Featured Research

from universities, journals, and other organizations

Gravitational Wave Background

Date:
January 31, 2007
Source:
American Institute Of Physics
Summary:
In the standard model of cosmology, the early universe underwent a period of fantastic growth. This inflationary phase, after only a trillionth of a second, concluded with a violent conversion of energy into hot matter and radiation. This "reheating" process also resulted in a flood of gravitational waves.

In the standard model of cosmology, the early universe underwent a period of fantastic growth. This inflationary phase, after only a trillionth of a second, concluded with a violent conversion of energy into hot matter and radiation. This "reheating" process also resulted in a flood of gravitational waves. (Interestingly, some cosmologists would identify the "big bang" with this moment and not the earlier time=0 moment.)

Let's compare this gravitational wave background (GWB) with the more familiar cosmic microwave background (CMB). The GWB dates from the trillionth-of-a-second mark, while the CMB sets in around 380,000 years later when the first atoms formed. The CMB represents a single splash of photons which were (at that early time) in equilibrium with the surrounding atoms-in-the-making; the microwaves we now see in the sky were (before being redshifted to lower frequencies owing to the universe's expansion) ultraviolet waves and were suddenly freed to travel unimpeded through space. They are now observed to be mostly at a uniform temperature of about 3 degrees Kelvin, but the overall map of the microwave sky does bear the faint imprint of matter inhomogeneities (lumps) existing even then.

What, by contrast, does the GWB represent? It stems from three different production processes at work in the inflationary era: waves stemming from the inflationary expansion of space itself; waves from the collision of bubble-like clumps of new matter at reheating after inflation; and waves from the turbulent fluid mixing of the early pools of matter and radiation, before equilibrium among them (known as thermalization) had been achieved. The gravity waves would never have been in equilibrium with the matter (since gravity is such a weak force there wouldn't be time to mingle adequately); consequently the GWB will not appear to a viewer now to be at a single overall temperature.

A new paper by Juan Garcia-Bellido and Daniel Figueroa (Universidad Autonoma de Madrid) explain how these separate processes could be detected and differentiated in modern detectors set up to see gravity waves, such as LIGO, LISA, or BBO (Big Bang Observer). First, the GWB would be redshifted, like the CMB. But because of the GWB's earlier provenance, the reshifting would be even more dramatic: the energy (and frequency) of the waves would be downshifted by 24 orders of magnitude. Second, the GWB waves would be distinct from gravity waves from point sources (such as the collision of two black holes) since such an encounter would release waves with a sharper spectral signal. By contrast the GWB from reheating after inflation would have a much broader spectrum, centered around 1 hertz to 1 gigahertz depending on the scale of inflation.

Garcia-Bellido suggests that if a detector like the proposed BBO could disentangle the separate signals of the end-of-inflation GWB, then such a signal could be used as a probe of inflation and could help explore some fundamental issues as matter-antimatter asymmetry, the production of topological defects like cosmic strings, primoridal magnetic fields, and possibly superheavy dark matter.


Story Source:

The above story is based on materials provided by American Institute Of Physics. Note: Materials may be edited for content and length.


Cite This Page:

American Institute Of Physics. "Gravitational Wave Background." ScienceDaily. ScienceDaily, 31 January 2007. <www.sciencedaily.com/releases/2007/01/070130122115.htm>.
American Institute Of Physics. (2007, January 31). Gravitational Wave Background. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2007/01/070130122115.htm
American Institute Of Physics. "Gravitational Wave Background." ScienceDaily. www.sciencedaily.com/releases/2007/01/070130122115.htm (accessed October 1, 2014).

Share This



More Matter & Energy News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Japan Looks To Faster Future As Bullet Train Turns 50

Japan Looks To Faster Future As Bullet Train Turns 50

Newsy (Oct. 1, 2014) Japan's bullet train turns 50 Wednesday. Here's a look at how it's changed over half a century — and the changes it's inspired globally. Video provided by Newsy
Powered by NewsLook.com
US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins