Narrow Results

The dielectric properties of a material determine its response of the material to the Electromagnetic field (EM field). It comprises dielectric constant (${\epsilon }^{\prime }$), which is the ability to store energy of EM fields, and dielectric loss (${\epsilon }^{\prime \prime }$) which is the amount of dissipated Electromagnetic energy in the form of heat. Dielectric properties are affected by various factors such as frequency, temperature, bulk density, moisture content, etc. Dielectric constant and dielectric loss were determined in this study for milk powders viz. Whole Milk Powder, Skim Milk Powder, and Infant Milk Powder at various microwave frequencies (5.68, 7.45, 10.25GHz). The method used to determine dielectric properties is the Two-point Method which is implemented on a microwave bench. It became apparent that when frequency increases dielectric constant decreases and dielectric loss first decreases and then increases. It was also observed that the fat content can have an impact on the milk powders’ dielectric properties.

This research focuses on formulating a physical model for spherically symmetric system incorporating electromagnetic fields within the framework of $f(Q)$ gravity. To accomplish this, we investigate $f(Q)$ gravity’s field equations in the setting of anisotropic matter and solve these equations by choosing viable solution, i.e. Tolman-IV model. Matching conditions help us calculate the constants in terms of physical parameters. For this, we choose exterior geometry as Reissner–Nordström corresponding to charged anisotropic matter in the interior of spherically symmetric metric. To ensure that the obtained solution is physical viable and well-behaved, we rigorously examine the accessibility conditions (casualty conditions, TOV equations, adiabatic index, Harrison–Zeldovich–Novikov criterion and energy conditions) through graphically with software like Mathematica. Next, we implement this model to investigate various well-known compact objects, including LMC X-4 having mass $(1.04\pm 0.09)$ and a radius of $(8.301\pm 0.2)$ kilometers.

This study employs $f(R,T)$ gravity, where $R$ is the Ricci scalar, and $T$ is the trace of energy–momentum tensor, to analyze charged spherically symmetric fluid distributions governed by a polytropic equation of state, thereby exploring the impact of direct coupling between matter fields and the curvature of spacetime on stellar configurations. We present two families of relativistic polytropes for both anisotropic and isotropic matter sources in the presence of electromagnetic field and derive the structural equations (mass conservation and modified Tolman–Oppenheimer–Volkoff equations). The numerical method is utilized to solve structural equations by varying the values of arbitrary parameters and polytropic constants. Using energy constraints, the physical feasibility of polytropes is examined. In addition to this, some other stellar properties such as compactness, redshift and adiabatic index are found to be well-behaved as they fulfill the required criteria. Also, the speed of sound parameter fulfills the stability criterion of the stellar body. For both isotropic and anisotropic stellar configurations, the effects of charge and the curvature-matter coupling parameter are important since they highly affect how compact these structures are.

We study dynamical synchronization in a model of a neural system representing 47 cortical regions of Macaque brain under the effect of an electromagnetic field. This system is constituted by local networks of densely interconnected excitatory and inhibitory neurons. Coupling between the local networks is introduced through sparsely distributed excitatory connectivity. Voltage- and ligand-gated ion channels determine the neural dynamics of the networks. The effect of electromagnetic field on the neural system is studied by modulating magnetic flux on the membrane potential using memristor coupling. With the application of electromagnetic field and the modulation of long-range synaptic coupling, the system easily makes transition to synchronization. It is found that the threshold for synchrony between coupled local networks is lowered by the applied electromagnetic field. Also, electromagnetic field causes the neural subsystems to make low amplitude oscillations with an approximate frequency of 130 Hz. This indicates that electromagnetic field gives rise to high-gamma activity in the cortical regions of the brain which increases selective attention. This may facilitate adaptive brain function by giving rise to a rich collection of dynamics and contribute to the origin of complex patterns observed in the EEG.

In this paper, the effect of electromagnetic field has been investigated on the spherically symmetric gravitational collapse with the perfect fluid in the presence of positive cosmological constant. Junction conditions between the static exterior and non-static interior spherically symmetric spacetimes are discussed. We study the apparent horizons and their physical significance. It is found that electromagnetic field reduces the bound of cosmological constant by reducing the pressure and hence collapsing process is faster as compared to the perfect fluid case. This work gives the generalization of the perfect fluid case to the charged perfect fluid. Results for the perfect fluid case are recovered.

