Torsion Components Research Articles

A note on the torsion dependence of D-brane RR couplings

The dependence on the torsion H= db of the Wess–Zumino couplings of D-branes that are trivially embedded in space–time is studied. We show that even in this simple set-up some torsion components can be turned on, with a non-trivial effect on the RR couplings. In the special cases in which either the tangent or the normal bundle are trivial, the torsion dependence amounts to substitute the standard curvature with its generalization in the presence of torsion, in the usual couplings involving the roof genus Â.

On free partially associative triple systems

A triple system is partially associative (by definition) if it satisfies the identity (abc)de + a(bcd)e + ab(cde) ≡ 0. This paper presents a computational study of the free partially associative triple system on one generator with coefficients in the ring Z of integers. In particular, the Z-module structure of the homogeneous submodules of (odd) degrees ≤ 11 is determined, together with explicit generators for the free and torsion components in degrees ≤ 9. Elements of additive order 2 exist in degrees ≥ 7, and elements of additive order 6 exist in degrees ≥ 9. The most difficult case (degree 11) requires finding the row-reduced form over Z of a matrix of size 364 × 273. These computations were done with Maple V.4 on a Sun workstation.

Mechanical Properties of a Migrating Fiber

A mathematical model of a helix with variable radius is developed to analyze geo metric and mechanical properties of a migrating fiber. The factors concerned include the frequency and amplitude of fiber migration as well as the equivalent radial position and equivalent helix height of the fiber. This treatment permits the application of experimentally determined migration patterns defined by those factors. The derived properties are the curvature and torsion components of the migrating fibers, bending moments, torque, strain energy distribution, and total strain energy. The terminal force and couple are calculated as functions of the length of the helix axis. A critical migration amplitude is identified where the axial component of the couple and trans verse component of the force change their direction. The implication of these behaviors for yam properties such as total yam torque and local pressure distribution is also revealed. Cylindrical and sinuous helices are compared, with the effects of the amplitude and frequency of fiber migration quantitatively determined.

In vitro determination of equine third metacarpal bone unloading, using a full limb cast and a walking cast

Abstract Objective To improve fracture treatment, in vitro experiments were performed to study the influence of a full limb cast and a walking cast on the loading regimen of bones in the distal portion of the equine forelimb. Animals 6 forelimbs of 6 Shetland ponies. Procedure Loading of the third metacarpal bone was considered a representative measure for distal limb loading. Electrical resistance rosette strain gauges were attached to the dorsal, palmar, medial, and lateral surfaces of the midshaft of this bone in 6 forelimbs of 6 Shetland ponies. The limbs were tested in a pneumatic loading device to a maximal load of 1,500 N. Results Both casts decreased the amount of compressive forces acting on the metacarpal bone. Application of a full limb cast resulted in a variable and eccentric decrease, remaining strains ranging from 84 to 7% of the baseline value. A walking cast was superior in that it gave a centric and more uniform reduction of compressive loading to <11 % of the baseline value. Moreover, a walking cast neutralized the bending and torsion components of the loading. Conclusion This study confirmed the clinical experience that a walking cast creates more reliable and favorable conditions for healing of fractures than does a full limb cast. (Am J Vet Res 1996;57:1386-1389)

Asymptotic approximation of an elastic beam with a rotating cross section

Asymptotic approximation of an elastic beam with a rotating cross section

Displacement and natural frequencies of tall building structures by finite story method

An approximate approach, termed finite story method (FSM), is proposed for the analysis of tall building structures under lateral loads. The method is based on nodal displacement fields obtained from two-story substructures and intended to approximate shear, bending and torsion components of global deformations. Because floor slabs are considered in-plane rigid, these deformations are described by translational and rotational displacements of the slabs. Thus, nodal displacements are obtained by interpolating the floor slab displacements, where the interpolation coefficients come from the nodal displacement fields. The latter represent deformation patterns corresponding to unit relative floor slab displacements of the two-story substructures. By introducing this interpolation, the overall structural analysis is simplified to only five principal unknowns per floor. The efficiency and accuracy of the method are demonstrated for static and dynamic examples by comparing the results with standard three-dimensional finite element analysis.

Rotational Centers of Plates Regulating Distortion of Box Girders

In thin‐walled prismatic members, three different points regulate the cross‐sectional properties. Among these, the centroid and shear center are important for beams with nondeformable cross section, while the rotational centers of plates are important for beams with deformable cross sections. This paper provides methods for determining the rotational centers of plates regarding the distortional problems of thin‐walled, multicell box girders, and proves that the rotational centers of plates can be explained by the same concept as the shear center. The general characters of distortion and location of the rotational center of each plate are derived for typical box girders with a trapezoidal section. A method for resolution of an eccentric load into components of pure bending, pure torsion, and pure distortions is also given.

Two-dimensional black hole with torsion

The 2D model of gravity with zweibeins e a and the Lorentz connection one-form ω a b as independent gravitational variables is considered and it is shown that the classical equations of motion are exactly integrated in a coordinate system determined by the components of the 2D torsion. The metric can be written in a Schwarzschild-like form. The general solution describes a black hole of charged type in asymptotic de Sitter space-time. The ADM mass and the Hawking temperature of the black hole are calculated.

Torsion and interaction of polarized photons

The contribution of the interacting vector and pseudovector torsion components to the interaction of polarized photons in an atomic sodium vapor is investigated. Estimates are obtained for the parameters of the gauge-theoretical model of gravitation.

A new class of exact solutions of the vacuum quadratic Poincar� gauge field theory

A class of algebraically special exact solutions of the vacuum quadratic Poincare gauge field theory is presented. These solutions are of type III and type N and have a nonexpanding, shear-free and twist-free geodesic repeated principal null congruence. The metric is of Kundt's class, and the torsion components are solutions of certain differential equations. The solutions have been obtained using a generalised spin coefficient formalism.

