Axial Current Research Articles

Helical massive fermions under rotation

The properties of a massive fermion field undergoing rigid rotation at finite temperature and chemical potential are discussed. The polarisation imbalance is taken into account by considering a helicity chemical potential, which is dual to the helicity charge operator. The advantage of the proposed approach is that, as opposed to the axial current, the helicity charge current remains conserved at finite mass. A computation of thermal expectation values of the vector, helicity and axial charge currents, as well as of the fermion condensate and stress-energy tensor is provided. In all cases, analytic constitutive equations are derived for the non-equilibrium transport terms, as well as for the quantum corrections to the equilibrium terms (which are derived using an effective relativistic kinetic theory model for fermions with helicity imbalance) in the limit of small masses. In the context of the parameters which are relevant to relativistic heavy ion collisions, the expressions derived in the massless limit are shown to remain valid for masses up to the thermal energy, except for the axial charge conductivity in the azimuthal direction, which presents strong variations with the particle mass.

Anode spots of low current gliding arc plasmatron

In this work a gliding arc plasmatron consisting of a filamentary discharge rotating in a nitrogen vortex flow at low DC current (I = 100 mA) is investigated. The gas flow swirl of the plasmatron is produced by six tangential gas inlets. The Reynolds number of the nitrogen flow through these tubes at the flow rate of Q = 10 slm amounts to about 2400, which is in the intermediate range. Under these conditions, the formation of micro-vortices can be caused by small gas flow disturbances like e.g. a tube edge. The operation of the GA plasmatron at these conditions is accompanied by the production of plasma spots at the anode surface, namely near the gas inlets. Melted and solidified metal is found in erosion traces left by plasma spots at the anode surface. It is established that melting of stainless steel cannot be caused by an axial current of I = 100 mA of plasma spots and an helical current is supposed. This assumption is confirmed by microscope images of eroded traces with toroidal melting areas. These experimental results corroborate a hypothesis of previous studies, concerning the gliding arc physics, about the formation of plasma objects with an axial magnetic field by the interaction of micro-vortices with the plasma channel.

Λ(1405) as a K¯N Feshbach resonance in the Skyrme model

We describe the Lambda(1405) hyperon as a Feshbach resonance of a bar-KN quasi-bound state coupled by a decaying channel of pi Sigma in the Skyrme model. A weakly bound bar-KN state is generated in the laboratory frame, while the Sigma hyperon as a strongly bound state of bar-KN in the intrinsic frame. We obtain a coupling of bar-KN and pi Sigma channels by computing a baryon matrix element of the axial current. This coupling enables the decay of the bar-KN bound state to pi-Sigma . It is shown that the Skyrme model supports the Lambda(1405) as a narrow Feshbach resonance.

Can the Comprehensive Model (CM4) predict global features of sudden commencements?

We investigate the capability of the Comprehensive model CM4 to predict features of geomagnetic sudden commencements (SCs) focusing on observations from five ground-based observatories along the African chain. A list of 153 SC events has been selected within the period 2011–2015 to compare between modelled and observed SCs at different seasons and local times. The study reflects the degree of consistency between the CM4 model and the real physics occurring at each ground station. It also compares the characteristics of observed and modelled SC field to show how well the model performs for predicting the SC field variation. Results of feeding the CM4 model by the SYMH index data shows that the CM4 model provides a reasonable fit of the observed SC field at stations located closer to the average latitude of Dst index stations. Positive SC field variations during the day and night times for both CM4 modelled and observed fields are expected to be a signature of the magnetopause and field aligned currents rather than the axial ring current. The dawn-dusk asymmetry of the SC modelled field, which resembles the observed field at stations located poleward of the equatorial region, reveals a significant contribution from the partial ring current. At the magnetic equator, the equatorial ionospheric electrojet current plays a significant role in enhancing the observed SC field during daytime hours, which is not parameterized in the CM4 model. The latitudinal profile of the modelled field exhibits its maximum variation at the magnetic equator, decreasing towards the poles. This latitudinal profile resembles the observed field but is weaker. The modelled field at the latitudes of the Dst index stations has the same local time features of the observed field, but its strength is much smaller than the observed field and also it does not exceed its corresponding SYMH variations. In addition, the modelled SC field has a weak smooth variation with respect to local time, unlike the broad scattering of the observed field. Despite the substantial correlation between the modelled SC field and its associated SYMH field variations, the model always under-estimates the SYMH variations even at the magnetic equatorial station. Also, the CM4 model has no information about the SC seasonal variation, even at stations located within the same latitudes of the Dst index stations. These limitations should be considered when using the CM4 model to describe the external magnetospheric field.

