The Dynamo-Driven Magnetic Helicity Transport

In this paper, a new set of the evolution equations for the helicity of the mean magnetic field and the mean helicity of the fluctuating magnetic field is derived from the Maxwell equations and the generalized Ohm's law with the dynamo action. It is shown that there exist two kinds of the dynamo-driven magnetic helicity transport. One of them makes the mean magnetic field helicity transfer to the fluctuating magnetic field, yielding an anomalous loop voltage. The other makes the fluctuating magnetic field helicity transfer to the mean magnetic field, which provides a convincing evidence for the existence of the dynamo current. Therefore, the two kinds of the magnetic helicity transport describe the mutual conversion between the regular and irregular motions. The formulas of the loop voltage and the dynamo current are given. In particular, we give out the formula of the dynamo current-generated equilibrium magnetic field which provides a concrete mode of the magnetic field creation and maintenance in both astrophysical and laboratory (e.g., reversed-field pinch) plasmas.     

Bifurcation in viscoresistive MHD: the hartmann number and the reversed field pinch

A scaling approach to the simplest viscoresistive MHD model reveals that the Prandtl number acts only through the inertia term. When this term is negligible the dynamics is ruled by the Hartmann number H only. This occurs for the reversed field pinch dynamics as seen by numerical simulation of the model. When H is large the system is in a multiple helicity state. In the vicinity of H = 2500 the system displays temporal intermittency with laminar phases of quasi-single-helicity (SH) type. For lower H's two basins of SH are shown to coexist. SH regimes are of interest because of their nonchaotic magnetic field.     

Amplification of mean magnetic field and magnetic helicity production in hot lepton plasma of early universe

We argue that the magnetic helicity conservation is violated at the lepton stage in the evolution of early Universe owing to the parity violation in the Standard Model of electroweak interactions. As a result, a cosmological magnetic field which can be a seed for the galactic dynamo obtains from the beginning a substantial magnetic helicity which has to be taken into account in the magnetic helicity balance at the later stage of galactic dynamo. The particle physics mechanism suggested in our works depends neither on helicity of matter turbulence with plasma vortices resulting in the standard α effect in dynamo theory nor on general rotation. The mechanism can result in a self-exitation of an (almost) uniform cosmological magnetic field. The text was submitted by the authors in English.     

Indecomposable representations of Poincaré group and quantization of weak gravitational and electromagnetic fields

In this paper a quantization procedure of the electromagnetic and the weak gravitational fields, in an indefinite (but non-negative) metric space of states, is presented. We show that the covariance axiom can only be formulated with non-unitary representations (of the Poincaré group) whose restrictions to the one-particle states are indecomposable. In the gravitational case the corresponding indecomposable representation describes six states of helicity for gravitons. The quantized field appears as six interacting massless fields of helicities 2, ?2,1, ?1,0 and 0. These six values of helicity correspond to the six modes of polarization in the most general metric theory of gravity. For the electromagnetic field one obtains an indecomposable representation of the Poincaré group with helicities 1, ?1 and 0 corresponding to transverse and longitudinal photons.     

Non-existence of Goldstone bosons with non-zero helicity

In a local relativistic quantum field theory a conserved covariant tensor current may lead to a spontaneously broken symmetry if it generates zero mass states from the vacuum (Goldstone theorem). Here it is shown that in addition it is necessary that these massless states have helicity zero if the underlaying state space has a positive metric.     

Force-free magnetic relaxation in driven plasmas

Taylor relaxation in a driven plasma with normal magnetic field intercepting the boundary is described by the Jensen-Chu theory, which predicts infinite energy and helicity barriers that constrain the accessible relaxed states to system scale. For a partially relaxed force-free (j=kB) plasma where k is a field line constant, nonlinearity regularizes the Jensen-Chu singularities and new branches of relaxed state become accessible, such as the flipped spheromak and other high k states.     

