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xt writes "The Boltzmann equation is old news. What's news is that the 140-year-old equation has been solved, using mathematical techniques from the fields of partial differential equations and harmonic analysis, some as new as five years old. This solution provides a new understanding of the effects due to grazing collisions, when neighboring molecules just glance off one another rather than collide head on. We may not understand the theory, but we'll sure love the applications!"

Does it matter? The text below the comic says "I’m guessing any guys that can solve that might as well be hooking up a flying car," but even if you assume it's jumping ramps, it still makes sense because it looks like the car would make a "grazing collision" on one of those obstacles, and they now have a solved equation for that. So just take your pick and enjoy it either way.

hahah yeeeeah! we could have suspensors and personal shields and even interstellar travel, providing, that is, we are able to get some melange..that part might be a bit tough..

You poor guy. Reading any new Dune book is like spitting in Frank Herbert's face. It has none of the original visionary writing, it just feels like someone trying to exploit the series.

Yes, I agree. Brian Herbert / Kevin J Anderson books feels more like adventure story, like Indiana Jones without the comedy. Plus there is a heck load of repetition. You could probably take half of the pages in the books out and the story would still be understandable. But because Brian is Frank's son I just had to buy his books also (I have bought the original Dune saga years ago).

It's worth noting that someone says that an equation has been "solved" in modern mathematics, they typically don't mean that you plug in the initial conditions and then get a formulae for your answer. Generally what they mean is that you can apply some other--probably numerical or approximate--techniques in an effort to solve the equation, and as long as you are careful, use enough computational resources, and don't go to far out, your solutions will be reasonably accurate.

This appears to be more or less what the team has done. They've proven the "the global existence of classical solutions and rapid time decay to equilibrium for the Boltzmann equation with long-range interactions". In other words, they've proven that the equation has "well behaved" solutions and not solutions for which something goes horribly wrong at some distance from your starting point.

While it doesn't sound like much, this is actually a very big deal. If the proof had gone the other way, it would mean that the equation would produce something akin to "ultraviolet catastrophes" under certain conditions, which means that the equation did not properly describe physical systems. With this proof, that's not an issue anymore and we now know that the equation will always produce reasonable solutions when given reasonable (i.e. physical) initial conditions.

Perhaps they've gone farther than just existence proofs and also provided a formula or technique for obtaining or approximating solutions. However, the Proceedings of the National Academy of Sciences journal is a closed publisher and the article is locked behind a paywall, so I guess the vast majority of us will never know.

So, like, in other words, they have 'proven' the correctness of the Boltzmann equation, or at the very least, made the correctness of the Boltzmann equation more probable, rather than 'solved' it ?

No, they just showed that there *is* a solution, and the solution behaves "well".

Mathematically speaking, it makes little sense to say the "correctness" of the Boltzmann equation. It is Just Another Equation (TM). Physically speaking, the application of said equation to physical bodies has been established in physical ways.

Mathematically speaking, it makes little sense to say the "correctness" of the Boltzmann equation

Hrm. And I always was under the impression that an equation, like 'a+b=c' could be proven correct or not. Oh well, guess that proves that I should have payed more attention at school then.

(for number systems that have fully associative addition and subtraction)

However, the Boltzmann equation is more like your example:

a+b=c

That can never be proven correct or incorrect, because it depends on a, b, and c. However, given that equation, and the values for two of the variables, you can solve for the value of the third. Or given that equation and just one variable's value, you can solve for a new equation that shows a relationship between the other two variables. But asking whether "a+b=c" is correct has little meaning. It's correct when a=b=c=0, and incorrect when a=b=c=1, and the Boltzmann equation is similar.

Well, ask a physical chemist, they're all in the ground floor labs with the heavy equipment pretending to be physicists (while all the physicists are off pretending to be mathematicians).

Ask a chemist.
Well, ask a physical chemist, they're all in the ground floor labs with the heavy equipment pretending to be physicists (while all the physicists are off pretending to be mathematicians).

If the proof had gone the other way, it would mean that the equation would produce something akin to "ultraviolet catastrophes"

You know, I've read your post several times... and things like this only reinforce the fact that this is way over my head.:-P

So, they've likely demonstrated numerically that the formula isn't gibberish, and that it actually describes some physical phenomenon with some modest degree of accuracy without spiraling out of control?

Is an ultraviolet catastrophe a math term, or a physics one? The opposite of a "crimson success", or literal run-away UV event from particle decay?

As usual, explanations from mathematicians leave me confused -- especially when that math is describing phyics.;-)

Re:Meaning of "Solved" (1, Informative)

Anonymous Coward | more than 4 years ago | (#32255850)

Providing a link to ultraviolet catastrophe [wikipedia.org] . Posting as AC to avoid Karma whoring.

Re:Meaning of "Solved" (-1, Flamebait)

Anonymous Coward | more than 4 years ago | (#32256308)

Posting as AC to avoid Karma whoring.

I love it how you fucking elitist cocksuckers add "the Posting as AC to avoid Karma whoring." to point out that you have karma and you're cool and shit.

Fucking Niggers! What makes you so sure you would get any karma??

Somebody please explain the ultraviolet catastrophe to me. What is the underlying reason for the old model providing incorrect predictions? I am very science-minded but cannot understand this. The wikipedia page could not help much.

Somebody please explain the ultraviolet catastrophe to me. What is the underlying reason for the old model providing incorrect predictions? I am very science-minded but cannot understand this. The wikipedia page could not help much.

I won't try to explain the specifics, but...

Some calculation indicated that 'black bodies' (which I think means "radiates heat" or something) would emit infinite energy. However, this didn't correspond to the reality that those things don't, in fact, radiate infinite energy.

The solution these guys got for this equation showed that the equation (which describes particle collisions in a gas I think) doesn't spiral out of control and emit infinite energy. It's still an exceedingly complex equation that we can't solve, but this tells them they're on the right track.

Which is good, because that very complex equation has been shown to at least usable. Which I think lets us do better CGI of water for Avatar 2, plus the real science that comes from being able to model fluids accurately and look at the wacky physics there.;-)

Any actual physicists can now pillory me and my lame attempt to explain this.:-P

Is an ultraviolet catastrophe a math term, or a physics one?

Physics, the Boltzmann Equation describes the behavior of gas. "Ultraviolet catastrophes" don't happen, so if the equation allows for them (or similar bad behavior), then the equation is wrong.

What they've shown is that it still accurately describes gassy behaviors that were hitherto unknown until a few years ago.

"Ultraviolet catastrophe" is a physics term, talking about a time when math that had seemed to work out well produced some puzzling answers. The solution was that they had to scrap the old math and replace it with something radically different. Equivalent to somebody accidentally proving that there was no such thing as molecules, and having to re-do chemistry from scratch.

In the case of the "ultraviolet catastrophe", the old math said that a hot object should emit photons at every wavelength. Fewer at shorter, higher-energy wavelengths, but some nonetheless. The math worked for longer wavelengths, but for shorter ones (say, ultraviolet) it got worse. For ultra-short wavelengths, any body hotter than absolute zero should be emitting photons of near-zero wavelength with arbitrarily large amounts of energy. Infinite, in fact. Quite a catastrophe.

