Magnetic Field Curves and Magnetic Equipotential Surfaces around Crossing Electrical Wires Replacing Classical Magnetic Field Lines

This article is based on a recent model specifically defining magnetic field values around electrical wires. With this model, calculations of field around parallel wires were obtained. Now, this model is extended with the new concept of magnetic equipotential surface to magnetic field curves around crossing wires. Cases of single, double, and triple wires are described. Subsequent article will be conducted for more general scenarios where wires are neither infinite nor parallel.

Atom-field dynamics in curved spacetime

Some aspects of atom-field interactions in curved spacetime are reviewed.Of great interest are quantum radiative and entanglement processes arising out of Rindler and black hole spacetimes,which involve the role of Hawking-Unruh and dynamical Casimir effects.Most of the discussion surrounds the radiative part of interactions.For this,we specifically reassess the conventional understandings of atomic radiative transitions and energy level shifts in curved spacetime.We also briefly outline the status quo of entanglement dynamics study in curved spacetime,and highlight literature related to some novel insights,like entanglement harvesting.On one hand,the study of the role played by spacetime curvature in quantum radiative and informational phenomena has implications for fundamental physics,notably the gravity-quantum interface.In particular,one examines the viability of the Equivalence Principle,which is at the heart of Einstein’s general theory of relativity.On the other hand,it can be instructive for manipulating quantum information and light propagation in arbitrary geometries.Some issues related to nonthermal effects of acceleration are also discussed.

Geometric Backreaction of Modified Quantum Vacua and Diffeomorphrisim Covariance

In this paper I have shown that squeezed modified quantum vacua have an effect on the background geometry by solving the semi-classical Einstein Field Equations in modified vacuum. The resultant geometry is similar to (anti) de Sitter spacetime. This geometry could explain the change of causal structure—speed of light—in such vacua without violating diffeomorphism covariance or causality. The superluminal propagation of photons in Casimir vacuum is deduced from the effective electromagnetic action in the resultant curved geometry. Singling between different vacua is shown not to violate causality as well when the geometric effect on the null rays is considered, causing a refraction of those rays when traveling between unbounded and modified vacua.

Vector Field Based Sliding Mode Control of Curved Path Following for Miniature Unmanned Aerial Vehicles in Winds

In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles（UAVs） in winds with constant speed and altitude is developed. Different to the widely considered line or orbit following, the curved path to be followed is defined in terms of the arc-length parameter, which can be straight lines, orbits, B-splines or any other curves provided that they are smooth. The proposed path following control algorithm, named by VF-SMC, is combining the vector field（VF） strategy with the sliding mode control（SMC） method. It is proven that the designed algorithm guarantees the tracking errors to be a bounded ball in the presence of winds, with the aid of the Lyapunov method and the BIBO stability. The algorithm is validated both in Matlab-based simulations and high-fidelity semi-physical simulations. In Matlab-based simulations, the proposed algorithm is verified for straight lines, orbits and B-splines to show its wide usage in different curves.The high-fidelity semi-physical simulation system is composed of actual autopilot controller, ground station and X-Plane flight simulator in-loop. In semi-physical simulations, the proposed algorithm is verified for B-spline path following under various gain parameters and wind conditions thoroughly.All experiments show the accuracy in curved path following and the excellent robustness to wind disturbances of the proposed algorithm.

Performance improvement of air-breathing proton exchange membrane fuel cell(PEMFC) with a condensing-tower-like curved flow field

Air-breathing proton exchange membrane fuel cells(PEMFCs) are very promising portable energy with many advantages. However, its power density is low and many additional supporting parts affect its specific power. In this paper, we aim to improve the air diffusion and fuel cell performance by employing a novel condensing-tower-like curved flow field rather than an additional fan, making the fuel cell more compact and has less internal power consumption. Polarization curve test and galvanostatic discharge test are carried out and proved that curved flow field can strengthen the air diffusion into the PEMFC and improve its performance. With appropriate curved flow field, the fuel cell peak power can be 55.2%higher than that of planar flow field in our study. A four-layer stack with curved cathode flow field is fabricated and has a peak power of 2.35 W(120 W/kg).

Study of scalar particles through the Klein–Gordon equation under rainbow gravity effects in Bonnor–Melvin-Lambda space-time

In our investigation,we explore the quantum dynamics of charge-free scalar particles through the Klein–Gordon equation within the framework of rainbow gravity,considering the Bonnor–Melvin-Lambda(BML)space-time background.The BML solution is characterized by the magnetic field strength along the axis of the symmetry direction which is related to the cosmological constantΛand the topological parameterαof the geometry.The behavior of charge-free scalar particles described by the Klein–Gordon equation is investigated,utilizing two sets of rainbow functions:(i)f(χ)=■,h(χ)=1 and(ii)f(χ)=1,h(χ)=1+βХ/2.Here 0<(Х=■)≤1 with E representing the particle's energy,Ep is the Planck's energy,andβis the rainbow parameter.We obtain the approximate analytical solutions for the scalar particles and conduct a thorough analysis of the obtained results.Afterwards,we study the quantum dynamics of quantum oscillator fields within this BML space-time,employing the Klein–Gordon oscillator.Here also,we choose the same sets of rainbow functions and obtain the approximate eigenvalue solution for the oscillator fields.Notably,we demonstrate that the relativistic approximate energy profiles of charge-free scalar particles and oscillator fields get influenced by the topology of the geometry and the cosmological constant.Furthermore,we show that the energy profiles of scalar particles receive modifications from the rainbow parameter and the quantum oscillator fields by both the rainbow parameter and the frequency of oscillation.

