How do you know if you ran through a wall? Testing the nature of dark energy and dark matter

January 7, 2013 by Paul Preuss, Lawrence Berkeley National Laboratory

When Earth crosses a domain wall, the Global Network of Optical Magnetometers for Exotic Physics (GNOME) could detect the event using four magnetometers (Northern Hemisphere in this sketch) to determine the normal velocity of the wall and predict its passing at other locations. One or more remaining magnetometers would verify the prediction and the measurements.
(Phys.org)—Researchers from Canada, California, and Poland have devised a straightforward way to test an intriguing idea about the nature of dark energy and dark matter. A global array of atomic magnetometers – small laboratory devices that can sense minute changes in magnetic fields – could signal when Earth passes through fractures in space known as domain walls. These structures could be the answer to the universe's darkest mysteries.

Dark energy opposes the of matter and causes the to accelerate; it's thought to account for three-quarters of the universe's mass-energy. Another fifth is dark matter, sharing nothing with the remaining five percent of "ordinary" matter except gravitational attraction. There are plenty of theoretical ideas to explain dark matter and dark energy, but there's little to help scientists choose among them.

An early candidate for both is a hypothetical particle called the . Arising from a field theory proposed in 1977 as the solution to quite a different problem in , axions were quickly recognized as possible constituents of dark matter. Soon after dark energy was discovered in 1998, theorists realized that axions might be the key to dark energy as well.

The field theory that gives rise to axion-like particles can also give rise to – boundaries between distinct regions of space with different properties, analogous to in crystalline alloys. As the universe expanded and cooled, a space-filling network of energy-storing domain walls may have formed, connecting large spatial domains of the same . If Earth crossed such a boundary, the properties of its atoms might be briefly affected. But what are the chances that that could happen? And if it did, how could it be detected?

Maxim Pospelov, a particle theorist at Canada's University of Victoria and Perimeter Institute for Theoretical Physics in Waterloo, has an interest in such defects, and Dmitry Budker of Berkeley Lab's Nuclear Science Division and UC Berkeley's Department of Physics is a leader in constructing atomic magnetometers. They and their colleagues, Szymon Pustelny and Micah Ledbetter at UC Berkeley, Derek Jackson Kimball of Cal State University East Bay, and Wojciech Gawlik of the Jagiellonian University in Kraków, estimate that chances of encountering domain walls are good.

Although a single magnetometer would have no hope of distinguishing an exotic event like the passing of a domain wall from mundane sources of spurious noise, a domain wall could be unambiguously detected with five magnetometers. Four, widely spaced, could calculate the wall's speed and direction and the fifth could check the prediction.

Budker and Ledbetter have built one of two magnetometers already in place in Berkeley, which measures weak external fields by seeing how they affect the nuclear spin orientation of a collection of atoms. Another placed in Kraków uses a different principle. Both are synchronized by GPS and act as a prototype for the proposed Global Network of Optical Magnetometers for Exotic Physics (GNOME).

Explore further: Euclid mission gets go-ahead to probe Universe's darkest secrets

More information: For more information on the GNOME proposal, visit arxiv.org/abs/1205.6260

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6 comments

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mouloud_aitkaci
3.6 / 5 (9) Jan 07, 2013
Dark energy was never "discovered", it is completely hypothetical. You can reformulate by saying: dark energy was "postulated".
Shootist
3 / 5 (6) Jan 07, 2013
Dark energy was never "discovered", it is completely hypothetical. You can reformulate by saying: dark energy was "postulated".


don't be so pedantic.

Saying dark energy is just easier than saying, "a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe."
Torbjorn_Larsson_OM
4.2 / 5 (6) Jan 07, 2013
We can expect a spat of papers on axions as DM candidates, as the early LHC results exclude an easy observation of supersymmetry WIMP candidates.

However, axions are not encouraged by WMAP results, at most 25 % and more likely a vanishing contribution, early WMAP gave 4 %, of the CMB fluctuations can be predicted by it.

[ http://arxiv.org/...3402.pdf ]

So no DM candidate, and I assume less likely a DE candidate as well.

@ mouloud_aitkaci, Shootist, natello: You are all wrong.

DE is an observation, a result of theory, under the inflationary standard cosmology, and the latest WMAP results gives an uncertainty of ~1.5 % of its value.

It is also a hypothesis of cosmological constant under the same theory, which in turn is given by the dominant theory of vacuum energy.

[ http://lambda.gsf...ults.pdf ]
Torbjorn_Larsson_OM
5 / 5 (1) Jan 07, 2013
@ rubberman: DM doesn't appear to have charge. But remember that quantum mechanics (or rather quantum field theory) splits quantum properties.

It is like the neutrino: no charge, small magnetic moment at best [ http://arxiv.org/...13v1.pdf ], interacts weakly, by gravity, by collision with others and by annihilation with self.

It is relatively cold (large mass) though, so the hot (small mass) neutrinos isn't it.
vacuum-mechanics
1 / 5 (1) Jan 07, 2013
(Phys.org)—Researchers from Canada, California, and Poland have devised a straightforward way to test an intriguing idea about the nature of dark energy and dark matter. A global array of atomic magnetometers – small laboratory devices that can sense minute changes in magnetic fields – could signal when Earth passes through fractures in space known as domain walls. These structures could be the answer to the universe's darkest mysteries.

This seems to be quite a big and complicate method to do! Maybe this simple device could also do as an indirect test (the same way as testing neutrino's existence)…
http://www.vacuum...14〈=en
yash17
2 / 5 (4) Jan 07, 2013
Dark energy? That energy is really there and isn't dark. We can study it. Those all dynamics in cosmos is by respect to that energy and not by imaginary space expanding (current most reliable theory).

Dark matter in cosmos functions as cosmic atmosphere. It continuously intrudes galaxies. The major amounts of it become cloud of source of new stars constructing in galaxies. That's why galaxies keep building new stars. As an example, Milky Way keeps producing about 10 stars per year. At the same time, minor amounts of dark matter keep converting into CMBR.

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