Caltech announces discovery in fundamental physics(phys.org)
phys.org
Caltech announces discovery in fundamental physics
http://phys.org/news/2015-08-caltech-discovery-fundamental-physics.html
9 comments
Hmmm, interesting. If I understand correctly this is a breakthrough in our understanding of the underlying physics related to superconductivity. Which could potentially lead not just to an improved understanding of superconductivity and toward new kinds of superconductors but also to new electronic phenomena in metals which might possibly be equally as interesting. This is a significant breakthrough in condensed matter physics, which may end up being one brick of a foundation of theoretical models which form the basis of a vastly superior understanding of matter compared to what we have today. Which might potentially enable uses that we cannot even envision today. Pretty exciting stuff.
Well this is debatable. These anomalies figure into the so-called nodal gap in the antiferromagnetic, not the superconducting phase, of certain high temperature superconductors. There is hope that this might spread light on the nature of superconductivity.
Right. There's a lot of maybes and potentially with this research. It's something new and interesting but how much it will allow us to unlock some of the secrets of condensed matter physics that have so far eluded us remains to be proven.
Obligatory
http://sci-hub.org/10.1038/nphys3416
Looks like Nature makes the whole paper readable online: http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys...
Not to me it doesn't. I see this near the bottom of the page:
READ THE FULL ARTICLE
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This appears to point to an unrelated article, "An instability of unitary quantum dynamics" but one of the co-authors of the paper that the article describes.
this is not the article.
Ai sorry, I thought it was the pre-press version of the paper.
See:
https://news.ycombinator.com/item?id=10037257
See:
https://news.ycombinator.com/item?id=10037257
Oops, maybe I unwittingly had access by being on work VPN. Sorry bout that! Thanks for the open link, jacquesm.
Your link is correct (but paywalled). I have no idea what jacquesm is linking to.
Here is the free full-text (provided by Nature as an in-browser read-only version):
http://rdcu.be/dCSH
Would anyone ELI5 please?
Free supplementary materials PDF here: http://authors.library.caltech.edu/58610/3/nphys3416-s1.pdf
Edit: thanks for the downvotes!
Edit: thanks for the downvotes!
Please read the HN guidelines, which say:
Please resist commenting about being downvoted. It never does any good, and it makes boring reading.
It often takes threads off-topic as well, as here.
https://news.ycombinator.com/newsguidelines.html
Please resist commenting about being downvoted. It never does any good, and it makes boring reading.
It often takes threads off-topic as well, as here.
https://news.ycombinator.com/newsguidelines.html
<downvote>
its cool man, my all my accounts are throw away, so even if they get down votes it does not refrain me from speaking my opinion.
voting on comments is stupid, and should be removed.
voting on comments is stupid, and should be removed.
I really don't think down voting is very helpful for the community unless people are being racist/sexist/obvious troll. Better people comment on why they disagree, clarifying ideas rather than a no response and arbitrary unlike.
[deleted]
tl;dr abstract of the paper:
---snip---
Abstract. Instabilities of equilibrium quantum mechanics are common and well-understood. They are manifested for example in phase transitions, where a quantum system becomes so sensitive to perturbations that a symmetry can be spontaneously broken. Here, we consider the possibility that the time evolution governing quantum dynamics may be similarly subject to an instability, at which its unitarity spontaneously breaks down owing to an extreme sensitivity towards perturbations. We find that indeed such an instability exists, and we explore its immediate consequences. Interpretations of the results both in terms of extreme sensitivity to the influence of environmental degrees of freedom, and in terms of a possible fundamental violation of unitarity are discussed.
---snip---
Is this suggesting that quantum superpositions have a tendency to spontaneously collapse, or am I misreading it?
---snip---
Abstract. Instabilities of equilibrium quantum mechanics are common and well-understood. They are manifested for example in phase transitions, where a quantum system becomes so sensitive to perturbations that a symmetry can be spontaneously broken. Here, we consider the possibility that the time evolution governing quantum dynamics may be similarly subject to an instability, at which its unitarity spontaneously breaks down owing to an extreme sensitivity towards perturbations. We find that indeed such an instability exists, and we explore its immediate consequences. Interpretations of the results both in terms of extreme sensitivity to the influence of environmental degrees of freedom, and in terms of a possible fundamental violation of unitarity are discussed.
---snip---
Is this suggesting that quantum superpositions have a tendency to spontaneously collapse, or am I misreading it?
Uh, this isn't the abstract of that nature paper at all
You're quite right. It's not. This is the correct abstract:
---snip---
Charge ordering in metals is a fundamental instability of the electron sea, occurring in a host of materials and often linked to other collective ground states such as superconductivity. What is difficult to parse, however, is whether the charge order originates among the itinerant electrons or whether it arises from the ionic lattice. Here we employ high-resolution X-ray diffraction, combined with high-pressure and low-temperature techniques and theoretical modelling, to trace the evolution of the ordering wavevector Q in charge and spin density wave systems at the approach to both thermal and quantum phase transitions. The non-monotonic behaviour of Q with pressure and the limiting sinusoidal form of the density wave point to the dominant role of the itinerant instability in the vicinity of the critical points, with little influence from the lattice. Fluctuations rather than disorder seem to disrupt coherence.
