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20:00
@EricSilva Sorry, really weird typo. I mean loans.
To which careers does that which is intrinsic to a Philosophy PhD point?
being the sort of quant that would make that much money sorta seems like it'd involve selling your soul multiple times over
I don't know I'm not a philosophy PhD Kamil
@Eric: has your full handle always been EricSilva and I'm just noticing it now?
I think philosophy PhDs should either go into academia or just do anything.
20:01
no I changed it yesterday @Eric
well there's two EricS's now; I hope you're happy :P
lol who's seen The Accountant?
But at least now it's possible to ping one of us and not the other
20:02
It's always been possible though
In general, if you have a PhD in X, you should do something directly related to X, or you can do anything. It's quite simple, really. =)
I find that a little reductive. Doing PhD work in physics, for instance, will for some people mean a lot of experimental labwork. for others, it's basically a lot of applied math.
You'd click on the name of the person you want to ping (works on phone as well)
my backup for math is to go do woodworking in a cabin in the mountains or something
Oh damn @Daminark I didn't know that
TIL
I am considering a career in singing, but I don't know who to talk to and where to go for that.
20:05
My backup is to starve
@Daminark You can both become a mathematician and starve!
Jk I've got at least some kind of affinity for theoretical compsci
And I'm pretty sure that non-theorists have use for theorists even outside academia
You wouldn't even be the first
certainly not the last
Did anyone here watch The Real Cancun? It was the first movie Laura Ramsey acted in. It's actually like reality TV.
Or did anyone here actually visit Cancun, Mexico for spring break? It looks like a cool place for vacation!
20:10
main problem I have with all this is that I have no real idea what jobs are out there.
i mean, one hears vague handwaving about quants, but that's not really specific at all
It's not easy to be hired as a quant either.
Basically, if you do math, nothing is easy. =)
Generic career websites say math majors have the best job prospects and are often guaranteed six figures, which may be true in a sense
@Brody Erm...
I can well believe that the jobs are out there; that seems plausible enough.
Guaranteed six figures?
Maybe in rupees.
20:13
Okay, that seems dubious
I think those are the people who more double majored in stuff like math and some variant of finance or engineering
But I find it hard to find people in academia who actually know what a STEM degree can be used for.
(setting aside Engineering, I guess. I think there the career prospects may be more obviosu)
But vanilla math is way iffy
@JasonBourne Sorry, I'm paraphrasing very badly. Median starting at or near six figures
which is very different oc
(but I'm not an engineer, soooo)
20:15
and what constitutes a "mathematician" to them may not exactly align with our preferred conceptions
Anyway, if people really wanted money they wouldn't be doing math. Math professors are quite poor, compared to accountants, lawyers, bankers, and actors.
semic, my understanding from the far-too-many panels I've been to is something like: the market for math PhDs is fairly big but "sparse": most companies don't need any, and most that do only need one or two. But it seems that there's a lot of communication between the companies that need a few, and if you apply in one place but don't fit what they're looking for, they tend to know others that are hiring, and can give very strong recommendations.
3
All Daniel Craig has to do is one Bond movie and he gets paid 39 million dollars!
@Astyx hello
Even getting the apparent quant jobs requires more stuff like math-related fields like stats/coding, and within math stuff more like numerical analysis. Algebraic geometry is not nearly as surefire
20:16
ehh, that's a pretty silly comparison. The high-end for acting may be really really high, but the low-end is really low.
@Daminark Actually, probability and PDE.
In the same vein, I know a PhD in clinical psychology with an 8 figure salary
@EricStucky That sounds like it'd lend itself to a consulting model.
