Antisymmetric Field Research Articles

Stable Lorentz-breaking model for an antisymmetric two-tensor

In this work we investigate possible actions for antisymmetric two-tensor field models subject to constraints that force the field to acquire a nonzero vacuum expectation value, thereby spontaneously breaking Lorentz invariance. In order to assure stability, we require that the associate Hamiltonian be bounded from below. It is shown that this requirement rules out any quadratic action constructed only from the antisymmetric tensor field. We then explicitly construct a hybrid model consisting of the antisymmetric two-tensor field together with a vector field, subject to constraints forcing nonzero expectation values, that is stable in Minkowski space. Published by the American Physical Society 2024

Gravity with spacetime torsion

The duality between a higher-curvature f(R) gravity model and a scalar-tensor theory helps to bring out the role of the additional degree of freedom originating from the higher-derivative terms in the gravity action. Such a degree of freedom which appears as a scalar field has been shown to have multiple implications in the cosmological/astrophysical scenario. The present work proposes a novel generalization to this correspondence between f(R) gravity and a dual scalar-tensor theory when the affine connection is considered to have an antisymmetric part. It turns out that the f(R) action in the presence of spacetime torsion can be recast to a coupled scalar-tensor theory with a 2-rank massless antisymmetric tensor field in the Einstein frame, where the scalar field gets coupled with the antisymmetric field through derivative coupling(s).

Entanglement entropy and the boundary action of edge modes

We consider an antisymmetric gauge field in the Minkowski space of d-dimension and decompose it in terms of the antisymmetric tensor harmonics and fix the gauge. The Gauss law implies that the normal component of the field strength on the spherical entangling surface will label the superselection sectors. From the two-point function of the field strength on the sphere, we evaluate the logarithmic divergent term of the entanglement entropy of edge modes of p-form field. We observe that the logarithmic divergent term in entanglement entropy of edge modes coincides with the edge partition function of co-exact p-form on the sphere when expressed in terms of the Harish-Chandra characters. We also develop a boundary path integral of the antisymmetric p-form gauge field. From the boundary path integral, we show that the edge mode partition function corresponds to the co-exact (p − 1)-forms on the boundary. This boundary path integral agrees with the direct evaluation of the entanglement entropy of edge modes extracted from the two-point function of the normal component of the field strength on the entangling surface.

Massive covariant colour-kinematics in 3D

We explore topologically massive gauge theories using the covariant colour kinematics duality recently introduced in [1]. We show that the massive bi-adjoint scalar field is simply related to topologically massive gauge theory by the duality, and that enacting the same duality on the gauge theory produces topologically massive gravity coupled to a scalar or, equivalently, an antisymmetric field. We also show that different choices for the replacement of the colour structure constants with kinematic structure constants lead to different theories, including a topologically massive generalisation of Born-Infeld theory.

Spherically symmetric teleparallel geometries

We are interested in the development of spherically symmetric geometries in F(T) teleparallel gravity which are of physical importance. We first express the general forms for the spherically symmetric frame and the zero curvature, metric compatible, spin connection. We then analyse the antisymmetric field equations (the solutions of which split into two cases, which we subsequently consider separately), and derive and analyse the resulting symmetric field equations. In order to further study the applications of spherically symmetric teleparallel models, we study 3 subcases in which there is an additional affine symmetry so that the resulting field equations reduce to a system of ordinary differential equations. First, we study static spherical symmetric geometries and solve the antisymmetric field equations and subsequently derive the full set of symmetric field equations. In particular, we investigate vacuum spacetimes and obtain a number of new solutions. Second, we consider an additional affine frame symmetry in order to expand the affine frame symmetry group to that of a spatially homogeneous Kantowski–Sachs geometry. Third, we study the special case of spherical symmetry with an additional fourth similarity affine vector.

Quantization of Weyl invariant unimodular gravity with antisymmetric ghost fields

The enforcement of the unimodularity condition in a gravity theory by means of a Lagrange multiplier leads, in general, to inconsistencies upon quantization. This is so, in particular, when the classic linear splitting of the metric between the background and quantum fields is used. To avoid the need of introducing such a Lagrange multiplier while using the classic linear splitting, we carry out the quantization of unimodular gravity with extra Weyl symmetry by using Becchi–Rouet–Stora–Tyutin (BRST) techniques. Here, two gauge symmetries are to be gauge-fixed: transverse diffeomorphisms and Weyl transformations. We perform the gauge-fixing of the transverse diffeomorphism invariance by using BRST transformations that involve antisymmetric ghost fields. We show that these BRST transformations are compatible with the BRST transformations needed to gauge-fix the Weyl symmetry, so that they can be combined in a set of transformations generated by a single BRST operator. Newton’s law of gravitation is derived within the BRST formalism we put forward as well as the Slavnov–Taylor equation.