The solution turned out to be to say that the energy had to come in discrete packets. The new theory is perplexing, but more accurate and way more useful. (Computers, lasers, etc etc etc.)

Ultimately it turned out well, but nobody at the time really wanted to have to throw out everything they knew about energy. In this case, it's unsurprising that the new solutions should confirm that we're not looking at another similar revolution. I don't think anybody was looking forward to scrapping what we think we know about gases.

Unanticipated future we live (0)

Anonymous Coward | more than 4 years ago | (#32257546)

The solution turned out to be to say that the energy had to come in discrete packets. The new theory is perplexing, but more accurate and way more useful. (Computers, lasers, etc etc etc.)

In other words, it spelt doom for Jules Verne style world of tomorrow (Steampunk)! Who knows what surprises await in the future. Perhaps one day most or whole of contemporary Sci Fi will be regarded as "Spacepunk" or perhaps "Laserpunk", due to some revolutionary twist in Physics that will make some now popular and "futuristic" concepts bizarre.

I believe the term came from blackbody radiation (this is just the electromagnetic radiation of anything with a finite temperature; think infrared night-vision goggles.). Originally, the measured and theoretical emission spectra increased with frequency like the frequency squared. If you try to add up the total emission, though, you get something infinite (because you can't integrate x^2 from 0 to infinity). This is nonsense, because warm bodies, such as yourself, are not radiating infinite power. This is the ultraviolet catastrophe.

The answer to the problem is that quantum mechanical effects cause the spectrum to turn around again and head toward zero at high frequency, giving you something with a finite integral.

So the original poster meant that sometimes you can prove that what you have isn't the whole picture, but that is not the case here.

Is an ultraviolet catastrophe a math term, or a physics one?

A mathematical one. The simplest example would be something like the solution to the equation dy/dx=y^2, with y=1 at x=0. This has the solution 1/(1-x), which "blows up" at x=1. Technically, you would say the solution has a singularity at x=1. The singularity is characteristic of the differential equation itself, and not really of the initial conditions or the methods used to solve it. Inherently, you're going to face this problem when attempting to solve the differential equation.

A "blow" up or pole is just one kind of singularity. There are many others. In the context of physical equations, their presence suggests that the assumptions of your equation break down as the solution approaches the singularity, or that your assumptions were flawed to begin with. In the context of mathematics, it means that any numerical system you use to solve the equation is going to break down horribly as it gets close to the singularity. This is a huge problem as if you're using a numerical solver, you typically have no idea where the singularities are anyway. What's worse, most numerical methods will actually continue along happily after they have passed the singularity, the only problem being every number they return after that point is more than likely totally wrong.

It depends on what the authors mean by "classical solutions", but my reading of it is that they mean solutions without singularities and which decay quickly, both of which are reasonable solutions for the equation in question. Since the paper (at the arXiv) is 50 pages long, I'm not entirely sure. Their solution might allow certain other types of singularity or govern the propagation of singularities. I honestly have no idea, which I understand is fairly common [abstrusegoose.com] these days.

Re:Meaning of "Solved" (0)

Anonymous Coward | more than 4 years ago | (#32257890)

It's a little of both. Catastrophes belong to complex analysis. Ultraviolet light belongs to physics.

Re:Meaning of "Solved" (1, Funny)

Anonymous Coward | more than 4 years ago | (#32258116)

A "blow" up or pole is just one kind of singularity.

Reminds me of a joke: Q: Why did the Polish Airliner crash? A: All the poles were in the right half plane.

Is an ultraviolet catastrophe a math term, or a physics one?

It's a physics term, but math and physics are pretty intertwined at that point.

The basic idea is that random populations of things tend to follow a normal distribution, or bell curve. If you have a bunch of molecules bouncing about then some will be moving fast, some slow, but most will be at a moderate speed. All things being equal the percentage of slow vs fast should be roughly similar, producing a graph that looks like a bell - round peak in the middle, the sides falling off and leveling out.

According to classical physics a "black body" (an ideal object at a certain temperature) should emit some photons of higher energy, and some photons of lower energy, with most photons of a moderate energy. The graph of these should follow a bell curve, if everything else was equal. At lower temperatures the curve was approximately a bell curve, centered around the infrared wavelengths. However, as the temperature is raised there is a shortfall of higher energy photons. The graph starts to develop a "lean", it looks like it has a fat tail on the lower energy photon side and a long, thin tail on the higher energy photon side. Because many of those high energy photons are in the ultraviolet range it was called the "ultraviolet catastrophe" - it was a highly unexpected result which turned the physics community on its head.

Ultimately quantum theory explained the reason for this. Quantum energy levels for the electrons in atoms results in the lower energy transitions being more likely than higher energy transitions, thus tending to produce a higher amount lower energy photons and a lower amount of higher energy photons than classical physics predicted.

Eh, never mind my explanation here. Parts of it are correct but some of it is muddled and misleading. I blame it on the head cold I'm suffering through today! I should know better than to have a nasty headache and stuffed-up head and trying to explain quantum theory...

Re:Meaning of "Solved" (0)

Anonymous Coward | more than 4 years ago | (#32257760)

First I thought it was just a typo for "ultraviolent"

Re:Meaning of "Solved" (0)

Anonymous Coward | more than 4 years ago | (#32255772)

This is actually a roundabout way of saying that they could have plugged in the numbers but didn't want to because they are mathematicians, right?

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

In layman's terms: the Butterfly Effect is bogus. It takes a very large perturbation to convert a stable portion of atmosphere into a storm, and the flutter of a butterfly's wings is not significant to tipping the balance.

I think most people have the wrong idea about the "Butterfly Effect." IIRC, the weather
scientists were talking about the precision with which they would need to know
air movement to make longer term predictions. i.e. the longer the forecast the more
digits of precision are needed in your measurement. They were referring to the
level of precision and not to butterflies causing a tornado or other such nonsense.
Unfortunately, the media like to report it otherwise.

I think most people have the wrong idea about the "Butterfly Effect." IIRC, the weather scientists were talking about the precision with which they would need to know air movement to make longer term predictions. i.e. the longer the forecast the more digits of precision are needed in your measurement. They were referring to the level of precision and not to butterflies causing a tornado or other such nonsense.

I think this paper [csuchico.edu] says that the butterfly/tornado link came directly from Edward Norton Lorenz, an American mathematician and meteorologist, and a pioneer of chaos theory:

In the title of a talk given by Lorenz at the 139th meeting of the American Association for the Advancement of Science in December, 1972, the butterfly made its first appearance: ''Does the flap of a butterfly's wings in Brazil set off a tornado in Texas?'' In this talk, Lorenz raised the fundamental issue: ''The question which really interests us is whether they (the butterflies) can do even this--whether, for example, two particular weather situations differing by as little as the immediate influence of a single butterfly will generally after sufficient time evolve into two situations differing by as much as the presence of a tornado. In more technical language, is the behavior of the atmosphere unstable with respect to perturbations of small amplitude?''

