Constant External Magnetic Field Research Articles

Magneto-Thermoelastic Response in an Unbounded Medium Containing a Spherical Hole via Multi-Time-Derivative Thermoelasticity Theories.

This article introduces magneto-thermoelastic exchanges in an unbounded medium with a spherical cavity. A refined multi-time-derivative dual-phase-lag thermoelasticity model is applied for this reason. The surface of the spherical hole is considered traction-free and under both constant heating and external magnetic field. A generalized magneto-thermoelastic coupled solution is developed utilizing Laplace’s transform. The field variables are shown graphically and examined to demonstrate the impacts of the magnetic field, phase-lags, and other parameters on the field quantities. The present theory is examined to assess its validity including comparison with the existing literature.

Position-space representation of charged particles\u2019 propagators in a constant magnetic field as an expansion over Landau levels

We have obtained propagators in the position space as an expansion over Landau levels for the charged scalar particle, fermion, and massive vector boson in a constant external magnetic field. The summation terms in the resulting expressions consisted of two factors, one being rotationally invariant in the 2-dimensional Euclidean space perpendicular to the direction of the field, and the other being Lorentz-invariant in the 1+1-dimensional space-time. The obtained representations are unique in the sense that they allow for the simultaneous study of the propagator from both space-time and energetic perspectives which are implicitly connected. These results contribute to the development of position-space techniques in QFT and are expected to be of use in the calculations of loop diagrams.

Localization of Polymer Chains at Two Penetrable Interfaces in a Constant Magnetic Field

We investigate the polymer chain localization in the system of two penetrable interfaces in an external constant magnetic field within the mean-field approximation. The saturation of a polymer chain in the limiting case of zero bulk concentration is studied. We obtain a non-monotonous behavior of the amount of adsorbed polymers as a function of the distance between the interfaces.

Testing of Magnetoactive Elastomeric Composite Materials

Dynamic tests of new magnetoactive elastomers were carried out in various amplitude-frequency modes on vibrodynamic stands. These materials regular changes in resonance properties under the external constant magnetic fields and loads influence have been established. The relationship between vibrodynamic and damping properties in these composites and atomic force microscopy data on the magnetic fillers restructuring under magnetic field action in a silicone elastomers matrix is discussed.

Experimental study on liquid metal free surface flow under magnetic and electric field for nuclear fusion

In the future application of nuclear fusion, the liquid metal flows are considered to be an attractive option of the first wall of the tokamak which can effectively remove impurities and improve the confinement of plasma. Moreover, the flowing liquid metal can solve the problem of the corrosion of the solid first wall due to high thermal load and particle discharge. In the magnetic confinement fusion reactor, the liquid metal flow experiences strong magnetic and electric, fields from plasma. In the present paper, an experiment has been conducted to explore the influence of electric and magnetic fields on liquid metal flow. The direction of electric current is perpendicular to that of the magnetic field direction, and thus the Lorentz force is upward or downward. A laser profilometer based on the laser triangulation technique is used to measure the thickness of the liquid film of Galinstan. The phenomenon of the liquid column from the free surface is observed by the high-speed camera under various flow rates, intensities of magnetic field and electric field. Under a constant external magnetic field, the liquid column appears at the position of the incident current once the external current exceeds a critical value, which is inversely proportional to the magnetic field. The thickness of the flowing liquid film increases with the intensities of magnetic field, electric field, and Reynolds number. The thickness of the liquid film at the incident current position reaches a maximum value when the force is upward. The distribution of liquid metal in the channel presents a parabolic shape with high central and low marginal. Additionally, the splashing, i.e. the detachment of liquid metal is not observed in the present experiment, which suggests a higher critical current for splashing to occur.

Optical properties of one-dimensional plasma photonic crystals with inhomogeneous plasma density distribution functions.

This paper investigates the optical properties of the two plasma photonic crystal structures. The first structure contains periodic thin layers of plasma with heterogeneous densities, and in the second one, the heterogeneous plasma layer has been applied as the defect layer of a one-dimensional photonic crystal. Herein, the plasma density distribution function is considered a continuous function of plasma critical density as follows: n=ncrf(r→), where ncr=meε0ω2/e2 represents the critical density of the plasma and f(r→) indicates the plasma density distribution function. The heterogeneous plasma layer is assumed to be composed of several homogeneous sublayers with constant density. The transfer-matrix method is applied in calculations, and the total transfer matrix is obtained by multiplying the transfer matrices of each sublayer. Properties and behavior of the photonic bandgap and the defect mode for five different plasma density distribution functions and applied external constant magnetic field are comparatively investigated. Results show that, in the first structure, increasing the incident angle from 0° to 30° causes a bandgap shift to higher frequencies. So, the incident angle is a parameter that can control the bandgap. In the defective structure, the intensity of the defect modes is almost the same in all five distributions, but their locations in the spectrum are different. The effect of the lateral position of the maximum density and external constant magnetic field on the defect mode position is also investigated. The capability of controlling the photonic bandgaps and defect modes of the plasma photonic crystals creates wide applications in promising tunable optical devices, such as optical filters.

