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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Berry curvature Weyl and Dirac points
I understand that Berry curvature sinks and sources correspond to Weyl points. However, I'm curious about the identity of points exhibiting a Berry curvature spiral, highlighted by red circles in the ...
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Magnetic Reissner-Nordstrom Black holes
I am studying the RN black hole from Carroll, but i have a hard time following his explanations given in page 254.
To solve for the purely electrically charged black hole, one introduces the four-...
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Why there are no Dirac $B $ boson monopoles?
This differs from an earlier post in that the writing is new and hope better, it uses MathJax, and it gives some details about the particle that poses a problem for certain commonly used theories of ...
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Why do compasses always align with the magnetic field, when the spin of individual particles only align half of the time?
If I have an electron orbiting a nucleus and I apply a magnetic field there will be two effects:
Larmor precession given by the cross product of the magnetic moment and the field of the experiment
$$...
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Single-valuedness of the monopole harmonics
It is known that it is impossible to have a non-singular vector potential for the monopole magnetic field.
How about the monopole harmonics?
Could the wave functions be made single-valued and finite ...
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Why are there no diccussions of hypercharge conservation or Dirac hypercharge monopoles?
The Maxwell equations can be derived from an equation for a spin 1 field with $U(1)$ symmetry. From this field equation is possible to postulate Dirac monopoles by simply roting the real and complex ...
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Could there exist a Magnetic equivalent to the Schwinger Limit?
The Schwinger limit is a scale above which the electromagnetic field is expected to become nonlinear.
It's associated with the Schwinger effect where It is a prediction of quantum electrodynamics (QED)...
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How do Magnetically charged black holes behave
The existence of Magnetic monopoles has not been proven or disproven.
There are equartions for Charge black holes, There are equations for Rotating black holes, but are there equations for ...
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Contracdicting qualitative statements regarding magnetic polarization
Consider a cube of metalic material (either it is paramagnetic or diamagnetic can be both discussed). An external magnetic field $\textbf{B}$ is applied along the +x axis.
We expect $\textbf{B}$ to be ...
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Joining Magnets to Make Larger Uni-Pole
I would like to know;
if it is possible to force magnet wedges (as seen in picture) together to form a "Uni-Pole Radial Ring Magnet?"
Also, if it is possible to force smaller "Uni-...
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Dirac String force?
Assume that the Dirac string is lying along the negative $z$-axis, and is subject to a magnetic field $B$. Assume throughout this question that we are considering a static situation. The force on the ...
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Is there an explanation for why electric charge, or hypercharge, are rational multiples of each other? [duplicate]
Electromagnetic charges are obviously quantized - I suppose the lowest charge being the $d$ charge of $e/3$. Every other charged particle has a multiple of that charge (actually all stable free ...
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Electric and magnetic field strength of a magnetic monopole. (In absence of electric charges.)
According to Wikipedia, in the presence of magnetic monopoles Maxwell's equations will look like:
Whilst the potentials will look like:
So my question is, how would the electric and magnetic field ...
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Dirac string and nature of singularities
The Dirac magnetic monopole is defined as
\begin{align}
\vec{B}=\frac{g\vec{r}}{r^3}\,,
\end{align}
where $g$ is the strength of the monopole and $\vec{r}$ a vector. It is possible to show that the ...
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How do they know Magnetic Field Lines run from South to North inside a magnet?
I get how they can plot the field lines outside the magnet, but how do they know how it runs inside the magnet to form a closed loop? Isn't the direction fo the field lines the direction of the force ...
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Electricity and magnetism monopoles
If a bar magnet is spun about its north-south axis, an electric field is produced, which is directed radialy outward in all directions.
As the length of the north-south axis is reduced, while keeping ...
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Magnetic field due to singular gauge transformation
In $SU(2)$ gauge theory over $\mathbb R^3$, consider the following gauge transformation (in spherical polar coordinates)
$$ \Omega=\begin{bmatrix}e^{i\phi}\cos(\theta/2)&\sin(\theta/2)\\-\sin(\...
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Large and small gauge transformations
I've a question about the definition of 'large' gauge transformations. There are two competing definitions:
small gauge transformations are equal to the identity at spatial infinity while large gauge ...
