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Mathematicians Find Wrinkle in Famed Fluid Equations

quantamagazine.org

11–20 of 124 posts

Re: Mathematicians Find Wrinkle in Famed Fluid Equations

#11
post #8
post #5

Based off the abstract, there's one class of weak solutions, the Leray solutions, which are known to exist. And now they've shown for a different class of weak solutions to NS that the solutions are not unique. Is that right?

That's correct, while taking away the entropy inequality as well. The thing is that very inequality is one of these laws of thermodynamics we so love, so I kind of see this as hot air.

Isn't that possible though if the fluid isn't a closed system? (which it probably isn't)

Re: Mathematicians Find Wrinkle in Famed Fluid Equations

#12
post #9
post #8

Earlier quoted context omitted.

That's correct, while taking away the entropy inequality as well. The thing is that very inequality is one of these laws of thermodynamics we so love, so I kind of see this as hot air.

Aye either they have upturned a theory as august as general relativity or they’ve thrown the baby out with the bath water somewhere.

Based on my fairly layman understanding it could be as simple as the "weak solutions" not being as useful as they were thought to be.

Re: Mathematicians Find Wrinkle in Famed Fluid Equations

#14

Using this approach, Buckmaster and Vicol prove that these very weak solutions to the Navier-Stokes equations are nonunique. They demonstrate, for example, that if you start with a completely calm fluid, like a glass of water sitting still by your bedside, two scenarios are possible. The first scenario is the obvious one: The water starts still and remains still forever. The second is fantastical but mathematically p…

Yeah, I wondered about this too since the typical NS BVP, velocity vector is assumed to be confined to the domain of real numbers[0].

[0] https://warwick.ac.uk/fac/sci/statistics/staff/academic-rese...

Re: Mathematicians Find Wrinkle in Famed Fluid Equations

#17
post #9
post #8

Earlier quoted context omitted.

That's correct, while taking away the entropy inequality as well. The thing is that very inequality is one of these laws of thermodynamics we so love, so I kind of see this as hot air.

Aye either they have upturned a theory as august as general relativity or they’ve thrown the baby out with the bath water somewhere.

The laws of thermodynamics are quite a bit more august than GR

Re: Mathematicians Find Wrinkle in Famed Fluid Equations

#18

Using this approach, Buckmaster and Vicol prove that these very weak solutions to the Navier-Stokes equations are nonunique. They demonstrate, for example, that if you start with a completely calm fluid, like a glass of water sitting still by your bedside, two scenarios are possible. The first scenario is the obvious one: The water starts still and remains still forever. The second is fantastical but mathematically p…

> Also permissible, and also vanishingly unlikely, under quantum theory.

Navier-Stokes has nothing to do with Quantum Mechanics..

Re: Mathematicians Find Wrinkle in Famed Fluid Equations

#19
post #18

Using this approach, Buckmaster and Vicol prove that these very weak solutions to the Navier-Stokes equations are nonunique. They demonstrate, for example, that if you start with a completely calm fluid, like a glass of water sitting still by your bedside, two scenarios are possible. The first scenario is the obvious one: The water starts still and remains still forever. The second is fantastical but mathematically p…

> Also permissible, and also vanishingly unlikely, under quantum theory. Navier-Stokes has nothing to do with Quantum Mechanics..

No one said it does. But given that statistics based on complex probabilities are effective in one domain, maybe they're worth investigating in another.

Re: Mathematicians Find Wrinkle in Famed Fluid Equations

#20
post #9

Earlier quoted context omitted.

Aye either they have upturned a theory as august as general relativity or they’ve thrown the baby out with the bath water somewhere.

The laws of thermodynamics are quite a bit more august than GR

I’ll leave such distinctions to more seasoned minds.
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