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Is it impossible to make a general theory...
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Is it impossible to make a general theory of nonlinear partial differential equations? Isee them everywhere, from plasma confinement tonjosephson junctions, and im curious if you can derive those named equations from a Universal theory. I see most of the millenium prize probelems dealing with them too, so im curious if there is a profound nature behind understanding what a solution is in a general way.
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>>7837924

Not many differential equations are explicitly solvable, OP. Often times you have to settle for a description of qualitative behavior as opposed to an explicit solution. Any "general theory of nonlinear partial differential equations" would have to be so general that it is in practice virtually unusable.
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I'm on to you OP
http://mathoverflow.net/questions/15292/why-cant-there-be-a-general-theory-of-nonlinear-pde
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>>7838400
>Not many differential equations are explicitly solvable, OP
Literally prove it faggit.
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>>7838400
can't you make an axiomatic framework like Zermelo Frankel set theory did to exclude those cases?
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>>7838541
>can't solve 5-th degree polynomial equation with certainty
>expects to solve all differential equations
spaceX is bringing my sides back to earth after they go get them.
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>>7838614
I've seen a rigorous proof for the unsolvability of 5th order polynomials, I have not seen a proof for non-linear PDE classes. We have exact analytical solutions to many non-linear PDEs, a statement like "not many differential equations are explicitly solvable" is extremely premature.
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>>7838614
>thinks there's an algebraic hierarchy for resolvability

the only sides in orbit are mine, friendo.
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>>7838614
your sides will probably explode then
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>>7838618
it's not premature seeing as PDEs have been of great consideration for nearly as long as ODEs--and the former theory still has a great deal of trouble in finding exact solutions. His statement is from experience, there simply isn't a general approach to ODEs. There is great numerical approach to linear ODEs, but these still usually do not have a nice closed form expression (again, in practice). Non-linear ODEs can be tricky as you don't have a large toolset to approach them. PDEs increase the difficulty in that your solution space gets more complex. The nature of PDEs is finicky, which is not a precise statement but I mean to describe the relative ease in which even simple looking PDEs can not only lack a closed form solution, but lack any solution entirely.
Rather than complain on an anonymous imageboard, you should ask yourself 'what do I mean by a general PDE?' and work from there to see what troubles you might encounter. A great deal of mathematics from Lie Algebras to Differential Geometry and the more structured spaces studied in Functional Analysis are motivated by alternative perspectives on solving PDEs.
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>>7838614
>>can't solve 5-th degree polynomial equation with certainty
you fucked up.
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I'm really interested in differential equations but I'm only in an undergrad DE course

Any tips or useful tricks?

I really like the annihilator method
Thread replies: 12
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Thread DB ID: 512931



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