Exact Steady State of the Open XX -Spin Chain: Entanglement and Transport Properties

We study the reduced dynamics of open quantum spin chains of arbitrary length $N$ with nearest neighbour $XX$ interactions, immersed within an external constant magnetic field along the $z$ direction, whose end spins are weakly coupled to heat baths at different temperatures, via energy preserving couplings. We find the analytic expression of the unique stationary state of the master equation obtained in the so-called global approach based on the spectralization of the full chain Hamiltonian. Hinging upon the explicit stationary state, we reveal the presence of sink and source terms in the spin-flow continuity equation and compare their behaviour with that of the stationary heat flow. Moreover, we also obtain analytic expressions for the steady state two-spin reduced density matrices and for their concurrence. We then set up an algorithm suited to compute the stationary bipartite entanglement along the chain and to study its dependence on the Hamiltonian parameters and on the bath temperatures.

Исследование процесса рассеяния электрона на ионе в плазме инерционного термоядерного синтеза в магнитном поле

In this paper, the processes of electron-ion scattering in the plasma of inertial confinement fusion in a magnetic field were studied. The proposed model for studying the processes of scattering between charged particles is based on solving the equation of motion in a central field taking into account the external magnetic field, as well as the Coulomb logarithm, which is determined using the scattering angle in a pair collision. Collisions between an electron and an ion that interact via the Yukawa potential were investigated. Also, the Coulomb logarithm in a dense plasma in a magnetic field was calculated. The effect of taking into account the magnetic field on the scattering angles, the scattering cross-section and the Coulomb logarithm are studied. From the results obtained, it is established that taking into account the magnetic field led to a non-monotonic change in the scattering angle and a decrease in the scattering cross-section for weak particle interactions. It is also revealed that for large values of the interaction parameterβ, the magnetic field does not affect the value of the Coulomb logarithm. Thus, the obtained results allow us to study the effect of taking into account the magnetic field on the processes of electron scattering on an ion in the approximation of pair collisions in an external constant magnetic field in a dense plasma.

Fractional blood flow in rotating nanofluid with different shapes nanoparticles in the influence of activation energy and thermal radiation.

A fractional blood flow model, in the presence of magnetic nanoparticles, is considered in this work. The effects of activation energy and thermal radiation on the blood flowing in the oscillating elastic tube are studied. The nanofluid inside the tube is activated by the rotating effect of the charged particles, a constant external magnetic field, and the activation energy. The blood is assumed to be at a temperature and a concentration that vary with the speed of the particles. The study takes advantage of a model, which includes a fractional-order derivative of Caputo's type. The shape of nanoparticles and the speed of blood and the distributions of temperature and concentration are assimilated to Brownian motion and thermophoresis. They are calculated numerically using the L1-algorithm method. The results show that the applied magnetic field and the effects of the fractional-order parameter reduce the velocity of the nanofluid and nanoparticles, which considerably affects the temperature and concentration of the fluid. It is also found that the particle shape and fractional derivative parameters significantly influence velocities and heat transfer.

On Existence of Ground States in the Spin Boson Model

We show the existence of ground states in the massless spin boson model without any infrared regularization. Our proof is non-perturbative and relies on a compactness argument. It works for arbitrary values of the coupling constant under the hypothesis that the second derivative of the ground state energy as a function of a constant external magnetic field is bounded.

An actively compensated 8 nT-level magnetic shielding system for 10-m atom interferometer.

We design and develop a high-performance magnetic shielding system for a long baseline fountain-type atom interferometer. The shielding system is achieved by a combination of passive shielding using permalloy and active compensation with coils. An 11.4 m-long three-layer cylindrical shield is completed by the process of welding, local annealing, and entire annealing. The active compensations compress the residual magnetic field to 8.0 nT max-to-min and the corresponding gradient below 30 nT/m over 10m along the axial direction in which external compensation, internal compensation, and constant magnetic field (C-field) compensation reduce the inhomogeneities to 25.0, 12.6, and 1.7 nT (standard deviation) sequentially. We estimate that this system could reduce the systematic error of the quadratic Zeeman shift to the 10-13 level for the weak equivalence principle test with a simultaneous 85Rb-87Rb dual-species atom interferometer.

