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Bill S. #54352 08/28/15 01:37 AM
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In them rocks the process would be slow probably negligible the problem really opens up in metals especially conducting and malleable ones.

So consider a pure alloy metal so there are no macroscopic or microscopic discontinuities (like crystals etc) it is a pure metal lattice.

The only real mechanism for failure then is dislocation.
https://en.wikipedia.org/wiki/Dislocation

You are here => Until the 1930s, one of the enduring challenges of materials science was to explain plasticity in microscopic terms.

Your problem is your perfect metal lattices should be much stronger than you will measure.

Quote:
As shear modulus in metals is typically within the range 20 000 to 150 000 MPa, this is difficult to reconcile with shear stresses in the range 0.5 to 10 MPa observed to produce plastic deformation in experiments.


Dislocation theory from 1934 on sorts out all the problems and it is relatively easy to understand in classical terms. Inbuilt in the classical view however is the thing just wants to stay how it is sitting there quietly on the desk with no forces at play.

In the Quantum world view it is not quite so easy to work out what is going on. How does one describe a dislocation in quantum terms?

So the magic you are after is a Quantum Theory of Dislocation Motion in Metals and now you have gone well outside my areas of expertise smile

Last edited by Orac; 08/28/15 01:44 AM.

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Orac #54353 08/28/15 03:27 AM
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I recall that about 20 years ago there was work being done involving the lattice nonlinear Schrödinger equation and the Peierls-Nabarro barrier potential. Would that have anything to do with a Quantum Theory of Dislocation Motion in Metals?


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Bill S. #54354 08/28/15 04:22 AM
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Yes that would be the stuff and other than recognize what they are dealing with I don't know a huge amount of material science stuff. Basically they would be attacking the orbital stability within the lattice structure in the normal QM realm.

At a guess they will model it as lots of little harmonic oscillators so you have atom oscillations and the lattice oscillations superimposed over the top. Ultimately the atoms around on the surface wont be fully balanced so you need to model them and superimpose that over the top of the internal result. What you end up with is a model of seething vibrating complex oscillations in quantum fields and you and I would see the result as a solid in classical physics. It is probably a lot worse than that and I will have missed important stuff but that would be my initial guess.

In sort of layman terms those larger resonances will have a sort of inertia effect and resist the solid changing shape the old conservation of energy again. It would really only want to change shape if it was energy effective to do so as the resonance has to collapse to a new one.

That is why you can do weird things with metamaterials as there is a pronounced composite effect as well as an atomic effect and that isn't obvious when you look at it from a classical viewpoint. Your are also getting into areas as superconductive materials etc and it's not fully complete yet.

Last edited by Orac; 08/28/15 05:11 AM.

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Orac #54367 08/29/15 03:05 AM
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Now this is a cool experiment I love it

http://phys.org/news/2015-08-quantum-motion.html


Last edited by Orac; 08/29/15 03:06 AM.

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Orac #54369 08/29/15 02:01 PM
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Am I right in thinking that this technique reduces the “quantum jitters” in one direction such that this reduction could, in principle, be used to improve measurement, but that the overall motion remains unchanged, so the uncertainty is not diminished?


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Bill S. #54374 08/30/15 03:25 AM
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Yes correct the energy in the vibrations remains unchanged so it has to increase in the unconstrained directions.

The overall uncertainty is the same, you traded more uncertainty in one direction for less in another which might help improved accuracy in the one direction if you can utilize it in an experimental setup.

Interesting week looks like we have the first crack in the standard model as well those details will be released as they clear review, so should be an interesting month.

Last edited by Orac; 08/30/15 03:49 AM.

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Orac #54375 08/30/15 03:42 PM
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Originally Posted By: Orac
Interesting week looks like we have the first crack in the standard model


Is that the same lepton universality break that BaBar thought they had discovered? If so, I guess this is the first "confirmation" of their finding.

Big fun!


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Bill S. #54379 08/31/15 02:50 AM
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Yes two more experiments are showing the same result, they agree with each other but not the standard model.

First one is out Sept 4th.

http://www.sciencealert.com/the-lhc-finds-evidence-of-particle-activity-beyond-the-standard-model

What most think this detail on is
https://en.wikipedia.org/wiki/Strong_CP_problem

Now if you take the propose solutions to the strong CP problem and you get something resembling what is described in Next-to-Minimal Supersymmetric Standard Model.

Yes it's a string theory model but it will tell you what to expect.
https://en.wikipedia.org/wiki/Next-to-Minimal_Supersymmetric_Standard_Model

You might want to look at it's other prediction
https://en.wikipedia.org/wiki/Neutralino

Whatever the case I think most are happy they have new physics to play with smile

Last edited by Orac; 08/31/15 03:41 AM.

