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Questions tagged [magnetic-monopoles]

A magnetic monopole is a hypothetical particle with only one magnetic pole. Their magnetic fields would not be divergence-less. Predicted by certain modern theories, including string theory, supergravity, and various popular grand unified theories.

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How should I think of monopoles in a 3+1D lattice $U(1)$ gauge theory?

The Hamiltonian for 3+1D compact $U(1)$ gauge theory on a cubic lattice is of the form \begin{equation} H = J\sum_{\text{links}\ l}E^2_{l}+ g \sum_{\text{plaquettes}\ P}\cos(\Phi_P), \end{equation} ...
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Why are magnetic field lines closed? [duplicate]

If there were two charges placed at a large distance, won't their (say) magnetic fields interact? What if that large distance is something like close to infinity? Even if they experience a feeble ...
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Principle of equivalence between a magnetic dipole and a closed loop with electric current

There is a principle in classical magnetism, sometimes called "Ampere's equivalence principle": A magnetic dipole is equivalent to a closed loop of electric current in terms of the generated ...
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73 views

Showing the force on magnetic dipole

We're given a situation where the circuit can move under the influence of a magnetic force. Now I need to show that the force on the magnetic dipole is $$\vec{F} = (\vec{m} \nabla) \vec{B} $$ Could ...
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Why will we never run into a magnetic field that falls off as $\frac 1 {r^2}$?

For example, Walter Lewin says in many lectures that we will never find a magnetic field $B\propto \frac 1 {r^2}$ - why is this? I believe it must be related to $\nabla \times E= -\partial_t B$, but ...
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201 views

Singularity of $B$-field in a Dirac String

I was assigned this question related to Dirac strings: Given a vector potential $\vec{A}= \frac{1-\cos(\theta)}{r\sin(\theta)}\hat{\phi}$, show that there is a singularity in the B field ...
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Why magnetic monopole has't been shown in the particle physics's Standard Model context?

For various reasons, experts, since Dirac, believe that a unified field theory must have a magnetic monopole. For example, Polyakov said: "I am quite certain that magnetic monopoles really exist. How, ...
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Is the magnetic force real or illusion?

Reading this talk. Mind blown. It explains how the concepts of special relativity and length contraction between inertial reference frames converts magnetic forces to electrostatic forces depending on ...
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What would happen if you put a superconductor shell around a magnetic monopole?

According to Meissner effect, there would be no magnetic field outside. But according to Gauss's law, the total magnetic flux must be non zero.
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Why does Witten say that his work only makes sense if magnetic monopoles exist?

Witten emphasises (in the Q&A session after his talk on introductory knot theory) that he works on theories which admit magnetic monopoles. But how would the theories break down if magnetic ...
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Internal magnetic field of dipole and bar magnet

I am approximating the magnetic field of a cylindrical permanent magnet using two fictitious magnetic monopoles with separation (magnetic length) of 2L. This model is analogous to an electric dipole, ...
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147 views

Have we observed magnetic monopole already? If not, why?

Please see 'here' for the energy scale of a (topological) magnetic monopole. It is around 11 TeV and I am impressed that the LHC reaches the scale of 14TeV already. Then have we observed the monopole ...
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Why are there two different SI units of magnetic charge?

Taking a look at the wiki on magnetic charge, there are two different forms of the Dirac Quantization Condition in SI units: the Weber form $$\frac{q_e q_m}{2 \pi \hbar} \in \mathbb{Z}$$ and the ...
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Why isn't Dirac credited with the discovery of the Aharonov-Bohm effect?

Above equation (8) of Dirac's famous 1931 paper in which he proposes his quantization condition for magnetic monopoles, he says "the change in [an electron's] phase around [a] closed curve [is] $2 \pi ...
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Is magnetic field always circular?

I want to ask if magnetic field lines are always circular and If YES , Then WHY ??? Or on What basis we can say that magnetic field lines are always circular ?? I am confused with the topic . It is my ...
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Magnetic monopole and quantisation of angular momentum

I read chapter 6.12/6.13 in J. D. Jackson's Classical Electrodynamics about the magnetic monopole and a certain detail is confusing me. First in a semiclassical consideration of a magnetic monopole, ...
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Do magnetic monopoles exist? [duplicate]

According to Gauss's law in magnetism, we know that there is no magnetic monopoles. But my teacher told in the class that magnetic monopoles exists but he didn't told us where instead told to search ...
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Which charge to use in the Dirac quantization condition?

I have a follow-up question to Dirac magnetic monopoles and quark fractional electric charge quantization, regarding whether the "unit of electric charge" in the Dirac quantization condition should be ...
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Magnetic monopoles in field theory

In standard QED, we couple the electron to electromagnetism by replacing $$\partial_\mu \to \partial_\mu + i e A_\mu.$$ Upon taking the classical limit, we find that this gives electrons an electric ...
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What is the explanation of the non-existence of magnetic monopoles? [closed]

Electric monopoles do exist, but why cannot magnetic monopoles exist? The question is closed because I need to clarify it, but I don't know how I could ask it another way. However, I've recieved ...
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311 views

Why is Seiberg duality called an electromagnetic duality?