I think most people have the wrong idea about the "Butterfly Effect." IIRC, the weather scientists were talking about the precision with which they would need to know air movement to make longer term predictions. i.e. the longer the forecast the more digits of precision are needed in your measurement. They were referring to the level of precision and not to butterflies causing a tornado or other such nonsense.

No, they were referring to both.

One of the issues with chaotic systems is that there are regions in the regime where a small perturbation DOES expand without limit and small changes produce large effects. Weather is such a system.

On one hand, it means that current instrumentation can only measure things down to the point where the models track the actual weather for 3 to 5 or so days (depending on conditions) before they diverge into uselessness. On the other it means that there are literally situations where a landing plane makes the difference between a foggy and a clear morning, a contrail grows into a storm system, or a butterfly taking off makes the difference, weeks later, of whether a hurricane hits Cuba or Texas - or even forms at all.

Not EVERY butterfly takeoff creates or destroys the next month's hurricanes. But some do. Go out far enough and the details of the recoil of a molecule can make the difference between El Nino and La Nina.

Which does not necessarily mean that weather doesn't converge into predictable climate. Many chaotic systems still follow a predictable set of tracks.

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

In layman's terms: the Butterfly Effect is bogus. It takes a very large perturbation to convert a stable portion of atmosphere into a storm, and the flutter of a butterfly's wings is not significant to tipping the balance.

Um since when was weather on this planet equivalent to an ideal gas? An ideal gas is not a chaotic system. So the Boltzmann equation has nothing to do with the butterfly effect. You're talking out of your arsehole, and slashdot is collectively too ignorant to call you for it, hence you've been modded informative. Fucking sad.

Re:Ideal gas is not chaotic, weather is (0)

Anonymous Coward | more than 4 years ago | (#32263106)

We don't like the butterfly effect/chaos theory any more, because it competes with global warming/climate change theory, and we want to gain power/make money via the latter.

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

In layman's terms: the Butterfly Effect is bogus. It takes a very large perturbation to convert a stable portion of atmosphere into a storm, and the flutter of a butterfly's wings is not significant to tipping the balance.

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

In layman's terms: the Butterfly Effect is bogus. It takes a very large perturbation to convert a stable portion of atmosphere into a storm, and the flutter of a butterfly's wings is not significant to tipping the balance.

Uhm, no. You do not understand what systems are modelled by the Boltzmann equation, what Lyapunov exponents are nor what "global in time solutions" actually are.
Lets pretend that the Boltzmann equation is a good model, on it's own, for atmospheric dynamics. This paper proves global existence of various norms of the solution, so that says that there is no time T less than infinity at which those norms become unbounded. Solution trajectories that start arbitrarily close are allowed to diverge exponentially in time. That is, there can be exponential sensitivity to initial conditions (ie. butterfly effect) with no violation of these results.
Someone above mentioned the example y' = y^2, y(0) = 1 which has solutions which become unbounded as t approaches 1 from below. These results rule out that behaviour but not behaviour like y' = y. Solutions here are bounded as t goes to infinity but are bounded for all bounded times.
Please, go back to grad school for a few years before claiming to understand what you clearly don't.

However, the Proceedings of the National Academy of Sciences journal is a closed publisher and the article is locked behind a paywall, so I guess the vast majority of us will never know.

This has bothered me a lot lately. Bittorent to the rescue?

Good luck having it spread far enough... Perhaps if you put something along the lines of "Brittney_Spears_naked_with_LolCAts" in the title, it might get distributed...

Maybe if there's enough articles - a year's worth for each journal. I suppose someone would have to download each one individually - where there's a will there's a way right?

Re:Meaning of "Solved" (0)

Anonymous Coward | more than 4 years ago | (#32256808)

This is a brief announcement of our recent proof of global existence and rapid decay to equilibrium of classical solutions to the Boltzmann equation without any angular cutoff, that is, for long-range interactions.

Isn't the PNAS article just an announcement of the proof? The paper itself should be this http://arxiv.org/abs/0912.0888 [arxiv.org] .

Solved huh? (-1)

Anonymous Coward | more than 4 years ago | (#32255726)

I'm not sure of any direct uses (flying cars won't be one), but it has implications in other areas of mathematics.

One of the big problems for computational fluid dynamics is that the equations evolved are a real pain. So much so that most of the engineers who need CFD often don't trust the results as better than a first approximation. The new solutions found to the Boltzman equations doesn't really help directly, as CFD uses customized versions of the Navier-Stokes equations for specific types of conditions, but the tools developed to find those new solutions may be useful in producing more generic CFD solutions and may result in analytics techniques that produce far more valid results than current CFD methods.

(A gas can often be treated as a compressible fluid in CFD, so if you can model a gas better, or even just sanity-check intermediate calculations, you can improve CFD for those types of calculations.)

The actual article (as opposed to the blog posting) mentions that the system is 7-dimensional. In maths, this has a different meaning than in physics. It doesn't mean 7 spacial dimensions, it means that in order to define anything you have to have 7 parameters. So, no, boiling water and turning it into a gas won't open a portal to a parallel universe. (If it were that easy, you think I'd still be here?)

For those interested in actually doing the maths, rather than talking about it, there are a great many open source PDE solvers. I've listed a few on Freshmeat, but you could spend the rest of your life collecting them. Might make for a unique hobby, but applying them to this sort of problem seems much more interesting.

A gas can often be treated as a compressible fluid in CFD,

A gas is a compressible fluid.

there are a great many open source PDE solvers

The most general solvers are the most handicapped. Even the ridiculously costly commercial solvers (Ansys, Fluent, etc.) solve a limited number of problems. I was working on a project that attempted to numerically simulate the effect of electromagnetic waves on the brain. Obviously, you need to solve the Maxwell's equations in horrible medium that is your brain. That's when I realized how woefully indadequate the commercial solvers (that claim to simulate the problem) are.

But it cannot be treated as such when the density gets too low. You couldn't treat the edge of the atmosphere as a fluid. I don't care what it is when I use a CFD, only what it behaves like.

The most general solvers are the most handicapped. Even the ridiculously costly commercial solvers (Ansys, Fluent, etc.) solve a limited number of problems. I was working on a project that attempted to numerically simulate the effect of electromagnetic waves on the brain. Obviously, you need to solve the Maxwell's equations in horrible medium that is your brain. That's when I realized how woefully indadequate the commercial solvers (that claim to simulate the problem) are.

My brain's a medium? I thought I heard some dead people in there.:)

Seriously, I entirely agree. I don't for a moment pretend that I'm anything like up enough on PDEs or high-end maths problems (it's been a while) to identify the best packages either. The best I can do is say such software exists. I'll list here the packages I list and use - not just for PDEs but for maths and logic problems as a whole. I'll leave it to you and others skilled in the subject to pass judgement on their quality.

