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posted by CoolHand on Sunday August 30 2015, @11:21PM   Printer-friendly
from the fun-with-magnets dept.

From EurekAlert (Australian National University):

Physicists have found a radical new way [to] confine electromagnetic energy without it leaking away, akin to throwing a pebble into a pond with no splash. The theory could have broad ranging applications from explaining dark matter to combating energy losses in future technologies. However, it appears to contradict a fundamental tenet of electrodynamics, that accelerated charges create electromagnetic radiation, said lead researcher Dr Andrey Miroshnichenko from The Australian National University (ANU).

"This problem has puzzled many people. It took us a year to get this concept clear in our heads," said Dr Miroshnichenko, from the ANU Research School of Physics and Engineering. The fundamental new theory could be used in quantum computers, lead to new laser technology and may even hold the key to understanding how matter itself hangs together.

"Ever since the beginning of quantum mechanics people have been looking for a configuration which could explain the stability of atoms and why orbiting electrons do not radiate," Dr Miroshnichenko said. The absence of radiation is the result of the current being divided between two different components, a conventional electric dipole and a toroidal dipole (associated with poloidal current configuration), which produce identical fields at a distance. If these two configurations are out of phase then the radiation will be cancelled out, even though the electromagnetic fields are non-zero in the area close to the currents.

Dr Miroshnichenko, in collaboration with colleagues from Germany and Singapore, successfully tested his new theory with a single silicon nanodiscs between 160 and 310 nanometres in diameter and 50 nanometres high, which he was able to make effectively invisible by cancelling the disc's scattering of visible light.

Nonradiating anapole modes in dielectric nanoparticles and arXiv PDF.


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  • (Score: 1, Touché) by Anonymous Coward on Sunday August 30 2015, @11:33PM

    by Anonymous Coward on Sunday August 30 2015, @11:33PM (#229989)

    Did they the whole thing?

    • (Score: 0) by Anonymous Coward on Monday August 31 2015, @02:14PM

      by Anonymous Coward on Monday August 31 2015, @02:14PM (#230161)

      You forgot 'accidentally.'

    • (Score: 0) by Anonymous Coward on Monday August 31 2015, @03:06PM

      by Anonymous Coward on Monday August 31 2015, @03:06PM (#230204)
      Their stuff cancelled out more than just radiation.
  • (Score: 4, Insightful) by stormwyrm on Monday August 31 2015, @12:36AM

    by stormwyrm (717) on Monday August 31 2015, @12:36AM (#229997) Journal

    I always thought that atoms didn't radiate because quantum theory had it that there were only discrete quantum states at specific energy levels that the electrons could occupy, so they could only gain or lose energy in steps, hence the discrete emission spectra of atoms when they make those quantum state transitions. For an atom to radiate its electrons would need to make such a state transition, but for most ordinary atoms the electrons are in the ground state, with no lower energy state where they could go, and hence no radiation. I suppose they must be talking about a new theory then rather than attempting to second-guess Schrödinger and Feynman.

    By the way, the "radical way confine" typo seems to be in the original article.

    --
    Numquam ponenda est pluralitas sine necessitate.
    • (Score: 2) by Non Sequor on Monday August 31 2015, @02:21AM

      by Non Sequor (1005) on Monday August 31 2015, @02:21AM (#230015) Journal

      I'm not sure if there's really a difference between having a discrete state space or having a larger state space where most of the states have a negligible presence due to destructive interference.

      --
      Write your congressman. Tell him he sucks.
    • (Score: 2) by eof on Monday August 31 2015, @02:43PM

      by eof (5559) on Monday August 31 2015, @02:43PM (#230182)

      When the scientist says "Ever since the beginning of quantum mechanics people have been looking for a configuration which could explain the stability of atoms and why orbiting electrons do not radiate," I think they are putting things in context. According to classical electrodynamics, an atom would be unstable because its electrons accelerate as they move in their classical orbits. An accelerating electron radiates and loses energy. This would result in the electron orbit decaying until it was stuck on the nucleus.

      Bohr hypothesized that there were only discrete states to take care of the observed existence of atoms. This and his other hypotheses were moderately successful. Eventually physicists came to a more formal theory of quantum mechanics in which the idea of energy levels came about "naturally." Schrödinger was among those who developed the more formal theory; Feynman came along later.

      I haven't read the paper, but I doubt the authors claim to overthrow quantum theory. Given that the calculations appear classical, it would be interesting to revisit the classical atom to see if its decay can be avoided.

  • (Score: 0) by Anonymous Coward on Monday August 31 2015, @12:37AM

    by Anonymous Coward on Monday August 31 2015, @12:37AM (#229998)

    I don't remember EM theory separating electric current between dipole/toroidal config. Is this something in QED?

    • (Score: 3, Informative) by c0lo on Monday August 31 2015, @01:15AM

      by c0lo (156) Subscriber Badge on Monday August 31 2015, @01:15AM (#230004) Journal

      Seems like. EM is usually taught in terms of E and B. Looks like the things change in a quite interesting if adopting a potential approach.

        gauge fixing [wikipedia.org] - transforms the classical EM in QED using potential functions (instead of their derivatives E,B). Then toroidal moment [wikipedia.org] and the experimental confirmation by Aharonov–Bohm effect [wikipedia.org].