Spontaneous symmetry breaking and the cosmological constant

An approach that allows studying the relationship between the neutralization of the cosmological constant and instantons for cosmology coupled to antisymmetric fields is proposed. Using suitable variables, the Lagrangian leading to the FRW equations can be written analogously to a Ginzburg–Landau theory, and we show how spontaneous symmetry breaking appears.

Low resistance large area terahertz detector based on antimony telluride thin film

Terahertz technology has great potential for various applications in fields like biomedicine, astronomy, communications, and security inspection. Therefore, terahertz detectors that can operate at room temperature with fast response times, high sensitivity, wide detection bandwidth, and can be seamlessly integrated. To achieve this, a metal–semiconductor-metal structure with a subwavelength gap is used, which creates an electromagnetic induced potential well within the semiconductor by utilizing the antisymmetric electric field of terahertz radiation. This structure allows for the injection and retention of electrons from the metal, enhancing electrical conductivity. Experimental results have shown that reducing the spacing between the forked finger electrodes improves the detection performance of the device. At room temperature, with a bias voltage of 1 V and 0.28 THz radiation, the device achieves an equivalent noise power of 9.76 × 10−13 W/Hz/2 and a detection rate of 2.41 × 1011cm Hz1/2W−1. Additionally, the device's simple structure and large effective detection area make it suitable for producing low-resistance and large-area terahertz detectors.

Bound states in the continuum in anisotropic photonic crystal slabs

We investigate the bound states in the continuum (BICs) in photonic crystal slabs composed of alternating anisotropic and isotropic dielectric materials. According to the orientation of optical axis plane, three different configurations are proposed for analyzing various types of BICs, associated with extremely large quality factors and vanishing spectral linewidths. In particular, symmetry-protected (SP) BICs exist at the Brillouin zone center for zero rotation angle of the optical axis, which exhibit antisymmetric field patterns that are decoupled from the symmetric radiating fields. Accidental BICs and Friedrich-Wintgen (FW) BICs also occur at the Brillouin zone center for particular rotation angles of the optical axis. The former emerge on isolated bands with quasi-symmetric or quasi-antisymmetric field patterns, while the latter appear near the avoided crossing between two dispersion bands. At off the Brillouin zone center, SP BICs do not exist while accidental BICs and FW BICs appear at particular optical axis rotation angles, with similar features but somewhat more asymmetric field patterns than those at the Brillouin zone center.

Study of Unsteady Surface Flowfields on and Around Turrets with Different Protrusions

Wind-tunnel experiments were conducted to measure the unsteady surface pressure field on and around a hemisphere-on-cylinder turret of varying protrusion in subsonic flow. These measurements were obtained using fast-response pressure-sensitive paint coupled with pressure transducers. The surface pressure field data resulting from Mach 0.5 flow () over a partially submerged hemisphere, a hemisphere, and a hemisphere on a cylinder were analyzed using proper orthogonal decomposition modal analysis, as well as a variant of this approach referred to as joint proper orthogonal decomposition. The results showed that decreased turret protrusion into the freestream flow reduced the prevalence of antisymmetric surface pressure field fluctuations caused by antisymmetrical vortex shedding. The frequency associated with this fluctuation was found to be around . When a partial hemispherical turret geometry was used, it was shown that the antisymmetric mode was greatly suppressed; and the wake was dominated by a symmetric mode with a broadband spectral peak at a higher frequency of . This suggests that there is a “mode switching” as the protrusion is changed from the hemisphere to the partial hemisphere configuration. An optical flow approach was used to find the convective velocity field in the wake, from which topological flow features could be identified. The size of the wake separation region was found to grow smaller with the decreased protrusion while keeping a similar shape.

Spoof surface plasmon polariton supported by square ring metasurface for wearable body area network

A metasurface consisting of a 2D periodic square lattice of metallic square ring resonators is considered for supporting spoof surface plasmon polariton (SSPP) modes. First, SSPP modes are highlighted by simulated dispersion curves. The dispersion curves are analyzed by considering hybridization of modes in either a patch or an aperture array with frequency shifts. Hybridization of modes is also supported by means of surface current and electric field mappings showing consistent symmetric and anti-symmetric fields. Second, it is shown that a dipole antenna located near the metasurface is able to generate SSPP modes. The transmission spectra between two antennas located at each extremity of the metasurface show transmission enhancements compared with propagation in free space. The transmission enhancements are shown for different locations of the antennas either facing each other or positioned in diagonal. Finally, the transmission enhancement is connected to SSPP modes by comparing the transmission spectra and the measured dispersion curves with each other. Specifically, two transmission windows measured for an embroidered metasurface are related to the cutoff frequency of the two SSPP modes supported by the metasurface as evidenced by the measured dispersion curves.