ATLAS [sourceforge.net] - A nice, optimized BLAS (Basic Linear Algebra System) implementation

HOL4 [sourceforge.net] - Higher Order Logic proof assistant

Hypre [llnl.gov] - Preconditioner for linear equation solvers

LAPack [netlib.org] - Linear Algebra Package that runs over BLAS

ScaLAPack [netlib.org] - Subset of LAPack optimized for highly parallel computers

It's my site and it had some issues due to this post/link and a surge in traffic. It's now back up. Stay tuned tomorrow, as I'll be continuing this storyline.

How would you explain the possible practical applications of this to a non-higher-maths guy? I just don't see calculating the collisions of gaseous particles having anything to do with flying cars...

It's more a confirmation that gases behave (or rather, the equations we use to model them) as we expect.

As to practical applications, pretty much any physical chemistry with gasses, CFD, etc. It's less "new" than it is "we don't have to come up with some new maths for this".

Did submitter actually read his own links?
No one "solved" equation. They proved existence of couple of soulutions with specific properties.
"Penn mathematicians proved the global existence of classical solutions and rapid time decay to equilibrium for the Boltzmann equation with long-range interactions. "
http://www.upenn.edu/pennnews/news/university-pennsylvania-mathematicians-solve-140-year-old-boltzmann-equation-gaseous-behaviors [upenn.edu]
"Penn mathematicians proved the global existence of classical solutions and rapid time decay to equilibrium for the Boltzmann equation with long-range interactions. "

Wow... (0)

Anonymous Coward | more than 4 years ago | (#32261690)

an advance in maths that hasn't been made by Dr. Long Duk-Dong of Shanghai Jiaotong University or something. I'm amazed.

These guys must be crazy. Why waste your career proving the regularity of solutions to the Boltzmann equation when you could get a million bucks [claymath.org] for doing the same for the Navier-Stokes equations.

## I don't get the comic (0)

## Anonymous Coward | more than 4 years ago | (#32255452)

Are they flying? or are they jumping ramps?

## Re:I don't get the comic (2)

## fishexe (168879) | more than 4 years ago | (#32256498)

Are they flying? or are they jumping ramps?

Does it matter? The text below the comic says "I’m guessing any guys that can solve that might as well be hooking up a flying car," but even if you assume it's jumping ramps, it still makes sense because it looks like the car would make a "grazing collision" on one of those obstacles, and they now have a solved equation for that. So just take your pick and enjoy it either way.

## Holtzmann equation (5, Funny)

## weicco (645927) | more than 4 years ago | (#32255460)

For I second I thought the title said "Holtzmann equation solved". That's probably because I was just reading Dune: The Battle of Corrin :)

## Re:Holtzmann equation (-1, Offtopic)

## Anonymous Coward | more than 4 years ago | (#32255556)

Offtopic FP fag!

## Re:Holtzmann equation (0)

## Anonymous Coward | more than 4 years ago | (#32255566)

Win. If I had an actual account, and by that merit, mod points. I would so mod up.

## Re:Holtzmann equation (1, Funny)

## Anonymous Coward | more than 4 years ago | (#32255626)

For I second I thought the title said "Holtzmann equation solved".

I thought it said the

Bozemanequation and wondered what kind of math there were doing up there in Montana.## Re:Holtzmann equation (2)

## Profane MuthaFucka (574406) | more than 4 years ago | (#32260280)

I thought it said MY PENIS equation and I wondered just how hard it could be to count to two and a half.

## Re:Holtzmann equation (1)

## Zelkan (1794876) | more than 4 years ago | (#32255790)

## Re:Holtzmann equation (1)

## Bigjeff5 (1143585) | more than 4 years ago | (#32255852)

Thatwould be frickin awesome!## Re:Holtzmann equation (2, Funny)

## jd (1658) | more than 4 years ago | (#32256100)

I'd have preferred a solution to Block Transfer Computation and the Skasis Paradigm.

## Re:Holtzmann equation (1)

## can.you.feel.my.808 (1322153) | more than 4 years ago | (#32257658)

## Re:Holtzmann equation (1)

## initialE (758110) | more than 4 years ago | (#32261042)

You poor guy. Reading any new Dune book is like spitting in Frank Herbert's face. It has none of the original visionary writing, it just feels like someone trying to exploit the series.

## Re:Holtzmann equation (1)

## weicco (645927) | more than 4 years ago | (#32261564)

Yes, I agree. Brian Herbert / Kevin J Anderson books feels more like adventure story, like Indiana Jones without the comedy. Plus there is a heck load of repetition. You could probably take half of the pages in the books out and the story would still be understandable. But because Brian is Frank's son I just had to buy his books also (I have bought the original Dune saga years ago).

## Research paper here: (5, Informative)

## gzipped_tar (1151931) | more than 4 years ago | (#32255462)

For the math-inclined:

http://arxiv.org/abs/0912.0888 [arxiv.org]

(yes, that was from 2009)

## Re:Research paper here: (2, Informative)

## gzipped_tar (1151931) | more than 4 years ago | (#32255572)

Well apparently it only recently passed peer-review, if you consider 3 months "recent". That's not unusual for a research paper anyway.

http://www.pnas.org/content/107/13/5744.short [pnas.org]

(behind a paywall)

## Re:Research paper here: (2, Informative)

## jd (1658) | more than 4 years ago | (#32256066)

Given that hard maths can take months to work through, three months is actually quite impressive.

## Thanks! (2, Funny)

## hoytak (1148181) | more than 4 years ago | (#32256468)

I

thoughtI was math-inclined.## this sounds like science (5, Funny)

## Anonymous Coward | more than 4 years ago | (#32255534)

## Re:this sounds like science (1)

## NatasRevol (731260) | more than 4 years ago | (#32256292)

And vice versa to stir up the other half!

## Re:this sounds like science (1, Funny)

## Anonymous Coward | more than 4 years ago | (#32257714)

please post more stories about how much we hate apple and love flash.

FUCK YOU! We LOVE Apple and HATE Flash!

## Re:this sounds like science (1, Funny)

## Anonymous Coward | more than 4 years ago | (#32258994)

please post more stories about how much we hate apple and love flash.

FUCK YOU! We LOVE Apple and HATE Flash!

FUCK YOU ALL! We LOVE CP/M and HATE GUIs!

## Meaning of "Solved" (4, Informative)

## ObsessiveMathsFreak (773371) | more than 4 years ago | (#32255612)

It's worth noting that someone says that an equation has been "solved" in modern mathematics, they typically

don'tmean that you plug in the initial conditions and then get a formulae for your answer. Generally what they mean is that you can apply some other--probably numerical or approximate--techniques in an effort to solve the equation, and as long as you are careful, use enough computational resources, and don't go to far out, your solutions will be reasonably accurate.This appears to be more or less what the team has done. They've proven the "the global existence of classical solutions and rapid time decay to equilibrium for the Boltzmann equation with long-range interactions". In other words, they've proven that the equation has "well behaved" solutions and not solutions for which something goes horribly wrong at some distance from your starting point.

