Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A New methods to find magnetic monopoles?

  1. Nov 12, 2015 #1
    Everyone is familiar with magnets and their attraction to iron and several other elements.

    Ferromagnetic attraction has been observed for thousands of years.

    It has an "opposite", the Meissner effect. However, mankind could not observe such an effect before the advent of refrigeration, which enables us to cool metals enough to become superconductors and hence exhibit Meissner repulsion.

    We have yet to observe the elusive twin to electric charge, magnetic monopoles. If there are any magnetic monopoles here on Earth, they are all probably bound in dipole pairs into magnetic neutrals.

    If we invent a new technology/technique, such as supercooling, we might be able to separate the magnetic neutrals into their constituent monopoles.

    So far, what are the techniques that people have suggested for obtaining magnetic monopoles?
  2. jcsd
  3. Nov 12, 2015 #2
    of course, there is also room temp. para and diamagnetism, but it still requires the manufacturing of powerful neodymium magnets to produce noticeable effects mostly.
  4. Nov 12, 2015 #3
    I think the idea that there could be elementary particles which are magnetic monopoles comes out of string theories.
    So you would have to be pretty convinced about that first before thinking about what kind of detector would be needed.
    Magnetic monopoles are not necessary to explain ordinary magnetism.
  5. Nov 13, 2015 #4


    User Avatar
    Gold Member

    I believe magnetic monopoles' idea came before the arrival of string theory.
  6. Nov 13, 2015 #5
    One idea is mentioned in Carroll's GR text (chapter 2), where a monopole can be introduced to reinstate a symmetry found in the vacuum version of maxwell theory.
    This symmetry is a duality transformation in which we interchange ##F\leftrightarrow \star F## and ##J\leftrightarrow J_M##.
    F is the two-form maxwell field strength while J is the current one-form.

    The one-form ##J_M## is manually added to "force" this symmetry.
  7. Nov 13, 2015 #6
    This is true. It was the earliest prediction of stringtheory. We think that on the end of Strings we can describe a coupling of Quarks and Gluon with monopols. The string itself is a gluon and the monopols the coupling as Quark. This was the beginning of Stringtheory
  8. Nov 13, 2015 #7


    User Avatar
    Gold Member

    @MacRudi are you sure this idea of magnetic monopole didn't appear before the arrival of string theory?
    The first arrival of string theory is in Venziano's article (I can't rememeber the name of his paper, but you can check it in google).
  9. Nov 13, 2015 #8
  10. Nov 13, 2015 #9
    yes the very first was the veniziano amplitude to explain strings as itself. But the earliest prediction to explain coupling in a finite way (instead of Diracs infinite way) was the monopoles.
    Last edited: Nov 13, 2015
  11. Nov 13, 2015 #10
    Why is the monopole for stringtheorists so important?
    We can build a bosonic world without fermions. No kinetic terms are important for fermions in lagrangian language. We can build a complete geometric and deterministic theory then with a massless bosonic description. Like we try it with Quasiparticles. Monopoles are the oil in the machine to let it work. This is why we hoped to find fast a theory for everything.
  12. Nov 13, 2015 #11
    I would hazard a guess that magnetic mono poles probably don't exist. it seems to me to cause problems because the entire idea of a magnetic field is that it has magnetic field lines which go from the negative to the positive end. Once you don't have something going from negative to positive then in what sense is it a magnet? It seems like if magnetic mono poles exist then there also has to be a positive and negative "magnetic particle" which you could accumulate in some space. I was always under the impression that magnetism was an alteration of space.
  13. Nov 13, 2015 #12
    What about an electric field? Charges have field lines as well, see for example http://www.physicsclassroom.com/class/estatics/Lesson-4/Electric-Field-Lines
  14. Nov 13, 2015 #13
    So? An electric field doesn't have the same definition as a magnetic field. A point charge can produce an electric field. If you have a magnetic monopole it actually just looks exactly like an electric field from a point charge. SO again then in what sense is it magnetic?
  15. Nov 13, 2015 #14
    But then why can't magnetic monopoles exist? I don't get your arguments.
  16. Nov 13, 2015 #15
    I didn't say they can't, i said they probably don't. but anyways its because of the definition of a magnetic field is: 59b1cd2b325266989a216d796687ef79.png

    The number of lines going in equals the number of lines going out. Electric fields dont have this definition. Therefore if magnetic monopoles exist they aren't really magnetic since the lines going in don't equal the lines going out. In other words this integral has some value other than zero. So, again, in what sense is a magnetic monopole magnetic if it doesn't have curved field lines? Its kind of a semantics argument but at the same time what's the point in calling something magnetic which doesn't fit the behavior of things which are magnetic. To me its like saying non wet water. its just a contradiction that makes no sense. if you have some explanation which suggests why a magnetic field doesn't need curved lines and can still be called a magnetic field, then please enlighten me.
  17. Nov 13, 2015 #16
    I do not know how monopoles behave to give use "every day" magnetism.
    However what your equation shows is that a positive magnetic monopole is always observed together with a negative monopole.

    You cannot uniquely state that it is unlikely. We can probably make some argument based on the supposedly huge mass of monopoles.

    RE: magnetic field lines are curved, what about the field line on the axis of a bar magnet?
    If I'm not mistaken this field line forms an infinite circle. You can show that an infinite circle is the same as a straight line.
    So not all lines ought to be straight. The explanation above also circumvents/avoids straight field lines in our observations.
  18. Nov 13, 2015 #17
    Ok yeah the curved statement isn't correct at all-- that was a mistake; rather, it is more valid to say that the definition only says lines coming in = lines going out regardless of direction. However, a magnetic monopole doesn't follow the essential definition of what a magnet is because all the lines go out and none come back in as far as im aware. Therefore its not a magnet by the typical definition. Its something different. And what argument is there that there are a huge mass of monopoles? If you can demonstrate monopoles through argument how can you make the justification that they're magnetic as opposed to a new kind of force--something in between electric and magnetic fields but neither? Also im confused on your infinite circle point--first, how would it be infinite in a finite space, and how does that mean its a straight line just because its infinite? You would also be implying that an infinite sphere is in fact a box. I'd love to see some mathematical proof that an infinite circle is in fact just a straight line. I haven't heard such a claim before.

    Apparently it is just a straight line though because magnetic capacitors do exist.
  19. Nov 13, 2015 #18


    User Avatar

    Staff: Mentor

    Thread closed for Moderation...
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: New methods to find magnetic monopoles?