We consider non-adiabatic flow of the fluid possessing dissipation in the form of shearing viscosity in electromagnetic field. The scalar functions (structure scalars) for charged plane symmetry are formulated and are related with the physical variables of the fluid. We also develop a relationship between the Weyl tensor and other physical variables by using Taub mass formalism. The role of electric charge as well as its physical significance for the evolution of the shear tensor and expansion scalar are also explored. Finally, we discuss a special case for dust with cosmological constant.

In this work, we aim to identify the effects of electromagnetic field on the energy density inhomogeneity in self-gravitating plane symmetric spacetime filled with imperfect matter in terms of dissipation and anisotropic pressure. We formulate the Einstein–Maxwell field equation, conservation laws, evolution equations for the Weyl tensor and the transport equation for diffusion approximation. Inhomogeneity factors are identified for some particular cases of non-dissipative and dissipative fluids. For non-dissipative case, we analyze the inhomogeneity factor for dust, isotropic and anisotropic matter distributions while dissipative matter distribution includes the inhomogeneity factor only for geodesic dust fluid. We conclude that electric charge increases the inhomogeneity in the energy density which is due to shear, anisotropy and dissipation.

This paper investigates the dynamics of anisotropic viscous spherical star under the effects of electromagnetic field for a radially moving observer relative to the matter distribution, i.e. a tilted observer. We formulate relationship between tilted and non-tilted quantities using the Einstein–Maxwell field equations. The dynamical equations and equations for the Weyl tensor are constructed to examine the inhomogeneities in the fluid configuration. It is found that different factors like heat radiation, shear viscosity, electric charge and in particular congruence of the tilted observer, affect the energy density inhomogeneity of the spherical star. Finally, we study stability of the system with non-tilted frame in the presence of charge.

In this paper, we study the stability of static charged anisotropic cylindrically symmetric compact object through cracking. The Einstein–Maxwell field equations and conservation equation are formulated. We then apply local density perturbation and study the behavior of force distribution function. Finally, the cracking is explored for two models satisfying specific form of Chaplygin equation of state. It is found that these models exhibit cracking and the instability increases as the value of charge parameter is increased.

This paper studies the effects of charge on spherically symmetric collapse of anisotropic fluid with a positive cosmological constant. It is observed that electromagnetic field places restriction on the bounds of cosmological constant, which acts as repulsive force against the contraction of matter content and hence the rate of destruction is faster in the presence of electromagnetic field. We have also noted that the presence of charge affects the time interval between the formation of cosmological horizon (CH) and black hole horizon (BHH). When the electric field strength E(t, r) vanishes, our investigations are in full agreement with the results obtained by Ahmad and Malik [Int. J. Theor. Phys.55, 600 (2016)].

This paper studies the gravitational collapse of charged anisotropic spherical stellar objects in $f({𝒢})$ gravity. For this purpose, we derive dynamical equations by considering Misner–Sharp mechanism and explore physical impact of charge, anisotropy and effective pressure on the rate of collapse. We establish the relationship between matter variables, Weyl tensor and the Gauss–Bonnet (GB) terms. For constant value of $f({𝒢})$, it turns out that conformal flatness condition is no longer valid due to the effect of anisotropic factor in the present scenario. To obtain conformally flat metric, we impose the condition of isotropic matter distribution which provides energy density homogeneity and conformal flatness of the metric. We conclude that GB terms lead to decrease in the collapse rate due to their anti-gravitational effects.

In this paper, we investigate the behaviors of quantum correlation quantified by trace norm measurement-induced nonlocality (TMIN) for two uniformly accelerated atoms coupled with electromagnetic vacuum fluctuation in the Minkowski vacuum. We firstly discuss the solving process of master equation that governs the system evolution based on the Pauli matrix presentation for two-qubit state. Similar to [Y. Q. Yang et al., Phys. Rev. A94, 032337 (2016)], we analyze the degradation, creation, revival and enhancement of quantum correlation for different initial states and polarizations of two atoms, and the influence of interatomic separation and acceleration on quantum correlation. Compared with the entanglement dynamics discussed in [Y. Q. Yang et al., Phys. Rev. A94, 032337 (2016)], it is found that quantum correlation exhibits better robustness than entanglement. This may be helpful for quantum information processing.

The aim of this paper is to study the gravitational collapse of charged cylindrical star in $f({𝒢})$ gravity. For this purpose, we derive dynamical equations by applying Misner–Sharp formalism and examine the effects of effective pressure and charge on the collapse rate. We also construct a relationship between matter variables, Gauss–Bonnet (GB) terms, and the Weyl tensor. For the constant value of $f({𝒢})$, it is found that spacetime is conformally flat if and only if the energy density is homogeneous. We conclude that the rate of collapse slows down in $f({𝒢})$ gravity due to anti-gravitational effects.