Model Fitting of Wind Magnetic Clouds for the Period 2004 – 2006

We give the results of parameter fitting of the magnetic clouds (MCs) observed by the Wind spacecraft for the three year period – 2004 to the end of 2006 (the “Present period”) using the force-free MC model of Lepping, Jones, and Burlaga (J. Geophys. Res.95, 11957, 1990). There were 19 MCs identified in the Present period, which was mainly in the declining phase of the solar cycle. The long-term occurrence rate of MCs is 10.3/year (1995-2015), whereas the occurrence rate for the Present period is only 6.3/year, similar to that for the period 2007-2009. Hence, the MC occurrence rate has had an appreciable decrease for the six years 2004-2009. The MC modeling gives such basic MC quantities as size, axial orientation, field handedness, axial magnetic field strength, center time, and closest approach vector. A statistically based modification of the modeled field intensity is tested. Also calculated are derived quantities, such as axial magnetic flux, axial current density, and axial current. Quality ( $Q_{0}$ ) estimates are assigned representing excellent (1), good/fair (2), and poor (3). We provide error estimates on the specific fit parameters for the individual MCs for the $Q_{0} =1,2$ cases, and give a distribution of MC types (i.e. N ⇒ S, S ⇒ N, All N, All S, etc., ten categories in all). There is an inordinately large percentage of the N ⇒ S type in the Present period (32%). The Present period basic model fitting results are compared to the results of the full Wind mission and other 3-year periods. First, we notice that during the Present period the MCs are, on average, significantly faster (by 21%), distinctly stronger in axial magnetic field (by 37%), and smaller in diameter (by 5.5%), than those in the Long-term period. The quality of the MCs in the Present period is significantly better than that of the Long-term period, where the ratio $N(Q_{0} =1,2)/N(Q_{0} =1,2,3)$ for each is 0.79 and 0.58, respectively. The Present period is quite different from the Long-term period (1995-2015), it is from the other three 3-year periods between 2006 and the end of 2015. In the Present period upstream shocks occur for the first 12 MCs of the 19 cases (63%); for comparison the Long-term rate is 56%.

Box diagram contribution to the axial two-nucleon current

Recently, we have worked out the axial two-nucleon current operator to leading one-loop order in chiral effective field theory using the method of unitary transformation. Our final expressions, however, differ from the ones derived by the JLab-Pisa group using time-ordered perturbation theory (Phys. Rev. C 93, no. 1, 015501 (2016) Erratum: [Phys. Rev. C 93, no. 4, 049902 (2016)] Erratum: [Phys. Rev. C 95, no. 5, 059901 (2017)]). In this paper we consider the box diagram contribution to the axial current and demonstrate that the results obtained using the two methods are unitary equivalent at the Fock-space level. We adjust the unitary phases by matching the corresponding two-pion exchange nucleon-nucleon potentials and rederive the box diagram contribution to the axial current operator following the approach of the JLab-Pisa group, thereby reproducing our original result. We provide a detailed information on the calculation including the relevant intermediate steps in order to facilitate a clarification of this disagreement.

Magneto-vortical effect in strongly coupled plasma

Based on a holographic model incorporating both the chiral anomaly and the gravitational anomaly, we study the effect of magneto-vortical coupling on the transport properties of a strongly coupled plasma. The focus of present work is on the generation of a vector charge density and an axial current, as response to vorticity in a magnetized plasma. The transport coefficients parameterizing the vector charge density and axial current are calculated both analytically (in the weak magnetic field limit) and also numerically (for general values of the magnetic field). We find the generation of vector charge receives both non-anomalous and anomalous contributions, with the non-anomalous contribution dominating in the limit of a strong magnetic field and the anomalous contribution sensitive to both chiral anomaly and gravitational anomaly. On the contrary, we find the axial current is induced entirely due to the gravitational anomaly, thus we interpret the axial current generation as chiral vortical effect. The corresponding chiral vortical conductivity is found to be suppressed by the magnetic field. By the Onsager relation, these transport coefficients are responsible for the generation of a thermal current due to a transverse electric field or a transverse axial magnetic field, which we call the thermal Hall effect and the thermal axial magnetic effect, respectively.

