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Ferromagnetic half levitation of LK-99-like synthetic samples

arxiv.org

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Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#301

Post by stavros »

loeg wrote: post #278
stavros wrote: post #190

Earlier quoted context omitted.

That's not the issue, though, the issue is staunchly defending something on behalf of some other group. It's noble, but it sometimes backfires because the group itself doesn't even care that much about the thing being defended. It reminds me of the time that I got reprimanded at work for saying I'll "wear a rainbow scarf" together with a gay coworker and friend, when the coworker didn't even see what could be offensi…

What is offensive about wearing a rainbow scarf?

If I remember correctly (it's been a few years), it's because I'm not gay.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#302

Post by jacquesm »

willis936 wrote: post #238
jacquesm wrote: post #236

Earlier quoted context omitted.

If it is a fluke or not doesn't matter. The only thing that matters is whether or not it is real, not how it was made. If it is real then we can expend a fortune on the 'how it was made' question, if it isn't real we can all descend from this holding pattern.

What benefit does that bring?

To stop the waste of resources in case the whole thing turns out to be a dud. By providing proof that it is not many more resources would become unlocked.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#303

Post by postalrat »

ldjkfkdsjnv wrote: post #38

I knew it was fake, there would have been a huge rise in the stock market. Financial markets would have sniffed this out. The market never lies. If anything, this was an obvious opportunity to short it on prediction markets.

I think you meant to say the REAL market never lies. Because the market obviously lies but the real market is whatever you say it is.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#304

Post by OJFord »

martindbp wrote: post #271
OJFord wrote: post #246

Earlier quoted context omitted.

That's not what GP means - even if you assume they're independent variables, 2x 10% probabilities combine to a 1% ('10% of 10%', they multiply, not add) probability of the total outcome, not 20%.

Huh? I think he's saying OR not AND. Why would two separate pieces of evidence make the whole less probable, that makes no sense, whether you spell out the whole thing more formally or not.

Ok yeah I think maybe I misunderstood the original argument. But those are absolutely not independent (which was probably the repliers point, unless we made the same misreading).

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#305

Post by OJFord »

rytill wrote: post #295
layer8 wrote: post #192

Earlier quoted context omitted.

That's not how probabilities combine.

They are only 1% off. They’re trying to say “there are two independent 10% probability events that imply RTSC”. You can’t add them, but you can multiply 90% by 90% and get an 81% chance of not RTSC, or a 19% chance of RTSC according to this model.

1pp or 5%

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#306

Post by throwanem »

falcor84 wrote: post #300
throwanem wrote: post #286

Earlier quoted context omitted.

"Not even wrong." An event about whose outcome you by definition have no information ("I have absolutely no idea") is an event to which you cannot assign any probability, including by assuming it's a coin flip and then treating the assumption as axiomatic. It encodes no information whatsoever because there is none to encode, and it biases all future results because you're averaging over a range that includes "data" y…

I'm having trouble following your reasoning. "Not even wrong" typically is used to refer to something unfalsifiable, but I specifically provided an empirical process and even a mechanism to explain why it might work - a person in a given position would likely be asked to make predictions with a different base likelihood of success than a person in another position. In any case, it is precisely my argument (and Scott…

A prediction based on no information is definitionally unfalsifiable.

I'm well aware of the nature of the argument, having been an SSC reader since long before the whole Cade Metz kerfuffle, and still being an ACX reader now - admittedly these days more to see what Alexander is on about lately; it's been some time since I've taken him seriously. A major reason why that's the case is because I've yet to see from any source a substantiation of that argument which is sustainable in the absence of a lot of handwaving. Granted, nobody waves hands like Scott Alexander! That's a lot of why I still find him so entertaining. But the handwaving is still handwaving.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#307

Post by nullc »

p-e-w wrote: post #125
segfaultbuserr wrote: post #106

Earlier quoted context omitted.

A magnetic levitation demo indicates a possible Meissner effect (which is refuted here by this paper), and this is so much easier than a resistance measurement, which is a delicate task and susceptible to experimental errors. So levitation is used as a quick "first check", especially when you don't have a full lab setup to do other tests, which are much more complicated (in addition to a levitation test or a resistan…

> One cannot measure superconductivity with an ordinary ohmmeter. But one can measure electrical resistivity, and if the material's resistivity is much lower than that of ordinary materials, that would be super interesting and valuable, regardless of whether it is a "true" superconductor or not. If this relatively cheap material had a resistivity around 1/100th that of copper, that would be an engineering breakthroug…

if you were talking about a meter long segment of pure LK99 you'd have a point. But the pieces in question are so small that even if the LK99 were just copper their resistance would be so low that experimental error in a casual test would be substantial compared to the resistance.

