358 research outputs found
BPS States in 10+2 Dimensions
We discuss a (10+2)D N=(1,1) superalgebra and its projections to M-theory,
type IIA and IIB algebras. From the complete classification of a second-rank
central term valued in the so(10,2) algebra, we find all possible BPS states
coming from this term. We show that, among them, there are two types of
1/2-susy BPS configurations; one corresponds to a super (2+2)-brane while
another one arises from a nilpotent element in so(10,2).Comment: 31 pages, Latex, typos corrected, references adde
Multi-Field Generalisations of the Klein-Gordon Theory associated with p-Branes
The purpose of this article is to initiate a study of a class of Lorentz
invariant, yet tractable, Lagrangian Field Theories which may be viewed as an
extension of the Klein-Gordon Lagrangian to many scalar fields in a novel
manner. These Lagrangians are quadratic in the Jacobians of the participating
fields with respect to the base space co-ordinates. In the case of two fields,
real valued solutions of the equations of motion are found and a phenomenon
reminiscent of instanton behaviour is uncovered; an ansatz for a subsidiary
equation which implies a solution of the full equations yields real solutions
in three-dimensional Euclidean space. Each of these is associated with a
spherical harmonic function.Comment: 13 pages, Late
Integrable Top Equations associated with Projective Geometry over Z_2
We give a series of integrable top equations associated with the projective
geometry over Z_2 as a (2^n-1)-dimensional generalisation of the 3D Euler top
equations. The general solution of the (2^n-1)D top is shown to be given by an
integration over a Riemann surface with genus (2^{n-1}-1)^2.Comment: 8 pages, Late
Higher-dimensional WZW Model on K\"ahler Manifold and Toroidal Lie Algebra
We construct a generalization of the two-dimensional Wess-Zumino-Witten model
on a -dimensional K\"ahler manifold as a group-valued non-linear sigma
model with an anomaly term containing the K\"ahler form. The model is shown to
have an infinite-dimensional symmetry which generates an -toroidal Lie
algebra. The classical equation of motion turns out to be the
Donaldson-Uhlenbeck-Yau equation, which is a -dimensional generalization of
the self-dual Yang-Mills equation.Comment: 12 pages, Late
Order 1/N3 corrections to the conformal anomaly of the (2,0) theory in six dimensions
Using Supergravity on AdS7Ă—S4 we calculate the bulk one-loop contribution to the conformal anomaly of the (2,0) theory describing N coincident M5 branes. When this is added to the tree-level result, and an additional subleading order contribution calculated by Tseytlin, it gives an expression for the anomaly that interpolates correctly between the large N theory and the free (2,0) tensor theory corresponding to N=1. Thus we can argue that we have identified the exact N-dependence of the anomaly, which may have a simple protected form valid away from the large N limit
New Vector Field and BRST Charges in 2-form Einstein Gravity
A new vector field is introduced into 2-form Einstein gravity in four
dimensions to restore a large symmetry of its topological version. Two
different expressions for the BRST charge are given in the system: one of them
associated with a set of irreducible symmetries and the other with a set of
on-shell reducible symmetries.Comment: 9 pages, phyzzx, TIT/HEP-206/COSMO-2
SMC Development Guidelines for Axial Flux PM Machines Employing Coreless Rotor Structure for Enhancing Efficiency Based on Experimental Results
In recent years, there has been growing demand for flat electrical machines in order to minimize system size while also maintaining high efficiency. In general, axial flux machines (AFMs) are more suitable for flat form than radial flux machines (RFMs). AFMs usually employ a soft magnetic composite (SMC) for the stator core, and their efficiency can be improved by employing an SMC that has low iron loss. However, this reduces the average torque because there is generally a tradeoff relationship between iron loss and magnetic permeability in SMCs. This article, therefore, proposes an AFM with a coreless rotor structure in which the torque performance is not easily affected by the permeability of the SMC. This article aims to reveal the ideal SMC characteristics for high efficiency in AFMs. First, many virtual SMC materials with different iron loss and permeability are used for simulations of AFMs in order to investigate sensitivity to material properties. The simulations by virtual SMCs take into account the experimental increase in the iron loss. As a result, guidelines for developing SMCs are constructed based on the experimental results. Finally, prototype AFMs employing new SMCs developed by following the guidelines are shown, and it is found that they offer higher efficiency in all operating area than conventional AFMs. In particular, one prototype achieves an extremely high efficiency of over 96% at 6000 r/min, 0.8 Nm in experiments
A Proposal of an Axial-Flux Permanent-Magnet Machine Employing SMC Core With Tooth-Tips Constructed by One-Pressing Process: Improving Torque and Manufacturability
This study aims to improve the torque performance and manufacturability of axial-flux permanent magnet (AFPM) machines. Hence, we propose a novel AFPM machine that employs a soft magnetic composite (SMC) core with tooth-tips constructed by a one-pressing process and die. In this paper, the proposed AFPM machine is compared to two conventional AFPM machines using an SMC core. One of them has open-slot structure without tooth-tips. Another model employs an SMC core with tooth-tips pressed by a conventional pressing process that requires multiple operations and dies. As a result of the comparison, the proposed AFPM machine realizes a much higher torque than the two conventional machines. Additionally, the manufacturability of an SMC core with tooth-tips pressed by the proposed method is superior to the conventional one because the proposed structure can be realized by the one-pressing process and die. Furthermore, two prototypes of the proposed AFPM machine and the conventional one with an open-slot structure are fabricated, and then, they are compared by experiments. Consequently, the proposed AFPM machine achieves a 15.7% higher torque than that of the conventional machine using an open-slot structure. Finally, this paper presents an improved design of an AFPM machine with SMC cores using the proposed pressing process. As a result, the proposed AFPM realizes a 20% larger torque than that of a conventional model employing an open-slot structure
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