified scalar functions with and without varying Ricci scalar for perfect and imperfect spherical systems.

A six-moment multi-fluid plasma model

We present a six-moment multi-fluid model, which solves the governing equations for both ions and electrons, with pressure anisotropy along and perpendicular to the magnetic field direction, as well as the complete set of Maxwell equations. This set of equations includes the Hall effect, different temperatures for different species and pressure anisotropy. It is more comprehensive than the five-moment equations with isotropic pressures and significantly less expensive than the ten-moment equations with a full pressure tensors. Similarly to the five- and ten-moment equations, the wave speeds are naturally limited by the speed of light, which eliminates the issue of unlimited whistler wave speeds present in Hall magnetohydrodynamics (MHD). It is also possible to simulate multiple negatively charged fluids, which cannot be done in MHD models. The six-moment model is a reasonable description of the plasma outside magnetic reconnection regions and therefore well-suited to be coupled with an embedded particle-in-cell model that covers the reconnection region. Our numerical implementation uses a point-implicit scheme for the stiff source terms, and we use a second-order accurate Rusanov-type scheme with carefully selected wave speeds. For the plasma variables and the magnetic field the maximum wave speed is based on the fast magnetosonic speed of MHD with anisotropic pressures that we derive. For the electric field related variables the speed of light is used. The divergence of the magnetic field and Gauss's law are controlled with a hyperbolic-parabolic scheme. We present a number of numerical tests to demonstrate that this numerical model is robust without being excessively diffusive.

A necessary condition ensuring the strong hyperbolicity of first-order systems

We study strong hyperbolicity of first-order partial differential equations for systems with differential constraints. In these cases, the number of equations is larger than the unknown fields, therefore, the standard Kreiss necessary and sufficient conditions of strong hyperbolicity do not directly apply. To deal with this problem, one introduces a new tensor, called a reduction, which selects a subset of equations with the aim of using them as evolution equations for the unknown. If that tensor leads to a strongly hyperbolic system we call it a hyperbolizer. There might exist many of them or none. A question arises on whether a given system admits any hyperbolization at all. To sort-out this issue, we look for a condition on the system, such that, if it is satisfied, there is no hyperbolic reduction. To that purpose we look at the singular value decomposition of the whole system and study certain one parameter families ([Formula: see text]) of perturbations of the principal symbol. We look for the perturbed singular values around the vanishing ones and show that if they behave as [Formula: see text], with [Formula: see text], then there does not exist any hyperbolizer. In addition, we further notice that the validity or failure of this condition can be established in a simple and invariant way. Finally, we apply the theory to examples in physics, such as Force-Free Electrodynamics in Euler potentials form and charged fluids with finite conductivity. We find that they do not admit any hyperbolization.

Effect of trapped ion on the shock properties in opposite charged dusty plasma

The dust acoustic frequency properties and dissipative electrostatic field characteristics in opposite charged viscous dusty fluid plasma having trapped ion have been disused for quasineutrality case. The modified dissipative Burgers equation was analytically derived. The contributions of positive dust parameter, trapped ion, ion temperatures and charge to mass ratio between polarity grains on shock potential and its related electrostatic field have been investigated.

Static conformal models for anisotropic charged fluids

We investigate the role played by conformal symmetries in the study of exact solutions in static spherically symmetric spacetimes. We consider the gravitational field associated with anisotropic charged fluids. The existence of a conformal symmetry provides us with a functional relation between the metric functions. This relationship yields a general solution to the Einstein-Maxwell equations. Various conformally symmetric models for fluids that are charged or anisotropic or both are shown to be special cases of the general exact solution generated in this paper. In particular we generate a conformally flat Finch-Skea type model for an isotropic charged fluid.

A parametric model to study the mass–radius relationship of stars

In static space–time, we solve the Einstein–Maxwell equations. The effective gravitational potential and the electric field for charged anisotropic fluid are defined in terms of two free parameters. For such configurations, the mass of the star as a function of stellar radius is found in terms of two aforementioned parameters subjected to certain stability criteria. For various values of these two parameters, one finds that such a mass–radius relationship can model stellar objects located at various regions of the Hertzsprung–Russel diagram.

Relativistic disks with two charged perfect fluids components

A method to describe exact solutions of the Einstein-Maxwell field equations in terms of relativistic thin disks constituted by two perfect charged fluids is presented. Describing the surface of the disk as a single charged fluid we find explicit expressions for the rest energies, the pressures and the electric charge densities of the two fluids. An explicit example is given. The particular case of the thin disks composed by two charged perfect fluids with barotropic equation of state is also presented.

Spherically Symmetric Static Charged Anisotropic Fluid in Rosen's Bimetric Theory of Gravitation

ABSTRACTIn this paper we have obtained an exact solution for the static spherically symmetric space-time with charged anisotropic fluid distribution in context of Rosen's Bimetric General Relativity (BGR).

Symmetries of spacetimes embedded with an electromagnetic string fluid

The electromagnetic string fluid (EMSF) is an anisotropic charged string fluid interacting with a strong magnetic field. In this fluid we consider the double congruence defined by the 4-velocity of the fluid $u^a$ and the unit vector $n^a$ along the magnetic field. Using the standard 1+3 decomposition defined by the vector $u^a$ and the 1+1+2 decomposition defined by the double congruence ${u^a,n^a}$ we determine the kinematic and the dynamic quantities of an EM string fluid in both decompositions. In order to solve the resulting field equations we consider simplifying assumptions in the form of collineations. We decompose the generic quantity $L_{X}g_{ab}$ in a trace $\psi$ and and a traceless part $H_{ab}$. Because all collineations are expressible in terms of the quantity $L_{X}g_{ab}$ it is possible to compute the Lie derivative of all tensors defined by the metric i.e. the Ricci tensor, the Weyl tensor etc. This makes possible the effects of any assumed collineation on the gravitational field equations. This is done as follows. Using relevant identities of Differential Geometry we express the quantity $L_{X}R_{ab}$ where $R_{ab}$ is the Ricci tensor in terms of the two irreducible parts $\psi,H_{ab}$. Subsequently using the gravitational field equations we compute the same quantity $L_{X}R_{ab}$ in terms of the Lie derivative of the dynamic variables. We equate the two results and find the field equations in the form $L_{X}{\text{Dynamic variable}}=F(\psi,H_{ab},{\text{ dynamic variables}})$. This result is general and holds for all gravitational systems and in particular for the EMSF. Subsequently we specialize our study at two levels. We consider the case of a Conformal Killing Vector (CKV) parallel to $u^a$ and a CKV parallel to $n^a$.

Magnetic Field of Neutron Stars with a Quark Core

The mechanism for magnetic field generation by hybrid neutron stars containing a 2SC quark phase is examined. It is assumed that S-vortices with quantized angular momentum develop in the superconducting quark fluid. Entrainment of the charged quark fluid in a superfluid motion around the S-vortex leads to the development of currents that generate a magnetic field. It is shown that S-vortices have a magnetic structure in the form of a cluster of Abrikosov magnetic vortices with quantized magnetic flux. The distribution of the magnetic induction in the quark core of neutron stars is also studied.