While it doesn't sound like much, this is actually a very big deal. If the proof had gone the other way, it would mean that the equation would produce something akin to "ultraviolet catastrophes" under certain conditions, which means that the equation did not properly describe physical systems. With this proof, that's not an issue anymore and we now know that the equation will always produce reasonable solutions when given reasonable (i.e. physical) initial conditions.

Perhaps they've gone farther than just existence proofs and also provided a formula or technique for obtaining or approximating solutions. However, the Proceedings of the National Academy of Sciences journal is a closed publisher and the article is locked behind a paywall, so I guess the vast majority of us will never know.

## Re:Meaning of "Solved" (1)

## lbalbalba (526209) | more than 4 years ago | (#32255742)

## Re:Meaning of "Solved" (5, Informative)

## gzipped_tar (1151931) | more than 4 years ago | (#32255802)

No, they just showed that there *is* a solution, and the solution behaves "well".

Mathematically speaking, it makes little sense to say the "correctness" of the Boltzmann equation. It is Just Another Equation (TM). Physically speaking, the application of said equation to physical bodies has been established in physical ways.

## Re:Meaning of "Solved" (1)

## lbalbalba (526209) | more than 4 years ago | (#32256258)

Mathematically speaking, it makes little sense to say the "correctness" of the Boltzmann equation

Hrm. And I always was under the impression that an equation, like 'a+b=c' could be proven correct or not. Oh well, guess that proves that I should have payed more attention at school then.

## Re:Meaning of "Solved" (3, Informative)

## Your.Master (1088569) | more than 4 years ago | (#32256364)

Some equations can be proven, eg:

a+b+c-a-b = c

(for number systems that have fully associative addition and subtraction)

However, the Boltzmann equation is more like your example:

a+b=c

That can never be proven correct or incorrect, because it depends on a, b, and c. However, given that equation, and the values for two of the variables, you can solve for the value of the third. Or given that equation and just one variable's value, you can solve for a new equation that shows a relationship between the other two variables. But asking whether "a+b=c" is correct has little meaning. It's correct when a=b=c=0, and incorrect when a=b=c=1, and the Boltzmann equation is similar.

## Re:Meaning of "Solved" (1)

## wealthychef (584778) | more than 4 years ago | (#32258298)

## Re:Meaning of "Solved" (1)

## yoyoq (1056216) | more than 4 years ago | (#32258712)

## Re:Meaning of "Solved" (2, Funny)

## jo_ham (604554) | more than 4 years ago | (#32259960)

Ask a chemist.

Well, ask a physical chemist, they're all in the ground floor labs with the heavy equipment pretending to be physicists (while all the physicists are off pretending to be mathematicians).

## Re:Meaning of "Solved" (2, Informative)

## Samah (729132) | more than 4 years ago | (#32261198)

Ask a chemist.

Well, ask a physical chemist, they're all in the ground floor labs with the heavy equipment pretending to be physicists (while all the physicists are off pretending to be mathematicians).

For anyone who doesn't get the reference:

http://xkcd.com/435/ [xkcd.com]

## Re:Meaning of "Solved" (1, Informative)

## Anonymous Coward | more than 4 years ago | (#32260164)

Some equations can be proven, eg:

a+b+c-a-b = c

(for number systems that have fully associative addition and subtraction)

Actually, to prove this you also need the addition to be commutative. From associativity, only

a+b+c=c+b+a

follows, and that is not a trivial equation in some systems.

## Re:Meaning of "Solved" (0)

## Anonymous Coward | more than 4 years ago | (#32256422)

It proves nothing!

## Re:Meaning of "Solved" (1)

## gstoddart (321705) | more than 4 years ago | (#32255748)

You know, I've read your post several times ... and things like this only reinforce the fact that this is way over my head. :-P

So, they've likely demonstrated numerically that the formula isn't gibberish, and that it actually describes some physical phenomenon with some modest degree of accuracy without spiraling out of control?

Is an ultraviolet catastrophe a

mathterm, or a physics one? The opposite of a "crimson success", or literal run-away UV event from particle decay?As usual, explanations from mathematicians leave me confused -- especially when that math is describing phyics. ;-)

## Re:Meaning of "Solved" (1, Informative)

## Anonymous Coward | more than 4 years ago | (#32255850)

Providing a link to ultraviolet catastrophe [wikipedia.org] . Posting as AC to avoid Karma whoring.

## Re:Meaning of "Solved" (-1, Flamebait)

## Anonymous Coward | more than 4 years ago | (#32256308)

Posting as AC to avoid Karma whoring.

I love it how you fucking elitist cocksuckers add "the Posting as AC to avoid Karma whoring." to point out that you have karma and you're cool and shit.

Fucking Niggers! What makes you so sure you would get any karma??

## Re:Meaning of "Solved" (1)

## Kagura (843695) | more than 4 years ago | (#32258928)

## Re:Meaning of "Solved" (3, Informative)

## gstoddart (321705) | more than 4 years ago | (#32260180)

I won't try to explain the specifics, but ...

Somecalculation indicated that 'black bodies' (which I think means "radiates heat" or something) would emit infinite energy. However, this didn't correspond to the reality that those things don't, in fact, radiate infinite energy.The solution these guys got for this equation showed that the equation (which describes particle collisions in a gas I think)

doesn'tspiral out of control and emit infinite energy. It's still an exceedingly complex equation that we can't solve, but this tells them they're on the right track.Which is good, because that very complex equation has been shown to at least usable. Which I think lets us do better CGI of water for Avatar 2, plus the real science that comes from being able to model fluids accurately and look at the wacky physics there. ;-)

Any actual physicists can now pillory me and my lame attempt to explain this. :-P

## Re:Meaning of "Solved" (2, Informative)

## Bigjeff5 (1143585) | more than 4 years ago | (#32255906)

Is an ultraviolet catastrophe a math term, or a physics one?

Physics, the Boltzmann Equation describes the behavior of gas. "Ultraviolet catastrophes" don't happen, so if the equation allows for them (or similar bad behavior), then the equation is wrong.

What they've shown is that it still accurately describes gassy behaviors that were hitherto unknown until a few years ago.

In other words, it still works. :)

## Re:Meaning of "Solved" (5, Informative)

## jfengel (409917) | more than 4 years ago | (#32256028)

"Ultraviolet catastrophe" is a physics term, talking about a time when math that had seemed to work out well produced some puzzling answers. The solution was that they had to scrap the old math and replace it with something radically different. Equivalent to somebody accidentally proving that there was no such thing as molecules, and having to re-do chemistry from scratch.

In the case of the "ultraviolet catastrophe", the old math said that a hot object should emit photons at every wavelength. Fewer at shorter, higher-energy wavelengths, but some nonetheless. The math worked for longer wavelengths, but for shorter ones (say, ultraviolet) it got worse. For ultra-short wavelengths, any body hotter than absolute zero should be emitting photons of near-zero wavelength with arbitrarily large amounts of energy. Infinite, in fact. Quite a catastrophe.