0
Q: Indefiniteness of $\mathbf{P}$ and positive definiteness of $(\mathbf{I}_K\otimes \mathbf{X})^T\mathbf{P}(\mathbf{I}_K\otimes \mathbf{X})$

JuliusConsider the following elements with $K\geq 2$. $\mathbf{X}$ is a $K\times 1$ real vector. $\mathbf{P}$ is a $K^2\times K^2$ real symmetric matrix of the form \begin{equation*} \mathbf{P} = \begin{pmatrix} \mathbf{P}_{11} & \mathbf{P}_{12} & \cdots & \mathbf{P}_{1K} \\ \mathbf P_{12}^T & \m...

Either way, the classes you take if you're interested in math for its own sake seems to be different enough from those you take if you're interested in math-heavy industry jobs, enough that caution is important
20:18
Damin: the topic of study is rarely important. Everyone knows that an industry PhD is not doing the same sort of work they did for their thesis. You're valuable as someone who knows how to read the literature and commit to a problem for many years, not as someone who happens to know how to find stable solutions for nonlinear PDEs.
3
ah yeah, but for bachelors you might want to be a bit more careful
@user243301 What sort of approximation are you looking for? $g$ is given as a power series about $0$, that series converges absolutely and uniformly on the closed unit disk, so truncation of the series gives polynomials approximating $g$ pretty well. These polynomials are also the best approximations of $g$ in the $L^2$ sense.
That's interesting @EricStucky
Similarly with physics, I suspect, at least on the theory side.
Also lel
@DanielFischer Hello Daniel. How is your health these days? I hope you are OK.
20:19
@EricSilva You know Stella, right?
yeah a little
we've only spoken a couple times
What I worry a bit about is what people actually mean by 'coding.'
I don't know anything about coding or cryptography.
sorry, I know a PhD in clinical psychology with an *$80M salary
Her type of work right now is the sort of thing I'd want to do if academic aspirations burn
20:20
If it means CS-level programming, I can't do that.
Not too bad, Jasper. How's yours?
80m salary ?
What is she doing @Daminark?
What I mainly know how to do is numerical computations in Mathematica.
therapy for unicorns with that salary
20:21
albeit he's also an internationally recognized cultural TV icon
Which is closer to coding than some things, but farther from it than others.
ah
@DanielFischer I am still struggling with mental problems. Still bad, still hanging in there, still sorting out my thoughts, still hoping for a miracle.
Working with a group that contracts with the government, her stuff is a lot of graph theory
20:21
speaking of, I don't know what Ted looks like, but I always picture him as Dr Phil
i do a lot of programming for A.I which is fun
Hence why I always am a bit uneasy when someone says that industry is looking for people who can 'code.'
(Details are classified since I think a lot of the stuff is for DoD so I don't know too many specifics)
@Brody I think you can try finding some pics of him online. =)
I really don't want to work in industry personally, I really think if I left the math world I'd go off and do something completely unrelated
like taking care of livestock or building instruments or something
20:23
building guitars is fun
@JasonBourne Yeah, he mentioned some lecture recordings to me ages ago,which I've yet to check out
I interpret coding as being a bit closer to what you'll see in a compsci major
at least to me
@EricSilva Then emerge years later with a solution to a Millennium Problem, lol.
but expensive
20:23
Nah, just playing tunes
@EricSilva you'll be the next Perelman
could do a newton be great at maths then go work in a bank :P
I would never ever work in a bank
The other thing I find frustrating is that inevitably people will ask "oh, did you like working with students? okay, go be a teacher!"
Eric: XD you get irritated by the immorality of the farming community and return back to math, later writing a book about your life in obtuse mathematics metaphors #reversegrothendeick
20:25
and fffff**** that
All i ever see of teacher friends is them marking work non stop till midnight
I do not think I'd be up for teaching in like, high school or something
@EricSilva Never say never. That's one of my favourite Justin Bieber songs...
I actually do like working with students, but I can't stand education.
20:25
you dont like education? or the system ?
Idk @Jason, I know myself pretty well
Like, half dealing with discipline issues, and half teaching to a state test
I don't like being in charge of grades and such.
