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11:00
etc.
@Thorgott @BalarkaSen Ok thank you very much. I go. See you!
@LeakyNun: I know that a direct (external) product $Z_{n_1}\times Z_{n_2}$ is cyclic iff $n_1$ and $n_2$ are coprime
Any hint which used that?
just read what i sent you lol
I did but please try to understand I don't know that CRT etc
I don't know (yet) may of the words being used there
:'(
@LeakyNun
11:06
the proof isn't that straightforward, you need to use a bit of theory
It would seem so. I am allowed to use Lagrange's theorem
the classification of (finitely generated) abelian groups uses torsion subgroups. do you know these?
Torsion?
No
I know only classification of 2p order groups where p is prime
I saw an answer here which gave a hint that: prove that 5 has order 2^{n-2} or something
I don't know how to proceed using the hint also
oh, you need torsion subgroups only for the full classification of when $(\mathbb{Z}/n\mathbb{Z})^\times$ is cyclic
I see so I'll wait till I learn these concepts then
11:10
@Koro yes, the case for $n = 2^k$ is pretty much the principle of the CRT with a bit of arithmetic
proving that $U(\mathbb{Z}_{2^n}) \cong \mathbb{Z}_2 \oplus \mathbb{Z}_{2^{n-2}}$ consists of two things:
1) finding an element of $U(\mathbb{Z}_{2^n})$ with order $2^{n-2}$
2) finding an element of $U(\mathbb{Z}_{2^n})$ with order $2$ that does not belong to the first one
3) proof it!
so first prove that thing about 5. that will be your first generator
then find an element of order 2 that is not in the subgroup generated by the first element
since $|U(\mathbb{Z}_{2^n})|=\phi(2^n) = 2^{n-1}$ and the product (as sets) of these subgroups will also be a group and since their intersection is trivial, it will have $2\times 2^{n-2} = 2^{n-1}$ elements. so it will be the whole group. now, they are both normal subgroups since $U(\mathbb{Z}_{2^n})$ is cyclic. thus they are an inner direct sum, which is isomorphic to a external direct sum, etc.
@Koro e.g.?
CRT for example @LeakyNun
but theorem 5 didn't say CRT
the whole article might be too much, but that specific theorem @Leaky sent you is just arithmetic
you need to learn to read top-down, as my professors tell me
that means, read theorem 5 first, and when (and only when) they reference some lemma, read those lemmas
instead of reading everything from P.1 to P.11
11:22
oops, I said $U(\mathbb{Z}_{2^n})$ is cyclic. sorry. I meant abelian
@LeakyNun: Some how I was seeing theorem 7 on page 11
I somehow didn't see theorem 5.. I'll take a look. Thanks
@LucasHenrique @LucasHenrique: I am yet to go through your explanation.
Sorry to repeat myself, but I'd just like to make sure my message stays visible.
Hello everyone. I'm 17, and I've written 2 papers on quite separate topics in maths. I believe the results to be new, but I am seeking a professional opinion about them.
Would any mathematician be willing to have a look at at least 1 of them and comment on it within about a week or two?
They aren't very complicated, so going through them shouldn't take too long.
I'm not the person you are looking for, but it would help in any case if you mentioned the topics of these papers
@Thorgott I'd prefer not to say the exact topics for fear of someone else figuring out the same results as I have, but I can say that the topics covered are understandable to a strong(ish) high school student.
Why don't you get one of your teachers to take a look?
11:36
hi all, could someone help me understand a sentence from here imgur.com/a/EipKJF7 , 'Roughly speaking, a manifold is a space $X$ that locally looks like $\mathbb{R}^n$ and a submanifold is a subset of $X$ which locally looks like an affine subspace in $\mathbb{R}^n$', what I dont see is why an affine subspace doesn't locally 'look like' the linear subspace its a translation of
@LucasHenrique Ahh I see, so that's the deal with 5
Thanks a lot @LucasHenrique :)
@EdwardEvans One of my teachers said it was too complicated for him, but I think he must have been joking; he was probably too busy to have a look at it. The other maths teacher of mine did look at 1 paper, but he isn't a professional mathematician at all: he's done a BsC in maths and sometimes I feel like I know more than him.