CALCULATION-EXPERIMENTAL DETERMINATION OF THE AVERAGE NUMBER OF QUANTIZED LONGITUDINAL ELECTRON DE BROGLIE HALF WAVES IN A CYLINDRICAL CONDUCTOR WITH PULSED AXIAL CURRENT

Purpose: Implementation of calculation-experimental determination of average number n0m of the quantized longitudinal electron de Broglie half waves of length λezm/2 in the metal cylindrical conductor with the pulsed axial current of high density. Methodology. Scientific bases of theoretical electrophysics and quantum physics, theoretical bases of the electrical engineering, electrophysics bases of technique of high-voltage and high pulsed currents. Results: The results of calculation-experimental estimations of average number n0m of the quantized longitudinal electron de Broglie half waves in the round continuous zincked steel wire of radius 0.8mm and of length 320 mm with aperiodic pulsed axial current i0(t) of temporal shape 9 ms/160 ms of high density (at its amplitude of δ0m=0.37 kA/mm2). It is shown that in examined case the numeral value of the average quantized number from data of calculation and experiment makes n0m=9, and test average length of quantized longitudinal electron de Broglie half waves in the indicated steel wire appears approximately equal to λezm/2≈34 mm. Electrophysical results are confirmed during the high current high temperature experiment conducted by a powerful high-voltage equipment calculation information on the choice of average value of quantized number n0m for longitudinal «hot» areas of the width Δz of the wire, different anomalous enhanceable concentration of drifting lone electrons and accordingly temperature of Joule heating. Originality: On the basis of the known conformities to the law of atomic and quantum physics new quantum-mechanical calculation correlation is obtained for determination in a metallic conductor with axial current of conductivity i0(t) of different type (direct, alternating and pulsed) of average number n0m of the quantized longitudinal electron de Broglie half waves and accordingly longitudinal «hot» areas of the width Δz of periodic localization along the conductor of drifting lone electrons. Practical Value: Obtained results allow to make an evaluation prognosis on finding of possible places of longitudinal periodic localization of drifting lone electrons on narrow areas of the width Δz of current-carrying parts of power wires and cables of objects of electrical power energy, production and dwellings apartments, showing up most strongly (expressed) in malfunctions of operation of cable-conductor products with the currents of short-circuit and high current density.

Non-relativistic reduction of spinors, new currents and their algebra

A specific mapping is introduced to reduce the Dirac action to the non-relativistic (Pauli - Schrödinger) action for spinors. Using this mapping, the structures of the vector and axial vector currents in the non-relativistic theory are obtained. The implications of the relativistic Ward identities in the non-relativistic limit are discussed. A new non-abelian type of current in the Pauli - Schrödinger theory is obtained. As we show, this is essential for the closure of the algebra among the usual currents. The role of parity in the non-relativistic theory is also discussed.

Palynological dating of low-grade metamorphosed rocks: Applications to Early Paleozoic rocks of the Central Maine/Aroostook-Matapedia Basin and Fredericton Trough (Northern Appalachians) in eastern and east-central maine, U.S.A.

Identification of spores, acritarchs, and chitinozoans in weakly metamorphosed (≥ 300 °C) turbidites demonstrates the usefulness of palynological dating for hitherto unfossiliferous strata that underlie much of the Gander terrane in Maine. Combined with sparse macrofossil ages and geochronologic data from detrital zircons, volcanic horizons, and plutons, the fossils constrain the ages of strata in the Central Maine/Aroostook-Matapedia (CMAM) basin and Fredericton trough and help to resolve paleogeographic and tectonic problems. Ages for the provisional Brewer (Upper Ordovician to Llandovery) and Bangor (Wenlock) formations in the Bangor area fill the last remaining gap in CMAM basin stratigraphy and permit correlation across the entire basin, from western Maine to the New Brunswick border. Resulting lithofacies patterns document basinward facies changes from both eastern and western external sources, and also indicate internal sources within the basin. A progressive decrease in carbonate sediment in the CMAM basin toward the south suggests interaction between axial and basinward currents in which micrite transported by axial currents from the Matapedia platform in northern New Brunswick was progressively overwhelmed to the south by clastic sedimentation from flanking highland sources. Middle to late Silurian age ranges for the Flume Ridge Formation, the most extensive unit in the Fredericton trough, and the newly named County Road Formation permit correlation with rocks in similar structural positions in New Brunswick. Recent geologic mapping, the new age control, and improved understanding of facies relationships show that the CMAM basin was perhaps as wide as 800 to 1000 km prior to deformation; developed on continental crust after mid-Ordovician plate accretion; contained a body of deep water with anoxic bottom conditions and mostly pelagic organisms; and contains a series of overlapping submarine fans derived from multiple sources.