Or an AP/IB thing or whatever
@EricSilva Never say never again is also the title of a James Bond movie, lol.
20:26
^^^ Same, I dislike that deeply
@Semic
@Jason I don't like James bond movies
@Daminark Add in the fact that K-12 teaching typically requires a licensure program
Are the students in the average American high school very naughty?
I mean I'd be more fine with teaching at a college level, I think I'd potentially like that part of academia more than the research
Yeah, I could believe that as well.
I could see doing community college, though that doesn't seem to be a panacea either.
20:28
Students care more, I'm not held to some test that I need to teach for, and then when I get through that content spend all my time doing practice problems for that test, etc
I am not American so if someone can answer my question above it would be good.
@JasonBourne disrespect and general iffiness is prevalent enough that you're best off being ready to accept that before going in
@Daminark math is a service field though, lots of students won't care at all
I've successfully repressed my memories of high school.
(Though high school > middle school, by far.)
@whoever starred my comments: you may be interested in this blog post I wrote a while back.
5
20:29
Well, I don't think it is a service field, it serves as one in various contexts
@Daminark I taught in some average schools here, and I can tell you this: The classroom behaviour is atrocious. The worst behaviour you see on TV is actually the best in reality.
tutoring is different beast than education
But if all the applications of math ceased to exist, I'd still push it for its own sake
And I mean, it depends on which class
@JasonBourne Can't say what the "average" is but the climate varies very widely regardless
If you're teaching business calculus 1, then good luck
If you're teaching algebraic topology you're in better shape
20:31
@Daminark there are schools where math basically exists to serve other departments (this is far more typical than our school obviously)
@Daminark Hey those business students could become Bill Gates and then give you a million bucks!
Or they could become Donald Trump and decide to sue you for reasons.
The likelihood of that happening is low enough that I'd say it's far negated by other considerations @Jason
Or you could sue them and get a nice settlement
Let us impeach Trump. It is time.
20:32
impeaches Trump k we're good
politically unwise to do so this early
the fallout from impeaching him might be reaaaaally bad
at least this quickly
says the next President Miller
Yeah, I'm nervous about it as well.
Anyway I'll suggest that we don't get too far down the politics train
20:33
All action is political :)
Even $\int p\,dq$? Daaang.
I thought action is Hamiltonian. =)
I don't know if I buy that. Fourier analysis is not Republican
Double sniped
I have actually fired rifles before, you know.
something not being republican definitely doesn't mean it's not political
20:34
M16, in particular.
Let's have a referendum on the definition of $\Bbb N$
@Brody No need for that, just different conventions!
I mean I was shitposting in that particular example, I mean it doesn't need to have anything to do with, say, modern politics/governance. It's rather possible to stay mostly away from this sort of thing
@Brody I use which ever one lets me write less
it has 0, peace
20:36
something being political has nothing to do with governance
Or how about the $\pi$ vs $\tau$ discussion?
@Mike word
If I only care about multiplication, then it doesn't include 0.
Define "political action" then
Bourbaki includes 0. Set theorists do too.
20:36
If I care about addition, then it does include 0.
@Brody that one is easy, do you want $\Bbb N$ to be a monoid under $+$ or do you want to be wrong?
I would say any social action has to be political by its nature
Idt you can engage in any social activity without entangling yourself in power relations
(and finite ordinals should coincide with the natural numbers)
By contrast, the whole $\pi$ vs. $\tau$ seems nonsense to me. $\pi$ is what's conventional, so it's what we use. full stop
Just now I went to a rock band performance and some kids were like jumping around in a trance.
@Semiclassical I don't even know tau exists until a few months ago.
20:38
That, and it'd make Euler's formula for -1 ugly.
well, $e^{i\tau}=1$ they argue instead
@AlessandroCodenotti We'll include that in the referendum's comments
You've already got $e^{2\pi i}=1$.
