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### Explicit Ewald equations for dipole-dipole interaction in a simulation

I'm starting to work with spin ice simulations and I found that it is usual to use the Ewald method for the long-range interactions computation (dipole-dipole in this case). Although I've been reading ...
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### What is meant by 'a perfect dipole'?

Question What is meant by a perfect (electric) dipole? Additional information I came across the term in this question Force from point charge on perfect dipole and also in a textbook (which does ...
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### The dipole moment P in a metallic sphere

A metallic sphere is in a homogenous field $\vec{E}=E \cdot \vec{e_z}$. Put a dipole moment P at the origin, so the total potential is constant on a surface of a sphere with radius $a$. Which $p$ is ...
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### What do we mean with magnetic monopole and dipole?

What do we mean with magnetic monopole and dipole? I can not find a way to relate magnetic monopoles and dipoles with electric ones. I do not understand their outcomes. Also,what is their role in ...
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### Why doesn't a quantum pairwise Hamiltonian couple states in which more than one interaction occurs?

This question is about the standard quantum mechanical pairwise interaction Hamiltonian. I'll phrase it in terms of an example using Rydberg atoms, but you could just as well imagine spins (for ...
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### Born approximation and dipole approximation

I'm having some trouble really understanding when it's okay to use these approximations and why. I've been looking myself blind on equations, but I'm not even sure I understand it qualitatively. So I ...
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### What is retardation effect?

I have in my book a passage which states: "We also remark that the dipole approximation (obtained by setting $\exp(i \textbf{k} \cdot \textbf{r}) = 1$ in the matrix element Eq. #) yields the leading ...
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### Force between two point dipoles

What would the force between two parallel point dipoles be? I was thinking of doing it the way force between two point charges is found out, by finding the field and then the force but I am not able ...
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### How to derive the electron dipole selection rule in coupled bases?

We need to find $| \psi_f \rangle$ fulfilling the condition that $$| \langle \psi_f | \mathbf{x} | \psi_i \rangle |^2 \neq 0.$$ When using the uncoupled bases $| l,m,m_s \rangle$ I can derive the ...
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### Dielectric heating - does EM field transfer energy to polar molecules?

In AC field, polar molecule are trying to align with external field. At high freguencies, changes of field are so quict, that molecules cannot align with it. This leads to increasing kinetic energy of ...
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### Change in work done by dipole

How would you explain the intuition behind the equation $dW = -\tau d\phi$ for an electric dipole?
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### Calculation of Magnetisation current$(I_m)$

A Permanent magnet in the shape of a thin cylinder of length $10 \;\mathcal{cm}$ has $M=10^6A/m$. Calculate the Magnetisation Current $I_m$ (Here $M$ is the intensity of magnetisation) My ...
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### What makes an insulator good for polarizing?

Water in an electric field become polarized easily, since the natural dipoles twist and turn to align with the field. In non-polar insulating materials, a redistribution of charge can happen in the ...
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### Dipole approximation in solids

I have seen the use of dipole approximation (where the extent of the wave function is assumed to be much smaller than the wavelengths of the transitions or that of the electromagnetic field applied) ...