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Orac #54393 09/03/15 03:04 AM
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Worth a read from Sabine

http://backreaction.blogspot.com.au/2015/09/loops-and-strings-and-stuff.html

She has come around to the same point and problem Lubos Motl put me in when I wanted QM and a classical theory of gravity. I can have one or the other but not both. Strangely I probably end up exactly where she is that I still don't believe the string theory story but the mathematics of it may be very useful in making predictions.

We all complain string theory can be a theory of anything but that is factually not true it CAN'T ACTUALLY make the standard model, it predicts it has to be wrong. The anti-string theory lobby have had great delight in pronouncing string theory dead because of that fact and as the standard model results initially strengthened. Now we appear to have cracks in the standard model and if it drops back to a string theory model the payback on the anti-string lobby will be large. There will be certain people like Peter Woit going for cover.

Lubos would have both Sabine and My head stuck up on a pole as a warning to other scientists but it is the case we can always be convinced by a compelling argument.

Lets see what the next results show and I will give you my thoughts.

Last edited by Orac; 09/03/15 03:13 AM.

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Orac #54394 09/03/15 12:46 PM
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I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Orac #54397 09/04/15 08:45 PM
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http://backreaction.blogspot.com.au/2015/09/loops-and-strings-and-stuff.html

Interesting read, indeed.

I guess you'll be adding "semi-shittical sentence" to your English vocabulary. smile


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Orac #54443 09/15/15 05:01 PM
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If you really have gone, Orac, I hope you are still looking at SAGG.

I want to say thanks for all the times you have made me think. True, you can be a pain in the arse at times, and some of the things you said sounded like "flapdoodle", but that has to be balanced against the positives.


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Orac #54833 11/24/15 09:58 PM
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I met this recently, and wonder if it could be an explanation as to why we don’t see run-away gravity.

Quote:
Gravitons participate in the gravitational field, which means that a graviton can emit gravitons. But remember that 4-momentum is conserved. A "spray" of gravitons from a decay collectively has the same 4-momentum which means that the gravitational field strength has not increased.


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Bill S. #54839 11/25/15 03:24 AM
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Sigh, ok lets do this quickly from the top, as we haven't even discovered a graviton and it's all speculation smile

Gravitons would be heralded as particles in a field which would be effected by energy and/or mass. So given energy is a "fictional" quantity technically you get the situation where a movement of energy or mass creates a runaway effect creating more gravitons. It is the situation that a country decided to leave it's printing presses on for it's money.

The post you have given simply says that is okay because the observer will see that the new created gravitons have the same combined currency. So in your money world if a country keeps printing presses on the currency devalues relative to some other country.

So I guess you could say if I devalued the USA dollar by 50%, my dollar is worth less but the entire GDP of USA is still the same when expressed in Euros but twice as much when expressed in USA dollars. That is the same as your post statement above.

So although correct it doesn't solve the problem because the gravitons would continue the process until there was infinite of them all worth nearly nothing. The same thing happens in economics and it is called hyperinflation, if you really leave the money press on.

So lets look at the proposed process, a graviton in a small space has something happen to make another graviton pop into existance near it. That energy in the space section causes yet another graviton to pop into existence. This cycle continues infinitely and we would say the graviton theory is nonrenormalizable.

The usual way to stop the runaway process is to invoke planck distance. That two gravitons can't exist in the same planck distance and string theory for example would give you a physical reason for why that is.

The alternative answer is the process is somehow held in check and as we haven't discovered a graviton that is a bit hard to even guess at what.

All pure speculation take whichever answer you like best.

Last edited by Orac; 11/25/15 03:26 AM.

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Orac #54860 11/28/15 06:32 PM
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Could there be two distinct concepts being confused here?

1. A graviton could give rise to another (albeit lesser) graviton, thus increasing the total gravitational energy.

2. A graviton might convert into a number of lesser gravitons, thus increasing the number of gravitons, but not the total gravitational energy.

If 1 is the case, how could this contribute to run-away gravity?

If 2 is the case; where does the additional energy come from?


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Bill S. #54868 11/29/15 01:09 AM
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The answers would depend if gravity is a Quantum field or not

Quote:
1. A graviton could give rise to another (albeit lesser) graviton, thus increasing the total gravitational energy.

Not sure what you mean, lesser particle meaning a different particle? If you mean a graviton with a different value, in a Quantum field it's not possible as it would be quantized. For example every electron has exactly the same value there is no such thing as a lesser value electron. All particles in Quantum fields are quantized to exact identical values and as that process extends up, you build the concept of an atomic table where each atom of each element is identical except for isotopes.

