5,558 research outputs found
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
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
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
Effects on sleep of noise from two proposed STOL aircraft
Responses, both overt behavior and those measured by electroencephalograph, to noise by eight male subjects were studied for sixteen consecutive nights. Test stimuli were: (1) The simulated sideline noise of a short takeoff and landing aircraft with blown flaps; (2) the simulated sideline noise of a STOL aircraft of turbofan design; (3) the simulated takeoff noise of the blown flap STOL aircraft; and (4) a four second burst of simulated pink noise. Responses to each noise were tested at three noise intensities selected to represent levels expected indoors from operational aircraft. The results indicate that the blown flap STOL aircraft noise resulted in 8 to 10 percent fewer sleep disturbance responses than did the turbofan STOL aircraft when noises of comparable intensities from similar maneuvers were used
A technique for automatic real time scoring of several simultaneous sleep electroencephalograms
Automatic real-time scoring of simultaneous sleep electroencephalogram
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
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
Effects of aircraft noises on the sleep of women
The electroencephalographic and behavioral responses during sleep of eight women subjects, aged 29 to 49 years, to subsonic jet flyover noise and simulated sonic booms were tested over 14 consecutive nights. Stimulus intensities were 101, 113, and 119 PNdB (as if measured out-of-doors) for the subsonic jet flyover and 0.67, 2.50, and 5.0 psf (as if measured out-of-doors) for the simulated sonic booms. It was found that the women were awakened, on the average, by approximately 42 percent of the flyover noises and by approximately 15 percent of the simulated sonic booms. Comparison of the results of this study with those of a similar study using men as subjects revealed that women were awakened more frequently by the subsonic jet flyover noise then were the men, while men were awakened more frequently by the simulated sonic boom
D=7 / D=6 Heterotic Supergravity with Gauged R-Symmetry
We construct a family of chiral anomaly-free supergravity theories in D=6
starting from D=7 supergravity with a gauged noncompact R-symmetry, employing a
Horava-Witten bulk-plus-boundary construction. The gauged noncompact R-symmetry
yields a positive (de Sitter sign) D=6 scalar field potential. Classical
anomaly inflow which is needed to cancel boundary-field loop anomalies requires
careful consideration of the gravitational, gauge, mixed and local
supersymmetry anomalies. Coupling of boundary hypermultiplets requires care
with the Sp(1) gauge connection required to obtain quaternionic Kahler target
manifolds in D=6. This class of gauged R-symmetry models may be of use as
starting points for further compactifications to D=4 that take advantage of the
positive scalar potential, such as those proposed in the scenario of
supersymmetry in large extra dimensions.Comment: 43 pages, plain Latex; Clarification of discussion and references
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Brane-world inflation without inflaton on the brane
Inspired by the Randall-Sundrum brane-world scenario, we investigate the
possibility of brane-world inflation driven not by an inflaton field on the
brane, but by a bulk, dilaton-like gravitational field. As a toy model for the
dilaton-like gravitational field, we consider a minimally coupled massive
scalar field in the bulk 5-dimensional spacetime, and look for a perturbative
solution in the anti-de Sitter (AdS) background. For an adequate range of the
scalar field mass, we find a unique solution that has non-trivial dependence on
the 5th dimensional coordinate and that induces slow-roll inflation on the
brane.Comment: 10 pages, 2 figures, final version, to be published in Phys. Rev.
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