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Computer proof ‘blows up’ centuries-old fluid equations

quantamagazine.org

131–140 of 223 posts

Re: Computer proof ‘blows up’ centuries-old fluid equations

#131

I remember my math professor at university telling me that truth in mathematics was a social construct, and that nothing was true until a social consensus had been reached between mathematicians. This struck me at the time as a very powerful statement, yet unexpected, since very much not what most people expect from mathematics. After all, it's supposed to be a field where there is such a thing as a (most of the time…

I don't know why you're being downvoted, but that is a perfectly valid statement. Everyone thinks proofs are this holy grail and totally rigorous, and they are on a certain level. But the idea is floating around that Mathematicians are infallible when in fact lots of proofs in highly complex areas of mathematics are NOT 100% perfectly rigorous. They contain a lot of skipping, because "it's trivial" and consensus. Thi…

You should read "Proofs and Refutations by Imre Lakatos" if you haven't already.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#132

Earlier quoted context omitted.

The issue with bit-patterns are, at least, they're discrete. And so cannot, eg., represent pi. This project is about real-valued functions which are taken to describe physical reality. Almost all of physical reality has no closed-form analytical description that "traditional mathematics" can operate on. So there arent any relevant symbolic rules of inference yet invented to resolve this problem. If you want to progra…

Computers work with perfect representations of pi all the time. The TI-89 will do it routinely. All of your objections continue to apply just as strongly to human mathematicians as they do to computers. But you apparently believe there is a difference between what the mathematicians can do and what the computers can do. This is false. Any problem that occurs in computers' representations of values will also occur in…

So this is just not true, and I'm not exactly sure where these premises are coming from. Is it a misunderstanding of theoretical computer science, mathematics, engineering, or what?

But I can at least now see why you're attached to extremely strange notions about, eg., floats being sufficient representation for mathematical reasoning. Ie., some article of faith that "computers" must be capable of everything.

There is no "symbolic computation on pi" that arent rules of inference created by people. We arent born with these rules, we create them. So if we havent yet created them, there's no sense in saying any actual computer is capable of anything. Actual computers are merely implementations of rules we'd have to create.

The process of conceptualising the world is, in my view, continuous and non-cognitive. One example of it is in the generative capacities of the imagination, which presents situations as wholes and it's latent space imv is continuous -- having to do with the structure of the sensory-motor system.

In any case, regardless of whether you believe animals have access to a continuous reality which cannot be formalised in discrete mathematics, we arent talking about whether there are possible computers which can reason this way -- we're talking about actual computers. (Though we have no reason to suppose there are such possible computers, and proofs against such things, ie., the non-computability of the reals).

It's relatively trivial to show that all existing computers are woefully incapable of a vast amount of things. Consider, only, the exponential space complexity of storing the parameters of a chaotic system. In any existing computer, we'd need an electronic system the size of a planet merely to track what's going on inside an atom.

It requires vast arrays of machines to track surface properties of particles interacting in the LHC, for example.

Yet, of course, we can formulate QFT. There are a near infinite number of such "existence proofs" of the power of animal mental capacities: AND NOT A SINGLE ONE! Of machine capacities.

No existing actual computer has ever created a system of concepts to formalise a hitherto unformalised domain. No one has even solved the problem of how it would be possible for a machine to do so (ie., the framing problem).

This makes actual computers, and all possible ones we can presently even imagine useless for open problems with unformalised domains.

The only role a computer can play here is providing an implementation of a discrete aproximation we have created, and this aproximation is woefully inadequate to the task. Even using a computer here is just a means of improving the power of human speculation.

In any case, this article of faith in the power of discrete mathematics and the electrical systems which we use to implement it, blinds you to the overwhelming and woeful inadequacy of all existing systems.

To the point you're even defending floating pt representations of infinity. If you really wish to cling to that religion, you're going to have to get better at choosing which hills to die on. Saying floats here are a sensible means of representing problems in continuous mathematics is absurd, and discredits your views greatly.

The only computers you should be defending here are "presumably possible" ones, yet to do be defined, yet even to be specified.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#133

Earlier quoted context omitted.

> What prediction is that? For example, all the predictions that make us capable of building skyscrapers that don't fall down for centuries. Does it matter that two bricks are not "the same piece of matter" if our predictions work the same for both of them? In terms of their behavior under particular circumstances, they are the same.

> Does it matter that two bricks are not "the same piece of matter" if our predictions work the same for both of them No, because of a dense, interconnected web of other social truths (the rest of the arithmetic model), the relative error of this one truth/model is negligible. However, confusing your model for reality is a fallacy perhaps older than time.

