# Questions tagged [boundary-conditions]

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### Boundary condition not working on infinite place (uniformly charged) with dielectric on one side and vacuum on the other

To describe this situation mathematically, we have an infinite place at $z = 0$. For $z > 0$ a vacuum is present while for $z < 0$ a linear dielectric with dielectric constant $\epsilon_{r}$ is ...
93 views

### Why do we take the wave function to be zero at the edges of the box when solving the Schrödinger Equation for particle in a box?

The evanescent wave would be penetrating the box so why don't we account for that even if it decays, there might be some part protruding the box with walls of infinite potential.
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### General relativity, quantum gravity, and boundaries?

Does it make sense to have a spacetime in general relativity that has a finite extent or boundary. I'm not talk about a hyper-torus or hypersphere shaped spacetime but rather has there been studies of ...
38 views

### Gauge transformation and phase matching in cylinder coordinate for the Aharonov-Bohm Effect

I'm trying to get through Sakurai The Aharonov-Bohm Effect where on page 141. According t0 Eq 2.7.53, if the original equation was transformed by a gauge $\tilde A=A+\nabla \Lambda$, then the ...
87 views

### pn junction: band bending vs. fermi level bending [closed]

① I have two semiconductors of the exact same material. Hence, the conduction band and the valence band are exactly on the same level. The same holds for the vacuum level. Now the left one is p-doped, ...
30 views

### How do we get Maupertuis Principle from Hamilton's Principle?

Maupertuis principle says that if we know the initial and final coordinates but not time, the total energy and the fact that energy is conserved, we can choose the "right" path from all mathematically ...
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### What does the Neumann boundary condition imply for the electric flux lines?

If I prescribe a Neumann boundary condition in an electrostatic problem, that means that I am prescribing a surface charge density, and in the way I understand it that means that the electric flux ...
45 views

### Is there any meaning for the path found by Hamilton's Principle to an impossible state?

Hamilton's principle is written as a statement about the path taken between two states of the system which occur. Is there any meaning found in solving the variational problem for points which can ...
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### Derivation of boundary conditions of electric and magnetic fields

In the proof of boundary conditions given in some books on electrodynamics, the approach was to a take a pillbox and use the Maxwell's law on this pillbox-like surface and apply some limits on the ...
23 views

### Open boundary condition or no condition at all?

I want to write a model for a 1-D wave $\rho(x,t)$, with boundary conditions at $x=0$ and initial conditions at $t=0$. I want this wave to be free to propagate after any distance $L$. Should I just ...
55 views

### Intuitive explanation for why reflected waves change phase by $π$? [duplicate]

I have seen the equations that show the coefficient of reflection etc. But I'm searching for an intuitive rather than solely mathematical explanation for why waves change phase by π when reflected (...
27 views

### Delta functions for surface of non trivial shapes

Say I'm trying to solve Laplace's equation on an object that isn't a sphere or a trivially characterized surface. I will want to solve: \nabla^2G\left(\mathbf{r},\mathbf{r}'\right)=-4\pi\delta\left(...
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### Why is an experimental basis used to solve the scattering state problem of the finite well when they do not represent a physical particle?

The first time I was doing the finite square well problem in QM, there was a dissection of the problem into bound and scattering states. For the bound states, the appropriate boundary conditions were ...
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### Infinite sheet in static magnetic field [duplicate]

What happens if I add a infinite sheet of a perfect conductor in a constant applied magnetic field perpendicular to the surface? e.g. I have a sheet in the x-y plane and I apply $B_0 \hat{\mathbf{z}}$....