Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Gravity wave "smoking gun" fizzles, according to Case Western Reserve University physics researchers

17.04.2008
But gravitational waves may be more sensitive probe of early universe physics than previously thought

A team of researchers from Case Western Reserve University has found that gravitational radiation—widely expected to provide "smoking gun" proof for a theory of the early universe known as "inflation"—can be produced by another mechanism.

According to physics scholars, inflation theory proposes that the universe underwent a period of exponential expansion right after the big bang. A key prediction of inflation theory is the presence of a particular spectrum of "gravitational radiation"—ripples in the fabric of space-time that are notoriously difficult to detect but believed to exist nonetheless.

"If we see a primordial gravitational wave background, we can no longer say for sure it is due to inflation," said Lawrence Krauss, the Ambrose Swasey Professor of Physics and Astronomy at Case Western Reserve.

At the same time the researchers find that gravitational waves are a far more sensitive probe of new physics near the highest energy scale of interest to particle physicists than previously envisaged. Thus their work provides strong motivation for the ongoing quest to detect primordial gravitational radiation.

Krauss, along with Case Western Reserve colleagues Katherine Jones-Smith, a graduate student, and Harsh Mathur, associate professor of physics, present these findings in an article "Nearly Scale Invariant Spectrum of Gravitational Radiation from Global Phase Transitions" published in Physical Review Letters this month.

Inflation theory arose in the 1980s as a means to explain some features of the universe that had previously baffled astronomers such as why the universe is so close to being flat and why it is so uniform. Today, inflation remains the best way to theoretically understand many aspects of the early universe, but most of its predictions are sufficiently malleable that consistency with observation cannot be considered unambiguous confirmation.

Enter gravitational radiation—the key prediction of inflation theory is the presence of a particular spectrum of gravitational radiation. Detection of this spectrum was regarded among physicists as "smoking gun" evidence that inflation did in fact occur, billions of years ago.

In 1992 Krauss, then at Yale, argued that another mechanism besides inflation could give rise to precisely the same spectrum of gravitational radiation as is predicted by inflation. The argument given by Krauss in 1992 provided a rough estimate of the spectrum.

Last year Krauss teamed up with Case Western Reserve colleagues, Jones-Smith, a graduate student in physics, and Mathur, associate professor of physics, to do a more complete calculation. They found that the exact calculation predicts the signal to be much stronger than the rough estimate.

Describing their results, Krauss said, "It is shocking and surprising when you find the answer is 10,000 times bigger than the rough estimate and could possibly produce a signal that mimics the kind produced by inflation."

Gravitational radiation is a prediction of Einstein's Theory of General Relativity. According to the theory, whenever large amounts of mass or energy are shifting around, it disrupts the surrounding space-time and ripples emanate from the region where the mass/energy shift.

These space-time ripples, known as gravitational radiation, are imperceptible on the human scale, but highly sensitive experiments (such as the Laser Interferometer Gravitational Wave Observatory (LIGO) in Livingston, La.) are designed precisely to look for such radiation and are the only hope for detecting them directly.

However, gravitational radiation from the early universe can also be detected indirectly through its effect on the cosmic microwave background (CMB) radiation (relic radiation from the Big Bang which permeates all space). The radiation from the CMB would become polarized in the presence of gravitational radiation. Detecting such polarized light is the mission of a satellite based experiment (Planck) set to launch in 2009.

The gravitational radiation produced by either inflation or the mechanism proposed by Jones-Smith, Krauss and Mathur would imprint itself on the CMB and be detected as polarization. Until now it was widely believed that a detection of polarized light from the CMB was a "smoking gun" for inflation theory. But with the publication of their recent paper in Physical Review Letters, Krauss and co-workers have raised the issue of whether that polarized light can be unambiguously tied to inflation.

The mechanism proposed by Krauss and coworkers invokes a phenomenon called "symmetry breaking" that is a central part of all theories of fundamental particle physics, including the so-called standard model describing the three non-gravitational forces known to exist. Here, a "scalar field" (similar to an electric or magnetic field) becomes aligned as the universe expands. But as the universe expands each region over which the field is aligned comes into contact with other regions where the field has a different alignment. When that happens the field relaxes into a state where it is aligned over the entire region and in the process of relaxing it emits gravitational radiation.

For more information contact Susan Griffith, 216.368.1004.

Susan Griffith | EurekAlert!
Further information:
http://www.case.edu

More articles from Physics and Astronomy:

nachricht When helium behaves like a black hole
22.03.2017 | University of Vermont

nachricht Astronomers hazard a ride in a 'drifting carousel' to understand pulsating stars
22.03.2017 | International Centre for Radio Astronomy Research

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Pulverizing electronic waste is green, clean -- and cold

22.03.2017 | Materials Sciences

Astronomers hazard a ride in a 'drifting carousel' to understand pulsating stars

22.03.2017 | Physics and Astronomy

New gel-like coating beefs up the performance of lithium-sulfur batteries

22.03.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>