and if an affine subspace does look like a linear subspace its a translation of (which as far as I can see it should, its even homeomrphic to it by that very translation), isn't the introduction of affine subspaces a little redundant? Can't they have just written 'and a submanifold is a subset of $X$ which locally looks like a subspace of $\mathbb{R}^n$'
@A-LevelStudent well I still think you should just mention the topics here. Nobody's gonna scoop you lol
@A-LevelStudent you shouldn't be afraid since if simply speaking of which topics it's about makes one figure out the results then it's trivial. :p
11:41
Let me be frank. 1.) If the result is easily replicated just by you giving an indication about it in an online chatroom, it likely isn't worth publishing (unless it's expository in nature, in which case replicability is a non-concern)
2.) It's very unlikely someone will agree to unconditionally proofread something when you're not even willing to disclose what it is. Being understandable to a strong high school student is one thing, but if you want to do serious mathematics, you want the opinion of an actual expert. A high schooler might be able to understand the content, but that is incompa
I made a paper about combinatorics and generating functions on algebraically closed fields. very vague ideia on what it is about - try telling us
@Jam You don't have to worry about that - if a room is inactive for 14 days, it gets frozen. (If it had low number of messages, it is already after 7 days.)
@porridgemathematics you are correct, affine or not is an insubstantial difference
@Jam Re: "dont know how to invite people". See meta: How do I invite a user to chat?
maybe the authors are doing affine subspaces cause it's more convenient for what they plan on doing, I don't know, but I wouldn't overly concern myself with it
11:46
alright, thanks @Thorgott
I'd rather be on the safe side, thank you though @LucasHenrique and @EdwardEvans . I'll say what areas they're in though:
The 1st paper is number theory.
The 2nd paper is to do with the Fibonacci numbers.
@Thorgott Is that still too vague?
if you've proved Collatz, you haven't
well, I'm pretty sure less qualified than @Thorgott and, since he isn't your person, neither am I :p
maybe there's some number theorist hanging around...
but you're probably gonna want to wait. get to uni, talk to a professor you trust and he'll tell.
not to drag you down but it's really possible that you didn't prove something new. that's a disappointing part of maths. so it's better to wait, get more resources and math culture to refine your results.
11:58
@LucasHenrique I understand the sense in that, but I thought it'd actually be a good thing for uni's to see if I'd published 2 research papers while still 17, so I would prefer to publish sooner than that.
I know what you mean about the disappointment; I've discovered results I thought to be new loads of times and then found out they were already known :)
I'm trying to prove
I tried to combine
CIF and Caratheodory inequality
By CIF, $\frac{f^{(n)}(z_0)}{n!} = \frac{1}{2\pi i}\int_{|z|=R}\frac{f(z)}{(z-z_0)^{n+1}}dz$
But the problem is if I apply B-C inequality to the integrand of CIF,
we take the integral over $|z|=R$ not $|z|=r$ so I can't directly apply the inequality
Any help for this?
Especially I don't understand where that $2^{n+2}$ came from
12:39
So far, I got A((r+R)/2) in the desired inequality
Now I'm doubting if it's a typo...
13:36
every non strict monoidal category is equivalent to a strict monoidal category
lol @ abstract nonsense
isn't a skeleton automatically strict
hmm, I guess it's not entirely clear whether a skeleton inherits a monoidal structure
whatever
@BalarkaSen Why have you posted that here? I don't speak French, but I don't think Tintin has anything to do with Mathematics :) Please refrain from posting things like that.
its a skeleton joke
also you can post non-math things here as long as its not spam
@BalarkaSen Lol, I hadn't realized your intention :) My mistake, no offence intended.
13:45
see top right corner for chat guidelines
whats the translation?
"this... is bizarre"
"where the hell could it have gone?"
thanks :) I think i've read the comic this is from before.. good memories
13:50
From Destination Moon...no clue what the title is in French :)
I love how portuguese inherits latin structure. The comic is barely understandable to me and I haven't ever studied french
the story is that thomson and thompson kept seeing each other crossing the other side of the x-ray plate and freaking out about a skeleton haunting the halls
@lucas oh cool
speaking of french
hi @astyx
Hey
It's not a coincidence
i guessed so
Although I do appreciate the Tintin ref
13:55
I'm going offline now. If anyone agrees to have a look at any of my papers please do use @A-LevelStudent to grab my attention. Thanks, and have fun :)
@A-LevelStudent but only professional mathematicians right?
i will ask around in my department and get back to you
not many people specializing in fibonacci identities that i know of
@A-LevelStudent im starting a phd in september, so im not professional but im on summer holiday and dont mind taking a look at it
of course there are probably way better candidates than me
Hi. Without using calculator, can we find the value of sin80?
depends
what if you are the calculator
13:58
lol
you can use a taylor series expansion
sin(80) = sin(90 - 10) = sin(10), then use taylor series for sin(x) around x = 0
i assume 80 means 80 degrees and not 80 radians
14:12
@A-LevelStudent In this day and age, you should not fear being "scooped". Post the papers to arXive, or to your own personal website, or to github, or to some other place where you have a timestamp indicating a "publication date". Done. You have asserted priority.
