Chronicles of Harry - Dreamwidth Studios
An argument I've gotten into several times on the internet regards why psychological trauma occurs. There's a common idea you see that psychological trauma consists of some sort of damage to the brain's system, the result of an input that is simply too far out of range in some regard (too negative-valance, e.g.). I have often replied that this can't be right -- for one thing, out-of-range inputs…
And yes, it limits to 1. That, although the authors presumably did not realize it, is to my mind the upshot of this recent paper by Bahig et al. (Yes, I've written to them about this fact.) In it, they determine all numbers whose shortest addition-multiplcation chains have at most 1 small step -- in other words, all numbers with addtion-multiplication chain defect at most 1! From their…
So when Kappa unpacked her boxes of books last year , there's two boxes she didn't open. These two boxes weren't books she'd packed away -- they were two boxes of books sent to her by her uncle, quite some time ago; just books he thought she'd like. She'd never opened them, though, and didn't know what was inside. Well, this past weekend, she finally did that, and on doing so found that she only…
So I a few months ago I noticed that on John St there is now a pho restaurant called "Pho John St". By itself, there's nothing particularly noteworthy there -- it's a pho restaurant with a straightforward name. OK. But then a few weeks ago I noticed that there's now also -- one block over on Fulton St -- a second one, called "Pho Fulton". I say "a second one"; I haven't been inside and checked a…
It's out! Look, I've talked about this here before , that I don't feel a need to recap its contents. (Edit: Oops, turns out my previous post on the matter didn't explain it either. Oh well.) But, y'know... we prove Juan Arias de Reyna's conjecture 8 on the self-similarity of the defect set, and also, we show that when if a is a stable number, then ||a3 k +1||=||a||+3k+1 for all sufficiently large…
Instead of saying "the trail has gone cold", we should say "the trail has gone warm". We tend to conceptualize recent things as hot, and as cooling off over time. But, cold things also return to room temperature over time. If you've deliberately chilled your drink for instance, then if you wait too long it goes warm, not cold! So, if we restrict ourselves to that level, then either metaphor works.…
So joshuazelinsky recently sent me a link to this paper and wow! This paper contains just two theorems but both are huge advances in integer complexity; one on the upper bound, one on the lower bound. First the upper bound. Let's review -- what upper bounds are known on integer complexity? If one wants a bound that works for all n, well, there's the naive bound ||n||≤3log 2 n, and then there's…
So, New York City recently got rid of the Metro Card (the card readers are still there, so if you have one it's still usable for now, but you can no longer get a new one nor refill your existing one) and replaced it with the OMNY card. The OMNY card has one big obvious advantage: It's much easier to use. Tapping your OMNY card is much easier than the mess that was swiping your Metro Card several…
Someone else has written about Snake! You might remember my webpage on the problem, which unfortunately they don't seem to have turned up in their lit review (I guess that's what happens when you don't publish properly :P ). But these people are studying the same problem and have turned up some cool new results! One thing to beware of, they numbered their theta graphs differently than I did. Their…
Hey, they finally put up the public version! This post has been a bit delayed while I waited for the public version of Mystery Hunt to go up. Let's see what I still remember. So I decided to stay home for Mystery Hunt this year and solve remotely. This is because I'd been to the JMM down in DC shortly before. Admittedly, these were two weeks apart, so yeah I probably could have swung it, but, eh.…
People keep needlessly adding vowels to things, and I think it'd be better if they didn't. The other day my roommate Geoff received a package via the US Postal Service -- the USPS. He decidedly to jokingly pronounce this initialism as if it were a word -- "uspis", he said. (Sorry, no, I'm not going to bother with IPA or anything here.) Except... "uspis"? No. That should be "usps". One syllable.…
It seems PAMS never actually told me when they published my paper with Andreas, seems it went out (or at least up) in September . And MathReviews has finally indexed it... which means, that's right, I finally have a finite Erdös number! Namely, 4. And joshuazelinsky gets 5. I won the race! :P comments
We're down to just 120 books left! And the origami supplies are all gone, too... comments
So, I have recently been reading/thinking a bit about central groupoids . This is a quite misnamed class of object; they're not groupoids, the term comes from an old use of "groupoid" to mean "magma". (Blech.) They're magmas (sets with a binary operation) satisfying the central identity, (ab)(bc)=b. You may recall my project regarding equational probabilities in algebraic structures . I…
I never properly wrote about this question here -- only obliquely referred to it here with the text "proving it seems annoying" -- but now it has an answer! This is a question about automatic sets, so I should probably explain what those are, since a lot of you won't know. A b-automatic set is a set of whole numbers which is given by, you have some DFA on the alphabet {0,...,b-1}, you write…
Imagine if someone organized a big festival to celebrate slugs. They could call it SlugFest. comments
The "numbers rant" is someting I've posted various places on the internet in the past, but it seems like I've never posted it here. Figured made sense to get it down here. So, sure. Here we go. People who haven't seriously studied mathematics might reasonably assume that mathematicians have a unified notion of "number". There are numbers, you can add them, you can subtract them, you can multiply…
But that time it involved ping pong comments
If you're unfamiliar with the concept, the idea of natural units is that you can create a "natural" system of units, determined by physical constants, by declaring that certain dimensioned physical constants should be equal to 1. E.g., when doing relativity, one often sets c=1, causing length and time to have the same dimensions; the idea is that by extending this convention to other physical…
Inspired by seeing this old article on Hacker News, here's a challenge for you: In the (current) NYC subway system, find two stops A and B such that to get from A to B, you need to take 4 trains. (This isn't 1980 anymore; I'm pretty certain there aren't any pairs requiring 5 trains.) We can set out several difficulty levels: 1. Ultra-easy version: There just has to be some time of day / day of the…
So, remember this ? Well, I finally found out where it's coming from! What's going on here is that these flags are included in my system's emoji font, which is from Google's Noto Emoji family. And the version of this font included with Debian and Ubuntu, at least, includes these nonstandard flags. Which ones? Well, the files for them are right here ! And yup, it's exactly the ones I said. So yay,…
So, last summer, I learned from HK about the horeshoe crabs in New York City. She had -- I think, I forget the exact story -- been out exploring the distant parts of the city, and had come across Broad Channel, and she saw the horseshoe crabs on the beach there, and she gathered some people to go see them again. So she and I and some other friends went out to see them. See, around May and June,…
Huh, I never posted about this, did I? So Kappa finally moved in back in January, and with her, many boxes of books. This month she finally unpacked most of those boxes. (There's still two remaining, to be handled at some undetermined future date.) There had been preparations earlier -- she and Geoff had gotten new bookshelves to replace Geoff's old bookshelves in the main room, that had been kind…
So, here's something that had bugged me for a long time. Jacobsthal multiplication is associative, but the proof of this is unsatisfying. Normally the way you prove an operation is associative is that you show that a multiary version of it makes sense; you don't just literally show that a(bc)=(ab)c, you show that abc makes sense on its own as a ternary thing (or with even more operands) and that…
I'm trying to just write down more old thoughts, and you know what, I haven't written this one down. The Python programming language has an interesting construct I haven't seen elsewhere: while/else. A while block with an else block following. Now this is terribly misnamed; based on the name you'd think that, like, the else block executes if the while block ends up being skipped, like if/else, but…