Mode transitions in nonlinear evolution of the electron drift instability in a 2D annular E × B system

Nonlinear development of electron drift instability is studied using 2D3V azimuthal-radial Particle-in-Cell simulations of an annular Hall thruster channel of 10 cm diameter. The full 2π azimuthal domain of the annular cross section is simulated with reflecting boundary conditions at the radial boundaries. It is shown that the instability, which starts as a short length scale linear instability, undergoes a sequence of nonlinear transitions into longer wavelength modes. The transitions in the mode wavelengths are accompanied by related transitions of the magnitude of anomalous axial current. In the nonlinear stages, there is evidence of azimuthal trapping and dragging of ions by the propagating wave resulting in saturation of instability. It is demonstrated that the size of the azimuthal domain influences mode dynamics and, thereby, the anomalous cross field electron transport.

The effect of permanent magnet position on axial and radial load capability in axial hybrid magnetic bearing

The axial and radial load capacity of axial hybrid magnetic bearing (HMB) is critical for the magnetic levitation system. In this paper, the effect of permanent magnet (PM) position on axial and radial magnetic force and stiffness in axial HMB is investigated. Six different configurations are considered and the equivalent magnetic circuits of HMBs for each configuration is built and studied based on the distribution of magnetic field and magnetic leakage. The dependence of axial and radial magnetic force and stiffness on the axial displacement, radial displacement and control current is calculated and investigated for different configurations. To validate the calculated results, the axial and radial magnetic forces for each configuration are simulated by finite element method. A good agreement between the calculated and simulated results validated the proposed magnetic circuit models.

Holographic approach to the light-by-light contribution to the muon (g-2)

We discuss how holographic models of QCD are used to study the the hadronic light-by-light (HLbL) scattering amplitude contribution to the muon anomalous magnetic moment. After a brief description of the various models, we focus on a particular one, introduced by Hirn and Sanz, emphasizing the role it assigns to the pion, and the vector and-axial vector resonances. We review how the parameters of the model are fixed by imposing condition on the low energy and the deep Euclidean limit of two-point correlators of QCD vector and axial vector currents. We then focus on the evaluation of the three-point axial-vector-vector current correlator and the pion anomalous transition form factor to be used in the one-pion exchange HLbL diagram and study its asymptotic properties. Finally, we present preliminary results on the four vector current correlator that defines the Hadronic Light-by-Light tensor. We find that axial-vector resonances play an important rule in recovering the correct asymptotic behaviour predicted by QCD at large Euclidean momenta.

Polarised amplitudes and soft-virtual cross sections for bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{b} $$\\end{document}→ Z H at NNLO in QCD

Production of the Higgs boson, H in association with a massive vector boson, V, i.e., the V H process, plays an important role in the explorations of Higgs physics at the Large Hadron Collider, both for a precise study of Higgs’ Standard Model couplings and for probing New Physics. In this publication we present the two-loop corrections in mass- less quantum chromodynamics (QCD) to the amplitude of the Higgs production associated with a Z boson via the bottom quark-antiquark annihilation channel with a non-vanishing bottom-quark Yukawa coupling, which is a necessary ingredient of the full next-to-next- to-leading-order QCD corrections to the V H process in the five-flavour scheme. The computation is performed by projecting the D-dimensional scattering amplitude directly onto an appropriate set of Lorentz structures related to the linear polarisation states of the Z boson. We provide analytic expressions of the complete set of renormalised polarised amplitudes in terms of polylogarithms of maximum weight four. To give an estimation of the size of contributions from amplitudes considered in this work, we compute numerically the resulting cross sections under the soft-virtual approximation. We also take the opportunity to make a dedicated discussion regarding an interesting subtlety appearing in the conventional form factor decomposition of amplitudes involving axial currents regularised in D dimensions.