A unified treatment of electromagnetic decays,electroproduction, and pair production in e+e− annihilation for hadrons of arbitrary spin

We gather together in a unified notation formulas for electromagnetic decay rates of resonances and cross sections for electroproduction and e⁺e^? annihilation for all those processes which can be expressed in terms of matrix elements of the electromagnetic current between single particle (or resonant) helicity states. We show in complete generality how to decompose such helicity matrix elements into form factors which are free of all kinematic singularities and constraints simultaneously at both physical thresholds, and relate them to the familiar multipole moments and to some others which have been used in data analysis. Tables are given of the form factor decomposition of the helicity matrix elements for many cases of actual and potential practical interest.     

de Sitter QED

Attention is called to the fact that the well-known and straightforward generalization of electrodynamics to de Sitter space is incompatible with conformal invariance. In addition, there is difficulty in reconciling the space of one-photon states in de Sitter QED, for which the field carries no degree of freedom related to helicity, with that of flat space QED in which both signs of the helicity appear. The requirement of conformal invariance leads to the introduction of two vector potentials in de Sitter electrodynamics and resolves the helicity problem. A conformally invariant, indefinite metric quantization is carried out, and the nature of the flat space limit is clarified. Implications for a theory of composite massless particles are discussed, as well as applications to supersymmetry and supergravity.     

Spin-12 particles in the field of monopoles

The equations of motion of a $\text{spin}\text{-}\text{1}\text{2}$ particle in the field of a point-like (Abelian and non-Abelian) monopole are solved; helicity states and scattering solutions are constructed. The motion in an extended monopole and dyon source is discussed: charge-exchange scattering amplitudes are computed in the distorted-wave Born approximation. By the introduction of suitable spinors, the separation of variables is accomplished for any value of isospin. The non-existence of fermion zero modes in the field of an SU(2) monopole when $\text{T > 1, J >}\text{1}\text{2}$ is shown.     

Nonlinear current helicity fluxes in turbulent dynamos and alpha quenching

Large scale dynamos produce small scale current helicity as a waste product that quenches the large scale dynamo process (alpha effect). This quenching can be catastrophic (i.e., intensify with magnetic Reynolds number) unless one has fluxes of small scale magnetic (or current) helicity out of the system. We derive the form of helicity fluxes in turbulent dynamos, taking also into account the nonlinear effects of Lorentz forces due to fluctuating fields. We confirm the form of an earlier derived magnetic helicity flux term, and also show that it is not renormalized by the small scale magnetic field, just like turbulent diffusion. Additional nonlinear fluxes are identified, which are driven by the anisotropic and antisymmetric parts of the magnetic correlations. These could provide further ways for turbulent dynamos to transport out small scale magnetic helicity, so as to avoid catastrophic quenching.     

Four-electron shell structures and an interacting two-electron system in carbon-nanotube quantum dots

Low-temperature transport measurements have been carried out on single-wall carbon-nanotube quantum dots in a weakly coupled regime in magnetic fields. Four-electron shell filling was observed, and the magnetic field evolution of each Coulomb peak was investigated. Excitation spectroscopy measurements have revealed Zeeman splitting of single particle states for one electron in the shell, and demonstrated singlet and triplet states with direct observation of the exchange splitting at zero-magnetic field for two electrons in the shell, the simplest example of Hund's rule.     

Partial Wave Analysis of J/ψ Decays into ρρπ

The possible place to search for exotic states in J/ψ hadronic decays is in J/ψ →ρρπ. Because of the symmetry of identical particle and the symmetry of isospin, the physical analysis on this channel is quite complicated. In this paper, the method to use the partial wave analysis based on covariant helicity amplitude analysis to study the invariant mass spectrum of ρρπ and to find the evidence of exotic states in ρρπ spectrum is discussed. The decay amplitude for the decay sequence J/ψ→ρX, X →ρπ is given first. Then we discuss how to realize the identical particle symmetry and the isospin symmetry in the decay amplitude, which is the key point in the analysis of this channel. Then the total decay amplitude of this channel including all decay components is given. After that, how to identify the exotic states in the ρρπ spectrum is discussed. What is discussed in this paper is the theoretical basis on experimentally searching for exotic states at BEPC/BES.     

