Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.

# 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.

268 questions
Filter by
Sorted by
Tagged with
170 views

### 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} ...
1k views

### 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 ...
2k views

### 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 ...
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 ...
126 views

### 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 ...
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 ...
582 views

### 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, ...
1k views

### 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 ...
116 views

### 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.
130 views

### 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 ...
495 views

### 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, ...
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 ...
1k views

### 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 ...
384 views

96 views

### 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 ...
115 views

### 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 ...
93 views

### 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 ...