Solving Logistic ODE with Non-commuting Matrices

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Discussion Overview

The discussion revolves around finding a general solution for the logistic ordinary differential equation (ODE) involving non-commuting matrices. Participants explore potential solutions and the implications of matrix commutation on the formulation of the problem.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes a solution for the logistic ODE in the form of U=(I+e^{-Ax})^{-1}, but notes that this does not hold when U and A do not commute.
  • Another participant suggests that the general solution to the scalar equation might inform a similar solution for the matrix version, presenting E^(A x)/(E^(A x) + E^C) as a potential form.
  • A participant asserts that if U is a function of A, then U commutes with A, implying a restriction on the form of U.
  • Another participant counters that U being a function of both A and the initial condition leads to non-commutation unless the initial condition also commutes with A.
  • A suggestion is made to transform the ODE by diagonalizing A and expressing U in terms of a transformation involving a diagonal matrix D, leading to a new form of the ODE.
  • One participant mentions attempting to diagonalize both A and the initial condition but reports no success in resolving the commutation issue.
  • A question is raised regarding the practical goals behind seeking a formal solution to the ODE.

Areas of Agreement / Disagreement

Participants express differing views on the implications of matrix commutation for the solution of the logistic ODE, with no consensus reached on a general solution or approach.

Contextual Notes

The discussion highlights limitations related to the assumptions about commutation between matrices and the dependence of U on both A and initial conditions, which complicates the search for a solution.

Who May Find This Useful

This discussion may be of interest to those studying advanced topics in differential equations, particularly in contexts involving matrix algebra and non-commuting operators.

Manchot
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I'm trying to find a general solution for the logistic ODE \frac{dU}{dx}=A(I-U)U, where A and U are square matrices and x is a scalar parameter. Inspired by the scalar equivalent I guessed that U=(I+e^{-Ax})^{-1} is a valid solution; however, U=(I+e^{-Ax+B})^{-1} is not when U and A don't commute. Any ideas?
 
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The general solution to the scaler equation is:

E^(A x)/(E^(A x) + E^C)

where C is a constant.
Maybe this can lead to a similar solution for the matricial version?
 
If U is a function of A,
then U commutes with A.
 
I tried all sorts of versions of the scalar equation, maajdl. They all run into the same commutation problem. Unfortunately, U is a function of both A and the initial condition, which means that it doesn't commute with A unless the initial condition does.
 
Could that help?

Assuming:

A = M-1DM where D is a diagonal matrix
V = MUM-1

The ODE becomes:

dV/dx = D(I-V)V
 
Yeah, I tried diagonalizing both A and the initial condition. No dice.
 
What is your practical goal?
Why do you need a formal solution?
 

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