Brownian ratchets driven by asymmetric nucleation of hydrolysis waves

We propose a stochastic process wherein molecular transport is mediated by asymmetric nucleation of domains on a one-dimensional substrate, in contrast with molecular motors that hydrolyze nucleotide triphosphates and undergo conformational change. We show that asymmetric nucleation of hydrolysis waves on a track can also result in directed motion of an attached particle. Asymmetrically cooperative kinetics between hydrolyzed and unhydrolyzed states on each lattice site generate moving domain walls that push a particle sitting on the track. We use a novel fluctuating-frame, finite-segment mean field theory to accurately compute steady-state velocities of the driven particle and to discover parameter regimes yielding maximal domain wall flux, leading to optimal particle drift.     

Magnetic helicity tensor for an anisotropic turbulence

The evolution of the magnetic helicity tensor for a nonzero mean magnetic field and for large magnetic Reynolds numbers in an anisotropic turbulence is studied. It is shown that the isotropic and anisotropic parts of the magnetic helicity tensor have different characteristic times of evolution. The time of variation of the isotropic part of the magnetic helicity tensor is much larger than the correlation time of the turbulent velocity field. The anisotropic part of the magnetic helicity tensor changes for the correlation time of the turbulent velocity field. The mean turbulent flux of the magnetic helicity is calculated as well. It is shown that even a small anisotropy of turbulence strongly modifies the flux of the magnetic helicity. It is demonstrated that the tensor of the magnetic part of the alpha effect for weakly inhomogeneous turbulence is determined only by the isotropic part of the magnetic helicity tensor.     

On the photon-drag effect of photocurrent of surface states of topological insulators

The photocurrent of surface states of topological insulator due to photon-drag effect is computed, being based on pure Dirac model of surface states. The scattering by disorder is taken into account to provide a relaxation mechanism for the photocurrent. The Keldysh–Schwinger formalism has been employed for the systematic calculation of photocurrent. The helicity dependent photocurrent of sizable magnitude transverse to the in-plane photon momentum is found, which is consistent with experimental data. Other helicity independent photocurrents with various polarization states are also calculated.     

New model of the higher spin particle

We elaborate on a new model of the higher spin (HS) particle which makes manifest the classical equivalence of the HS particle of the unfolded formulation and the HS particle model with a bosonic counterpart of supersymmetry. Both these models emerge as two different gauges of the new master system. Physical states of the master model are massless HS multiplets described by complex HS fields which carry an extra U(1) charge q. The latter fully characterizes the given multiplet by fixing the minimal helicity at q/2. We construct the twistorial formulation of the master model and discuss symmetries of the new HS multiplets within its framework. The text was submitted by the authors in English.     

Classical general relativity derived from quantum gravity

The existence of long range macroscopic attractive forces between masses implies the existence of a mediating helicity ± 2 particle in special relativistic quantum particle theory. It is shown that this fact alone, without assuming the existence of an underlying tensor field, uniquely determines the long wavelength structure of quantum gravitation to be that of Einstein's theory. This equivalence is shown by deriving, from the Ward identities associated with the graviton propagator, the tree graph structure of the graviton-graviton and graviton-matter interaction and establishing that the classical Einstein action is the generating functional. Some properties of closed loop effects are also exhibited.     

聚焦光场激发下中心对称球形粒子的二次谐波产生

在聚焦光场矢量衍射理论的基础上,利用贝塞尔函数的微分递推关系,推导了聚焦光场的梯度变化表达式。根据中心对称材料二次谐波产生的唯象模型,研究了单个中心对称球形纳米颗粒在聚焦光场激发下的二次谐波产生,考察了表面响应和体效应产生的二次谐波辐射分布随着数值孔径增大的变化规律,并利用聚焦光场及其梯度场分布特性讨论差异产生的原因。研究结果表明,激发光场的聚焦程度对体响应的影响更为显著。