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Creation of Magnetic Monopoles using Black Holes
If a very long bar magnet is made and is allowed to free fall in a black hole, a point will come when exactly the north pole is inside and south pole is outside the event horizon for a very small ...
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If principle $SU(N)$ bundles on 3-manifolds are trivial, how can there be magnetic monopoles?
Magnetic monopoles are solitons, i.e. field configurations on space (which is 3 dimensional). In pure $SU(N)$ gauge theory, magnetic monopoles can be constructed via 't Hooft's abelian projection (...
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Self-duality of Maxwell lagrangian in terms of magnetic gauge field
I have read at many places that the pure Maxwell theory (without any matter) is self-dual. This is the general form for Maxwell Lagrangian density:
$$\mathcal{L} = - \frac{1}{4} F_{\mu\nu} F^{\mu\nu},$...
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How is this term an angle?
This question is regarding the $\Theta_{\mu\nu}$ term given in equation (3.8) of the paper (https://arxiv.org/abs/2206.07725). The term ( I have typed it below )is defined right below in (3.9) and ...
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It is said that the dual Meissner effect can explain confinement, but where is the Higgs?
It is said that the dual Misner effect can explain confinement. This refers to when the monopole field acquires a v.e.v..
The t'Hooft-Polyakov monopole arises in a theory with a Higgs. So how does the ...
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What do monopoles have to do with strong coupling?
My understanding is that strong coupling effects arise from instantons in the path integral.
But I sometimes read that monopoles (see the electric-magnetic duality) can allow one to calculate strong ...
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Making a magnetic monopole using bar magnets [duplicate]
The common bar magnet has the north pole on one end and the south pole on the other. I was wondering if we cut the magnet into the following shape (a part of a thick spherical shell)
And then ...
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Monopole problem
Original question: So theory predicts that the monople number density at time of GUT was $10^{82}$ per cubic meter, due to inflation it's diluted and today it's about $10^{-16}$ per cubic Mpc.
This is ...
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Charged particle in a purely radial magnetic field, is the canonical angular momentum conserved?
Let $ \vec{B} = k \dfrac{\vec{u_r}}{r^2}$ (assuming magnetic monopoles exist) and let $q$ be a charged particle. The associated hamiltonian is $H = \dfrac{(\vec{p} - q \vec{A})^2}{2m}$ and the ...
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What is the physical significance of the negative sign in the lorentz force equation in presence of magnetic monopole?
This question is similar to that of: Why does the extended Lorentz force law have a negative sign?
The Lorentz force on a magnetic monopole is given as:
$$\vec{F}=q_m(\vec{B}-\vec{v}\times\frac{\vec{E}...
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Lagrangian formulation of Maxwell's equations with magnetic monopole
If we set $\nabla \cdot {\bf B}=\rho_m$ where pm is the density of magnetic charges we lose the ability to write ${\bf B}=\nabla \times{\bf A}$ . Can we get a new Lagrangian that leads to the new ...
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Are magnetic charges compulsory in string theory?
In this penultimate lecture of a series given by Freddy Cachazo, the differential forms corresponding to the massless excitations in the Ramond–Ramond sector signal the existence of p-branes sourcing ...
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EM radiation from monopole v.s. dipole
I'm confused about two conflicting ideas: the first is that monopoles cannot emit EM radiation (see here), and the second is that an accelerating point charge does produce EM radiation (see here). I ...
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What is the value of charge quantization?
Let me try to summarize what I understand of charge quantization:
We know that electrons can behave as particles with a well-defined charge $e_0 \approx 1.6 \cdot 10^{-19}$ C. From this it is clear ...
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What would happen if a magnetic monopole collides with a magnetic antimonopole?
According to Dirac, theoretically, each Magnetic Monopole (North mm) is connected with their counter partner in space, the Magnetic Antimonopole (South mm) via an infinite thin and possible long ...
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Monopoles in the fractual quantum Hall
What role do magnetic monopoles play in the fractional quantum Hall effect?
Also see here.
EDIT: I should add that I understand the fractual quantum Hall effect only from the perspective of minimal ...