Bound states in the continuum in asymmetric dual-patch metasurfaces.

We investigate the bound states in the continuum (BICs) in dielectric metasurfaces consisting of asymmetric dual rectangular patches in the unit cell of a square lattice. Various types of BICs are identified in the metasurface at normal incidence, associated with very large quality factors and vanishing spectral linewidths. In particular, symmetry-protected (SP) BICs occur when the four patches are fully symmetric, which exhibit antisymmetric field patterns that are decoupled from the symmetric incident waves. By breaking the symmetry of patch geometry, the SP BICs degrade to quasi-BICs that are characterized by Fano resonance. Accidental BICs and Friedrich-Wintgen (FW) BICs occur when the asymmetry is introduced in the upper two patches, while holding the lower two patches symmetric. The accidental BICs occur on isolated bands when the linewidth of either the quadrupole-like mode or LC-like mode vanishes by tuning the upper vertical gap width. The FW BICs appear when the avoided crossing is formed between the dispersion bands of dipole-like and quadrupole-like modes by tuning the lower vertical gap width. At a special asymmetry ratio, the accidental BICs and FW BICs may appear in the same transmittance or dispersion diagram, accompanied with the concurrence of dipole-like, quadrupole-like, and LC-like modes.

Numerical simulation of intracerebral hemorrhage detection using magnetic induction spectroscopy

Magnetic Induction Spectroscopy (MIS) is an emerging technique for contactless measurement of bioimpedance with promising application in intracerebral hemorrhage (ICH) detection. Here, we report numerical simulations of ICH detection based on the MIS. A novel MIS sensor using two planar rectangular spiral coils (TPRSC) as the exciter with frequency range 120 kHz-9 MHz is proposed for the first time. The exciter can generate an antisymmetric normal magnetic field at the detection sensor, and hence the primary voltage can be canceled theoretically. We construct symmetry-based and asymmetry-based ICH models with realistic anatomic structure and hexahedral discretization feature for numerical simulations. The numerical simulations based on the finite integration technique are conducted in the three-dimensional electromagnetic analysis software CST. The voltage phase spectrum, the phase change spectrum and the relative conductivity change spectrum at different hemorrhage volumes are calculated. We compare sensitivities between the TPRSC-based MIS sensor and the conventional type (CC MIS sensor) which uses the single planar rectangular spiral coil as the exciter. Using the constructed ICH models, the specific absorption rate (SAR) and the internal electric field strength are computed to evaluate the electromagnetic safety of the TPRSC-based MIS sensor. Results show that compared with the CC MIS sensor, the sensitivity of the TPRSC-based MIS sensor for measuring the voltage phase is improved by two orders of magnitude, and for measuring the phase change is improved by more than ten times. The phase change and relative conductivity change spectra for the TPRSC-based MIS sensor demonstrate good separability between different small-volume hemorrhages. In addition, the electromagnetic safety of the TPRSC-based MIS is also superior to that of the CC MIS sensor, which conforms to the IEEE standard and the ICNRP guidelines over a wide range of the amplitude of the excitation current.

Maxwell extension of f(R) gravity

Inspired by the Maxwell symmetry generalization of general relativity (Maxwell gravity), we have constructed the Maxwell extension of f(R) gravity. We found that the semi-simple extension of the Poincare symmetry allows us to introduce geometrically a cosmological constant term in four-dimensional f(R) gravity. This symmetry also allows the introduction of a non-vanishing torsion to the Maxwell f(R) theory. It is found that the antisymmetric gauge field B^{ab} associated with Maxwell extension is considered as a source of the torsion. It is also found that the gravitational equation of motion acquires a new term in the form of an energy–momentum tensor for the background field. The importance of these new equations is briefly discussed.

Chorus Wave Generation Modulated by Field Line Resonance and Mirror‐Mode ULF Waves

AbstractEarth's inner magnetosphere is a zoo of plasma waves where electromagnetic and electrostatic emissions with distinct frequencies coexist and interact. Spacecraft observations have shown that whistler‐mode chorus waves, one of the key components in the magnetospheric dynamics, are often modulated by ultralow frequency (ULF) waves. Here, we investigate the effects of two typical ULF wave modes (i.e., field line resonance and mirror mode) on the nonlinear generation process of chorus waves. We report for the first time periodic excitations of lower‐ and upper‐band chorus waves near ULF wave crests and troughs, respectively. Their anticorrelated occurrence is explained by the nonlinear theory, in which the threshold amplitude of nonlinear wave growth is modified by the ULF wave field configuration and the modulated electron distributions. In this framework, the newly observed feature of chorus wave occurrence near the ULF wave crests is attributed to the antisymmetric field profiles of mirror‐mode ULF waves, which periodically modulate the threshold amplitude by modifying the second‐order derivative of the background dipole field. In addition to the second‐order derivative, the first‐order derivative of the background magnetic field is also modulated by the ULF waves to regulate the size of the chorus wave source region.