The solution turned out to be to say that the energy had to come in discrete packets. The new theory is perplexing, but more accurate and way more useful. (Computers, lasers, etc etc etc.)

Ultimately it turned out well, but nobody at the time really wanted to have to throw out everything they knew about energy. In this case, it's unsurprising that the new solutions should confirm that we're not looking at another similar revolution. I don't think anybody was looking forward to scrapping what we think we know about gases.

## Unanticipated future we live (0)

## Anonymous Coward | more than 4 years ago | (#32257546)

The solution turned out to be to say that the energy had to come in discrete packets. The new theory is perplexing, but more accurate and way more useful. (Computers, lasers, etc etc etc.)

In other words, it spelt doom for Jules Verne style world of tomorrow (Steampunk)!

Who knows what surprises await in the future. Perhaps one day most or whole of contemporary Sci Fi will be regarded as "Spacepunk" or perhaps "Laserpunk", due to some revolutionary twist in Physics that will make some now popular and "futuristic" concepts bizarre.

## Re:Meaning of "Solved" (1)

## ChienAndalu (1293930) | more than 4 years ago | (#32261092)

Congratulations, your posting now is the top Google result for "ultraviolet catastrophe" [google.de]

## ultraviolet catastrophe (2, Interesting)

## Crispy Critters (226798) | more than 4 years ago | (#32256048)

The answer to the problem is that quantum mechanical effects cause the spectrum to turn around again and head toward zero at high frequency, giving you something with a finite integral.

So the original poster meant that sometimes you can prove that what you have isn't the whole picture, but that is not the case here.

## Re:Meaning of "Solved" (2, Interesting)

## ObsessiveMathsFreak (773371) | more than 4 years ago | (#32256088)

A mathematical one. The simplest example would be something like the solution to the equation dy/dx=y^2, with y=1 at x=0. This has the solution 1/(1-x), which "blows up" at x=1. Technically, you would say the solution has a singularity at x=1. The singularity is characteristic of the differential equation itself, and not really of the initial conditions or the methods used to solve it. Inherently, you're going to face this problem when attempting to solve the differential equation.

A "blow" up or pole is just one kind of singularity. There are many others. In the context of physical equations, their presence suggests that the assumptions of your equation break down as the solution approaches the singularity, or that your assumptions were flawed to begin with. In the context of mathematics, it means that any numerical system you use to solve the equation is going to break down horribly as it gets close to the singularity. This is a huge problem as if you're using a numerical solver, you typically have no idea where the singularities are anyway. What's worse, most numerical methods will actually continue along happily after they have passed the singularity, the only problem being every number they return after that point is more than likely totally wrong.

It depends on what the authors mean by "classical solutions", but my reading of it is that they mean solutions without singularities and which decay quickly, both of which are reasonable solutions for the equation in question. Since the paper (at the arXiv) is 50 pages long, I'm not entirely sure. Their solution might allow certain other types of singularity or govern the propagation of singularities. I honestly have no idea, which I understand is fairly common [abstrusegoose.com] these days.

## Re:Meaning of "Solved" (0)

## Anonymous Coward | more than 4 years ago | (#32257890)

It's a little of both. Catastrophes belong to complex analysis. Ultraviolet light belongs to physics.

## Re:Meaning of "Solved" (1, Funny)

## Anonymous Coward | more than 4 years ago | (#32258116)

A "blow" up or pole is just one kind of singularity.

Reminds me of a joke:

Q: Why did the Polish Airliner crash?

A: All the poles were in the right half plane.

## Re:Meaning of "Solved" (2, Informative)

## Graff (532189) | more than 4 years ago | (#32256090)

Is an ultraviolet catastrophe a math term, or a physics one?

It's a physics term, but math and physics are pretty intertwined at that point.

The basic idea is that random populations of things tend to follow a normal distribution, or bell curve. If you have a bunch of molecules bouncing about then some will be moving fast, some slow, but most will be at a moderate speed. All things being equal the percentage of slow vs fast should be roughly similar, producing a graph that looks like a bell - round peak in the middle, the sides falling off and leveling out.

According to classical physics a "black body" (an ideal object at a certain temperature) should emit some photons of higher energy, and some photons of lower energy, with most photons of a moderate energy. The graph of these should follow a bell curve, if everything else was equal. At lower temperatures the curve was approximately a bell curve, centered around the infrared wavelengths. However, as the temperature is raised there is a shortfall of higher energy photons. The graph starts to develop a "lean", it looks like it has a fat tail on the lower energy photon side and a long, thin tail on the higher energy photon side. Because many of those high energy photons are in the ultraviolet range it was called the "ultraviolet catastrophe" - it was a highly unexpected result which turned the physics community on its head.

Ultimately quantum theory explained the reason for this. Quantum energy levels for the electrons in atoms results in the lower energy transitions being more likely than higher energy transitions, thus tending to produce a higher amount lower energy photons and a lower amount of higher energy photons than classical physics predicted.

## Re:Meaning of "Solved" (1)

## Graff (532189) | more than 4 years ago | (#32256208)

Eh, never mind my explanation here. Parts of it are correct but some of it is muddled and misleading. I blame it on the head cold I'm suffering through today! I should know better than to have a nasty headache and stuffed-up head and trying to explain quantum theory...

## Re:Meaning of "Solved" (0)

## Anonymous Coward | more than 4 years ago | (#32257760)

First I thought it was just a typo for "ultraviolent"

## Re:Meaning of "Solved" (0)

## Anonymous Coward | more than 4 years ago | (#32255772)

This is actually a roundabout way of saying that they could have plugged in the numbers but didn't want to because they are mathematicians, right?

## Re:Meaning of "Solved" (1)

## $RANDOMLUSER (804576) | more than 4 years ago | (#32255880)

## Re:Meaning of "Solved" (1, Funny)

## Anonymous Coward | more than 4 years ago | (#32255926)

by $RANDOMLUSER

Wow. You just did more to validate your username than BadAnalogyGuy ever has.

But not more than you just did.

## Re:Meaning of "Solved" (1)

## $RANDOMLUSER (804576) | more than 4 years ago | (#32256130)

## Re:Meaning of "Solved" (2, Informative)

## blair1q (305137) | more than 4 years ago | (#32255882)

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

In layman's terms: the Butterfly Effect is bogus. It takes a very large perturbation to convert a stable portion of atmosphere into a storm, and the flutter of a butterfly's wings is not significant to tipping the balance.

