Questions tagged [boundary-value-problem]
For questions concerning the properties and solutions to the boundary-value problem for differential equations. By a Boundary value problem, we mean a system of differential equations with solution and derivative values specified at more than one point. Most commonly, the solution and derivatives are specified at just two points (the boundaries) defining a two-point boundary value problem.
1,828 questions
2 votes
0 answers
175 views
Proving bounds for differential equation system?
For the system $$ \begin{cases} x'(t)=-a(t) \cdot x(t)\cdot y(t)+y(t)-\varepsilon \cdot (z(t)+y(t))\cdot y(t)\\ y'(t)=k\cdot z(t)-y(t)+\varepsilon \cdot(y(t))^2=k\cdot (1-x(t))-(k+1)y(t)+\varepsilon \...
0 votes
0 answers
14 views
Boundary values for b splines under clamped knots
I am trying to proof this by induction Proposition (Boundary values under clamped knots): Let $\{t_i\}_{i=1}^{m=n+k}$ be a clamped knot sequence of order $k$ on the interval $[a,b]$, that is, $$ t_1 = ...
0 votes
0 answers
50 views
Why must the Green's function for a linear ODE satisfy homogeneous boundary conditions?
I am reviewing the method of Green's functions for solving boundary value problems of the form: $$ \mathcal{L}u = f(x), \quad \text{with} \quad u(0) = A, \quad u(L) = B, $$ where $\mathcal{L}$ is a ...
0 votes
0 answers
41 views
$H^{\frac{3}{2}}$-regularity of a specific elliptic mixed boundary valued problem.
Let $M$ be a compact Riemannian manifold with connected smooth boundary $\Sigma$. Let $\Sigma_D$ and $\Sigma_N$ be two disjoint smooth domains of $\Sigma$ with $\Sigma = \overline{\Sigma_D\cup\Sigma_N}...
1 vote
0 answers
49 views
Complex variable Biharmonic BVP
Consider the Complex variable Partial Differential Equation: $$ \Delta^2 w =f $$ with boundary conditions $$ w=\varphi_0 ~~\text{and}~~ \partial_{\bar{z}}w =\varphi_1. $$ A unique solution to this PDE ...
0 votes
0 answers
55 views
Does anyone know the identification of this boundary value problem? The coupled boundary conditions are what make it special
I've been reading THIS PAPER to handle a particular boundary value problem in my field, and the paper characterizes the finalized form of this problem as a "special problem of mathematical ...
11 votes
1 answer
341 views
Boundary value problem for Laplace's equation / probability a BMP leaves cone via the ice cream rather than the biscuit
Suppose I start a Brownian motion $X_t$ at position $(0,0,\varepsilon)$ in $\mathbb R^3$. Suppose also I have a cone with its apex at the origin, given by $U=\{(x,y,z):\sqrt{x^2+y^2}< z\tan\alpha\}$...
3 votes
2 answers
80 views
Problem on choosing the sign of the solution of a PDE using Fourier series
I'm trying to solve the following PDE using the Fourier series method: \begin{align} &\partial_t u(t, x) - t\partial^2 u(t, x) = 0 && x \in [0, \pi], \; t\in\mathbb{R}^+ \\ &u(t, 0) = ...
0 votes
1 answer
76 views
How unique are unbounded solutions to the Dirichlet Problem?
Let $\Omega$ be a domain, and consider the Dirichlet problem $\Delta u=0$ in $\Omega$, $u=f$ in $\partial\Omega$. If $\Omega$ is bounded, then the maximum principle says that solutions, if they exist, ...
1 vote
0 answers
30 views
Capacity–duty flux split for gated vs fixed window
Let $D\subset\mathbb{R}^3$ be a bounded $C^2$ domain. On its boundary $\partial D$, place two disjoint, tiny patches $S_\varepsilon$ and $T_\delta$ with diameters $\varepsilon,\delta\ll1$. Consider ...
0 votes
0 answers
61 views
Transient cylindrical heat equation in 1D, boundary conditions and Bessel functions
I apologize beforehand for the long question. Here is the case: A vertical pipe is in (assumed perfect) contact with the surrounding ground. We consider the initial temperature to be homogeneous for ...
3 votes
2 answers
145 views
Analytical solution to the following BVP
Consider the frequency domain problem $$\begin{align}v_{xx} -\lambda v &= \delta(x),\\-v_x(0)&=i\omega \alpha v(0),\\ v_x(1)=0,\end{align}$$ where $\lambda := -\omega^2$. I want to find the ...
0 votes
0 answers
26 views
Dominant balance in finding a uniform approximation to a BVP
My question comes from Example 3.11 (p.184) of Applied Mathematics 4th ed by J. David Logan. The example is on finding a uniform approximation to a boundary value problem. Here's the relevant snippet ...
3 votes
1 answer
45 views
Example for a domain which does not satisfy the Poincaré-Cone-Condition but has a unique solution for the Dirichlet-Problem
I am learning about the Dirichlet-Problem, especially the probabilistic Solution by Kakutani. I am following chapter 3.1 from the book 'Brownian Motion' written by Peter Mörters and Yuval Peres , ...
0 votes
0 answers
44 views
Definition of 'natural boundary conditions' for Vlasov problem
I am currently reading this paper covering a numerical scheme for solving the guiding-center Vlasov equation on a 2d square grid. The system is: $$\frac{\partial \rho}{\partial t} + \textbf{v}_D\cdot \...