Calculation of energy and magnetic susceptibility of Fe atomic system during dislocation motion in magnetic field

PurposeThe purpose is to calculate the change in the total energy of a small fragment of an idealized lattice of iron (in its pure form and with impurity atoms) containing an edge dislocation during its elementary motion at one interatomic spacing, both under the influence of a constant magnetic field and without it. The introduction of a magnetic field into the system is aimed at checking the adequacy of the description of the phenomenon of magnetoplasticity by changing the total energy of the atomic system.Design/methodology/approachThe design procedure is based on a quantum-mechanical description of the switching process of the covalent bond of atoms in the dislocation core. The authors used the method of density functional theory in the Kohn-Shem version, implemented in the GAUSSIAN 09 software package. Using the perturbation theory, the authors modeled the impact of an external constant magnetic field on the energy of a system of lattice atoms.FindingsThe simulation results confirmed the effect of an external constant magnetic field on the switching energy of the covalent bond of atoms in the dislocation core, and also a change in the magnetic susceptibility of a system of atoms with a dislocation. This complements the description of the magnetoplastic effect during the deformation of metals.Originality/valueThe authors created quantum-mechanical models of the dislocation motion in the Fe crystal lattice: without impurities, with a substitutional atom Cr and with an interstitial atom C. The models take into account the influence of an external constant magnetic field.

The Hartree equation with a constant magnetic field: well-posedness theory

We consider the Hartree equation for infinitely many electrons with a constant external magnetic field. For the system, we show a local well-posedness result when the initial data is the pertubation of a Fermi sea, which is a non-trace class stationary solution to the system. In this case, the one particle Hamiltonian is the Pauli operator, which possesses distinct properties from the Laplace operator, for example, it has a discrete spectrum and infinite-dimensional eigenspaces. The new ingredient is that we use the Fourier–Wigner transform and the asymptotic properties of associated Laguerre polynomials to derive a collapsing estimate, by which we establish the local well-posedness result.

Flavor, temperature and magnetic field dependence of the QCD phase diagram: magnetic catalysis and its inverse

We study dynamical chiral symmetry breaking for quarks in the fundamental representation of SU(N c) for the N f number of light quark flavors. We also investigate the phase diagram of quantum chromodynamics at finite temperature T and/or in the presence of a constant external magnetic field eB. The unified formalism for this analysis is provided by a symmetry-preserving Schwinger–Dyson equation treatment of a vector × vector contact interaction model which encodes several well-established features of quantum chromodynamics to mimic the latter as closely as possible. Deconfinement and chiral symmetry restoration are triggered above a critical value of N f at T = 0 = eB. On the other hand, increasing temperature itself screens strong interactions, thus ensuring that a smaller value of N f is sufficient to restore chiral symmetry at higher temperatures. We also observe the well-known phenomenon of magnetic catalysis for a strong enough magnetic field. However, we note that if the effective coupling strength of the model decreases as a function of magnetic field, it can trigger inverse magnetic catalysis in a certain window of this functional dependence. Our model allows for the simultaneous onset of dynamical chiral symmetry breaking and confinement for each case. Qualitative as well as quantitative predictions of our simple but effective model are in reasonably satisfactory agreement with lattice results and other reliable and refined predictions based upon intricate continuum studies of quantum chromodynamics.

The Magnetized Vlasov–Ampère System and the Bernstein–Landau Paradox

We study the Bernstein–Landau paradox in the collisionless motion of an electrostatic plasma in the presence of a constant external magnetic field. The Bernstein–Landau paradox consists in that in the presence of the magnetic field, the electric field and the charge density fluctuation have an oscillatory behavior in time. This is radically different from Landau damping, in the case without magnetic field, where the electric field tends to zero for large times. We consider this problem from a new point of view. Instead of analyzing the linear magnetized Vlasov–Poisson system, as it is usually done, we study the linear magnetized Vlasov–Ampère system. We formulate the magnetized Vlasov–Ampère system as a Schrödinger equation with a selfadjoint magnetized Vlasov–Ampère operator in the Hilbert space of states with finite energy. The magnetized Vlasov–Ampère operator has a complete set of orthonormal eigenfunctions, that include the Bernstein modes. The expansion of the solution of the magnetized Vlasov–Ampère system in the eigenfunctions shows the oscillatory behavior in time. We prove the convergence of the expansion under optimal conditions, assuming only that the initial state has finite energy. This solves a problem that was recently posed in the literature. The Bernstein modes are not complete. To have a complete system it is necessary to add eigenfunctions that are associated with eigenvalues at all the integer multiples of the cyclotron frequency. These special plasma oscillations actually exist on their own, without the excitation of the other modes. In the limit when the magnetic fields goes to zero the spectrum of the magnetized Vlasov–Ampère operator changes drastically from pure point to absolutely continuous in the orthogonal complement to its kernel, due to a sharp change on its domain. This explains the Bernstein–Landau paradox. Furthermore, we present numerical simulations that illustrate the Bernstein–Landau paradox. In Appendix 2 we provide exact formulas for a family of time-independent solutions.