## Re:Meaning of "Solved" (1, Insightful)

## deadline (14171) | more than 4 years ago | (#32256182)

## Re:Meaning of "Solved" (3, Informative)

## TheSync (5291) | more than 4 years ago | (#32257040)

I think most people have the wrong idea about the "Butterfly Effect." IIRC, the weather scientists were talking about the precision with which they would need to know air movement to make longer term predictions. i.e. the longer the forecast the more digits of precision are needed in your measurement. They were referring to the level of precision and not to butterflies causing a tornado or other such nonsense.I think this paper [csuchico.edu] says that the butterfly/tornado link came directly from Edward Norton Lorenz, an American mathematician and meteorologist, and a pioneer of chaos theory:

In the title of a talk given by Lorenz at the 139th meeting of the American Association for the Advancement of Science in December, 1972, the butterfly made its first appearance: ''Does the flap of a butterfly's wings in Brazil set off a tornado in Texas?'' In this talk, Lorenz raised the fundamental issue: ''The question which really interests us is whether they (the butterflies) can do even this--whether, for example, two particular weather situations differing by as little as the immediate influence of a single butterfly will generally after sufficient time evolve into two situations differing by as much as the presence of a tornado. In more technical language, is the behavior of the atmosphere unstable with respect to perturbations of small amplitude?''## Re:Meaning of "Solved" (2, Funny)

## haderytn (1232484) | more than 4 years ago | (#32258014)

## Both. (2, Interesting)

## Ungrounded Lightning (62228) | more than 4 years ago | (#32260254)

I think most people have the wrong idea about the "Butterfly Effect." IIRC, the weather scientists were talking about the precision with which they would need to know air movement to make longer term predictions. i.e. the longer the forecast the more digits of precision are needed in your measurement. They were referring to the level of precision and not to butterflies causing a tornado or other such nonsense.No, they were referring to both.

One of the issues with chaotic systems is that there are regions in the regime where a small perturbation DOES expand without limit and small changes produce large effects. Weather is such a system.

On one hand, it means that current instrumentation can only measure things down to the point where the models track the actual weather for 3 to 5 or so days (depending on conditions) before they diverge into uselessness. On the other it means that there are literally situations where a landing plane makes the difference between a foggy and a clear morning, a contrail grows into a storm system, or a butterfly taking off makes the difference, weeks later, of whether a hurricane hits Cuba or Texas - or even forms at all.

Not EVERY butterfly takeoff creates or destroys the next month's hurricanes. But some do. Go out far enough and the details of the recoil of a molecule can make the difference between El Nino and La Nina.

Which does not necessarily mean that weather doesn't converge into predictable climate. Many chaotic systems still follow a predictable set of tracks.

## Re:Meaning of "Solved" (2, Funny)

## grep -v '.*' * (780312) | more than 4 years ago | (#32258884)

... the flutter of a butterfly's wings is not significant...

It

alldepends on the size of the butterfly. Haven't you ever heard of Miracle-Gro, or seen the movie: Monsters vs. Aliens??## MOTHRA! (1)

## Ungrounded Lightning (62228) | more than 4 years ago | (#32260188)

Or Mothra vs. Godzilla [wikipedia.org] .

## Ideal gas is not chaotic, weather is (3, Insightful)

## syousef (465911) | more than 4 years ago | (#32259090)

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

In layman's terms: the Butterfly Effect is bogus. It takes a very large perturbation to convert a stable portion of atmosphere into a storm, and the flutter of a butterfly's wings is not significant to tipping the balance.

Um since when was weather on this planet equivalent to an ideal gas? An ideal gas is not a chaotic system. So the Boltzmann equation has nothing to do with the butterfly effect. You're talking out of your arsehole, and slashdot is collectively too ignorant to call you for it, hence you've been modded informative. Fucking sad.

## Re:Ideal gas is not chaotic, weather is (0)

## Anonymous Coward | more than 4 years ago | (#32263106)

We don't like the butterfly effect/chaos theory any more, because it competes with global warming/climate change theory, and we want to gain power/make money via the latter.

## Re:Meaning of "Solved" (2, Informative)

## jfw (2291) | more than 4 years ago | (#32259142)

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

In layman's terms: the Butterfly Effect is bogus. It takes a very large perturbation to convert a stable portion of atmosphere into a storm, and the flutter of a butterfly's wings is not significant to tipping the balance.

What they really proved, at long last, is that gaseous systems are stable for small perturbations.

Uhm, no. You do not understand what systems are modelled by the Boltzmann equation, what Lyapunov exponents are nor what "global in time solutions" actually are. Lets pretend that the Boltzmann equation is a good model, on it's own, for atmospheric dynamics. This paper proves global existence of various norms of the solution, so that says that there is no time T less than infinity at which those norms become unbounded. Solution trajectories that start arbitrarily close are allowed to diverge exponentially in time. That is, there can be exponential sensitivity to initial conditions (ie. butterfly effect) with no violation of these results. Someone above mentioned the example y' = y^2, y(0) = 1 which has solutions which become unbounded as t approaches 1 from below. These results rule out that behaviour but not behaviour like y' = y. Solutions here are bounded as t goes to infinity but are bounded for all bounded times. Please, go back to grad school for a few years before claiming to understand what you clearly don't.

## Re:Meaning of "Solved" (1)

## Dalambertian (963810) | more than 4 years ago | (#32256306)

However, the Proceedings of the National Academy of Sciences journal is a closed publisher and the article is locked behind a paywall, so I guess the vast majority of us will never know.

This has bothered me a lot lately. Bittorent to the rescue?

## Re:Meaning of "Solved" (1)

## Mindcontrolled (1388007) | more than 4 years ago | (#32256642)

## Re:Meaning of "Solved" (1)

## Dalambertian (963810) | more than 4 years ago | (#32257330)

## Re:Meaning of "Solved" (0)

## Anonymous Coward | more than 4 years ago | (#32256808)

This is a brief announcement of our recent proof of global existence and rapid decay to equilibrium of classical solutions to the Boltzmann equation without any angular cutoff, that is, for long-range interactions.

Isn't the PNAS article just an announcement of the proof? The paper itself should be this http://arxiv.org/abs/0912.0888 [arxiv.org] .

## Solved huh? (-1)

## Anonymous Coward | more than 4 years ago | (#32255726)

## That's quite interesting (5, Interesting)

## jd (1658) | more than 4 years ago | (#32255734)

I'm not sure of any direct uses (flying cars won't be one), but it has implications in other areas of mathematics.

One of the big problems for computational fluid dynamics is that the equations evolved are a real pain. So much so that most of the engineers who

needCFD often don't trust the results as better than a first approximation. The new solutions found to the Boltzman equations doesn't really help directly, as CFD uses customized versions of the Navier-Stokes equations for specific types of conditions, but the tools developed to find those new solutions may be useful in producing more generic CFD solutions and may result in analytics techniques that produce far more valid results than current CFD methods.(A gas can often be treated as a compressible fluid in CFD, so if you can model a gas better, or even just sanity-check intermediate calculations, you can improve CFD for those types of calculations.)

The actual article (as opposed to the blog posting) mentions that the system is 7-dimensional. In maths, this has a different meaning than in physics. It doesn't mean 7 spacial dimensions, it means that in order to define anything you have to have 7 parameters. So, no, boiling water and turning it into a gas won't open a portal to a parallel universe. (If it were that easy, you think I'd still be here?)