But it the "unnecessary" 2 matters
lol. I was joking of course, use the definition is more comfortable in the context you're using it in
/s
library closing, gotta go
20:39
Actually while I don't want to be pushy I'll just let this go to rest. Mentioned this before but I'm pretty sure the likelihood is higher that I die in a car accident than dealing with stuff like this so I'd rather not, I've had a rather bad aftertaste in all my previous interactions with this subject. I will fight to the death that $0\in\mathbb{N}$
@Brody riiiiight (Idontbeliveyou!)
I think other than naturals including zero or not, there is also the issue of whether rings have one or not, how to define the fourier transform, and how to write subset and proper subset.
@DanielFischer Now I see that truncating the series one has these obvious polynomials.Then ok, and many thanks one more time.
Like if you define the natural numbers set theoretically it just feels right that $0$ is the empty set, you know?
The main reason I'm hesitant to say 0 should be in the natural numbers (beyond just not having learned it that way) is that it makes multiplicative stuff more annoying.
20:41
the set theoretic definition of natural numbers is not my cognitive model of natural numbers though
Good night all users in chat, bye.
0 is in there because without 0 it's just the positive integers Z^+
Also it's nice to think of the integers as being negative natural numbers.
so long as you don't think of zero as positive :P
if you think of zero as positive we're gonna have a problem
20:42
In French texts translated into English, positive sometimes means more than or equals to 0.
We should create "bositive" to mean non-negative, and megative to mean non-positive
tbf non-negative is kind of weird
nah. nositive and pegative.
And Bourbaki also defines a compact space such that it must be Hausdorff.
20:43
cause we're thinking about a set as the negation of another set
@Semic Perfect!
pegative is maybe the best thing i've heard
Also was that from Yugioh abridged? The "riiiiight idontbelibeyou"
Hello all people and goblins
20:44
Hello Nate.
I'm out
bye chat
Peace
Eric hates me
Sad reacts only
I think I'm going to give up piano and become a mouse tamer as a hobby instead.
20:53
Live vicariously by taming mice to play the piano.
That's genius.
their little fingers.
genius.
Do mice have thumbs
I think so.
21:08
I am trying to show that any two open sets in $\Bbb{R}$ endowed with the finite complement topology intersect. Here is my attempt. Suppose we have two open sets $U$ and $V$ that do not intersect. Then $V$ must be contained in $U$'s complement, which is finite. But $V$ is infinite, which is absurd. So, $U$ and $V$ must intersect.
Does this sound right? If so, wouldn't it follow that $\Bbb{R}$ with this topology is not Hausdorff?
@AlessandroCodenotti Thanks!
Follow up questions, is this space connected? Is it compact?
@Semi You know, when I see you in the chat, I know that I'm safe when doing physics:P You're sort of the Ted of Physics, I would say. Sorry for the cheesiness, but I still can't get over the fact how much you've helped me. (Physics is like a lost love to me, that I've finally found back, thanks to the physics chat and your help:P)
21:24
Glad to be of help, heh. (When I say that I enjoy working with students, it's this kind of thing that I'm talking about.)
Hey, is anyone familiar with the pumping lemma for regular languages?
I just remembered while thinking about orientations right now that at one point while studying manifolds I was being utterly confused about orientation numbers. Feels a little weird now. :P
For some reason I couldn't comprehend the fact that positive and negative orientation of a certain basis of a vector space is just a random association of number, and could be done in any way whatsoever as there are exactly two equivalence classes of oriented basis.
21:42
Conjecture: $\mathbb{F}_p[i]$ is a field if and only if $p$ is a Gaussian prime or if it already contains a solution to $x^2 + 1 = 0$
Is this correct?
Does siunitx or similar exist for MathJax?
@Daminark that's a field iff $i$ is algebraic over $\Bbb F_p$ right? Because it's isomorphic to $\Bbb F[X]$ otherwise
So, finite integral domains are all fields
Which is what led to my conjecture
Hm, wait, isn't it always a field?