Two-State Quantum Systems Revisited: A Clifford Algebra Approach

We revisit the topic of two-state quantum systems using Geometric Algebra (GA) in three dimensions $\mathcal G_3$. In this description, both the quantum states and Hermitian operators are written as elements of $\mathcal G_3$. By writing the quantum states as elements of the minimal left ideals of this algebra, we compute the energy eigenvalues and eigenvectors for the Hamiltonian of an arbitrary two-state system. The geometric interpretation of the Hermitian operators enables us to introduce an algebraic method to diagonalize these operators in GA. We then use this approach to revisit the problem of a spin-$1/2$ particle interacting with an external arbitrary constant magnetic field, obtaining the same results as in the conventional theory. However, GA reveals the underlying geometry of these systems, which reduces to the Larmor precession in an arbitrary plane of $\mathcal G_3$.

Thermodynamic properties of a charged particle in non-uniform magnetic field

We solve the Schrödinger equation for a charged particle in the non-uniform magnetic field by using the Nikiforov–Uvarov method. We find the energy spectrum and the wave function, and present an explicit relation for the partition function. We give analytical expressions for the thermodynamic properties such as mean energy and magnetic susceptibility, and analyze the entropy, free energy and specific heat of this system numerically. It is concluded that the specific heat and magnetic susceptibility increase with external magnetic field strength and different values of the non-uniformity parameter, in the low temperature region, while the mentioned quantities are decreased in high temperature regions due to increasing the occupied levels at these regions. The non-uniformity parameter has the same effect with a constant value of the magnetic field on the behavior of thermodynamic properties. On the other hand, the results show that transition from positive to negative magnetic susceptibility depends on the values of non-uniformity parameter in the constant external magnetic field.

Fluctuation Relations for Dissipative Systems in Constant External Magnetic Field: Theory and Molecular Dynamics Simulations

We illustrate how, contrary to common belief, transient Fluctuation Relations (FRs) for systems in constant external magnetic field hold without the inversion of the field. Building on previous work providing generalized time-reversal symmetries for systems in parallel external magnetic and electric fields, we observe that the standard proof of these important nonequilibrium properties can be fully reinstated in the presence of net dissipation. This generalizes recent results for the FRs in orthogonal fields—an interesting but less commonly investigated geometry—and enables direct comparison with existing literature. We also present for the first time a numerical demonstration of the validity of the transient FRs with nonzero magnetic field via nonequilibrium molecular dynamics simulations of a realistic model of liquid NaCl.

Fractional calculus approach for the phase dynamics of Josephson junction

• Phase dynamics of inline Josephson junction in voltage state is discussed. • Phase difference between the wave functions is analyzed via fractional calculus. • Hereditary effects for phase dynamics of Josephson junction are explored. • Finite element scheme is used for the simulations of governing equations. This article presents the phase dynamics of an inline long Josephson junction in voltage state under the influence of constant external magnetic field. Fractional calculus approach is used to model the evolution of the phase difference between the macroscopic wave functions of the two superconductors across the junction. The governing non-linear partial differential equation is then solved using finite difference-finite element schemes. Other quantities of interest like Josephson current density and voltage across the junction are also computed. The effects of various parameters in the model on phase difference,Josephson current density and voltage are analyzed graphically with the help of numerical simulations.

Enhancing the efficiency of the hydrogen evolution reaction utilising Fe3P bulk modified screen-printed electrodes via the application of a magnetic field.

We report the fabrication and optimisation of Fe3P bulk modified screen-printed electrochemical platforms (SPEs) for the hydrogen evolution reaction (HER) within acidic media. We optimise the achievable current density towards the HER of the Fe3P SPEs by utilising ball-milled Fe3P variants and increasing the mass percentage of Fe3P incorporated into the SPEs. Additionally, the synergy of the application of a variable weak (constant) external magnetic field (330 mT to 40 mT) beneficially augments the current density output by 56%. This paper not only highlights the benefits of physical catalyst optimisation but also demonstrates a methodology to further enhance the cathodic efficiency of the HER with the facile application of a weak (constant) magnetic field.