I don't understand how is "the arithmetic model" a social truth, when it clearly corresponds to physical phenomena. You can make a skyscraper that doesn't fall, and it exists regardless of whether other people see it or not. You see it - it's there. What is "social" about that?

> However, confusing your model for reality is a fallacy perhaps older than time.

I think that the human perception the world is a robust enough model to be equated with reality without issues. If you go down the path of denying perception, you might as well go full solipsism, in which case it doesn't even make sense to discuss reality at all.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#134

The question that the referenced paper (1) is trying to answer is "do the 3D incompressible Euler equations develop a finite time singularity from smooth initial data of finite energy?" This is an important question in the theory of nonlinear partial differential equations, but is probably not as relevant to real fluid flow as a lay reader might imagine. The incompressible Euler equations model a very strange and unp…

What a wonderfully informative and educational comment. Thank you. Would you also be able to shed some light on what a singularity is? It was not intuitive to me that incompressiblity should lead to a singularity. The article dances around the term: > At that point, the Euler equations are said to give rise to a “singularity” — or, more dramatically, to “blow up.” > Once they hit that singularity, the equations will…

I think (not a physicist), simply put, an infinity or NaN value. As these are step-wise methods, having such values show up anywhere will seriously mess up subsequent calculation steps.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#135

I remember my math professor at university telling me that truth in mathematics was a social construct, and that nothing was true until a social consensus had been reached between mathematicians. This struck me at the time as a very powerful statement, yet unexpected, since very much not what most people expect from mathematics. After all, it's supposed to be a field where there is such a thing as a (most of the time…

Mathematical truth is socially constructed, but using rules, and it is the rules, rather than the process of social construction, which give this process its power.

An interesting meditation here on mathematics itself, which is also simply certain rules, and not others.

Merely invoking social construction ignores this difference, which is the essential difference, between mathematics and, say, hide and go seek.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#136

I remember my math professor at university telling me that truth in mathematics was a social construct, and that nothing was true until a social consensus had been reached between mathematicians. This struck me at the time as a very powerful statement, yet unexpected, since very much not what most people expect from mathematics. After all, it's supposed to be a field where there is such a thing as a (most of the time…

Truth in math is not a social construct. But belief in math is a social construct.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#137

I remember my math professor at university telling me that truth in mathematics was a social construct, and that nothing was true until a social consensus had been reached between mathematicians. This struck me at the time as a very powerful statement, yet unexpected, since very much not what most people expect from mathematics. After all, it's supposed to be a field where there is such a thing as a (most of the time…

I would have asked how he could assert the truth of the proposition "Truth in mathematics is a social construct", since its truthfulness has to be a social construct too. (I assume that mathematics encompasses formal logic too)

Re: Computer proof ‘blows up’ centuries-old fluid equations

#138

I remember my math professor at university telling me that truth in mathematics was a social construct, and that nothing was true until a social consensus had been reached between mathematicians. This struck me at the time as a very powerful statement, yet unexpected, since very much not what most people expect from mathematics. After all, it's supposed to be a field where there is such a thing as a (most of the time…

Social constructionalism is to my understanding least surprisingly found in universities.

I think the issue is if you call every type of thought and communication "social construction" then you don't end up with anything useful.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#139

Earlier quoted context omitted.

> Does it matter that two bricks are not "the same piece of matter" if our predictions work the same for both of them No, because of a dense, interconnected web of other social truths (the rest of the arithmetic model), the relative error of this one truth/model is negligible. However, confusing your model for reality is a fallacy perhaps older than time.

I don't understand how is "the arithmetic model" a social truth, when it clearly corresponds to physical phenomena. You can make a skyscraper that doesn't fall, and it exists regardless of whether other people see it or not. You see it - it's there. What is "social" about that? > However, confusing your model for reality is a fallacy perhaps older than time. I think that the human perception the world is a robust eno…

We have a model of physics which is pretty accurate. The engineers who designed the skyscraper did not even use this model, they used a much simpler one, with known errors. Why? It is simply good enough™. But you can't claim it is even "true" when we know more accurate methods.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#140

Earlier quoted context omitted.

An apple is not an apple. An apple is a subjective construct that summarises the distinguishing features of a certain kind of object as it appears to our sense. To a non-human consciousness those features may be uninteresting, irrelevant, or incomprehensible, so they might not see apples at all. But they could see " "s, which we don't even have a concept for, never mind a word. And which we either ignore or possibly…

> So cat math likely wouldn't have integers as we know them, but would have some kind of size-based analogue. Sorry, but no. Any species capable of actually creating some kind of math will have some mathematical structure isomorphic to the integers. If cats can't count, then that just says that cats are not capable of creating some kind of math.

IDK, it seems easy to imagine an alien mathematics based only upon continuous values? There's nothing obviously universal about discretizing things.
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