Keep in mind that the goal of academic inquiry is to discover "truth". We collaborate with each other to push human knowledge forward. Trying to keep your results secret is antithetical to that.
@XanderHenderson If I post them on arXiv, isn't it permanently on there even if it turns out the papers I wrote is utterly trivial? That's why I want a professional opinion about them, to make sure they are worth publishing. Once I have that I fully intend on publishing it on arXiv, so I definitely won;t keep the results secret.
@A-LevelStudent What you seem not to be understanding is that professional mathematicians share their work with others all the time.
@A-LevelStudent you can't have it everyway
We talk to each other and share ideas.
That is how we push our ideas forward.
Secrecy is antithetical to this.
There is always a risk involved.
14:17
Moreover, I highly doubt that someone with a high school background is going to have independently come up with something terribly significant. As an anecdote, I went to high school with an extremely talented and bright young man. As a freshman (in high school), he published a paper which made some progress on a problem which was open at the time (I can't remember which problem---it was either Fermat or Poincare---a complete resolution came a few years later).
Because of the structure of my high school, which was a part of the university system, he had advisors at the local university, and worked with folk at other R1 institutions.
He had a large support network.
Even then, the result he came up with was only a tiny step, and was rendered a dead end a few years later.
Of course, I made the mistake of Google stalking that guy a few years ago---he now works in astrophysics at UC Berkeley, has some named chair, and has over a thousand publications (and is first author or sole author on a significant number of them).
The point is that this guy was brilliant (based on my own personal knowledge of him, as well as his career path), and the best he could do as a high school student was make some very small progress on, and this was done with the help of a large number of experts, who shared ideas openly.
Secrecy is not good for academia. :\
I see. Still, it won't be a secret for long if someone does have a look at it. I'm also slightly worried that if I publish my papers and they turn out to be trivial (or worse, wrong) then it may affect my reputation if I try to become a professional mathematician. I'm wondering now, is that a silly worry?
Oh, I lied. The named position at UC Berkeley was a postdoctoral appointment. He is at University of Arizona now, in a tenure track position (I just Google stalked him again).
i think it is generally understood that your first work might not be your best. also, if it's not published, there's an open question as to whether people would even be able to track it down later. or how much they would care about it.
I actually should probably send him an email... I've been toying with the idea of taking some graduate hours in physics so that I can teach physics at my current institution (since we don't actually have any physics faculty here).
lots of people put unpublished notes/etc. on their web pages.
14:24
and in this chat room
@A-LevelStudent Nobody cares.
it would be a rare hiring committee that said, we like X, Y, and Z, and W, and R, and S, and T, but we found this thing on a web page from 10 years ago which doesn't seem up to that standard.
Like, really. There are probably about 20 people in the world who might be interested in reading my masters thesis (and I have had beers with about half of them). There are maybe 40 or 50 people in the world who might be interested in my phd thesis (and I've had beers with almost all of them).
Nobody cares.
my papers on researchgate get about one download a year. it is probably a web crawler.
@porridgemathematics thanks so much for offering! I'd really appreciate you having a look at it thanks. How can I contact you?
Thanks for quelling my worry @leslietownes and @XanderHenderson :)
14:27
@leslietownes My paper gets four or five downloads every year, but I think a lot of that has to do with the fact that one of my collaborators on that paper is a god damned machine. He cranks out another paper every five or ten minutes.
Most of them are pretty good, too.
those people need to slow down. :)
@leslietownes I mean, yes, but only because I need to protect my ego.
it's crazy when people can do that and also be doing good work. more common is the pattern of, each paper in a year has 1/3 of the last paper in it, and 1/3 of the next paper in it, and two parameters vary in the middle. easier to do in some fields than in others.
(Honestly, I figured out a long time ago that I am never going to be a superstar, and decided that I can make a much more powerful impact by teaching. I have a few papers that I really, really ought to get out, but haven't found the energy to deal with in the last year. I likely won't do a ton of research beyond that.)
i had an officemate who worked in PDE. there were a lot of people doing that in his field. slightly different boundary conditions or coefficients. turn the crank on the printing press.
i don't think it was professionally useful for people to do that, but they did it anyway.
14:31
@leslietownes I think that John got lucky, in that he is working in a field where there is, potentially, a fair amount of low-hanging fruit.
anything applied, it's fairly easy to do too. new data can be a new paper.
