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# Questions tagged [boundary-conditions]

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### Electric field boundary conditions proof

Good day I have a question regarding the boundary conditions proof: here is my question : in order to proof that the tangential component of the electric field are equal in the two mediums we start ...
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### Fluid-solid coupling, how to impose both normal stress and velocity?

I'm trying to solve the coupled Navier-Stokes/elasto-dynamics equations using a discontinuous Galerkin approach in order to propagate waves through a fluid-solid interface. I was wondering how to ...
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### An electrostatic problem for two disks in $\mathbb{R}^2$ - how can the solution be represented?

The electrostatic Laplace problem for the exterior of a disk can be solved in a straightforward manner using separation of variables. Suppose we have a unit disk $\Omega$ with a charge density of $f$ ...
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### What is the logic behind box normalization and periodic boundary condition?

Free particle energy eigenfunctions are $A\exp{[i(Et-\textbf{p}\cdot\textbf{r})/\hbar]}$ are non-normalizable. To normalize them one introduces a procedure called 'box normalization' where one imposes ...
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### Why is magnetic field parallel to the surface of a conductor?

On Jackson- Classical Electrodynamics it is said that, for a perfect conductor the magnetic field is always parallel to the surface, that is $$\mathbf{B} \cdot \mathbf {n}=0$$ I do not understand ...
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### Why the variation of a surface term is zero?

My original question is like: Why are the Euler-Lagrange equations invariant if we add a surface term to the action? And there is an answer by Javier: https://physics.stackexchange.com/a/...
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### Why is Hamilton's Principle not the 'Principle of Least Action'? [duplicate]

Hamilton's Principle is that the first order variations of $\displaystyle\int^{t_2}_{t_1} L$ $dt$ for an on-shell trajectory in the configuration space should vanish provided the varied off-shell ...
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### Clarification of this statement on image charges?

I am currently studying the uniqueness theorems and their applications in electrostatics. I then came across a problem which mentions: "The standard electrical image method fails because the image ...
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### Boundary conditions for the numerical particle in a box example

I want to solve the one-dimensional Schrödinger equation for the particle in a box example, and want to force the wavefunctions to zero on the boundaries. I am using the matrix, \begin{equation} \hat{...
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### What are the boundary conditions for D4-branes ending on D8-branes?

In a recent paper by Cordova and Jafferis, they perform the physical derivation of the AGT correspondence. A crucial step is recognizing that the appropriate boundary conditions for the 5D super Yang-...
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### Does the quantization come from that the wave function $\psi$ should vanish at infinity?

For one dimensional non-relativistic quantum mechanics, the solutions to $\hat H\psi=E\psi$ seems not requiring the energy $E_n$ to contain the "$n$" term without specific boundary conditions. Does ...
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### Why boundary conditions of an open string involve the time derivative?

I am trying to understand the boundary conditions of an open string stretching from one brane to another, in TIIA theory. Let's consider to D6-branes which spans a line along the $(x_4,x_5)$ plane ...
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### The derivation of the Planck distribution

I am trying to understand the Planck distribution and black body radiation. In the Wikipedia derivation of the Planck distribution, the photons confined within a cubic box, are emitting from and ...
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### Continuity of tension in falling objects

Imagine I'm holding a block of mass $m_1$. At the bottom of this block is a rope that is fastened to another block of mass $m_2$. We're in a uniform gravitational field $g$. In a minute I'm going to ...
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