Physics  College of Engineering 

Khanna publishes in a new APS journal, Physical Review X

Physical Review X (PRX) is a new, open-access, online-only journal that boasts a rapid and high-standard peer-review process and is open to all areas of physics. Its open-access, online model allows for completely free availability all over the globe, thus allowing all published articles to receive a very high degree of exposure.

Prof. Khanna collaborated with a colleague from Caltech to publish the first gravity-related paper in this new journal. The research published in this article was supported by the National Science Foundation and the US Air Force. The article is titled "Null Infinity Waveforms from Extreme-Mass-Ratio Inspirals in Kerr Spacetime" and is freely available at the location below:

A popular summary of the article appears below:

When a star plunges into a supermassive black hole like the one at the center of our Galaxy, space-time oscillations called gravitational waves are generated that carry information about the plunge and could be detected on Earth. These catastrophic events take place thousands and millions of light years away from us. However, when such events are simulated numerically, the large astrophysical domain is approximated by a small computational domain. This leads to conceptual and practical difficulties and introduces significant systematic errors in the predicted signals to be observed on Earth.

Recently, a clean and practical technique has been developed which allows simulations on infinite space-time domains on a finite computational layer. We apply this new "hyperboloidal-layer" technique to the computation of gravitational waves emitted from the in-spiraling of a small black hole (represented by a point particle) into a supermassive, rotating black hole (represented by a fixed space-time metric).

The most remarkable aspect of the new technique is that it gains an increase in accuracy at a negative cost: It computes more accurate gravitational waveforms with less computational resources than the standard methods. In a long-time simulation of an in-spiraling process that includes more than 10,000 orbital cycles of the small black hole, we demonstrate a 5000-fold gain in efficiency. When the central supermassive black hole has a mass comparable to the one assumed in the center of our Galaxy, the in-spiraling would take roughly a year in real time whereas our numerical simulation takes less than a day of computer time. Our technique opens the possibility of constructing gravitational waveform templates by scanning a large parameter space, which will aid experimental detection of gravitational waves. It also suggests the hyperboloidal-layer technique might be useful in other numerical computations on unbounded domains as performed in applied mathematics and computational engineering.

Author: "Gaurav Khanna [Contact]"
Date: 12-12-2011

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