In this work, we study the spectral properties of electron quantum dots (QDs) confined in 2D parabolic harmonic oscillator influenced by gravity, external uniform electromagnetic field together with an Aharonov–Bohm (AB) flux field. Our calculations are based on the Nikiforov–Uvarov method and we obtain exact solutions for the energy levels and normalized wave functions. The interband optical absorption QDs of the parabolic spherical shape in GaAs is studied theoretically and the total optical absorption coefficient has been calculated by using the energy eigenvalues spectra and the corresponding wave functions.

This paper is devoted to analyzing the stability of charged anisotropic cylinder using the radial perturbation scheme. For this purpose, we consider the non-static cylindrically symmetric self-gravitating system and apply both Eulerian as well as Lagrangian approaches to establish a linearized perturbed form of dynamical equations. The conservation of baryon number is used to evaluate perturbed radial pressure in terms of an adiabatic index. A variational principle is developed to find a characteristic frequency which helps to examine the combined effect of charge and anisotropy on the stability of gaseous star. It is found that dynamical instability can be prevented until the radius of cylinder exceeds the limit $R\ge 18$ and anisotropy increases the instability up to the limiting value of $\beta =-1.5$. Finally, we conclude that the system becomes more stable by increasing the definite amount of charge gradually.

In this paper, we examine the complexity factor for a dynamical spherical system with dissipative charged anisotropic fluid. We evaluate the Einstein-Maxwell field equations and structure scalars using Bel’s approach which help to discuss the structure as well as evolution of a self-gravitating system. We measure the complexity factor for the pattern of evolution through the homologous condition and homogeneous expansion. We also analyze the stability of vanishing complexity condition for dissipative and non-dissipative fluids. It is found that the complexity as well as stability of the spherical system increases and decreases, respectively, under the effects of electromagnetic field.

In this paper, the spherically symmetric gravitational collapse of anisotropic fluid in the presence of charge in metric $f(R)$ theory is analyzed. We consider the static and non static spherically symmetric spacetimes for outer and inner regions of collapsing object respectively. For the smooth matching of inner and outer regions, the Senovilla as well as Darmois matching conditions are utilized. The closed form solutions are obtained from field equations. Moreover, we examine the apparent horizons and their physical significance. The effect of cosmological constant and $f(R)$ term is same and the collapsing rate speeds up as compared to that of anisotropic fluid case when the electromagnetic field is introduced. Electromagnetic charge also affects the time interval of singularities and cosmological horizons.

We study the quantum teleportation under fluctuating electromagnetic field in the presence of a perfectly reflecting boundary. The noisy scheme of quantum teleportation affected by electromagnetic fluctuation is proposed. Then we calculate and investigate the behaviors of entanglement and fidelity, which are closely related to the plane boundary and atomic polarization. After a period of evolution, entanglement and fidelity evolve to zero and nonzero stable value respectively. Fidelity is closely related to the weight parameter and phase parameter of the teleported state. Besides, small two-atom separation makes entanglement and fidelity have better enhancement. Furthermore, the presence of boundary, atomic polarization and two-atom separation offers us more freedom to adjust the performance of the quantum teleportation. The results would give us new insight into quantum communication in an open quantum system since quantum teleportation plays an important role in quantum communication and quantum information.

This paper deals with the dynamics of charged plane symmetric collapse with dissipative fluid distribution in the framework of energy–momentum squared gravity. For this purpose, we consider non-static plane symmetric spacetime in the inner and static charged Vaidya spacetime in the outer regions of a star. We use Darmois junction conditions to match the interior and exterior geometries and find that masses of both spacetimes are identical if and only if their correspondence charges are same. To investigate the dynamics of the system, we apply Misner–Sharp and Müler–Israel–Stewart approaches to formulate dynamical as well as transport equations, respectively. We then couple these equations to analyze the effect of physical quantities and modified terms on the collapse rate. A relation among Weyl tensor, electromagnetic field and fluid variables, is also developed. Due to the influence of charge, anisotropic pressure and modified terms, the spacetime is not conformally flat. Further, we assume isotropic fluid and ignore the impact of electromagnetic field which yields the conformally flat spacetime and inhomogeneous energy density. We conclude that the collapse rate reduces as compared to general relativity due to the presence of a charge, effective pressure, heat flux and additional terms of this gravity.

We study the gravitational properties of a global monopole in (D=d+2)-dimensional space–time in the presence of electromagnetic field.