Quantum Field Effects of Acceleration and Rotation: the Chiral Vortical Effect and the Unruh Effect

The effects of vorticity and acceleration can be studied in the framework of a general fundamental approach based on the Zubarev density operator. The calculation of axial current is related to Chiral Vortical Effect (CVE) and hyperon polarization, while the calculation of acceleration corrections to energy density leads to the Unruh effect. The nonperturbative formula for CVE of massive fermions and the possibility of stabilization and suppression of the axial current in the plasma of elementary particles due to the appearance of an effective mass, depending on temperature, is discussed.

Quasi-one-dimensional approximation for Bose–Einstein condensates transversely trapped by a funnel potential

Starting from the standard three-dimensional (3D) Gross–Pitaevskii equation (GPE) and using a variational approximation, we derive an effective one-dimensional nonpolynomial Schrödinger equation (1D-NPSE) governing the axial dynamics of atomic Bose–Einstein condensates (BECs) under the action of a singular but physically relevant funnel-shaped transverse trap, i.e. an attractive 2D potential ∼−1/r (where r is the radial coordinate in the transverse plane), in combination with the repulsive self-interaction. Wave functions of the trapped BEC are regular, in spite of the potential’s singularity. The model applies to a condensate of particles (small molecules) carrying a permanent electric dipole moment in the field of a uniformly charged axial thread, as well as to a quantum gas of magnetic atoms pulled by an axial electric current. By means of numerical simulations, we verify that the effective 1D-NPSE provides accurate static and dynamical results, in comparison to the full 3D GPE, for both repulsive and attractive signs of the intrinsic nonlinearity.

Spontaneous drop of the Li-containing flake as a trigger of ITB-event in plasmas of the T-10 tokamak during simultaneous co+counter injection of EC waves

Various triggers of ITB-events (ITB-event is an abrupt and non-local reduction of the heat flux within a radius of ∼50% of the minor radius) have been previously found at the JT-60U, the T-10 tokamaks and the LHD stellarator. This short paper describes a new trigger of ITB-events discovered in the T-10 plasmas in experiments on simultaneous co+counter axial EC current drive performed using the X-wave with a frequency equal to the second ECR harmonic. In these experiments, the tungsten limiter and lithium wall coating were used. The ionization of atoms in the Li-containing flake, which occurs at the plasma edge, generally causes the rise of the electron temperature and density in the core of the plasma column. The electron heat flux reduces abruptly within the radial range of 0.2 < r/a < 0.8, just as it was at the LHD in experiments on the injection of small C8H8 pellets. The energy confinement time abruptly increases by ∼10%. After the transient phase, the ITB appears, which is located between the radii corresponding to the safety factors of q = 1 and q ≈ 1.4. Typically, the ITB lifetime is equal to the plasma energy lifetime. As far as we know, the triggering of ITB-events by the drop of Li-containing flake has been never reported in tokamaks and stellarators.

N*(1535)→N transition form-factors due to the axial current

The form-factors for the transition $ N^*(1535)\to N $ induced by isovector and isoscalar axial currents within the framework of light-cone QCD sum rules by using the most general form of the interpolating current are calculated. In numerical calculations, we use two sets of values of input parameters. It is observed that the $ Q^2 $ dependence of the form-factor $ G_A $ can be described by the dipole form. Moreover, the form-factors $ G_P^{(S)} $ are found to be highly sensitive to the variations in the auxiliary parameter $ \beta $.

Lattice field theory with torsion

Inspired by the duality between gravity and defects in crystals, we study lattice field theory with torsion. The torsion is realized by a line defect of a lattice, namely a dislocation. As the first application, we perform the numerical computation for vector and axial currents induced by a screw dislocation. This current generation is called the chiral torsional effect. We also derive the analytical formula for the chiral torsional effect in the continuum limit.

Schwinger model à la Very Special Relativity

In this work, we show that Lorentz invariant theories in 1+1 dimensions admit new terms inspired by Very Special Relativity (VSR) theories. We have studied the Schwinger model in VSR. We show the axial current is classically conserved in the presence of a mass term coming from the VSR invariant terms but without standard Lorentz invariant mass. Furthermore, it is shown that both the vector current as well as the axial current are modified with respect to the free case when the fermion is coupled to an external electromagnetic field due to the nonlocal operator present in the theory. The axial anomaly is computed, and we found the same standard topological invariant with a modification in the coefficient.