Many-Brane Extention of the Randall-Sundrum Solution

Recently, Randall and Sundrum proposed a static solution to Einstein's equations in five spacetime dimensions with two 3-branes located at the fixed points of $S^1/Z_2$ to solve the hierarchy problem. We extend the solution and construct static and also inflationary solutions to Einstein's equations in five spacetime dimensions, one of which is compactified on $S^1$, with any number of 3-branes whose locations are taken to be arbitrary. We discuss how the hierarchy problem can be explained in our model.Comment: PTPTeX 1.0(preprint style), 8 pages, no figures, references and typos correcte

Effective reduction of magnetisation losses in copper-plated multifilament coated conductors using spiral geometry

We wound copper-plated multifilament coated conductors spirally on a round core to decouple filaments electromagnetically under ac transverse magnetic fields and measured their magnetisation losses. Although the coated conductors were plated with copper, which connects all filaments electrically and allows current sharing among them, the spiral geometry decoupled filaments similar to the twist geometry, and the magnetisation loss was reduced effectively by the multifilament structure. The measured magnetisation loss of a 4 mm wide, 10-filament coated conductor with a 20 μm thick copper wound spirally on a 3 mm core was only 7% of that of the same 10-filament coated conductor with a straight shape under an ac transverse magnetic field with an amplitude and frequency of 100 mT and 65.44 Hz, respectively. We separated the measured magnetisation losses into hysteresis and coupling losses and discussed the influence of filament width, copper thickness, and core diameter on both losses. We compared the hysteresis losses with the analytical values given by Brandt and Indenbom and compared the coupling losses with the values calculated using a general expression of coupling loss with the coupling time constants and geometry factors

Vacuum Structure of Twisted Scalar Field Theories on M^{D-1} \otimes S^1

We study scalar field theories on M^{D-1} \otimes S^1, which allow to impose twisted boundary conditions for the S^1 direction, in detail and report several interesting properties overlooked so far. One of characteristic features is the appearance of critical radii of the circle S^1. A phase transition can occur at the classical level or can be caused by quantum effects. Radiative corrections can restore broken symmetries or can break symmetries for small radius. A surprising feature is that the translational invariance for the S^1 direction can spontaneously be broken. A particular class of coordinate-dependent vacuum configurations is clarified and the O(N) \phi^4 model on M^{D-1}\otimes S^1 is extensively studied, as an illustrative example.Comment: 27 pages, 4 figures, LaTex2

Shielding current in copper-plated multifilament coated conductor wound into single pancake coil and exposed to normal magnetic field

A single pancake coil wound with a copper-plated multifilament coated conductor, with four filaments, was put in a cusp magnetic field, and the magnetic field was measured near the coil at 30 K. A similar experiment was performed by using another reference single pancake coil wound with a monofilament coated conductor. Numerical electromagnetic field analyses of these coils were carried out, and the calculated shielding current-induced fields (SCIFs) were compared with the measured ones in both coils. The temporal behaviour of the calculated SCIF in the coil wound with the four-filament coated conductor was also compared with a series of exponential components, in which a coupling time constant extrapolated from short sample experiments was used as the time constant of the primary component. Current distributions in the coated conductors wound into the pancake coils were visualised. In particular, the temporal behaviours of the current distributions in the four-filament coated conductor and their influence on the SCIF were discussed

Thermal Runaway of Conduction-Cooled Monofilament and Multifilament Coated Conductors

We experimentally studied the thermal runawayinitiating at a low critical current ( I c ) part. This low I c part is determined by the combination of two reasons in a real coil: (a) the unavoidable defects caused by the manufacturing process, which reduce local critical currents (and might not be uniform across the width of a coated conductor) and (b) the magnetic field distribution along the coated conductor. To simulate the thermal runaway using a short monofilament/multifilament REBa₂Cu₃Oy (RE-123) coated conductor, we artificially created a local defect (low I c part) in a short sample by pressing using a drill bit (creating a defect close to one edge of a coated conductor) or bending (creating a uniform defect across the width of a coated conductor). The sample of the coated conductor was conduction-cooled to 30 K, and a magnetic field was applied (μ₀ H up to 2 T) perpendicular to the wide face of the conductor to control its critical current. Transverse voltages in a multifilament coated conductor were measured to obtain the transverse currents among the filaments through the copper layer. Thermal runaway currents (operating currents above which thermal runaway initiates) of the monofilament sample and those of the multifilament sample with additional Joule loss due to the transverse currents were determined and compared to study the effect of the transverse currents on the initiation of thermal runaway in the multifilament coated conductor. Experiments on the protection against thermal runaway were conducted. When a normal voltage (over a preset threshold) was detected, the supplied current would be decreased exponentially. The thresholds for protecting monofilament and multifilament coated conductors from degradation after thermal runaway were compared