Gravity  

A research paper has proposed, with supporting mathematical proof, a device with which to create detectable gravitational fields. Put into working practice the theory would mean scientists could manipulate gravity the same way they do magnetic fields today, which could produce whole new scientific breakthroughs.

Today, researchers study gravitational fields passively. They observe and try to understand existing gravitational fields produced by large inertial masses, such as stars or the Earth, without being able to change them as they can do with magnetic fields, for example.

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This frustration that led André Füzfa, from Namur University in Belgium to attempt a revolutionary approach: creating gravitational fields at will from well-controlled magnetic fields and observing how these magnetic fields could bend space-time.

In his article, Füzfa has proposed, with supporting mathematical proof, a device with which to create detectable gravitational fields. This device is based on superconducting electromagnets and therefore relies on technologies routinely used, for example, at CERN or the ITER reactor.

Although this experiment would require major resources, if conducted, it could be used to test Einstein’s theory of general relativity. If successful, it would certainly be a major step forward in physics: the ability to produce, detect and, ultimately, control gravitational fields. People could then produce gravitational interaction in the same way as the other three fundamental interactions (e.g. electromagnetic and strong and weak nuclear forces).

Füzfa concludes in his paper: "The generation of artificial gravitational fields withelectric currents could be in principle detected through the induced change in space-time geometry that results in a purely classical deflexion of light by magnetic fields. This effect does not invoke any new physics, as it is a consequence of the equivalence principle."

"It could lead to amazing applications like the controlled emission of gravitational waves with large alternative electric currents."

"Would this technology be developed, it could lead to amazing applications like the controlled emission of gravitational waves with large alternative electric currents," states Füzfa.  "Gravity would then cease to be the last of the four fundamental forces not under control by human beings."

This could usher gravitation into a new experimental and industrial era.

Until now, a scientific advance like this was a dream of science fiction, but it could open up many new applications tomorrow, for example in the field of telecommunications with gravitational waves: imagine calling the other side of the world without going through satellite or terrestrial relays.

SOURCE  Numur University

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Physics  

Rumors are swirling that the Laser Interferometer Gravitational-Wave Observatory experiment has actually observed gravitational waves predicted by Einstein's General Theory of Relativity over 100 years ago for the very first time and may be close to formally announcing the findings.

A major cosmological experiment designed to hunt for gravitational waves—ripples in the fabric of spacetime first predicted by Albert Einstein—has observed them directly for the very first time and may be close to formally announcing the findings. If confirmed, this would be one of the most significant physics discoveries of the last century. While no official announcement has been made, physicist Lawrence Krauss has posted a few Tweets that amount to a scientific spilling of the beans.

According to Einstein's general theory of relativity, gravity is how mass deforms the shape of space: near any massive body, the fabric of space becomes curved. But this curving does not always stay near the massive body. In particular, Einstein realized that the deformation can propagate throughout the Universe, just as seismic waves propagate in Earth's crust. Unlike seismic waves, however, gravitational waves can travel in empty space — and they do so at the speed of light.

My earlier rumor about LIGO has been confirmed by independent sources. Stay tuned! Gravitational waves may have been discovered!! Exciting.

— Lawrence M. Krauss (@LKrauss1) January 11, 2016

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The Laser Interferometer Gravitational-Wave Observatory (LIGO) has been hunting for gravitational waves since 2002 with no luck. But a more powerful, advanced LIGO that's about three times more sensitive than the original detector started operating in just last fall.

"Gravitational waves may have been discovered!! Exciting."

LIGO is designed to open the field of gravitational-wave astrophysics through the direct detection of gravitational waves. The multi-kilometer-scale gravitational wave detectors use laser interferometry to measure the minute ripples in space-time caused by passing gravitational waves.

These phenomena could have been created from cataclysmic cosmic sources like the merging of pairs of neutron stars or black holes, or by supernovae. LIGO consists of two widely separated interferometers within the United States—one in Hanford, Washington and the other in Livingston, Louisiana—operated in unison.

The confirmed discovery of gravity waves would further support the theory of inflation — the idea that in the first few moments the universe existed, it underwent a rapid and incredibly massive expansion. That kind of rapid expansion would almost certainly leave behind ripples through spacetime and imprinting the cosmic background radiation.