New curvature-torsion relations through decomposition of the Bianchi Identities

The Bianchi Identities relating asymmetric curvature to torsion are obtained as a new set of equations governing second-order curvature tensors. The usual contribution of symmetric curvature to the gravitational field is found to be a subset of these identities though with an added contribution due to torsion gradients. The antisymmetric curvature two-tensor is shown to be related to the divergence of the torsion. Using a model of particle-antiparticle pair production, identification of certain torsion components with electroweak fields is proposed. These components obey equations, similar to Maxwell's, that are subsets of these linear Bianchi identities. These results are shown to be consistent with gauge and other previous analyses.

Supergeometry of the coupled Yang-Mills/supergravity system in ten dimensions

Supergravity coupled to supersymmetric Yang-Mills theory in ten dimensions is constructed using the bundle of frames approach to superspace. The structure group Spin(9, 1) of simple supergravity is enlarged to Spin (9, 1) × G where G is the internal symmetry group, while the super-Yang-Mills spinor field generates additional torsion. The possibility of this coupling is traced to the fact that given the constraints on the spinorial torsion components, the Bianchi identities do not imply the complete transformation laws and equations of motion for the Fermi fields. The Chern-Simons form associated with the Yang-Mills connection arises from a constraint implied by the Bianchi identities.

Expanding Universe solutions for the Yang-Mills-Higgs system coupled to the Poincare gauge theory of gravitation

The authors found expanding Universe solutions for the Yang-Mills-Higgs system when it is coupled to the Poincare gauge theory of gravitation. The Yang-Mills fields are of the Wu-Yang-t' Hooft-Julia-Zee configurations. The torsion components for the spacetime are either constant, increasing, or oscillatory, depending on the nature of metric of the Universe.

Approximate solutions for theR +R 2 theories of gravitation: Torsion components

We search for vacuum solutions of a spherically symmetric and static field for the nineparameterR+R2 gravitational theories in a weak-field limit. In this paper approximate solutions of torsion are obtained.

Torsion and curvature in higher dimensional supergravity theories

This work is an extension of Dragon's theorems to higher dimensional space-time. We show that the first set of Bianchi identities allows us to express the curvature components in terms of torsion components and its covariant derivatives. It is also shown that the second set of Bianchi identities does not give any new information which is not already contained in the first one.

Supersymmetry breaking by torsion and the Ricci-flat squashed seven-spheres

In eleven-dimensional supergravity, unbroken supersymmetries may survive spontaneous compactification to V4 × V7 only for Freund-Rubin solutions to the equations of motion. A torsion which renders V7 Ricci-flat and breaks supersymmetry can then be induced spontaneously. Two squashed seven-spheres with torsion are obtained in this way: the flattening torsion components are constant and given by the octonion multiplication table.

Gauge fields with torsion

The Klein-Kaluza theory with a nonvanishing torsion is developed. The torsion is associated with spin and polarization of a gauge field. The electromagnetic polarization is considered as a source of additional components of torsion connected with the fifth dimension. New physical effects obtained due to this torsion are pointed out and some cosmological models are studied. It is proved that new effects are 1036 times bigger than the effects from the Einstein-Cartan theory. The usual Dirac equation is generalized to the Klein-Kaluza theory with and without torsion. The dipole electric moment of a fermion of order 10−32 cm is obtained. A new generalization of minimal coupling is proposed.

An almost simple off-shell version of SU(2) Poincaré supergravity

We present a new version of N = 2 Poincaré supergravity which is algebraically simple. We include the “non-trivial” SU(2) in the gauge group and can then impose constraints on the geometry of superspace such that all low-dimensional components of torsion and curvatures are constant. Then only a moderate number of non-linear terms appear in the supersymmetry transformation laws. This simplification makes it feasible to explicitly calculate the lagrangian for the gauge field multiplets of Yang-Mills symmetry groups and of the “non-trivial” SU(2). Propagating SU(2) gauge fields give rise to a cosmological constant and to spontaneous breaking of the supersymmetries and of the SU(2).

Formulation of 11-dimensional supergravity in superspace

We formulate on-shell 11-dimensional supergravity in superspace and express its equations of motion in terms of purely geometrical quantities. All torsion and curvature components are solved in terms of a single superfield W rstu , totally antisymmetric in its (flat vector) indices. The dimensional reduction of this formulation is expected to be related to the superspace formulation of N=8 extended supergravity and might explain the origin of the hidden (local) SU(8) and (global) E 7 symmetries present in this theory.

Analysis of Leg Loading in Snow Skiing

The complete excitation between the boot and ski was measured during skiing. Data from strain-gage force transducers mounted inside the test ski were FM transmitted to a receiving station about 3 km distant. Three skiing maneuvers (snowplow, stem christiana, parallel christiana) were tested and data from authentic falls were also recorded. Data were plotted in real-time and analyzed by digital computer. The loading histories reveal that the nonstationary loading is related to maneuver type. Torsion and bending component amplitudes, measured at the boot sole, are approximately equal to the static tibia ultimate strength in bending and torsion during both elementary skiing maneuvers and falls. In these high amplitude loading situations the skier was not injured. Data were analyzed for spectral content by the Fast Fourier Transform (FFT). Results show a 3.5 Hz cutoff frequency common to all load components and maneuvers. 3.5 Hz is a reasonable corner frequency for the human controller. Results suggest that below 3.5 Hz the skiing excitation is primarily muscle induced while above 3.5 Hz the excitation is due to ski-snow interaction.