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Dark Energy Modeled by Supercomputer

By Andrés Córdova
Epoch Times Staff
Created: July 12, 2011 Last Updated: November 23, 2011
Related articles: Science » Space & Astronomy
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Produced by the Sloan Digital Sky Survey, this three-dimensional map of the distribution of galaxies shows Earth at the center, and represents each galaxy with a single point. (M. Blanton, SDSS)

Produced by the Sloan Digital Sky Survey, this three-dimensional map of the distribution of galaxies shows Earth at the center, and represents each galaxy with a single point. (M. Blanton, SDSS)

Researchers from Ohio State University (OSU) are using a supercomputer to characterize and simplify dark energy—the cryptic force causing the ever-accelerating expansion of the universe.

Led by physicist Chris Orban, a team of experts are creating a dark matter clustering feature using Ohio Supercomputer Center (OSC) systems. This model will provide insights into dark energy’s behavior.

“Knowing how the dark matter ‘reacts’ to the expansion of the universe is crucial for learning the most about dark energy and dark matter from large astronomical surveys like the Sloan Digital Sky Survey, of which OSU is a collaborating member,” said Orban in a press release.

“In particular, there is a subtle clustering feature seen in this data set called ‘Baryon Acoustic Oscillations’ (BAO), which turns out to be very useful for constraining cosmological parameters like the equation of state of dark energy.”

The scientists have been working on this project since early 2009, amassing close to 200,000 processor hours on the OSC’s Glenn Cluster—capable of 75 trillion calculations per second—to model the appropriate conditions for the measurements.

These Baryon Acoustic Oscillations can be distinguished by measuring the cosmic microwave background, and were generated when the distribution of hot plasma shifted back and forth in the early universe.

Snapshots from cosmological simulations (left) performed on Ohio Supercomputer Center systems and a plot of the clustering of dark matter on different scales (right). (OSU)

Snapshots from cosmological simulations (left) performed on Ohio Supercomputer Center systems and a plot of the clustering of dark matter on different scales (right). (OSU)

“The BAO signature gets imprinted on the dark matter very early on, but the feature changes over cosmic time, potentially biasing its use as a cosmological tool,” said Orban.

“It’s a complicated non-linear problem, and physicists are very fond of simplifying complicated problems to gain a more in-depth understanding,” he explained. “This is exactly what we did for the first time, in our paper, using N-body simulations.”

Orban co-authored a study with OSU colleague David Weinberg, project scientist for the Sloan Survey. It is called “Self-similar Bumps and Wiggles: Isolating the Evolution of the BAO Peak with Power-law Initial Conditions,” and will be published in the journal Physical Review D.

Weinberg said guaranteeing the accuracy of their cosmological simulations will be vital in underpinning future surveys.

“For current state-of-the-art astronomical surveys, the main non-linear effects that we investigate in the paper are negligible compared to other sources of error, but next-generation surveys will need to be far more sophisticated in this regard,” said Weinberg in the release.

“This places the utmost importance on making reliable and precise predictions for these non-linear effects, a task which cosmological N-body simulations are in many ways well-suited to do.”




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