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Full-Text Articles in Physics

Kinematic Effects In Large Transport Aircraft, Shem Malmquist, Dennis Vincenzi, Dahai Liu Nov 2014

Kinematic Effects In Large Transport Aircraft, Shem Malmquist, Dennis Vincenzi, Dahai Liu

Dahai Liu

The control of an aircraft relies on sensory feedback. It follows that any aspect that could create a situation where that feedback is faulty can lead to unintended outcomes. The size of very large jet aircraft can result in kinematic effects that impact the perceptions of the flight crew. Due to the large amount of inertia involved, coupled with aerodynamic factors, when the aircraft pitch (θ) is initially changed, the short term actual motion of the aircraft, as viewed from the center of gravity, remains relatively unchanged. As a consequence of aircraft design, this results in the flight deck changing …


Some Mathematical Problems In Numerical Relativity, Maria Babiuc-Hamilton, B´Ela Szilagyi, Jeffrey Winicour Jun 2014

Some Mathematical Problems In Numerical Relativity, Maria Babiuc-Hamilton, B´Ela Szilagyi, Jeffrey Winicour

Maria Babiuc-Hamilton

The main goal of numerical relativity is the long time simulation of highly nonlinear spacetimes that cannot be treated by perturbation theory. This involves analytic, computational and physical issues. At present, the major impasses to achieving global simulations of physical usefulness are of an analytic/ computational nature. We present here some examples of how analytic insight can lend useful guidance for the improvement of numerical approaches.


Binary Black Hole Waveform Extraction At Null Infinity, Maria Babiuc-Hamilton, Jeffrey Winicour, Yosef Zlochower Jun 2014

Binary Black Hole Waveform Extraction At Null Infinity, Maria Babiuc-Hamilton, Jeffrey Winicour, Yosef Zlochower

Maria Babiuc-Hamilton

In this paper, we present a work in progress toward an efficient and economical computational module which interfaces between Cauchy and characteristic evolution codes. Our goal is to provide a standardized waveform extraction tool for the numerical relativity community which will allow CCE to be readily applied to a generic Cauchy code. The tool provides a means of unambiguous comparison between the waveforms generated by evolution codes based upon different formulations of the Einstein equations and different numerical approximation.


Gravitational Wave Extraction Based On Cauchy–Characteristic Extraction And Characteristic Evolution, Maria Babiuc-Hamilton, Yosef Zlochower, Béla Szilágyi, Ian Hawke Jun 2014

Gravitational Wave Extraction Based On Cauchy–Characteristic Extraction And Characteristic Evolution, Maria Babiuc-Hamilton, Yosef Zlochower, Béla Szilágyi, Ian Hawke

Maria Babiuc-Hamilton

We implement a code to find the gravitational news at future null infinity by using data from a Cauchy code as boundary data for a characteristic code. This technique of Cauchy–characteristic extraction (CCE) allows for the unambiguous extraction of gravitational waves from numerical simulations. We first test the technique on non-radiative spacetimes: Minkowski spacetime, perturbations of Minkowski spacetime and static black hole spacetimes in various gauges. We show the convergence and limitations of the algorithm and illustrate its success in cases where other wave extraction methods fail. We further apply our techniques to a standard radiative test case for wave …


Testing Numerical Evolution With The Shifted Gauge Wave, Maria Babiuc-Hamilton, Jeffrey Winicour, B´Ela Szilágyi Jun 2014

Testing Numerical Evolution With The Shifted Gauge Wave, Maria Babiuc-Hamilton, Jeffrey Winicour, B´Ela Szilágyi

Maria Babiuc-Hamilton

Computational methods are essential to provide waveforms from coalescing black holes, which are expected to produce strong signals for the gravitational wave observatories being developed. Although partial simulations of the coalescence have been reported, scientifically useful waveforms have so far not been delivered. The goal of the AppleswithApples (AwA) Alliance is to design, coordinate and document standardized code tests for comparing numerical relativity codes. The first round of AwA tests has now been completed and the results are being analyzed. These initial tests are based upon the periodic boundary conditions designed to isolate performance of the main evolution code. Here …