Antisymmetric Field Research Articles

Actions for non-abelian twisted self-duality

The dynamics of abelian vector and antisymmetric tensor gauge fields can be described in terms of twisted self-duality equations. These first-order equations relate the p-form fields to their dual forms by demanding that their respective field strengths are dual to each other. It is well known that such equations can be integrated to a local action that carries on equal footing the p-forms together with their duals and is manifestly duality invariant. Space–time covariance is no longer manifest but still present with a non-standard realization of space–time diffeomorphisms on the gauge fields. In this paper, we give a non-abelian generalization of this first-order action by gauging part of its global symmetries. The resulting field equations are non-abelian versions of the twisted self-duality equations. A key element in the construction is the introduction of proper couplings to higher-rank tensor fields. We discuss possible applications (to Yang–Mills and supergravity theories) and comment on the relation to previous no-go theorems.

Investigation of resonant peaks in the symmetric and asymmetric multilayer narrowband transmission filters

The resonant transmission peaks in the asymmetric and symmetric multilayer narrowband transmission filters are theoretically investigated based on the transfer matrix method. In an asymmetric filter there exists only one resonant peak within the photonic band gap, and its position can be changed when the design wavelength is varied. In a symmetric filter, it is found that there are two resonant peaks. Using Bloch wave approximation, an investigation of these two resonant peaks has been made, and they are shown to correspond to the symmetric and antisymmetric field solutions in the defect layer.

Notoph gauge theory: Superfield formalism

We derive absolutely anticommuting Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST symmetry transformations for the 4D free Abelian 2-form gauge theory by exploiting the superfield approach to BRST formalism. The antisymmetric tensor gauge field of the above theory was christened as the “notoph” (i.e. the opposite of “photon”) gauge field by Ogievetsky and Palubarinov way back in 1966–67. We briefly outline the problems involved in obtaining the absolute anticonimutativity of the (anti-) BRST transformations and their resolution within the framework of geometrical superfield approach to BRST formalism. One of the highlights of our results is the emergence of a Curci-Ferrari type of restriction in the context of 4D Abelian 2-form (notoph) gauge theory which renders the nilpotent (anti-) BRST symmetries of the theory to be absolutely anticommutative in nature.

Statistical characteristics of field-aligned currents in Saturn's nightside magnetosphere

During 2008, the Cassini spacecraft traversed Saturn's high-latitude field-aligned current systems on sequential north-south periapsis passes in the nightside magnetosphere. Two types of current systems have previously been identified, associated with antisymmetric azimuthal field signatures in the northern and southern hemispheres. The first exhibits exclusively lagging field morphology, while the second also includes an equatorward interval of leading field. Here we report the statistical characteristics of these currents, their strength, ionospheric location, and relationship to plasma boundaries. From high to low latitude, the first type comprises a downward current followed by an upward current, whose strengths are similar to 0.5-3.5 MA per radian of azimuth. The downward current maps to ionospheric colatitudes of similar to 13.5 degrees and similar to 16 degrees in the north and south, respectively, usually centered in the outer magnetosphere, while the upward current maps to similar to 16.5 degrees and similar to 19 degrees in the north and south, located within the ring current region. The second type comprises a distributed downward current of similar to 1-2 MA rad(-1) flowing in the open field and outer magnetosphere regions, followed by an upward current of similar to 2.5-5 MA rad(-1) mapping to similar to 15.5 degrees and similar to 18 degrees in the north and south, corresponding to the outer magnetosphere and outer ring current, and a further downward current of similar to 1-2.5 MA rad(-1) mapping to similar to 17.5 degrees and similar to 20 degrees in the north and south, corresponding to the inner ring current.

Stress fields due to inclined notches and shoulder fillets in shafts under torsion

Closed-form expressions of the stress fields in notched rounded bars subjected to torsion are obtained. The notch profile is mathematically described according to Neuber’s conformal mapping z = ( u + iv) q, which gives parabolic and hyperbolic profiles depending on q. The notch axis is inclined with respect to the rounded bar axis. This condition results in two eigenvalue functions: the former is associated with the antisymmetric stress field and gives a stress distribution of asymptotic nature when the notch radius is equal to zero. Conversely, the latter is associated with the symmetric stress field and results in a non-singular stress distribution. This specific condition has been noted in the literature only rarely, where only the antisymmetric part of the stress field is discussed in detail. Theoretical results are compared with numerical data as determined from two models weakened by a parabolic notch and a hyperbolic notch, both notches having the local axis inclined to 45° with respect to the bar longitudinal axis. The agreement is found to be satisfactory.