See my issue is that if a prime is neither Gaussian nor already contains i, you have 0 divisors
21:55
What are the $0$ divisors in $\Bbb F_5[i]$?
Well it already contains $i$
$2^2 + 1 = 0$
My issue would be with something like $\mathbb{F}_{13}$
I suspect that this isn't a field
$i$ is algebraic over $\Bbb F_{13}$ since it's a root of $X^2+1$, right? Simple extension by algebraic elements are fields
Yeah, it isn't. (3+2i)(3-2i) = 0
If p isn't a Gaussian prime it can just be factorized and you get 0 divisors
You can't solve $x^2 + 1 = 0$ in $\mathbb{F}_{13}$, like 12 isn't a square
Aless: It's probably relevant that $x^2+1=(x+5)(x+8)$ mod 13, so it's not irreducible.
22:01
aha here's the problem, $\Bbb F_{13}[X]/(X^2+1)$ won't be a field because of that
x^2+1 is irreducible mod p iff p is a Gaussian prime, I suspect?
sounds very plausible
Just curious, what's the difference between $1~\text{mol}^2$ (of dimension $\mathsf{N}^2$) and $(1~\text{mol}^2)\cdot N_{\text{A}}$ (of dimension $\mathsf{N}$)? Should I be asking this in chemistry.SE's chat instead?
I feel cheated for never having heard about this adjoining-i business before; it seems like a really obvious exercise I should have been forced to do in my algebra class :/
(Nice observation btw @EricStucky)
@Alessandro Sounds like a quadratic residues problem. Hmm
22:03
Lol this is one of Laci's puzzles
But yeah I don't yet have a characterization of Gaussian primes
That's what I'm hoping to do now
i feel bad for forgetting all my number theory but that's the issue
ok I'm still missing something. What does the kernel of $v_i:\Bbb F_{13}[X]\to\Bbb F_{13}[i]$ sending $\sum a_jX^j\mapsto\sum a_ji^j$ looks like?
The kernel is the ideal generated by (x+5)(x+8) isn't it?
@BalarkaSen I have a solution, I never knew any number theory so I can't forget it!
22:06
ah, right, $\Bbb F_{13}[i]$ isn't a field extension so minimal polynomials don't need to be irreducible
But number theory is dank! You should learn it with me
i have too many things to learn and relearn and forget it all
I can take an algebraic number theory course next year, I think I will
Say $x^2+1 = 0$ has the root $x = a$ in $\Bbb F_p$. Then $a^4 = 1$. That means $p+1$ is divisible by $4$, no? So $p$ is 3 mod 4, for one.
22:13
and if $p$ is $3$ mod $4$ then $-1$ will be a square in $\Bbb F_p$
Yeah, so it seems p being 3 mod 4 is sufficient...
are those Gaussian?
Oh yeah right
Gaussian primes are primes which are $3$ mod $4$ plus $a+ib$ with $a^2+b^2$ prime (the factors of the primes which are $1$ mod $4$)
it's the fermat's two squares theorem
p can be written as sum of two squares iff p = 1 mod 4, and non-gaussian immediately means i can write them as a product of sum of two squares hence as a sum of two squares
breaks 3 mod 4 hypothesis
Conjecture: If $Y$ is a subspace of $X$ endowed with the cofinite topology, then the topology Y inherits is cofinite. Proof: Since all of the closed sets in $X$ are finite, the intersection of a closed set in $X$ with $Y$, which will produce a closed in $Y$, is finite. Thus, all the closed sets in $Y$ are finite. Hence, if $U$ is open in $Y-U$ is closed and therefore finite.
Does this sound right?
Looks great to me
Make the last statement "Hence, if $U$ is open in $Y$, $Y - U$ is closed in $Y$ and therefore finite"
@Balarka: It's past un-unsleep time!
Heh, hi @Ted. Summer vacation starts from tomorrow.
