# Tagged Questions

Questions on the symbolic (DSolve, DifferentialRoot) and numerical (NDSolve) solutions of differential equations in Mathematica.

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### Does NDSolve iterate faster in a region where the system being solved is in equilibrium?

I was wondering how exactly the time it takes for NDSolve to iterate through a certain region of the domain depends on the local behaviour of the given system being solved. My guess would be the ...
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### How to speed up NDSolve?

I have a program where I need to iterate NDSolve thousands of times for different configurations of a diffusion problem. The thing is, I only need about 3 digits of accuracy. I looked thru previous ...
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### Lyapunov exponent of non-autonomous differential equation

I am trying to calculate the Lyapunov exponent for a non-autonomous system using M Sandri code, but it always shows me error "infinite expression 1/0 encountered". Does anyone know about this? Mr. ...
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### How do I extract the values returned as Root[,] after solving the Sturm Liouville problem to take the square root?

$y''+\lambda y=0, y'(0)=0,y(1)+y'(1)=0$ ...
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### Getting DSolve to return different solutions [on hold]

I am Using 10.0 I am trying to solve the following ODE: $$\frac{d^2 \psi}{d\theta^2}+ \nu \psi =0$$ , $$\psi(0)=0$$,$$\psi(3\pi/4)=0$$ and Mathematica only sppits out the trivial solution PS: I am ...
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### NDEigensystem returns incorrect eigenvalues for 2D coulomb problem, eigenfunctions contain discontinuity

I posted a similar question a short time ago regarding the 3D Coulomb problem. Jens' excellent answer to this thread allowed me to obtain the correct eigenvalues and eigenenergies for that system. I ...
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### Finding the correct boundary conditions to a specific problem

I want to reproduce the following problem in the figure: $$\phi''+c\phi'\sqrt{m^2\phi^2+\phi'^2}+m^2\phi=0$$ where $\phi=\phi(x)$ with $x \in (-\infty,\infty)$, $c=\sqrt{3/2} \$ and $m=0.2$. ...
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### System of partial differential equations using Mathematica [closed]

As you can I am trying to solve a system of partial differential equation using MATHEMATICA. However, I could not. Can anyone provide me with a code which is able to solve such equations in ...
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### Assigning Element Markers to 3D FEM Mesh

I have created a 3D graphic using GraphicsComplex and then use ToElementMesh to generate a 3D Mesh that I want to solve a PDE on, but I cannot figure out how to apply ElementMarkers to the Boundaries. ...
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### NDEigensystem cannot solve numerically the 3D Coulomb problem, while DSolve returns the right answer

After having derived by hand the eigenvalues and eigenfunctions for the 3D and 2D hydrogen atom, I want to solve the systems numerically using Mathematica. I need to do this because my next step is to ...
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### Finding Laplace Transform [closed]

With the following DE y"(t)+5 y'(t) +6y(t)= t 0 How do I find the Laplace Transform to find the IVP??? I've tried everything and I can't figure it out.
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### how to solve second order nonlinear coupled differential equations using NDSolve with hyperbolic function

i have to solve some solitons scattering through this coupled equations. i need to get two different graph, but still the graph did not come out. and also the equations quite complicated containing ...