Similarity solutions for a model arising from high frequency excitation of liquid metal in an antisymmetric magnetic field

Similarity solutions for a model arising from high frequency excitation of liquid metal in an antisymmetric magnetic field

Characterization of the terahertz near-field output of parallel-plate waveguides

We experimentally characterize the field confinement properties of various parallel-plate waveguide (PPWG) geometries in the terahertz spectral range. In contrast to infinite-width PPWGs with free-space diffraction along the unshielded direction, finite-width (and also tapered) PPWGs show well-confined THz fields at the output facet. Both the transverse field component, perpendicular to the inside surfaces, and the longitudinal component, parallel to the propagation direction, exhibit strong lateral confinement. We also observe an antisymmetric longitudinal field distribution across the air gap, analogous to the symmetric surface plasmon polariton mode observed in optical slot waveguides.

ON p-BRANES AND ANTISYMMETRIC NON-ABELIAN TENSORIAL GAUGE FIELD THEORIES OF DIFFEOMORPHISMS

It is shown how actions corresponding to antisymmetric non-Abelian tensorial gauge field theories of (p+1)-dimensional diffeomorphisms yield p-brane actions associated with their (p+1)-dimensional worldvolume evolution. We conclude with a discussion of how to obtain p-brane actions from the large N limit of covariant matrix models based on generalized hypermatrices. A deformation quantization of Nambu classical mechanics furnishing Nambu quantum mechanics by constructing the n-ary noncommutative product of n functions f1 •f2 • ⋯ •fn, the n-ary version of the Moyal bracket, and the analog of the Weyl–Wigner–Groenowold–Moyal map among operators and c-functions remains an open problem. A solution to this problem will reveal important relations between the physics of p-branes and matrix models based on generalized hypermatrices in the large N limit.

Antisymmetric field in string gas cosmology

We study how the introduction of a two-form field flux modifies the dynamics of a T-duality invariant string gas cosmology model of Greene, Kabat, and Marnerides which replaces the Newtonian-like kinetic terms in the dilaton gravity action by their relativistic counterparts. It induces a repulsive potential term in the effective action for the scale factor of the spatial dimensions. Without the two-form field flux, the Universe fails to expand when the pressure due to string modes vanishes. With the presence of a homogeneous two-form field flux, it propels three spatial dimensions to grow into a macroscopic four-dimensional space-time. We find that it triggers an expansion of a universe away from the oscillating phase around the self-dual radius. We also investigate the effects of a constant two-form field. We can obtain an expanding four-dimensional space-time by tuning it at the critical value.

Bulk antisymmetric tensor fields coupled to a dilaton in a Randall-Sundrum model

A string-inspired 3-form-dilaton-gravity model is studied in a Randall-Sundrum brane world scenario. As expected, the rank-3 antisymmetric field is exponentially suppressed. For each mass level, the mass spectrum is bigger than the one for the Kalb-Ramond field. The coupling between the dilaton and the massless Kaluza-Klein mode of the 3-form is calculated and the coupling constant of the cubic interactions obtained numerically. This coupling are of the order of Tev$^{-1}$, therefore there exist a possibility to find some signal of it at Tev scale.

Interaction between M2-branes and bulk form fields

We construct the interaction terms between the world-volume fields of multiple M2-branes and the 3-and 6-form fields in the context of ABJM theory with U(N)×U(N) gauge symmetry. A consistency check is made in the simplest case of a single M2-brane i.e., our construction matches the known effective action of M2-brane coupled to antisymmetric 3-form field. We show that when dimensionally reduced, our couplings coincide with the effective action of D2-branes coupled to R-R 3-and 5-form fields in type IIA string theory. We also comment on the relation between a coupling with a specific 6-form field configuration and the supersymmetry preserving mass deformation in ABJM theory.

Excitation of short range surface plasmon polariton mode based on integrated hybrid coupler

The short range surface plasmon polariton (SRSPP) mode, which has an antisymmetric field profile on the two sides of a thin metal film, has been excited efficiently based on an integrated vertical hybrid coupler. The coupler is composed of an Au (SRSPP) waveguide and a SiNx (dielectric) waveguide. Highly efficient coupling between the SRSPP mode and conventional dielectric waveguide mode was demonstrated. A compact (less than 90 μm long) polarizer with a low TE insertion loss and high TM extinction ratio up to 30 dB was realized by utilizing different characteristics of the TE and TM modes in the hybrid coupler.

