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Qualitative consequences of repeated eigenvalues #7

Open neldredge-unco opened 11 months ago

neldredge-unco commented 11 months ago

https://github.com/twjudson/odeproject-public/blob/43d1bb9e45837a51a1ed7d127c528ca2c1be09fb/source/linear05.ptx#L278

I think this passage could use some more explanation. We describe the equilibrium at 0 as a "nodal source" (or sink), but what do we mean by that? In what ways is it like a node, and in what ways is it like a source? As it's still the case that all solutions diverge from the origin, why is it necessary to distinguish this case from an ordinary source?

Basically, this chapter discusses the algebraic issues around solving the system in the case of a repeated eigenvalue, and how the solution takes a special algebraic form. But I think it would help to have some discussion of how the behavior of such a system differs qualitatively from other cases.

twjudson commented 11 months ago

I see your point. We really don’t have “nodal” sources or sinks. Actually, the repeated eigenvalues case is the situation where we are moving from spiral equilibrium solutions to nodal equilibrium solutions, but I am not quite sure what to say. For the time being, I have eliminated the word “nodal.” I will have to think about what, if any, elaboration is needed.

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I think this passage could use some more explanation. We describe the equilibrium at 0 as a "nodal source" (or sink), but what do we mean by that? In what ways is it like a node, and in what ways is it like a source? As it's still the case that all solutions diverge from the origin, why is it necessary to distinguish this case from an ordinary source?

Basically, this chapter discusses the algebraic issues around solving the system in the case of a repeated eigenvalue, and how the solution takes a special algebraic form. But I think it would help to have some discussion of how the behavior of such a system differs qualitatively from other cases.

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