# Tagged Questions

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

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### Need help understanding the output of DSolve

I give Mathematica 10 the following command: DSolve[I D[P[x], {x, 2}] f[x] - (P'[x])^2 f[x] + 2 I P'[x] f'[x] == 0, P, x] and I have the following output: ...
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### How can I handle interface thermal boundary conditions?

I am trying to solve a system of PDE´s coupled by interface boundary conditions, this is my code: ...
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### Solving non-linear differential equation

For my research project I need to solve the following integral ...
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### FM NMOR in Cesium with Atomic Density Matrix package [closed]

I am trying to use the atomic density matrix package in Mathematica to simulate FM NMOR in Cesium. The example given in the package is for a specific system from J=1 to J'=0. I am trying to simulate ...
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### How to determine the redundant equation in the set of DE?

my problem is messy, and I will use a simple problem to explain my problem. Suppose, we have a set of DE: ...
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### Struggling with WhenEvent in NDSolve

I am doing some biological system modeling and trying to use WhenEvent in the initial conditions section of my NDSolve code to allow me to periodically change the value of a parameter (which I've ...
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### NIntegrate::inumr: “The integrand E^(-0.9τ1) DiracDelta[t-τ1] v[t-τ1] x[t-τ1] has evaluated to non-numerical values ”

I am facing an interesting situation over here. The aim is to solve a system of IVP having an integral over a delay range. Here is my try ...
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### ParametricPlot that worked in Mathematica 9 stops working in Mathematica 10

I've updated to Mathematica 10 and I am trying to plot the solution of a system of ODEs and I'm using exactly the same file that used to work in Mathematica 9, but now when I want to plot the solution ...
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### Second Order ODE (Bessel Function) with a dependent variable in the BC

I have obtained an analytic solution to the following problem however I lack the knowledge to generate a numerical solution using mathematica. I'm reaching out to get an idea of what functions I may ...
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### Does NDSolve automatically simplify the system of equations for Hermitian matices?

I am currently starting to solve numerically a system of differential equations like this: $\dot{A}(t)=S(A)A(t)$ Here, the matrices are of dimension $d\times d$. $S(A)$ is some superoperator that ...
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### Strange behavior in ContourPlot?

I'm have a Abel's differential equation: ...
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### How to locate the position of a periodic orbit

These are the equations of the dynamical system ...
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### Can't NIntegrate my NDSolve results

I want to NIntegrate my NDSolve result. I don't have a exact function form because it is coming from the ...
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### DSolve documention on web differs greatly from distributed MMA 10.2.0 version

In the course of improving my answer to 95361, I noticed that the DSolve documentation on the web is much better written than that distributed with Mathematica 10.2....
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### Trying to model a chemical reaction - NDSolve::litarg error

I am trying to model a chemical reaction with NDSolve. I have specified the known differential equations and parameters, ...
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### DSolve gives an empty solution set to a solvable ODE

I really hope this isn't a duplicate, today I was answering this question and was to lazy to solve the quadratic equation on my own and so just asked mathematica to give me the solution of the ...
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### Plotting a Bifurcation diagram

I have the following system equation v'(t)=2*G*J1[v(t-τ)]cos(w*τ)-v(t) How do you plot the bifurcation diagram, τ in the x ...
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### Paramtric plot for 3 variable system

I have an system where I have calculated migration of "i" number of species "c" in "j" different habitats as a function of time. ...
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### Numerical Analisys and StepDataPlot

I'm using StepDataPlot to compare several methods for differential equations. Does exists a function, or something else, to find the number of steps that the choosen method used to find the numerical ...
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### WhenEvent stops working after first instance

I'm modelling a very simple physical situation is which an object is rested on two moving fingers. Sometimes the object moves with one finger while sliding over the other, while at other critical ...
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### Plot Lorenz system

I solved the Lorenz system by using Euler forward method (without using NDSolve). But I am not getting the attractor. The Mathematica code is as follows ...
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### Solving coupled ODEs with NDSolve to fit experimental data

I need to fit a multi-exponential data (Intensity x Time) using a model consisting of three differential equations. I want to find the parameters that gives the best fit to the experimental data. ...
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### NDsolve complicated function

I'm trying to solve a complicated second-order ODE with NDSolve. I've never used NDSolve before. I've looked a lot of forums and tried some things, but I haven't been able to get the ODE's solution. ...
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### Problems with multidimensional system of ODEs

I am trying to look at the migration of "i" number of species "c" in "10" number of habitats {designated as "j"} and to study their population size as a function of time "t". I have this following ...
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### NDSolve::ndode: Input is not an ordinary differential equation [closed]

I am new to Mathematica. I am working on solving the following different equations numerically written in the code as below. ...
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### DSolve gives no output

I have troubles finding a solution to a system of three coupled nonlinear ODEs. When I put it into Mathematica, I get back the input as an answer. Could anyone tell me what I'm doing wrong? Here is ...
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### Singularity problem of a 2nd order differential equation

I would greatly appreciate your help in implementation of Mathematica for solving a 2nd order differential equation expressing some important engineering problem. Apparently, this equation has no ...
Problem Suppose I have a differential equation such as $\qquad f'(x)+f(x)=0$ and I want to change it into $\qquad y'+y=0$ My Method Using rule = f[x] -> y,...