He studies notions of metric dimension (Assouad dimension, conformal dimensions, lower dimension, etc). While there are a lot of results about the Minkowsi-Bouligand dimension, Hausdorff dimension, and packing dimension, the Assouad dimension (and its relatives) didn't get a lot of attention until the late 90s or early 00s.
again, who knows if it helps. it tends to be pretty obvious when someone is write-only.
i've got a whole lot of stuff ready to go on the Leslie Dimension.
And, even then, it wasn't until a few papers came out around 2010 that anyone really started paying attention.
So there are a lot of basic results which need to be proved.
@leslietownes Heh.
worth reading norbert wiener's autobio if you are planning on being a super star
14:33
it sometimes bothered me in grad school that students in fairly new fields seemed to get outside funding more easily, simply because the aspirational stuff (or already proved but not published stuff) they put in their applications sounded rosier than realistic disclosure about work in more established fields.
@leslietownes Yeah. cough Applied category theory cough
Oh... I seem to have something caught in my throat...
ahem
Hey all!

Is there some place on the internet I can ask if a formula I conjectured (now proven) is worth publishing or useful for something? (I've done a physics masters)
@MoreAnonymous Not really. This seems more like a question you should put before an advisor or mentor.
Or, really, just write the paper and submit it somewhere. If it is accepted, you have an answer.
But, generally speaking, "a formula" is not publishable.
@XanderHenderson I don't think I as a physics student could possibly write math upto your level
@MoreAnonymous Why not?
14:37
you could post a question on math.SE in the form of "are other versions of this known? do people know of similar results?" with some background on what motivated you to care about it.
@XanderHenderson Have you seen the math a physicist uses its filled with black magic! :P
But if the claim is that a physics student can't write to a reasonable standard, that is an answer, too (it isn't publishable).
@leslietownes I posted it here
@MoreAnonymous No. I don't know the first damn thing about physics.
13
Q: The Definite Integral Problem (with a twist)?

More AnonymousThe Definite Integral Problem (with a twist) In the Riemann integral one essentially calculates the area by splitting the area into $N$ rectangular strips and then taking $N \to \infty$. Here's something I asked myself related to the Riemann integral. Let's say I split the area into say $3$ st...

14:38
oh, you beat me to it.
you stole my good idea, and covered your tracks by going back in time and doing it "first."
I took a semester of physics in high school (so I know a very little bit of Newtonian physics, from pre-calculus standpoint), and I took a quarter of quantum mechanics as a graduate student (so, like, I know about certain families of unbounded operators acting on Hilbert space).
@XanderHenderson Most physicists think there is only one hilbert space
:P
publishability of stuff is pretty context dependent. a lot of journals that focus on expository math, or stuff that might not be on any recognizable research frontier, usually like stuff that ties to something of 'general interest.' 'why should anyone care' is often the threshold question.
there is only one hilbert space.
:)
Oh, I also once read an astrophysics paper.
@leslietownes Some math people have pulled a fast one on me :p
14:40
Though, I admit, I only read it because it contained a 1-1 scale figure.
@XanderHenderson was the error bar +/- 50 km/ sec ?
well, there are finite dimensional ones, and then there's the one true hilbert space.
there is no such thing as an inseparable hilbert space.
@leslietownes This.
And then the C-* algebra folk go crazy, with their von Neumann algebras, and Type III factors, and whatnot.
one thing i'm ashamed of is in my dissertation, i put some kind of throaway remark at the beginning like "all X's are assumed separable unless otherwise stated." i never stated otherwise. i should have taken those weasel words out.
@leslietownes I see :////
14:42
it was about operators on von neumann algebras. :)
Oh, and don't forget Temperly-Lieb!
i love type III factors.
speaking of physicists, bob powers (constructor of the first continuum of non isomorphic type III factors) was educated as a physicist. and he was thinking physics when he came up with those.
@leslietownes I see ... : /
i had the odd experience of asking him to explain an aspect of that construction to me once, without realizing that he both had invented it and was kinda famous within the field for doing so.
sometimes ignorance really is bliss.
14:47
i never understood the temperley lieb algebra.
more anonymous: do you see?
:)
I'll be honest: I don't really get most of that stuff. But we had a couple of guys in our fractals research group at UCR who had a fair amount of expertise in that area (one was a postdoc who had done his phd work under Vaughan Jones; another had done his BS at Vanderbilt, and worked with Vaughan Jones).
