Featured Research

from universities, journals, and other organizations

Researchers propose a new way to detect the elusive graviton

Date:
March 4, 2014
Source:
Arizona State University
Summary:
A cosmologist and a physicist have proposed that measuring minute changes in the cosmic background radiation of the universe could be a pathway of detecting the telltale effects of gravitons.

Among the four fundamental forces of nature, only gravity has not had a basic unit, or quanta, detected. Physicists expect that gravitational force is transmitted by an elementary particle called a graviton, just as the electromagnetic force is carried by the photon.

While there are deep theoretical reasons why gravitons should exist, detecting them may be physically impossible on Earth.

For example, the conventional way of measuring gravitational forces -- by bouncing light off a set of mirrors to measure tiny shifts in their separation -- would be impossible in the case of gravitons. According to physicist Freeman Dyson, the sensitivity required to detect such a miniscule distance change caused by a graviton requires the mirrors to be so massive and heavy that they'd collapse and form a black hole.

Because of this, some have claimed that measuring a single graviton is hopeless. But what if you used the largest entity you know of -- in this case the universe -- to search for the telltale effects of gravitons. That is what two physicists are proposing.

In the paper, "Using cosmology to establish the quantization of gravity," published in Physical Review D (Feb. 20, 2014), Lawrence Krauss a cosmologist at Arizona State University, and Frank Wilczek a Nobel-prize winning physicist with MIT and ASU, have proposed that measuring minute changes in the cosmic background radiation of the universe could be a pathway of detecting the telltale effects of gravitons.

Krauss and Wilczek suggest that the existence of gravitons, and the quantum nature of gravity, could be proved through some yet to be detected feature of the early universe. They describe their work in the paper "Using Cosmology to Establish the Quantization of Gravity."

"This may provide, if Freeman Dyson is correct about the fact that terrestrial detectors cannot detect gravitons, the only direct empirical verification of the existence of gravitons," Krauss said. "Moreover, what we find most remarkable is that the universe acts like a detector that is precisely the type that is impossible or impractical to build on Earth."

It is generally believed that in the first fraction of a second after the Big Bang the universe underwent rapid and dramatic growth during a period called "inflation." If gravitons exist, they would be generated as 'quantum fluctuations' during inflation.

Ultimately these would evolve, as the universe expanded, into classically observable gravitational waves, which stretch space-time along one direction while contracting it along the other direction. This would affect how electromagnetic radiation in the cosmic microwave background (CMB) radiation left behind by the Big Bang, is produced causing it to become polarized. Researchers analyzing results from the European Space Agency's Planck satellite are searching for this "imprint" of inflation in the polarization of the CMB.

Krauss said his and Wilczek's paper combines what already is known with some new wrinkles.

"While the realization that gravitational waves are produced by inflation is not new, and the fact that we can calculate their intensity and that this background might be measured in future polarization measurements of the microwave background is not new, an explicit argument that such a measurement will provide, in principle, an unambiguous and direct confirmation that the gravitational field is quantized is new," he said. "Indeed, it is perhaps the only empirical verification of this very important assumption that we might get in the foreseeable future."

Using a standard analytical tool called dimensional analysis, Wilczek and Krauss show how the generation of gravitational waves during inflation is proportional to the square of Planck's constant, a numerical factor that only arises in quantum theory. That means that the gravitational process that results in the production of these waves is an inherently quantum-mechanical phenomenon.

This implies that finding the fingerprint of gravitational waves in the polarization of CMB will provide evidence that gravitons exist and it is just a matter of time (and instrument sensitivity) to finding their imprint.

"I'm delighted that dimensional analysis, a simple but profound technique whose virtues I preach to students, supplies clear, clean insight into a subject notorious for its difficulty and obscurity," said Wilczek.

"It is quite possible that the next generation of experiments, in the coming decade or maybe even the Planck satellite, may see this background," Krauss added.


Story Source:

The above story is based on materials provided by Arizona State University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Lawrence M. Krauss, Frank Wilczek. Using cosmology to establish the quantization of gravity. Physical Review D, 2014; 89 (4) DOI: 10.1103/PhysRevD.89.047501

Cite This Page:

Arizona State University. "Researchers propose a new way to detect the elusive graviton." ScienceDaily. ScienceDaily, 4 March 2014. <www.sciencedaily.com/releases/2014/03/140304113515.htm>.
Arizona State University. (2014, March 4). Researchers propose a new way to detect the elusive graviton. ScienceDaily. Retrieved July 26, 2014 from www.sciencedaily.com/releases/2014/03/140304113515.htm
Arizona State University. "Researchers propose a new way to detect the elusive graviton." ScienceDaily. www.sciencedaily.com/releases/2014/03/140304113515.htm (accessed July 26, 2014).

Share This




More Matter & Energy News

Saturday, July 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Europe's Highest Train Turns 80 in French Pyrenees

Europe's Highest Train Turns 80 in French Pyrenees

AFP (July 25, 2014) Europe's highest train, the little train of Artouste in the French Pyrenees, celebrates its 80th birthday. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) Video provided by AP
Powered by NewsLook.com
Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
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:
from the past week

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