      --
      https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
      • (Score: 2) by eof on Monday August 31 2015, @02:14PM

        by eof (5559) on Monday August 31 2015, @02:14PM (#230162)

        Potential functions (the electric potential and the vector potential) are not at all unique to quantum mechanics or QED. Even basic undergraduate courses in E&M introduce the electric potential--it is what differences in potential measured by voltmeters refers to. Choice of gauge (gauge fixing) and field moments are also well known classical concepts.

        The Aharonov-Bohm effect is a quantum phenomena dealing with the effect of the potential functions on the phase of the wavefunction. It has no classical analog, although it would fall under the general label of a Berry phase which does have both classical and quantum manifestations.

        • (Score: 2) by c0lo on Tuesday September 01 2015, @03:11AM

          by c0lo (156) Subscriber Badge on Tuesday September 01 2015, @03:11AM (#230624) Journal

          Even basic undergraduate courses in E&M introduce the electric potential

          But not the magnetic vector potential

          --
          https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
          • (Score: 0) by Anonymous Coward on Tuesday September 01 2015, @04:21AM

            by Anonymous Coward on Tuesday September 01 2015, @04:21AM (#230652)

            I don't know what E&M you learned, but it is literally on the cover (Griffiths [amazon.com]) of one of the undergraduate books on my shelf. Didn't you ever learn the reasoning for there not being magnetic monopoles? I learned Maxwell's Equations as an undergraduate (even had it on a tee shirt).

          • (Score: 2) by eof on Tuesday September 01 2015, @06:47PM

            by eof (5559) on Tuesday September 01 2015, @06:47PM (#230937)

            Freshman/sophomore level courses don't often introduce the magnetic vector potential (some do); it more often is taught in junior/senior level courses, and definitely graduate courses.

  • (Score: 0) by Anonymous Coward on Monday August 31 2015, @12:51AM

    by Anonymous Coward on Monday August 31 2015, @12:51AM (#230000)

    They describe a configuration where the far-field radiation pattern cancels to third order. Far-field radiation patterns are always the result of cancellation of various high order terms. The part about this I don't get is how this explains why atoms are stable. Even if electrons are whizzing around atoms producing the toroidal fields as suggested, the reason you don't seem them radiating is that they are radiating, but cancelling out their terms. This still doesn't explain why the electrons don't spiral in as they lose energy.

    • (Score: 0) by Anonymous Coward on Monday August 31 2015, @01:58AM

      by Anonymous Coward on Monday August 31 2015, @01:58AM (#230012)

      When (energy) waves cancel what happens to the energy that they had?

      • (Score: 2) by c0lo on Monday August 31 2015, @02:48AM

        by c0lo (156) Subscriber Badge on Monday August 31 2015, @02:48AM (#230018) Journal

        When (energy) waves cancel what happens to the energy that they had?

        Is redirected to the areas in which the waves don't cancel. The old good Huygens-Fresnel principle - ring any bell? (or was the bell radiation cancelled somehow?)
        If there's no radiation whatsoever at distance, it means that all the energy stays within the vicinity of the source - the "water" still sloshes at the point of impact of the pebble, except it sloshes in such a way that no wave is generated at distance.

        --
        https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
        • (Score: 1) by l3ert on Monday August 31 2015, @08:12PM

          by l3ert (5673) on Monday August 31 2015, @08:12PM (#230423)

          Kinda like a vibrating string?

          • (Score: 2) by c0lo on Tuesday September 01 2015, @03:06AM

            by c0lo (156) Subscriber Badge on Tuesday September 01 2015, @03:06AM (#230618) Journal
            Sorta - more like a soliton. But don't ask me what would that imply!
            --
            https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
    • (Score: 3, Informative) by c0lo on Monday August 31 2015, @02:40AM

      by c0lo (156) Subscriber Badge on Monday August 31 2015, @02:40AM (#230017) Journal

      This still doesn't explain why the electrons don't spiral in as they lose energy.

      Because the other electrons absorbs it (momentarily) and reradiate it back to the emitter. Sort-of a standing-wave inside a cavity.

      --
      https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
      • (Score: 0) by Anonymous Coward on Monday August 31 2015, @05:10AM

        by Anonymous Coward on Monday August 31 2015, @05:10AM (#230038)

        so what about hydrogen atoms?

        • (Score: 0) by Anonymous Coward on Monday August 31 2015, @05:57PM

          by Anonymous Coward on Monday August 31 2015, @05:57PM (#230312)

          Maybe that's partly why hydrogen tends to be a dimer and, as a monomer, it's unstable?

  • (Score: 4, Informative) by Anonymous Coward on Monday August 31 2015, @08:11AM

    by Anonymous Coward on Monday August 31 2015, @08:11AM (#230060)

    For arXiv papers, please link to the abstract page, not the PDF. From the abstract page, the PDF (and potentially some other formats) is just a click away. But from the PDF link, the only way to get to the abstract page is to edit the link. Besides, the abstract page contains information about new versions of the paper the author might upload.

    Here's the abstract page for the paper on arXiv: http://arxiv.org/abs/1412.0299 [arxiv.org]