@XanderHenderson I've met Roger Penrose thats the highlight of my academic life
:P
So I have sat through a lot of talks on planar algebras and the Temperley Lieb algebra and such. I know some of the big words, but found that most of it went over my head.
I only know Lie algebra
Oh, sh*t... Vaughan Jones died last year.
14:51
yes, that was a surprise to me.
way too soon.
one of the nicest people.
such a new zealander, too. you'd never guess he was a knight of the realm, or whatever he was.
I never met him, but his students were very fond of him... I should probably send Mike an email. :\
i didn't know him well but did learn the basics of von neumann algebras from him.
he had a draft of a really good book on the subject, probably still on his webpage. i don't think he ever published it.
"course.pdf" on math.berkeley.edu/~vfr/math20909.html if anyone is curious.
very good notes.
15:35
Oh, I just came across a terrible pun:
16:09
@XanderHenderson Jeez, you drink beer?
Drinking beer and smoking is a sin in our culture. Jeez, you guys on weed too?
@Permutator I am sorry that you come from a culture which encourages you to pass judgement on those who are not a part of your culture. Personally, I am inclined to live and let live. As long as you aren't hurting others, do what you like.
@XanderHenderson I like it, but then I am aberrant in my enjoyment from puns.
16:24
@XanderHenderson Your philosophy sounds good but you're aware that you're hurting yourself by derinking beers and bein on weed right?
Assuming someone smokes marijuana just because they drink beer is just wrong
@robjohn You seem quite knowledgeable in these things. Do you smoke marijuana?
something something cardiac benefits wine etc.
i dont get the connection between the jehovahs witnessing and the pun post
is there one?
@shintuku NO
16:26
And there is evidence that drinking moderate amounts of alcohol is not harmful and can even be somewhat beneficial.
@Permutator Never have, not that it's any of your business.
also there is evidence the russian monarchy used vodka sales to maintain the serfdom in utter stupidity, how are you to govern without alcohol?
have you seen what happens when you try to prevent people from drinking alcohol?
of course, you might be thinking of the american prohibition
@porridgemathematics follow the link, the comment is not about the pun
but actually I am thinking of the canadian prohibition, less well known but simultaneous to the american prohibition
quebec almost seceded because of the lack of alcohol
do you understand what this means
im dumb whats the link? like the link I click on to open the pun image?
now, if you want society to disintegrate, i strongly suggest you force everyone to stop drinking alcohol
they'll all become communists
trust me on this
they almost did because they couldn't watch baseball
imagine what would happen if they didn't have alcohol
16:33
@porridgemathematics see the arrow ^^^
ah much thanks
oh wow, lol, he must be really passionate about his agenda to link to something that far back
the world runs on passion not on fossil fuels, bless their misguided courage in imposing their views on the rest of the world
i see great things for their future
How do I prove that if A is finite than A is definable?
I know that union of deibale sets are definable, so would a direction of a union n singletongs (where n is the size of A) which are definable are a good start?
Definable in which language? Are you allowing parameters?
16:45
first order logic
say the set is $A = \{b_1,...,b_n \}$, if you're allowing parameters consider the formula $\phi(x,y_1,...,y_n) = (\lor_{i=1}^n x = y_i)$, then $a \in A$ iff $\mathcal{M} \models \phi[a,b_1,...,b_n]$
I think you can only really do it without parameters if your finite set is distinguishable using the functions/relations of your first order language
but I might be wrong
e.g. if your structure is $<\mathbb{N} ; \leq >$ where $\leq$ has the usual interpretation and you want the smallest $n$ natural numbers or something
Hi. If square root is shown with \sqrt, how can we show write cube root?
I tried \cubert, didn't work
Hello! Could someone help me with my question here?
How do I construct F, given f?
by the way, on the topic of first order logic, this has been bugging me for a while: in a first order language with equality, and one unary function $f$, with interpretation $f(x) = x^2$ in the structure $<\mathbb{N}, f > = S_1$ and interpretation $f(x) = x^3$ in the structure $<\mathbb{N},f> = S_2$ (so the only difference between these is the interpretation of $f$), are $S_1$ and $S_2$ elementarily equivalent?
if we change $\mathbb{N}$ to $\mathbb{R}$ they are not elementarily equivalent, since for instance $x^2$ has two fixed points is a sentence true in the first structure but not the second ($x^3$ has three fixed points in the second)
but im wondering if we can distinguish between these structures when we change the domain to $\mathbb{N}$ as far as true sentences
@epsilon-emperor Thankyou.
16:59
for that matter I could have said if we change $\mathbb{N}$ to $\mathbb{Z}$

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