---snip---
So. What does this mean in English? Also, can I downvote my own posts?
---snip---
Charge ordering in metals is a fundamental instability of the electron sea, occurring in a host of materials and often linked to other collective ground states such as superconductivity. What is difficult to parse, however, is whether the charge order originates among the itinerant electrons or whether it arises from the ionic lattice. Here we employ high-resolution X-ray diffraction, combined with high-pressure and low-temperature techniques and theoretical modelling, to trace the evolution of the ordering wavevector Q in charge and spin density wave systems at the approach to both thermal and quantum phase transitions. The non-monotonic behaviour of Q with pressure and the limiting sinusoidal form of the density wave point to the dominant role of the itinerant instability in the vicinity of the critical points, with little influence from the lattice. Fluctuations rather than disorder seem to disrupt coherence.
---snip---
So. What does this mean in English? Also, can I downvote my own posts?
It is a dense and difficult paper. I've made 5 attempts to summarize what I think they're saying and deleted them all, which is a reflection of both my lack of understanding and the difficulty of the underlying concepts.
As best I can make out, they're saying that electromagnetic phenomena depend more on chaotic subatomic processes than on the purity or exact configuration of a material's crystalline structure, and they know this because high-resolution observations at a range of temperatures and pressures correlate nicely with a particular set of theoretical predictions.
This might be significant in that you could optimize for superconductivity by tuning the aggregate electromagnetic characteristics of a material rather than requiring hard-to-achieve structural uniformity at the molecular level.
As best I can make out, they're saying that electromagnetic phenomena depend more on chaotic subatomic processes than on the purity or exact configuration of a material's crystalline structure, and they know this because high-resolution observations at a range of temperatures and pressures correlate nicely with a particular set of theoretical predictions.
This might be significant in that you could optimize for superconductivity by tuning the aggregate electromagnetic characteristics of a material rather than requiring hard-to-achieve structural uniformity at the molecular level.
No, they're not subatomic.
Charge density waves mean that there is a periodic modulation of charge (for a little more background, see the Quora answers here: http://www.quora.com/What-are-the-significances-of-charge-de... and this pdf: http://www.wien2k.at/reg_user/textbooks/WIEN2k_lecture-notes... ) What they are saying is that itinerant electrons (those not localized in a given orbital, but which occupy bands throughout the metallic system and hop, in contrast to an standard insulating magnet) have the instability within themselves, the lattice does not necessarily need to give them a push (this is called "dynamically generated"). In my answer I go into a bit of detail about the heretofore standard role of the lattice as well as the applications to superconductivity.
What this paper is saying is that the Peierls distortion (cf. answers cited or Wikipedia) in these systems is either paralleling or a consequence of the electronic instability. The bit about following the Q wave vector has to do with the discussion of "nesting" in the answers (that is, how well does the momentum of the electrons couple with that of the phonons/ionic lattice vibrations at a certain periodicity and do they steal energy away from the lattice leading to an overall lower state (and is this the _primary_ factor in that lowering, a conclusion this paper would seem to militate against)"
A good reference on this is the book by Assa Auerbach "Interacting Electrons and Quantum Magnetism"
Charge density waves mean that there is a periodic modulation of charge (for a little more background, see the Quora answers here: http://www.quora.com/What-are-the-significances-of-charge-de... and this pdf: http://www.wien2k.at/reg_user/textbooks/WIEN2k_lecture-notes... ) What they are saying is that itinerant electrons (those not localized in a given orbital, but which occupy bands throughout the metallic system and hop, in contrast to an standard insulating magnet) have the instability within themselves, the lattice does not necessarily need to give them a push (this is called "dynamically generated"). In my answer I go into a bit of detail about the heretofore standard role of the lattice as well as the applications to superconductivity.
What this paper is saying is that the Peierls distortion (cf. answers cited or Wikipedia) in these systems is either paralleling or a consequence of the electronic instability. The bit about following the Q wave vector has to do with the discussion of "nesting" in the answers (that is, how well does the momentum of the electrons couple with that of the phonons/ionic lattice vibrations at a certain periodicity and do they steal energy away from the lattice leading to an overall lower state (and is this the _primary_ factor in that lowering, a conclusion this paper would seem to militate against)"
A good reference on this is the book by Assa Auerbach "Interacting Electrons and Quantum Magnetism"
I guess subatomic was the wrong word, but we took the same thing away - that itinerant electrons are inherently unstable rather than being due to a particular lattice configuration.
Although, insofar as the electrons have the instability within themselves, to use your words, how is the cause not subatomic? Does it not arise out of some aspect of the electron's internal structure? Maybe I'm just using it too loosely.
Thanks for taking the time to explain it properly.
Although, insofar as the electrons have the instability within themselves, to use your words, how is the cause not subatomic? Does it not arise out of some aspect of the electron's internal structure? Maybe I'm just using it too loosely.
Thanks for taking the time to explain it properly.
It arises from their _collective dynamics_, this is a very important point and an excellent distinction you are making. It probably has more to do with their nature as fermions than anything else - see Wikipedia on a Wigner crystal for a similar phenomenon