Quote:
2. A graviton might convert into a number of lesser gravitons, thus increasing the number of gravitons, but not the total gravitational energy.

Really same as above, explain what you mean by lesser graviton?

In a no Quantum field situation I guess a graviton could be any size it would be controlled by whatever theory was at play. So I guess under such an idea it could vary from nothing to the size of a black hole unless the theory somehow imposed size constraints. Is that the situation you mean?

I can't answer the last bit unless I understand what you meant above.

The graviton page has been brought up todate and it would be worth a review
https://en.wikipedia.org/wiki/Graviton

The bit that might interest you is how hard gravitons are going to be to detect individually and possible problems detecting even a gravity wave.

Last edited by Orac; 11/29/15 01:35 AM.

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Orac #54872 11/29/15 06:40 PM
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I expressed that badly. I was thinking along these lines:

A photon is the quantum of the EM force, so it cannot be divided, but a photon can give rise to two photons carrying less energy.

A graviton would be the quantum of gravity. Could a graviton (hypothetically) divide to become two gravitons, each carrying less energy? The quote “Gravitons participate in the gravitational field, which means that a graviton can emit gravitons”, suggests that this might be the case.

If gravity creates gravity, and gravitons participate in this, does one graviton create another? If so, the process of creating more gravity must mean that there is more gravitational energy in the system after graviton A has created graviton B than there was before. Where would the additional energy come from?


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Bill S. #54880 11/30/15 03:54 AM
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Originally Posted By: Bill S.
A photon is the quantum of the EM force, so it cannot be divided, but a photon can give rise to two photons carrying less energy.

Be careful here, let me elaborate.

A photon like all elementary particles was thought not to divid at all because of feature of renomalization of a quantum filed called Ward–Takahashi identity ( Ward-Takahashi identity ), In laymans terms it's completely balanced. So for a long time it was thought it could not and would not split ... ever.

In 1970 an observation of splitting a photon was first observed by passing a laser thru a crystal lattice. The process is called Spontaneous parametric down-conversion ( SPDC description).

That work lead to the realization that while light is passing thru a medium you can play with QM statistics in the waveform and once it exits the medium when it reforms it can have new characteristics.

You may remember the photonic molecules of 2013 which in the science magazines seemed to cause excitement because someone thought they resemble the starwars lightsabre. (http://www.gizmag.com/photonic-molecules-pave-the-way-for-quantum-computers-and-lightsabers/29924/)

The reason for the caution is you need a medium in which the photons interact there is no situation they are ever known to do it in a vacuum (Ward–Takahashi holds).

Originally Posted By: Bill S.
A graviton would be the quantum of gravity. Could a graviton (hypothetically) divide to become two gravitons, each carrying less energy? The quote “Gravitons participate in the gravitational field, which means that a graviton can emit gravitons”, suggests that this might be the case.

So now when we look at this suggestion, if we are making a graviton a spin 2 quantum field particle we have to assume the same rules apply. So gravitons as per photons are never going to split in the vacuum of space but possibly could in the presence of matter or other suitable mediation layer.

Originally Posted By: Bill S.
If gravity creates gravity, and gravitons participate in this, does one graviton create another? If so, the process of creating more gravity must mean that there is more gravitational energy in the system after graviton A has created graviton B than there was before. Where would the additional energy come from?

You are looking at that, wrong the Quantum Statistics of the wave are being effected by the mediating layer. As per SPDC of a photon splitting the energy and indeed all QM statistics are preserved and that is why the two photons are actually known to be entangled.

SPDC is used often as a source of entangled photons for exactly that reason that the entanglement is guaranteed. So if a QM graviton existed you would expect the same behaviour and the split graviton pair should be entangled.

Last edited by Orac; 11/30/15 03:58 AM.

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Orac #54892 12/01/15 05:45 PM
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Originally Posted By: Orac
You are looking at that, wrong


No surprise there. smile

Quote:
the Quantum Statistics of the wave are being effected by the mediating layer. As per SPDC of a photon splitting the energy and indeed all QM statistics are preserved and that is why the two photons are actually known to be entangled.


I think I follow that, but don't see the link to gravity creating more gravity.


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Bill S. #54894 12/02/15 05:52 AM
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Originally Posted By: Bill S.
I think I follow that, but don't see the link to gravity creating more gravity.

It won't create more gravity because the energy would be conserved. The splitting is very controlled and not something that can lead to runaway.

Last edited by Orac; 12/02/15 06:37 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
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