Symmetry in differential equations

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Discussion Overview

The discussion revolves around the role of symmetries in differential equations, exploring how they can facilitate the transformation of equations into more manageable forms, such as separable equations. Participants inquire about the implications of symmetries in both theoretical and practical contexts, including the application of Lie point symmetries.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that symmetries provide a systematic approach to finding coordinate changes that simplify differential equations into separable forms.
  • Another participant explains that symmetries can allow for assumptions about the forms of solutions, particularly in the context of partial differential equations with rotational symmetry, which can lead to a reduction to ordinary differential equations.
  • A question is raised about whether any general symmetry can be transformed into a translational symmetry through suitable coordinate changes, implying a search for an existence theorem.
  • Another participant discusses the application of Lie point symmetries for finding general solutions to differential equations and notes that symmetries cannot be universally mapped into one another.
  • Resources are suggested for further learning, including a book by Peter Hydon and papers by Cheb-terrab et al. regarding algorithms for systematically searching for symmetries.

Areas of Agreement / Disagreement

Participants express various perspectives on the nature and implications of symmetries in differential equations, indicating that multiple competing views remain without a clear consensus on the transformation of symmetries or the existence of theorems related to them.

Contextual Notes

The discussion does not resolve the assumptions regarding the transformation of symmetries or the applicability of specific methods, leaving these points open for further exploration.

Getterdog
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Before I delve into this , I just wanted to know the basic approach. Do we look for symmetries because it gives us a systematic way to find coordinate changes that change the differential equation into a separable one? Thanks jf
 
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In general, you look for symmetries as a means of letting you assume particular forms of the solutions. For example, if you have a partial differential equation in three dimension that displays full rotational symmetry (including the boundary conditions!) then your solution cannot depend on the angular variables and you can reduce the problem to an ordinary differential equation for the radial solution.
 
Ok,so my next question is,can any general symmetry be transformed to a translational symmetry by a suitable change of coordinates,ie an existence theorem.? Thanks
 
Do you mean applying Lie point symmetries to find general solutions to differential equations? You can apply it as in your first post, and look for coordinate changes that will solve the (usually ordinary) differential equation. You can also use it for much more than that. Symmetries cannot be mapped into each other. A nice book to start with if you want to learn more is the introduction book (symmetry methods for differential equations) from Peter Hydon. Or if you are looking for algorithms that are systematically searching for symmetries, there are many papers from Cheb-terrab et al, who worked a lot on the ode solvers in Maple.
 

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