Kink-boundary collisions in a two dimensional scalar field theory

In a two-dimensional toy model, motivated from five-dimensional heterotic M-theory, we study the collision of scalar field kinks with boundaries. By numerical simulation of the full two-dimensional theory, we find that the kink is always inelastically reflected with a model-independent fraction of its kinetic energy converted into radiation. We show that the reflection can be analytically understood as a fluctuation around the scalar field vacuum. This picture suggests the possibility of spontaneous emission of kinks from the boundary due to small perturbations in the bulk. We verify this picture numerically by showing that the radiation emitted from the collision of an initial single kink eventually leads to a bulk populated by many kinks. Consequently, processes changing the boundary charges are practically unavoidable in this system. We speculate that the system has a universal final state consisting of a stack of kinks, their number being determined by the initial energy

Effects on muscle tension and tracking task performance of simulated sonic booms with low and high intensity vibrational components

Effects of simulated sonic booms with high and low intensity vibrational components on tracking task performance and muscle tension in human subject

Moving Five-Branes in Low-Energy Heterotic M-Theory

We construct cosmological solutions of four-dimensional effective heterotic M-theory with a moving five-brane and evolving dilaton and T modulus. It is shown that the five-brane generates a transition between two asymptotic rolling-radii solutions. Moreover, the five-brane motion always drives the solutions towards strong coupling asymptotically. We present an explicit example of a negative-time branch solution which ends in a brane collision accompanied by a small-instanton transition. The five-dimensional origin of some of our solutions is also discussed.Comment: 16 pages, Latex, 3 eps figure

Heterotic M-Theory Cosmology in Four and Five Dimensions

We study rolling radii solutions in the context of the four- and five-dimensional effective actions of heterotic M-theory. For the standard four-dimensional solutions with varying dilaton and T-modulus, we find approximate five-dimensional counterparts. These are new, generically non-separating solutions corresponding to a pair of five-dimensional domain walls evolving in time. Loop corrections in the four-dimensional theory are described by certain excitations of fields in the fifth dimension. We point out that the two exact separable solutions previously discovered are precisely the special cases for which the loop corrections are time-independent. Generically, loop corrections vary with time. Moreover, for a subset of solutions they increase in time, evolving into complicated, non-separating solutions. In this paper we compute these solutions to leading, non-trivial order. Using the equations for the induced brane metric, we present a general argument showing that the accelerating backgrounds of this type cannot evolve smoothly into decelerating backgrounds.Comment: 15 pages, Latex, 1 eps figur

A technique for automatic real time scoring of several simultaneous sleep electroencephalograms

Automatic real-time scoring of simultaneous sleep electroencephalogram

Domain walls in Born-Infeld-dilaton background

We study the dynamics of domain walls in Einstein-Born-Infeld-dilaton theory. Dilaton is non-trivially coupled with the Born-Infeld electromagnetic field. We find three different types of solutions consistent with the dynamic domain walls. For every case, the solutions have singularity. Further more, in these backgrounds, we study the dynamics of domain walls. We qualitatively plot various form of the bulk metrics and the potential encountered by the domain walls. In many cases, depending upon the value of the parameters, the domain walls show bouncing universe and also undergo inflationary phase followed by standard decelerated expansion.Comment: 18 pages,6 figures,latex, References added, Some points clarifie

Reliability of laboratory tests of VSTOL and other long duration noises

Paired-comparison and magnitude estimations of the subjective noisiness or unacceptability of noise from fixed wing jet aircraft and simulated noise of VSTOL aircraft were obtained from groups of subjects given different instructions. These results suggest that VSTOL noises can be evaluated in terms of their noisiness or unwantedness to people with reasonable accuracy by units of the physical measures designated as PNdBM, with or without tone corrections, and dBD sub 2. Also, that consideration should be given to the use of D sub 2 as an overall frequency weighting function for sound level meters instead of the presently available A weighting. Two new units of noise measurement, PLdB and dB(E), used for predicting subjective noisiness, were found to be less accurate than PNdBM or dBD sub 2 in this regard

Experimental demonstration of a mu=-1 metamaterial lens for magnetic resonance imaging

In this work a mu=-1 metamaterial (MM) lens for magnetic resonance imaging (MRI) is demonstrated. MRI uses surface coils to detect the radiofrequency(RF) energy absorbed and emitted by the nuclear spins in the imaged object. The proposed MM lens manipulates the RF field detected by these surface coils, so that the coil sensitivity and spatial localization is substantially improved. Beyond this specific application, we feel that the reported results are the experimental confirmation of a new concept for the manipulation of RF field in MRI, which paves the way to many other interesting applications.Comment: 9 pages, 3 figure