On the Nature of Things | Forum

Heracleum Persicum wrote:.

The beauty of this .. for certain these kind of sciences, very high level physics or mathematics, theoretical stuff, no laboratory, no instrument, nothing more than a pencil and sheet of paper needed

Einstein, afaik, developed all his theories by "day dreaming" .. he said (something to that effect) that “Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand.”

Heracleum Persicum wrote: To prove or disprove those theories you need instruments and laboratories .. though, testing and validating some of Einstein's theories needed very simple tests .. the beauty is in the simplicity

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Typhoon wrote:
Mathematics, yes. However, in the case of physics developing a theory based on thought experiments alone is the very rare exception.

Typhoon wrote:A new test of GR

And a strike against "spactime foam" theories attempting to unify GR with QFT.

Doc wrote:

Typhoon wrote:A new test of GR

And a strike against "spactime foam" theories attempting to unify GR with QFT.

Question CS How would there being no quantum foam effect things like virtual particles? Would that eliminate the possibility of their existence? Or would it just mean that there is a different explanation of where they come from?

Typhoon wrote:

Doc wrote:

Typhoon wrote:A new test of GR

And a strike against "spactime foam" theories attempting to unify GR with QFT.

Question CS How would there being no quantum foam effect things like virtual particles? Would that eliminate the possibility of their existence? Or would it just mean that there is a different explanation of where they come from?

"Spacetime foam" is not necessary for virtual particle creation and annihilation. Rather it is a hypothesis that it is created by virtual particles.

Typhoon wrote:

Doc wrote:

Typhoon wrote:A new test of GR

And a strike against "spactime foam" theories attempting to unify GR with QFT.

Question CS How would there being no quantum foam effect things like virtual particles? Would that eliminate the possibility of their existence? Or would it just mean that there is a different explanation of where they come from?

"Spacetime foam" is not necessary for virtual particle creation and annihilation. Rather it is a hypothesis that it is created by virtual particles.

Doc wrote:

Typhoon wrote:

Doc wrote:

Typhoon wrote:A new test of GR

And a strike against "spactime foam" theories attempting to unify GR with QFT.

Question CS How would there being no quantum foam effect things like virtual particles? Would that eliminate the possibility of their existence? Or would it just mean that there is a different explanation of where they come from?

"Spacetime foam" is not necessary for virtual particle creation and annihilation. Rather it is a hypothesis that it is created by virtual particles.

Really? That seems surprising But now that I think about it I guess I realized that at one time.

Typhoon wrote:

Doc wrote:

Typhoon wrote:

Doc wrote:

Typhoon wrote:A new test of GR

And a strike against "spactime foam" theories attempting to unify GR with QFT.

Question CS How would there being no quantum foam effect things like virtual particles? Would that eliminate the possibility of their existence? Or would it just mean that there is a different explanation of where they come from?

"Spacetime foam" is not necessary for virtual particle creation and annihilation. Rather it is a hypothesis that it is created by virtual particles.

Really? That seems surprising But now that I think about it I guess I realized that at one time.

Virtual particles are required for perturbative QFT calculations in [locally] flat spactime for electromagnetic, weak and strong nuclear forces.

Doc wrote:

Typhoon wrote:

Doc wrote:

Typhoon wrote:

Doc wrote:

Typhoon wrote:A new test of GR

And a strike against "spactime foam" theories attempting to unify GR with QFT.

Question CS How would there being no quantum foam effect things like virtual particles? Would that eliminate the possibility of their existence? Or would it just mean that there is a different explanation of where they come from?

"Spacetime foam" is not necessary for virtual particle creation and annihilation. Rather it is a hypothesis that it is created by virtual particles.

Really? That seems surprising But now that I think about it I guess I realized that at one time.

Virtual particles are required for perturbative QFT calculations in [locally] flat spactime for electromagnetic, weak and strong nuclear forces.

Virtual particles are also the explanation of Hawking radiation aren't they?

Typhoon wrote:Daily Exp | Scientists at Large Hadron Collider hope to make contact with PARALLEL UNIVERSE in days



Backreaction | No, the LHC will not make contact with parallel universes

Is the universe a hologram?
Date:April 27, 2015 Source:Vienna University of Technology Summary:The 'holographic principle,' the idea that a universe with gravity can be described by a quantum field theory in fewer dimensions, 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 three dimensional -- just like a hologram. Share:
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Is our universe a hologram?

Credit: TU Wien

At first glance, there is not the slightest doubt: to us, the universe looks 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. Results obtained by scientists at TU Wien (Vienna) now suggest that the holographic principle even holds in a flat spacetime.

The Holographic Principle

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 Daniel Grumiller (TU Wien).

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.

Correspondence Even in Flat Spaces

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 Daniel 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 at TU Wien (Vienna) 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.

Calculated Twice, Same Result

"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, Daniel 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 Daniel Grumiller.

This however, does not yet 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.

Story Source:

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

Azrael wrote:Weak Measurement

Does anyone have an opinion?

Typhoon wrote:

Azrael wrote:Weak Measurement

Does anyone have an opinion?

Sorry, no. Have not kept up to date in QM measurement theory.

Azrael wrote:This is a fascinating result. Perhaps Maldacena is worthy of a Nobel Prize.

Typhoon wrote:

Azrael wrote:This is a fascinating result. Perhaps Maldacena is worthy of a Nobel Prize.

Not yet. Physics is an experimental science.

An interesting idea that first has to be put into a form that is falsifiable and then tested.

Azrael wrote:

Typhoon wrote:

Azrael wrote:This is a fascinating result. Perhaps Maldacena is worthy of a Nobel Prize.

Not yet. Physics is an experimental science.

An interesting idea that first has to be put into a form that is falsifiable and then tested.

This may have occurred in 2008.

AdS/CFT was used to calculate the viscosity of a quark-gluon plasma and it was experimentally confirmed at the Large Hadron Collider.