1,777 karma · joined March 11, 2015
I do have a pet peeve about mathematical exposition. At some point, phrases like "obviously" and "it is easy to see" became verboten, or at the very least frowned upon. The problem is that it didn't become verboten to skip details (this would be impossible in general), and those phrases actually do contain information. Namely they contain the information that there actually is some detail remaining to fill in here. Often in papers there will be some missing detail which is not so hard to verify, but whose presence is so ghostly in the exposition that I think I've missed somewhere where it was stated explicitly, and have to go back. I feel like this is the case of someone excising an instance of "it is easy to see that" and replacing it with... nothing.
https://www.thestreet.com/personal-finance/cars-that-will-la...
But then he mentions a "hybrid sedan". Here I'm aware of the data. It's not close. Modern cars are much, much more reliable and durable than ones built at any time in the past.
[0] https://www.nytimes.com/2012/03/18/automobiles/as-cars-are-k...
[1] https://www.jdpower.com/business/press-releases/2021-us-vehi...
That's worth a lot. Some kind of hybrid state where you need to always have your eyes on the road but maybe can take your hands off the wheel? Yeah I agree, I don't really see the point in that case. Or at least it's not something I get excited over.
For example, I tried a bunch of times to get it to give a proof of the infinitude of the primes. This should be repeated many times in its training data, and it clearly is given it's responses, but it always goes off the rails around the third sentence. Here's an example:
> One way to prove that there are infinitely many prime numbers is to use the contradiction method. Assume for the sake of contradiction that there are only finitely many prime numbers, say, p₁, p₂, ..., pₙ. Then we can form a new number N by multiplying all of these prime numbers together and adding 1: N = p₁ * p₂ * ... * pₙ + 1. Because N is greater than any of the prime numbers p₁, p₂, ..., pₙ, it cannot be divisible by any of them. Furthermore, N is not 1, so it cannot be a composite number (i.e., a number that can be written as the product of two smaller numbers). Therefore, N must be a prime number, contradicting the assumption that there are only finitely many prime numbers. This contradiction shows that our assumption must be false, and therefore, there must be infinitely many prime numbers.
https://arxiv.org/abs/1801.00325
but would have been happy with a description of work related to this paper:
https://arxiv.org/abs/1905.11968
or any number of other things.
The page I got stated the following, obviously false, "theorem": let M be a metric space, and let S be a subset of M such that inf_{y in S} d(x, y) < infinity for all x in M. Then there exists a map f: M to S such that f(x) = x for all x in S. As far as I can tell, this isn't a garbling of something which is true, it's just nonsense.
It suggested that I look up "Whitney extension" which is indeed related to the first paper I posted, so I did that. The opening summary, if you squint hard enough, could arguably be interpreted as true:
> The theorems state that any sufficiently smooth function on a closed subset of Rn can be extended to a function on all of Rn with the same level of smoothness.
This is really vague though. Like if someone didn't know the actual statement of Whitney's theorem, they would not be able to intuit it from this sentence. You have to be really, really charitable to describe it as true. I'm not being nitpicky here, Whitney produced a pretty non-trivial definition of the notion of a C^m function on an arbitrary closed set (basically you have to specify the entire mth order Taylor polynomial at each point, or a section of the jet bundle if you're fancy). You can check out the actual wikipedia if you're interested:
https://en.wikipedia.org/wiki/Whitney_extension_theorem
The body of the generated article goes into more detail, and again produces something which is completely false, and not particularly close to anything that is true:
> Whitney's extension theorem states that any continuous function on a closed subset of Rn can be extended to a C∞ function on Rn.
Finally, I should just say that this is all still really impressive. The sentences are grammatical, and use words somewhat related to the subject at hand. I could imagine a student who hadn't studied the material and was totally in over his head in the class writing things like this on an exam! But I would never use this as a research tool.
I had a phone like this, although not that model. It was great, T9 sucked. In fact, it was much more pleasant to type on than a touch screen.