# Questions tagged [boundary-conditions]

The tag has no usage guidance.

605 questions
107 views

### Critical mass (radius) of U235

I am calculating the critical mass (radius) of $U^{235}$ sphere. I want to calculate the mass for three different cases: 1. air/vacuum surrounds the sphere (diffusion coefficient is infinite) 2. ideal ...
16 views

104 views

### boundary condition of perpendicular component of electric field of a thin sheet

This question is in reference to Introduction to Electrodynamics by David Griffith By Gauss's law: $\oint_{S} \vec{E}.d\vec{a}=\frac{Q_{enclosed}}{\epsilon_{0} }$ where $Q_{enclosed}$ is the ...
99 views

### Electromagnetic field in a box vs. boundary conditions

I understand that a commonly applied step (see Wikipedia for an example) in quantizing the electromagnetic field is "enclosing the field in a cubic box" and later taking a limit of that box to ...
109 views

136 views

202 views

### Boundary conditions in E&M

While deriving boundary condition for $B$ and $D$ we take a pill, box but for $E$ and $H$ we take a rectangular loop, why?
44 views

248 views

### Given total charge, how to calculate the surface-charge distribution

Suppose you given conductors $L_i$ with given geometry in space and the information that the conductor $L_i$ has the total charge $Q_i$ ($i = 1,\dots,n$). Suppose further that there are no additional ...
81 views

### Copenhagen interpretation and argument of boundary condition [duplicate]

Quote from https://en.wikipedia.org/wiki/Copenhagen_interpretation#Principles "...The wavefunction evolves smoothly in time while isolated from other systems." However, by the studying, my feeling ...
81 views

### Understanding the meaning of a certain boundary condition

Given, $$-k\frac{\partial T }{ \partial y}=h(T_f-T),$$ what does this term $$\left.{\partial T \over \partial y}\right|_{y =0}$$ physically describe in the convective boundary condition?
87 views

### Causally benign spacetimes and the Minkowski torus

A notion encountered in field theory on non-globally hyperbolic manifolds is the notion of a spacetime being causally benign with respect to some field $\phi$, which is defined thusly : A ...
172 views

### Why does a transmitted wave get narrower in space?

My question pertains to the following excerpt from my lecture notes: Part (b) of ﬁgure 2.12 shows a cartoon of a snapshot some time later. Both transmitted and reﬂected pulses have a smaller ...
103 views

### Fermion boundary condition for a thermal compact circle

Is this true that for fermion statistical systems in the thermal phase, with Euclidean time, $$\beta=1/T=t_E$$ the Euclidean time will be chosen to be anti-periodic for fermion boundary ...
47 views

### Elliptic genus on torus

The elliptic genus, in defined as $$\mathcal{E}=\text{Tr}\,q^{L_0-\frac{c}{24}}\bar{q}^{\bar{L}_0-\frac{c}{24}}y^{\alpha J^3}$$ can be computed as a path integral with different boundary ...
84 views

261 views

### Tangential component of Electric field

The above question i'm trying for so long but failed. This is from my class $12$ book(india).First of all i'm confused with tangential component of electric field, I mean why this? So far I've studied ...
211 views

### Governing equations and boundary conditions for a steady-state compressible viscous flow in an axisymmetric annular orifice

I'm trying to simulate a 2D axisymmetric model of steady-state compressible viscous flow using Mathematica, but I get some errors. There is a chance that I'm making some mistakes with the governing ...
34 views

### Query regarding putting boundary conditions to find the potential inside a box

In the examples given in textbooks, two or more sides of an infinite rectangular box are grounded, or have the same potential, so it becomes easier to put boundary conditions in solution obtained from ...
48 views

### Zigzag behavior on non-reflecting boundary

My goal is to simulate a 1D wave using the finite difference method, but I am having some trouble with the transparent boundary condition (TBC). I am trying to solve, \frac{\partial ^2y}{\partial t^...
246 views

### The consequence of electric field lines not being perpendicular to conductor (assuming a spherical one)

The following statement is from University Physics (chapter "Electric Potential"): "In particular, at any point just inside the surface the component of E vector tangent to the surface is zero. It ...
119 views

### Discontinuity of metric derivatives in the Israel junction formalism

It is often said that given the metrics $g^+$, $g^-$ on two sides of a hypersurface $\Sigma$, then, with a level-set function $\phi$ such that $\Sigma = \phi^{-1}(0)$, we can describe the metric on ...
69 views

### Incompressible 2D Navier-Stokes equation

I am trying to solve for and simulate the vorticity numerically (finite difference method), however there's one part I was hoping to get some help with. I need to find the fluid velocity $\mathbf{u}$ ...
410 views

### What does asymptotically flat solution mean?

Can somebody explain what does it mean when a solution is "asymptotically flat"? like the schwarzschild metric which is asymptotically flat solution to vacuum Einstein equations.
48 views

### How do waves get reflected at open end of an organ pipe? [duplicate]

Inside and outside of an open organ pipe usually medium used to be same (if i am not wrong) i.e Air, so in order to get standing wave reflection of wave is needed ( opp.in direction nd of same ...