For those interested in actually doing the maths, rather than talking about it, there are a great many open source PDE solvers. I've listed a few on Freshmeat, but you could spend the rest of your life collecting them. Might make for a unique hobby, but applying them to this sort of problem seems much more interesting.

## Re:That's quite interesting (3, Insightful)

## Warlord88 (1065794) | more than 4 years ago | (#32256546)

A gas can often be treated as a compressible fluid in CFD,

A gas

isa compressible fluid.there are a great many open source PDE solvers

The most general solvers are the most handicapped. Even the ridiculously costly commercial solvers (Ansys, Fluent, etc.) solve a limited number of problems. I was working on a project that attempted to numerically simulate the effect of electromagnetic waves on the brain. Obviously, you need to solve the Maxwell's equations in horrible medium that is your brain. That's when I realized how woefully indadequate the commercial solvers (that claim to simulate the problem) are.

## Re:That's quite interesting (1)

## enjerth (892959) | more than 4 years ago | (#32259072)

A gas

isa compressible fluid.Like, for instance, carbon dioxide?

## Re:That's quite interesting (1)

## jd (1658) | more than 4 years ago | (#32259092)

But it cannot be treated as such when the density gets too low. You couldn't treat the edge of the atmosphere as a fluid. I don't care what it

iswhen I use a CFD, only what it behaves like.My brain's a medium? I thought I heard some dead people in there. :)

Seriously, I entirely agree. I don't for a moment pretend that I'm anything like up enough on PDEs or high-end maths problems (it's been a while) to identify the best packages either. The best I can do is say such software exists. I'll list here the packages I list and use - not just for PDEs but for maths and logic problems as a whole. I'll leave it to you and others skilled in the subject to pass judgement on their quality.

## Re:That's quite interesting (1)

## Chris Burke (6130) | more than 4 years ago | (#32259990)

A gas is a compressible fluid.

I don't care what it is when I use a CFD, only what it behaves like.Heh. Science vs. engineering in a nutshell.

Or theorists vs experimentalists if you prefer.

## Re:That's quite interesting (1)

## lennier (44736) | more than 4 years ago | (#32258982)

So, no, boiling water and turning it into a gas won't open a portal to a parallel universe.

No? You haven't seen my attempts at cooking.

Let's just say I keep a crowbar by the microwave.

## Re:That's quite interesting (0)

## Anonymous Coward | more than 4 years ago | (#32259206)

## Re:That's quite interesting (0)

## Anonymous Coward | more than 4 years ago | (#32259894)

Maybe you should keep a few packets of peanuts and a towel!!

## Re:That's quite interesting (1)

## Ungrounded Lightning (62228) | more than 4 years ago | (#32260290)

... boiling water and turning it into a gas won't open a portal to a parallel universe. (If it were that easy, you think I'd still be here?)Well, that depends.

Maybe this IS the best of all possible worlds. B-)

## love the application? (3, Funny)

## roman_mir (125474) | more than 4 years ago | (#32255768)

We may not understand the theory, but we'll sure love the applications [notquitewrong.com] !"

- Yeah, apparently the application suspends notquitewrong.com accounts. I think it's a winner.

## Re:love the application? (1)

## blair1q (305137) | more than 4 years ago | (#32255910)

Yeah, apparently the application suspends notquitewrong.com accounts.Only in the presence of large perturbations delivered head-on with great force.

## Re:love the application? (1)

## roman_mir (125474) | more than 4 years ago | (#32255954)

simply put a bunch of gasbags in a DDOS configuration.

## Re:love the application? (1)

## The Archon V2.0 (782634) | more than 4 years ago | (#32256094)

We may not understand the theory, but we'll sure love the applications [notquitewrong.com] !"

- Yeah, apparently the application suspends notquitewrong.com accounts. I think it's a winner.

Fascinating. I thought the account-suspending equation was g + c where g=2 and c=1, g being the number of girls and c being the number of cups.

## Re:love the application? (1)

## Rosscott (1544535) | more than 4 years ago | (#32256312)

## Re:love the application? (1)

## roman_mir (125474) | more than 4 years ago | (#32256350)

It's a killer application.

## OK Boltzmann down (2, Interesting)

## gzipped_tar (1151931) | more than 4 years ago | (#32255810)

Navier-Stokes the next, good guys!

## Re:OK Boltzmann down (1)

## KliX (164895) | more than 4 years ago | (#32261802)

I'm entirely with this guy!

## As an iPad owner I must say... (1)

## Glarimore (1795666) | more than 4 years ago | (#32255920)

We may not understand the theory, but we'll sure love the applications!"

As long as they don't require Flash.

## Slashdotted (1)

## simonbas (1319225) | more than 4 years ago | (#32255932)

second link is DOWN

## Re:Slashdotted (1)

## tobiah (308208) | more than 4 years ago | (#32256396)

disappointing

## Re:Slashdotted (0)

## Anonymous Coward | more than 4 years ago | (#32257052)

Or not.

## Re:Slashdotted (1)

## Rosscott (1544535) | more than 4 years ago | (#32256752)

## Collisions (1)

## PPH (736903) | more than 4 years ago | (#32256162)

Head on vs grazing.

This calls for a Bad Car Analogy.

## (9) (1)

## Suzuran (163234) | more than 4 years ago | (#32256200)

No, this calls for a touhou reference.

## Re:Collisions (1)

## Locke2005 (849178) | more than 4 years ago | (#32256532)

## Re:Collisions (1)

## fishexe (168879) | more than 4 years ago | (#32256566)

Head on vs grazing.

This calls for a Bad Car Analogy.

I think the analogy was in the link. [notquitewrong.com]

## m:are (-1, Troll)

## Anonymous Coward | more than 4 years ago | (#32256832)

## Solving Boltzmann, the New Way... (1)

## Strange_Attractor (160407) | more than 4 years ago | (#32257720)

## Translation? (1)

## DryGrian (1775520) | more than 4 years ago | (#32259798)

## Re:Translation? (1)

## jo_ham (604554) | more than 4 years ago | (#32260012)

It's more a confirmation that gases behave (or rather, the equations we use to model them) as we expect.

As to practical applications, pretty much any physical chemistry with gasses, CFD, etc. It's less "new" than it is "we don't have to come up with some new maths for this".

## Uhm, it's not solved. (1)

## S3D (745318) | more than 4 years ago | (#32261576)

No one "solved" equation. They

proved existenceof couple of soulutions with specific properties."Penn mathematicians proved the global existence of classical solutions and rapid time decay to equilibrium for the Boltzmann equation with long-range interactions. "

http://www.upenn.edu/pennnews/news/university-pennsylvania-mathematicians-solve-140-year-old-boltzmann-equation-gaseous-behaviors [upenn.edu]

"Penn mathematicians proved the global existence of classical solutions and rapid time decay to equilibrium for the Boltzmann equation with long-range interactions. "

## Wow... (0)

## Anonymous Coward | more than 4 years ago | (#32261690)

## Mugs (2, Funny)

## csrster (861411) | more than 4 years ago | (#32261742)