Entanglement dynamics in κ-deformed spacetime

We treat two identical and mutually independent two-level atoms that are coupled to a quantum field as an open quantum system.The master equation that governs their evolution is derived by tracing over the degree of freedom of the field.With this,we compare the entanglement dynamics of the two atoms moving with different trajectories inκ-deformed and Minkowski spacetimes.Notably,when the environment-induced interatomic interaction does not exist,the entanglement dynamics of two static atoms inκ-deformed spacetime are reduced to that in Minkowski spacetime in the case that the spacetime deformation parameterκis sufficiently large as theoretically predicted.However,if the atoms undergo relativistic motion,regardless of whether inertial or non-inertial,their entanglement dynamics inκ-deformed spacetime behave differently from that in Minkowski spacetime even whenκis large.We investigate various types of entanglement behavior,such as decay and generation,and discuss how different relativistic motions,such as uniform motion in a straight line and circular motion,amplify the differences in the entanglement dynamics between theκ-deformed and Minkowski spacetime cases.In addition,when the environment-induced interatomic interaction is considered,we find that it may also enhance the differences in the entanglement dynamics between these two spacetimes.Thus,in principle,one can tell whether she/he is inκ-deformed or Minkowski spacetime by checking the entanglement behavior between two atoms in certain circumstances.

Erratum:Covariant Spin Kinetic Theory I:Collisionless Limit,[Y.-C.Liu,K.Mameda,and X.-G.Huang,Chin.Phys.C 44,094101(2020)]

After the publication of the paper,we found two incorrect signs in Eqs.(11)and(13).The correct form of Eq.

Spontaneous Excitation of an Accelerated Detector Interacting with a Massive Scalar Field and Unruh Effect

We study spontaneous excitation of both a static detector （modelled by a two-level atom） immersed in a thermal bath and a uniformly accelerated one in the Minkowski vacuum interacting with a real massive scalar field. Our results show that the mass of the scalar field manifests itself in the spontaneous excitation rate of the static detector in a thermal bath （and in vacuum） in the form of a selection rule for transitions among states of the detector. However, this selection rule disappears for the accelerated ones, demonstrating that an accelerated detector does not necessarily behave the same as an inertial one in a thermal bath. We lind the imprint left by the mass is the appearance of a grey-body factor in the spontaneous excitation and de-excitation rates, which maintains the detailed balance condition between them and thus ensures a thermal equilibrium at the Unruh temperature the same as that of the massless case. We also analyze quantitatively the effect of the mass on the rate of change of the detector＇s energy and find that when the mass is very small, it only induces a small negative correction. However, when it is very large, it then exponentially damps the rate, thus essentially forbidding any transitions among states of the detector.

Covariant spin kinetic theory I:collisionless limit

We develop a covariant kinetic theory for massive fermions in a curved spacetime and an external electromagnetic field based on quantum field theory.We derive four coupled semi-classical kinetic equations accurate to O(ℏ),which describe the transports of particle number and spin degrees of freedom.The relationship with chiral kinetic theory is discussed.As an application,we study spin polarization in the presence of finite Riemann curvature and an electromagnetic field in both local and global equilibrium states.

A massless scalar field in Robertson-Walker spacetimes:Adiabatic regularization and Green’s function

We study adiabatic regularization of a coupling massless scalar field in general spatially flat Robertson-Walker(RW)spacetimes.For the conformal coupling,the 2nd-order regularized power spectrum and 4th-order regularized stress tensor are zero,and no trace anomaly exists in general RW spacetimes.This is a new result that exceeds those found in de Sitter space.For the minimal coupling,the regularized spectra are also zero in the radiationdominant and matter-dominant stages,as well as in de Sitter space.The vanishing of these adiabatically regularized spectra is further confirmed by direct regularization of the Green's function.For a general coupling and general RW spacetimes,the regularized spectra can be negative under the conventional prescription.At a higher order of regularization,the spectra will generally become positive,but will also acquire IR divergence,which is inevitable for a massless field.To avoid the IR divergence,the inside-horizon regularization is applied.Through these procedures,nonnegative UV-and IR-convergent power spectrum and spectral energy density will eventually be achieved.

Hawking radiation of Dirac particles from soft-hairy black holes

In this paper,we study the Hawking radiation of Dirac particles via tunneling formalism from linearly supertranslated Schwarzschild black holes.We find that the radiation spectrum and the Hawking temperature remain the same as the one without soft hair.