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Why is the monopole problem a problem?
According to this Wikipedia article on cosmic inflation:
The magnetic monopole problem, sometimes called the exotic-relics problem, says that if the early universe were very hot, a large number of ...
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Is the Dirac monopole quantization condition out by 1/2?
Consider an electron with electric charge $e$ that is moved around a closed horizontal circular path $C$ centered around a magnetic monopole with magnetic charge $g$. Assume that the monopole produces ...
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Is force perpendicular to magnetic field in a bar magnet?
Recently I started this topic. My lecturer used
$$F_{B}=q_{n}B$$
I have two questions in this topic.
By this equation both the magnetic field and Force are in same direction. But aren't they supposed ...
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Mass curves spacetime. Is there any theorized "anti-mass" that counteracts this effect? [duplicate]
Things like faster-than-light travel have very good reasons for being believed theoretically impossible (e.g. they allow traveling backwards in time). Things like magnetic monopoles are seemingly ...
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If magnetic field is a bivector, then what is the pole strength?
I have an intuition that magnetic fields are bivectors. While trying to derive some equations with bivectors, I arrived at this formula
$$F=\frac{q_{m_a}q_{m_b}}{r^2}\hat r$$
So we have,
$$F=q_mB$$
...
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Magnetic Monopole mass-energy effect into Einstein-Field equations
I am just wondering, what is the effect of a magnetic monopole mass-energy term in the Einstein Field Equations. Options I thought: does it induce torsion? Non-metricity? Any other weird effect of ...
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Electromagnet attracting permanent magnet?
Permanent magnet gets attracted to electromagnets iron core ,but if we energize electromagnet for attraction force will it attract strongly?
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Are we sure that electric “monopoles” are not just ends of an “Electrical Dirac String”? [closed]
The Dirac String is used to model magnetic monopoles. So how are we sure that physical electric “monopoles” are not in fact the ends of an “Electrical Dirac String” produced by a solenoid carrying a ...
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Magnetic potential in spherical coordinates
In a current-free region, we have $\nabla \times \mathbf{B} = 0$, allowing us to write $\mathbf{B} = -\nabla V$ for some scalar function $V$. We also have $\nabla \cdot \mathbf{B} = 0$, meaning that ...
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Magnetic field of dipole derivation
How can we derive the following formula:
$$\vec{B}(\vec{r})=\frac{\mu_0}{4\pi}\left[ \frac{3(\vec{m}\cdot\vec{r})\vec{r}}{r^5} - \frac{\vec{m}}{r^3}\right]\; ,$$
I want to derive it as a limit of a ...
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Magnetic field lines are closed lines?
How is it proven that the magnetic lines are closed lines? Because the divergence of $\vec {B}$ is zero does not sound convincing, since fields like $\vec{F} = a\vec i +b\vec j+c\vec k$ (with $a$, $b$,...
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Is it possible to introduce magnetic monopoles without breaking $∇ · B = 0$?
In another word, the net magnetic charge is always zero everywhere, which means magnetic field is still strictly source free. On the other hand, the net magnetic current jm can be nonzero, which means ...
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Maximum $B$-field at the surface of a permanent magnet
I have the dipole formula for a permanent spherical magnet in coordinate-free form.
$\vec{B}=\frac{\mu_{0}}{4\pi}\frac{3(\vec{m}\cdot\hat{r})\hat{r}-\vec{m}}{r^{3}}$
I am trying to find the maximum $B$...
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Why are magnetic monopoles "incompatible" with quantum mechanics?
I'm reading this Physics Today article on magnetic monopoles, and I'm a bit confused by a discussion of the necessity of Dirac strings for compatibility with quantum mechanics. I'll reproduce the ...
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On rotating magnetic charges
Consider a sphere with magnetic charge $P$ and electric charge $Q$. We know that when the sphere is subjected to rotation about the $z$-axis, there is a magnetic dipole moment generated from the ...
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Is charge not quantized fundamentally and that is why we haven't come across magnetic monopole?
If protons are getting charged from quarks.. then the charge in quarks is fractional and not quantized. Does this mean that the charge we see is not fundamental? And the charges in quarks are just ...