Measuring the resistance would also be frustrated by the superconductive material being scattered in the mass separated by highly resistive impurities, making it easy to get a false negative.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#308

Post by lamontcg »

ironborn123 wrote: post #132
versteegen wrote: post #95

Very interesting comments on the paper by Prof. Michael S. Fuhrer https://nitter.net/i/status/1688755932275384320 > But I think they buried the lede a little. Ferromagnetism is novel and unexpected in this material system, and might be interesting. But strong diamagnetism even more so > Even if the diamagnetic fraction is the entire sample (appears less) then it would be the second-strongest diamagnet known (and pyro…

There are 2 things in favor of the Korean team - Hyun-Tak Kim is unlikely to ruin his career and legacy for something careless and frivolous. But stranger things have happened, so lets assign a 10% probability to give some benefit of doubt to the team. - The various DFT papers show interesting flat band structures. But DFT is an approximation and also they do not take into account electron electron correlations. So l…

> Hyun-Tak Kim is unlikely to ruin his career and legacy for something careless and frivolous.

Everyone is suddenly an expert in HT Kim's character who didn't have any idea who he was a month ago.

And this definitely is a sort of "black swan" event in the same sense that major airline crashes are absolutely atypical of normal air travel. Inherently this viral media event is going to involve atypical constituent parts.

The idea that we could have found some of the most overconfident and underqualified material science researchers out there, who could not realize they were committing career suicide, making these claims isn't very paradoxical at all.

Most aircraft maintenance is exceptionally high quality. You're going to find a lot of bad maintenance in the fatal air disasters that hit the headlines. The FAA doesn't approach an air disaster by assuming the good intent of everyone involved with the maintenance of the plane, and that their inherently understanding that lives are in their hands if they make mistakes should necessarily diminish the likelihood of maintenance issues. They assign "0%" significance to that kind of things and instead just investigate what caused the crash. If it was bad maintenance then the operator and/or the mechanic doing the maintenance take the hit to their reputations.

Same thing here.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#309

Post by 8note »

suslik wrote: post #222
bnralt wrote: post #203

Earlier quoted context omitted.

Yeah, Scott Alexander wrote a whole article about how people should use made up fake statistics instead of simply saying "I don't know"[1]. [1] https://slatestarcodex.com/2013/05/02/if-its-worth-doing-its...

Not always. "I don't know" is identical to saying "I have a uniform prior". In the particular case of LK-99, my prior is perfectly uniform - I know absolutely nothing about the subject matter and almost everything I read on the topic feels way above my head. As I refuse to be influenced by experts (or "experts") until there is some sort of consensus, I have absolutely no good reason to say anything but "I don't know"…

A perfectly uniform prior suggests that you think that it's easy to make a room temperature super conductor and that people have made them before with equal likelihood to it being hard to make a room temperature superconductor and people haven't made them before, doesnt it?

I don't know much about superconductors, but I do know that people have been trying to make them work at room temperature, and generally failing

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#310

Post by ironborn123 »

dcow wrote: post #284
martindbp wrote: post #271

Earlier quoted context omitted.

Huh? I think he's saying OR not AND. Why would two separate pieces of evidence make the whole less probable, that makes no sense, whether you spell out the whole thing more formally or not.

So if I find 10 people that claim, each with a 10% likelihood of being true, that the dark side of the moon has a scar that looks like Pikachu, then it’s 100% true? That doesn’t make sense either. Seems like someone is falling prey to an intuitive fallacy of probability. The weird model is just wrong in the first place. The commenter we’re discussing conflates the probability of two people saying something with the p…

No,even though the 10 pikachu fans assess independently, their estimations will be correlated. As you may already know the overall estimate wont be 100%, rather about 65%. The formula when the assessors are known to be independent, is simpler and has already been indicated by another commenter, P(A1 or A2 or A3 or ..An) = 1 - P(not A1)P(not A2)..P(not An)

On the other hand, if those 10 were engaged in complete groupthink (so no additional information beyond the first guy), the overall estimate would remain 10%.

In general, the answer would lie between 0.1 and ~0.65 depending on how their estimates influence each other.

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