The most important thing about this discovery, if proven, is that it could be a way to link up quantum and classical physics—a step to a Theory of Everything for physics.

SOURCE  Tech Insider Video Source: Nature

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Cosmology  

The idea that a universe with gravity can be described by a quantum field theory in fewer dimensions, the 'holographic principle,' has been used for years as a mathematical tool in strange curved spaces. New results suggest that the holographic principle also holds in flat spaces. Our own universe could in fact be two dimensional and only appear to be three dimensional.

When we experience the world, there isn't much doubt that the universe appears three dimensional. But one of the most fruitful theories of theoretical physics in the last two decades is challenging this assumption.

The "holographic principle” asserts that a mathematical description of the universe actually requires one fewer dimension than it seems. What we perceive as three dimensional may just be the image of two dimensional processes on a huge cosmic horizon.

Up until now, this principle has only been studied in exotic spaces with negative curvature. This is interesting from a theoretical point of view, but such spaces are quite different from the space in our own universe. Now, results obtained by scientists at TU Wien (Vienna) suggest that the holographic principle even holds in a flat spacetime.

Everybody knows holograms from credit cards or banknotes. They are two dimensional, but to us they appear three dimensional. Our universe could behave quite similarly: “In 1997, the physicist Juan Maldacena proposed the idea that there is a correspondence between gravitational theories in curved anti-de-sitter spaces on the one hand and quantum field theories in spaces with one fewer dimension on the other”, says TU Wien's Daniel Grumiller.

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Gravitational phenomena are described in a theory with three spatial dimensions, the behaviour of quantum particles is calculated in a theory with just two spatial dimensions – and the results of both calculations can be mapped onto each other. Such a correspondence is quite surprising. It is like finding out that equations from an astronomy textbook can also be used to repair a CD-player. But this method has proven to be very successful. More than ten thousand scientific papers about Maldacena’s “AdS-CFT-correspondence” have been published to date.

For theoretical physics, this is extremely important, but it does not seem to have much to do with our own universe. Apparently, we do not live in such an anti-de-sitter-space. These spaces have quite peculiar properties. They are negatively curved, any object thrown away on a straight line will eventually return. “Our universe, in contrast, is quite flat – and on astronomic distances, it has positive curvature”, says Grumiller.

However, Grumiller has suspected for quite some time that a correspondence principle could also hold true for our real universe. To test this hypothesis, gravitational theories have to be constructed, which do not require exotic anti-de-sitter spaces, but live in a flat space. For three years, he and his team have been working on that, in cooperation with the University of Edinburgh, Harvard, IISER Pune, the MIT and the University of Kyoto. Now Grumiller and colleagues from India and Japan have published an article in the journal Physical Review Letters, confirming the validity of the correspondence principle in a flat universe.

"If quantum gravity in a flat space allows for a holographic description by a standard quantum theory, then there must by physical quantities, which can be calculated in both theories – and the results must agree."

“If quantum gravity in a flat space allows for a holographic description by a standard quantum theory, then there must by physical quantities, which can be calculated in both theories – and the results must agree”, says Grumiller. Especially one key feature of quantum mechanics –quantum entanglement – has to appear in the gravitational theory.

When quantum particles are entangled, they cannot be described individually. They form a single quantum object, even if they are located far apart. There is a measure for the amount of entanglement in a quantum system, called “entropy of entanglement”. Together with Arjun Bagchi, Rudranil Basu and Max Riegler, Grumiller managed to show that this entropy of entanglement takes the same value in flat quantum gravity and in a low dimension quantum field theory.

“This calculation affirms our assumption that the holographic principle can also be realized in flat spaces. It is evidence for the validity of this correspondence in our universe”, says Max Riegler (TU Wien). “The fact that we can even talk about quantum information and entropy of entanglement in a theory of gravity is astounding in itself, and would hardly have been imaginable only a few years back. That we are now able to use this as a tool to test the validity of the holographic principle, and that this test works out, is quite remarkable”, says Grumiller.

This work doesn't prove that we are indeed living in a hologram – but apparently there is growing evidence for the validity of the correspondence principle in our own universe.


SOURCE  TU Wien (Vienna)

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