On affine geometrical structure, generalized of Born–Infeld models and Eddington’s world conjectures

In this work, we give a detailed description and discussion of the dynamic gravitational equations of the model with Lagrangian of the type [Formula: see text] as proposed by Eddington time ago but with [Formula: see text] being a non-Riemannian generalization of the Ricci tensor with the end to find the geometrical origin of the Eddington and Weyl conjectures concerning Lagrangian densities (generalized volume) and natural gauge. The Ricci tensor in our case is particularly based on an affine geometry with a generalized compatibility condition previously proposed in [B. McInnes, On the geometrical interpretation of ‘non-symmetric’ space-time field structures, Class. Quantum Grav. 1 (1984) 105–113; D. J. Cirilo-Lombardo, Non-Riemannian geometry, Born–Infeld models and trace-free gravitational equations, J. High Energy Astrophys. 16 (2017) 1–14]. Specifically, we show that: (i) the geometric action can be taken to a BI-type form considering a totally antisymmetric torsion field, (ii) Weyl’s proposal considering a universal gauge linked to a cosmological constant [Formula: see text] appears in the model naturally due to the proposed affine geometry, (iii) the Eddington conjecture that establishes a relationship between metric and curvature or fundamental tensor with constant of proportionality [Formula: see text] (natural gauge) is geometrically verified in the model with generalized affine geometry.

Twisted C‐Brackets

We consider the double field formulation of the closed bosonic string theory, and calculate the Poisson bracket algebra of the symmetry generators governing both general coordinate and local gauge transformations. Parameters of both of these symmetries depend on a double coordinate, defined as a direct sum of the initial and T-dual coordinate. When no antisymmetric field is present, the C-bracket appears as the Lie bracket generalization in a double theory. With the introduction of the Kalb-Ramond field, the B-twisted C-bracket appears, while with the introduction of the non-commutativity parameter, the θ-twisted C-bracket appears. We present the derivation of these brackets and comment on their relations to analogous twisted Courant brackets and T-duality.

Landau levels and snake states of pseudo-spin-1 Dirac-like electrons in gapped Lieb lattices

This work reports the three-band structure associated with a Lieb lattice with arbitrary nearest and next-nearest neighbors hopping interactions. For specific configurations, the system admits a flat band located between two dispersion bands, where three inequivalent Dirac valleys are identified. Furthermore, quasi-particles are effectively described by a spin-1 Dirac-type equation. Under external homogeneous magnetic fields, the Landau levels are exactly determined as the third-order polynomial equation for the energy can be solved using Cardano’s formula. It is also shown that an external anti-symmetric field promotes the existence of current-carrying states, so-called snake states, confined at the interface where the external field changes its sign.

Sequential deconfinement and self-dualities in 4d mathcal{N} = 1 gauge theories

We apply the technique of sequential deconfinement to the four dimensional mathcal{N} = 1 U sp(2N) gauge theory with an antisymmetric field and 2F fundamentals. The fully deconfined frame is a length-N quiver. We use this deconfined frame to prove the known self-duality of U sp(2N) with an antisymmetric field and 8 fundamentals. Along the way we encounter a subtlety: in certain quivers with degenerate holomorphic operators, a naive application of Seiberg duality rules leads to an incorrect superpotential or chiral ring.We also consider the reduction to 3d mathcal{N} = 2 theories, recovering known fully deconfined duals of U sp(2N) and U(N) gauge theories, and obtaining new ones.

Exploration of a Kilowatt-Level Terahertz Amplifier Based on Higher-Order Mode Interaction

The parameters for a kilowatt-level high-power terahertz amplifier were explored based on the higher-order mode and extended-interaction mechanism. It has been demonstrated that the antisymmetric electrical field mode (TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> ) has a unique advantage in achieving high power. Physical factors on power extraction were studied. In particular, the heavily reduced <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{{0}}$ </tex-math></inline-formula> has a great effect on the coupling characteristic as well as the output power. It is found that the critical coupling state, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{e} = {Q}_{{0}}$ </tex-math></inline-formula> , defines an upper limit of the power that can be extracted from the output circuit. The design of a complete interaction circuit was accomplished. The particle-in-cell (PIC) simulations showed that a saturated power of 1.2 kW can be achieved at 220 GHz with a voltage of 45 kV and a total current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times0.6$ </tex-math></inline-formula> A where two beams were used. The saturated gain is over 30 dB with a 3-dB bandwidth of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 400$ </tex-math></inline-formula> MHz.