Conditions for the formation of nongyrotropic current sheets in slowly evolving plasmas

This paper addresses the formation of nongyrotropic current sheets resulting from slow external driving. The medium is a collisionless plasma with one spatial dimension and a three-dimensional velocity space. The study is based on particle simulation and an analytical approach. Earlier results that apply to compression of an initial Harris sheet are generalized in several ways. In a first step a general sufficient criterion for the presence of extra ion and electron currents due to nongyrotropic plasma conditions is derived. Then cases with antisymmetric magnetic and electric fields are considered. After establishing consistency of the criterion with the earlier case, the usefulness of this concept is illustrated in detail by two further particle simulations. The results indicate that the formation of nongyrotropic current sheets is a ubiquitous phenomenon for plasmas with antisymmetric fields that have evolved slowly from initial gyrotropic states. A fourth case concerns a plasma with a unidirectional magnetic field. Consistent with the general criterion, the observed final state is fluidlike in that it is approximately gyrotropic. Momentum balance is shown to include a contribution that results from accumulation of an off-diagonal pressure tensor component during the evolution. Heat flux also plays an important role.

Human Action Recognition in Videos Using Kinematic Features and Multiple Instance Learning

We propose a set of kinematic features that are derived from the optical flow for human action recognition in videos. The set of kinematic features includes divergence, vorticity, symmetric and antisymmetric flow fields, second and third principal invariants of flow gradient and rate of strain tensor, and third principal invariant of rate of rotation tensor. Each kinematic feature, when computed from the optical flow of a sequence of images, gives rise to a spatiotemporal pattern. It is then assumed that the representative dynamics of the optical flow are captured by these spatiotemporal patterns in the form of dominant kinematic trends or kinematic modes. These kinematic modes are computed by performing Principal Component Analysis (PCA) on the spatiotemporal volumes of the kinematic features. For classification, we propose the use of multiple instance learning (MIL) in which each action video is represented by a bag of kinematic modes. Each video is then embedded into a kinematic-mode-based feature space and the coordinates of the video in that space are used for classification using the nearest neighbor algorithm. The qualitative and quantitative results are reported on the benchmark data sets.

Stability of sheared magnetic field in dependence on its critical level position

A horizontal layer rotating about a vertical axis z at angular velocity Ω = Ω 0 z ˆ and heated from below by an adverse temperature gradient β = ( d T / d z ) z ˆ , T being the temperature, is investigated. The layer filled by inviscid Boussinesq fluid of finite conductivity between the boundaries at z = ± d / 2 is under a gravitational field oriented vertically downwards, g = − g z ˆ , and permeated by a horizontal right-lined sheared magnetic field B 0 . The finite electrical conductivity is a destabilizing factor in such a system and resistive instabilities may rise under certain conditions. They are usually associated with the presence of a critical level defined by the condition k ⋅ B 0 = 0 , where k is the wave vector of perturbation and B 0 is the ambient magnetic field. This condition is automatically satisfied by the fields featuring zero point(s). In this work the imposed magnetic field of the form B 0 = B 0 tanh ⁡ γ ( z − z 0 ) y ˆ is considered, where B 0 is the magnitude of the field and z 0 measures its asymmetry with respect to the central plane z = 0 . We examine the effect of varying z 0 , the position of the critical level within the layer, on the stability of the system. The model is interesting from the geophysical and astrophysical point of view because of presence of an internal shear magnetic layer near the critical level associated with current sheet. The shear layer is controlled by the parameter γ which enables to change the sharpness of the magnetic field gradient across the shear layer and thereby it influences its thickness. For sufficiently large gradient of the field, the shear layer is found to be a source of hydromagnetic resistive instabilities and it is called the critical layer. A shift in the critical level location from the mid-plane towards a boundary causes the system to change in terms of the basic magnetic field (specifically its overall gradient). Boundaries were chosen to be either both perfectly conducting, insulating or a combination thereof. Linear stability analysis was performed. In general, the most preferred instabilities were found to take the form of stationary rolls. Sufficiently large gradient of the ambient magnetic field may provide conditions for exciting two distinct modes of instabilities, the whole-layer mode depending on global current distribution with its convective rolls extending throughout the whole layer, and the critical-layer mode confined to the region of the critical layer. It was found that for the layer with different electrical properties of the boundaries, the crucial importance for the onset of a particular mode (and its convective pattern) had not only the shift itself but also the fact to which boundary it was carried. Unlike the previous studies of the purely antisymmetric basic-state fields of linear and tanh profile ( Tucker and Jones, 1997), and of the asymmetric field of linear profile ( Marsenić and Ševčík, 2008) where only the stationary motions developed throughout the layer were possible, the presented model allows for qualitatively different modes localized mainly around the critical level. The confinement of the convection to the region of the critical layer was possible just for a sufficiently steep shear of the magnetic field and for the thin shear layer being shifted to the perfectly conducting boundary.

