@BernardMeurer I use an old pair of Sennheisers that are older than you are. They aren't the very best headphones but they are comfortable and I love them dearly. We geriatrics get sentimental about such things.
@BernardMeurer Oh, don't worry---the topics you talk about just don't interest me that much but it doesn't mean I don't want you hanging out here. You are a nice guy ;)
@BernardMeurer my speakers are Heybrook HB2s bought in 1980. I've tried many other speakers since and I like the sound of the Heybrooks more than any other speakers I've tried, including Linn exotica.
@BernardMeurer Well you were talking about getting a laptop and I have some broken ones here that would be easy to fix. I was going to say you can have one if you want, then i saw how much it would cost to ship one to Brazil.
@JohnRennie Well, maybe I should qualify that statement a little: When you go to the "QM limit" where wavefunctions make sense, it would be a plane wave. But in full-blown QFT, states are not given by wavefunctions, so "plane wave" as such doesn't make sense
@SirCumference : both. We have no evidence for an infinite universe. We have evidence for a "flat" universe, but that isn't actually evidence for an infinite universe. There's a non-sequitur in there. See this answer for more information.
@Danu Depends on your background. Analysts like my advisor like the heat kernel proof (see Gilkey), but if you're an algebraic toplogist/geometer you might like the K theory approach better.
I've got beef with our reviewing system. We seem to be closing questions as unclear all too often lately. Especially long questions. Are people too lazy to take the time to properly review long questions so they auto-vtc for whatever reasons are already there?
So anyhow, what I'm thinking is that if I can put together a laptop from bits that work or mostly work would be feasible to ship it to ACM and have him hold it for when you deliver the beer you owe him?
@Jim I do think that unclear what you're asking is often used in places where a custom reason would be more appropriate (and I'm probably guilty of that as well)
OK, when you firm up your plans give me a few weeks warning to sort something out. If ACM isn't around or for whatever reason that isn't possible we could use some other address in Germany.
@ACuriousMind I don't use unclear as a reason unless I'm familiar with the subject and the question simply makes no sense at all. If I can figure out a hidden question, maybe it's too broad, maybe it's off-topic, or maybe it's just too tedious for me to want to answer. But that last one isn't grounds for closing
@0celo7 Consider the shift operator in $\ell^2(\mathbb{C})$ that sends $(1,0,0,0,\dots)$ to $(0,1,0,0,\dots)$, $(0,1,0,0,\dots)$ to $(0,0,1,0,\dots)$ and so on
@0celo7 $\ell^2(\mathbb{C})$ is the space of square-summable complex sequences, the things I wrote there are sequences (the sequences that have 1 at the i-th spot and 0 else form a Hilbert basis of the space). Now you know what it means, and it should be clear that this thing doesn't have eigenvectors (try writing one down).
@Jim Well, I tend to use "unclear what you're asking " also when there's details missing that would be needed to unambiguously decide what kind of answer is needed there
In the days when the Commodore Pet was the peak of personal computing power I wrote a program that prompted the used for an adjective, then a noun, then randomly selected from the ones that had been entered and flashed up the message "you <adjective> <noun>"
@Jim : I had a look at the recent questions, and I struggled to find any intelligent questions by educated posters that were unfairly closed as being unclear. Is it my imagination or is the close queue much shorter these days? As if fewer questions are being nominated for closure?
@JohnDuffield mostly it's the really long or low-level questions that are unfairly closed as unclear. They could be fairly closed as something else, but using unclear as a default is what I find despicable
@Jim to be fair I think unclear is often used to mean you haven't explained your question clearly i.e. haven't given enough detail for it to be answerable.
@JohnRennie let's be fair. I've been reviewing long enough to know that constitutes unclarity. I'm talking about the questions that are worded outside the normal terminologies but still completely clear, the questions that have less than ideal prior research, the really long ones that take a while to as a clear question but you'd have to read the whole post.
@BernardMeurer I'm no comp sci expert, but I think it's saying that the language is "closed" with respect to Turing machines in the sense that if one element produces a Turing machine with a certain set of accepted inputs, then all other descriptions producing a Turning machine with the same accepted input are also elements of the language
[Rambles] Next time when I ask question and someone (Let's say X) got confused, I should invite them to join and debug exactly where and how X.exe stop working
@Jim I'm not sure I see how you can justify that argument. I think there is an issue in how charitable we want to be in accepting questions that are not well thought through.
@Jim: but at the end of the day this is a site for physicists and we expect a minimum level of effort to be put in to writing a question. We aren't reddit and don't try to be.
@JohnRennie I'm looking through the list. I think I should clarify my problem now. Most of these questions closed as unclear should be closed. Just not as unclear. My issue is with the usage of unclear more than with the questions that are closed
You now make a double differential complex $K=\bigoplus_{p,q\ge0}K^{p,q}$ where $K^{0,q}=\Omega^q(U)\oplus \Omega^q(V),K^{1,q}=\Omega^q(U\cap V),K^{p,q}=0$ for $p\ge2$
then by some tricky Riemannian geometry, you can cover your manifold with a countable collection of open sets, which are contractible, and all finite intersections are contractible
yes, what was the point of the AMAs again? People can already ask me anything in chat, why do I need to sign up for a specific timeslot for them to do that?
In the construction of a good cover for a manifold $M^n$, Bott & Tu use the fact that each point in $M$ is contained in a geodesically convex set (after picking a Riemannian metric). They then claim that the intersection of geodesically convex sets is a geodesically convex set, and that makes sen...
@JohnRennie Well, if you look at DanielSank's AMA, there were several non-regulars there, and they seemed rather interested (one even explicitly requested to keep the thing on-topic because they were interested in what Daniel had to say). I think the non-regulars come if they get someone interesting. A random physics.SE user isn't, a quantum engineer at Google is, and an actual quantum gravity researcher would probably also be
For me personally, it's more important to have a one sentence set-up like that at the beginning than the gory details---I lose interest when you get bogged down in the details.
@Danu Then you need to compose the URL manually, i.e. find out the postID by some other means. The easiest way is to click on "share" - the number behind the /a/ is the postID. Then you go to physics.stackexchange.com/posts/<postID>/timeline.
@Danu I suspect because it is a strain on the servers to generate the timeline and they don't want people to generate a timeline for a given post unless they really need it
@Danu @Danu when I first read it I thought it did address the question but was just wrong. and votes are there to point out that an answer is wrong. reading it again you are probably right it does not address the question at all, my bad... sometimes hard to tell the difference between "wrong answer" and "not an answer" :P
@JohnDuffield liked the hossenfelder ref to hydrodynamics and drops "pinching off" as a natural model of singularities, did you see that? think shes much closer to reality than she realizes.