An electromagnetic duality is a duality that maps electric to magnetic degrees of freedom of two distinct theories. Apart from source-less Maxwell electrodynamics, other theories require magnetic ...
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Magnetic monopoles gauge theories

I'm quoting 't Hooft: "[...] Locally stable field configurations may exist that have some topological twist in them [...].Careful analysis of the existing Lie groups and the way they may be broken ...
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Left-right topology

Are there non-trivial topological solutions (in particular 't Hooft-Polyakov magnetic monopoles) associated with the (local) breaking \begin{equation} SU(2)_R \times SU(2)_L \times U(1)_{B-L} \to SU(...
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Creating a Magnetic Monopole through a torus [duplicate]

Could you create a magnet in shape of a hollow torus and magnetize it so that the interior is south and the exterior is north in order for it to act as a monopole? Is that possible? Thanks
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Magnetic monopole in arbitrary dimension

Assume we have D-dimensional space-time in spherical coordinates $(t, r, \theta_1, ..., \theta_k)$. We have Maxwell equations for $k$-form $F^{\alpha_1, ..., \alpha_k}$ $$\partial_{\mu} F^{\mu \...
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Some questions about gauge theory

Let's talk quantum mechanics. I have a charged particle moving on a sphere. It has a wave function $\psi$. At time $t=0$, there is no magnetic flux piercing the sphere. Instantaneously, I introduce a ...
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Wave function constrained to a fixed trajectory? Really?

this is probably a very stupid question. First of all, I'm a mathematician so please try to use coordinate-free notations. It's often used in quantum mechanics a wave function depending on a fixed ...
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Why Dirac monopole is a topological defect in a $U(1)$ gauge theory? [duplicate]

How does $U(1)$ gauge group at long distances, give rise to magnetic monopoles? Also why is it said that Dirac monopole is a topological defect in a compact $U(1)$ gauge theory?
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A question from Professor Anthony Zee's book: “Quantum Field Theory in a Nutshell”

When Professor Anthony Zee is discussing the topological monopole in page 309 of his famous book "Quantum Field Theory in a Nutshell", Princeton University Press (2010), he writes: But I am still not ...
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Is there any property of a neutrino that prevents it from being considered the missing monopole that will make Maxwell's equations symetric

The zero in Gauss's magnetic law, is it an approximation? Could it be in reality be a really tiny number like the magnetic field strength of a neutrino? Neutrinos are members of the Lepton family ...
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Why are magnets in form of hollow sphere not a magnetic monopole? [closed]

If I place many micro-bar-magnets on the surface of hollow sphere such that the pole of every magnet points towards the same side then, you could imagine that a monopole would be produced. So, I just ...
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Theoretical magnetic Monopole

I'm trying to solve question B2 on the 2012 USAPHO semifinal exam (last page). The solutions are here on the last three pages. I don't understand the following line: The flux through the loop ...
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Permanent Magnet Lines & Currents:

A permanent magnet produces lines of magnet flux that we call a "magnetic field". Those lines come from inside the magnet, come out of the N pole, loop outside the magnet, & return back into the ...
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Question from Terning's book

In Chapter 7 of Terning's book (Modern Supersymmetry), the first example considered is that of an $SO(3)$ gauge theory, a complex scalar in the triplet representation of $SO(3)$ and a potential term: ...
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Dirac monopole of Berry curvature?

We know that there is an effective "magnetic field" in terms of Berry curvature, which leads to Luttinger's anomalous velocity, etc; and similarly there is also a "magnetic flux", which appears in ...
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54 views

Search for unpublished note on Magnetic Monopole Detection

Design of an electromagnetic detector for Dirac monopoles by Luis Alvarez This is an unpublished 1963 note from Lawrence Radiation Laboratory (Physics Note 470), and is heavily cited in all papers on ...
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173 views

How we can detect a magnetic monopole? [duplicate]

How we can detect magnet monopole? How we can distinguish it from electric monopole? If we change E to B and B to -E in Maxwell's equations we get proper equations for charge and current density which ...
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304 views

Dirac string and Nielsen–Ninomiya theorem

Nielsen–Ninomiya theorem states that in a lattice system one can not have just one chiral fermion. Fermions necessarily come in pairs of opposite chirality. I am wondering if one can "explain" this ...
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Magnetic monopole bound state

Magnetic monopole (mm) bound states Background: I'm an experimentalist, simple equations are appreciated. (Complicated equations are fine, as long as I can ask questions.) This is one of many ...
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951 views

Distinction of Dirac monopole and Polyakov-'t Hooft monopole

Can anybody explain the physical difference between Dirac monopole and Polyakov monopole? First, let me write down what I know briefly. Dirac monopole It comes from the symmetry of Maxwell ...
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240 views

Dyon condensation and generalized Meissner effect

In section 2.B of Metlitski and Vishwanath's paper: "Generally condensation of a dyon with charges $(q,m)$ gives rise to an analogue of a Meissner effect for the gauge field combination $q\vec{b}-2\...
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What is the difference between Reissner-Nordstrom (RN) black hole and dyonic black hole?

A RN black hole is a black hole with electric charge, and a dyonic black hole with both electric charge and magnetic charge. My Questions: Is the above statement correct? Is the charges the unique ...
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Coupling an electric charge to a gauge field. How is it done in this setup?

In page 9 of Tachikawa's N=2 susy dynamics for pedestrians it says that an electric particle with charge $n$ in the first quantised setup (in what sense first quantised?), Wick rotated to Euclidean ...
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Instantons and Fivebranes

What is the general relationship between instantons and fivebranes? In the paper ``Magnetic Monopoles in String Theory'' by Gauntlett, Harvey and Liu, the authors state the fivebrane ansatz of ...
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Quantising the magnetic monopoles the make Maxwell symmetric

I don't believe this has already been asked, but I might be wrong; sorry. One can add a magnetic charge density/magnetic monopoles to Maxwell's equations to make the theory symmetric between the ...
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Would magnetic charge (i.e., magnetic monopoles) be Lorentz invariant if it existed?

Would magnetic charge (i.e., magnetic monopoles) be Lorentz invariant if it existed? It is clear that Maxwell's equations in themselves permit magnetic charges but what would their relativistic ...