Giant transient Nernst–Ettingshausen effect in nearly gapless materials

We have measured a pulsed laser induced transient Nernst-Ettingshausen (TNE) effect for semimetal Bi and for nearly gapless materials Bi-Sb and Bi-Te alloy single crystals at 4.2 K and under magnetic fields up to 4 T. We have found the giant longitudinal-TNE (l-TNE) and transverse-TNE (t-TNE) signals for all materials. The l-TNE signals show a quite unusual antisymmetric magnetic field dependence, which suggests a mechanism of bipolar state caused by breakdown of space inversion symmetry.

Complex Resonances of a Hard Rectangular Cavity Coupled to a Half-Space Through a Narrow Aperture

Electromagnetic coupling through a small slot into a two-dimensional rectangular cavity is computed via a simple Ritz-Galerkin expansion of the aperture field for the case of transverse electric (TE) polarization. One term expansions for each of the symmetric and antisymmetric dynamic aperture fields use the exact solutions for harmonic potentials that solve the related Neumann problem of a slot in a hard plane. Source-free solutions exist at discrete, complex-values of the frequency variable. These eigenfunctions of the negative Laplacian are improper modes and several of the low-order, complex resonances are found from zeros of the variational expression that relates the aperture field to the excitation. The complex resonances are perturbations of the real, closed-cavity resonances and their presence is unmistakable in the net stored energy in the cavity under plane-wave excitation from the exterior half-space.

Semiclassical bosonic D-brane boundary states in curved spacetime

Abstract In this paper we discuss the existence of quantum D-brane states in the strong gravitational field and in the presence of a constant Kalb-Ramond field. A semiclassical string quantization method in which the spacetime metric g AB and the constant antisymmetric Kalb-Ramond field b AB are treated exactly is employed. In this framework, the semiclassical D-branes are defined at the first order perturbation around the trajectory of the center-of-mass of a string. The set of equations the semiclassical D-branes must satisfy in a general strong gravitational field are given. These equations are solved in the AdS background where it is shown that a D-brane coherent state exists if the operators that project the string fields onto the corresponding Neumann and Dirichlet directions satisfy a set of algebraic constraints. A second set of equations that should be satisfied by the projectors in order that the semiclassical state be compatible with the global structure of the D-brane are derived in the particle limit of a string in the torsionless AdS background.

Tachyon vacuum solution in open string field theory with a constant B field

We show that Schnabl's tachyon vacuum solution is an exact solution of the equation of motion of Witten's open bosonic string field theory in the background of a constant antisymmetric two-form field. The action computed at the vacuum solution is given by the Dirac–Born–Infeld factor multiplied to that without the antisymmetric tensor field.

Randall-Sundrum scenario with bulk dilaton and torsion

We consider a string-inspired torsion-dilaton-gravity action in a Randall-Sundrum braneworld scenario and show that, in an effective four-dimensional theory on the visible brane, the rank-2 antisymmetric Kalb-Ramond field (source of torsion) is exponentially suppressed. The result is similar to our earlier result in [B. Mukhopadhyaya, S. Sen, and S. SenGupta, Phys. Rev. Lett. 89, 121101 (2002); Phys. Rev. Lett. 89, 259902(E) (2002)], where no dilaton was present in the bulk. This offers an explanation of the apparent invisibility of torsion in our space-time. However, in this case the trilinear couplings {approx}TeV{sup -1} between the dilaton and torsion may lead to new signals in TeV-scale experiments, bearing the stamp of extra warped dimensions.