22:30
It feels like summer here.
By the way, this sounds completely false to me. I think I can even give examples with curves (as $N$) in $\Bbb R^2$ (as $M$) which bound nonconvex domains.
Hmm, I see that in my absence geometry devolves to number theory :P
I forgot all my number theory :( Daminark asked us to prove his conjecture, and it seems we did.
It's a very natural question, @Balarka. I need to think a moment. Of course, it's clearly false when $\mathcal N$ is itself $1$-dimensional and not a geodesic.
Hi @Alessandro
22:33
Yup, that's the case I had in mind. I think my examples extends to surfaces in R^3 easily.
bring a bit of the surface close to the line joining two arbitrary points on the surface
(of course, that makes the domain the surface bounds highly nonconvex)
What is the locus you get in a torus closest to a line parallel to the top of a torus?
Maybe I want the line perpendicular to one of the meridian curves (profile curves).
how do you render the Latex
it's not showing up
See the link to the right labelled LaTeX in chat.
thanks
@TedShifrin There are several points closest to any point on that line, right? It can be either half of the meridian curve
I hope you're thinking of the line which cuts the meridian curve diametrically
22:41
No, I want it parallel to the tangent plane of the torus on the top and instantaneously tangent to the top circle (perpendicular to the meridian). You always confuse meridians and parallels :P
Oh, that terminological muck up again
The top circle on the torus is very far from being a geodesic! All its curvature is geodesic curvature.
(That's why I parenthetically added profile curve — when saying meridian.)
I have no earthly (or unearthly) idea what the locus of closest points on the torus will be, even locally.
The $c(t)$ should be interesting in that case. There are two arcs on the parallel curves (I hope that's the right diffgeo terminology?) and some extra stuff
I doubt you pick up any of that top circle. I think it'll bend away from that.
I guess I need to do the computation. I don't see it at all in my head.
Yeah I mean locally near the endpoint you contain the parallel curves (the actual geodesics going through the top circle). I don't think you contain the top circle either.
22:46
No, you're calling parallels the wrong things again. The meridians=profile curves are geodesics.
The actual geodesic starting tangent to the top circle wobbles periodically on the outer half of the torus, touching both top and bottom circles tangentially.
I don't think you ever did this exercise with Clairaut.
Ok, I don't get the terminology. There are two family of circles on the torus: the tight ones, and the long ones. Which is which?
I know the tight ones are the geodesics.
Tight ones = profile curves = meridians; loose ones = parallels because they're all actually damn (in) parallel (planes) in $\Bbb R^3$.
Ok, great. Thanks :P
So I guess I'll do the calculus problem ... or maybe have Mathematica do it. I want to know when the chord joining the point on the line and a point on the torus is normal to the torus.
Hi Nate!
So let me rephrase what I think: the locus near the endpoints of the line are bits of the meridians passing through the endpoints.
22:52
My line is orthogonal to that, so I highly doubt it.
Oh, I misunderstood your line then. I thought it's the line which is tangent to the top circle and cuts the top circle diametrically. But it's the one which is orthogonal to the meridian. OK.
This seems a rather complicated scenario for a counterexample though.
Agh, Mathematica just gave me a 10-page answer.
Hey lads and lasses.
Tangent to the top circle, yes. Orthogonal to the meridian there.
You wanted basically the tangent line to the meridian. It has to veer off the meridian at some point. Hard to picture.
22:57
I'm going to have Mathematica plot the damn curve.
Have fun mathing it up.
I said hi, Nate. Should I ask?
No, that was not my query.
He was away from the desk....again....
talked to an assistant who said he'd be back in Tuesday.
22:58
All day? Did you ask to speak to someone else?
I asked and they said he's the one handling my application so he's all I've got.
OK. Well. NO word is better than the word NO.
Best case scenario now is the waitlist, so Queens is done.
Well, they've sent all the acceptances now... unfortunately.

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