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6:00 PM
Ahh
But not those that intersect the removed regions
I guess that it has to do with that the part of the intersection gets messed up
In one for the open sets, and the opposite for the closed ones
So that one is not open, and the other is not closed
 
@BrookTaylor Wrong
 
Hmm ok
Any clue?
 
Take a ball centered at the upper left corner.
You're trying to do math by guessing from the answer. Not recommended.
 
Yeah, I know
But it's just a bit frustrating
 
This is very concrete stuff …
 
6:05 PM
Sure, but I'm not a math major
 
So what?
 
So I don't take so many math courses
So I'm not so used to doing proofs like these
 
Why are you taking this course?
 
Because I was told that I might need it for my courses in computational science
If it's so easy, why isn't it easy to explain?
 
My point is that this particular question is all about concrete pictures. The rest of the course will be more abstract.
 
6:08 PM
Oh
 
Draw small balls centered at different points of that left edge and look at the projections.
 
but I don't get exactly how they get projected, that's my problem
I get that they land on the real line, but now how
 
vertically
 
What?
We're dealing with the $x$-axis
 
$(x,y)$ maps to $(x,0)$.
 
6:11 PM
imagine being in 2D and wayyy above the squares and looking down on them so you are looking parallel to the $y$-axis
 
I really hope data science and/or computational education isn't moving in the direction of pushing topology and analysis onto students without providing the proof-writing prerequisites...
 
@Clarinetist That's rude
 
Well said, Clarinet. I was gonna say something and kept mum.
 
Ok
Screw you guys
 
I was not referring to you in particular, Brook. I've been data science faculty for 2 years. I am super concerned about DS/computational education.
 
6:12 PM
that is actually rude
 
I am actually resigning at the end of this semester because I've had enough of it.
 
We were not being rude.
 
Then what?
You were insulting
Is that considered nice?
 
what
 
Perhaps you were advised to take a course without proper preparation.
 
6:13 PM
All I was doing was making a side comment about DS/computational education. I was not directing this at anyone.
Yes, Ted is pointing out exactly what I'm thinking.
 
@TedShifrin Yeah. Which is why I seek your help.
@Clarinetist Yes. I misunderstood you.
 
And then you yell at us.
 
Because I thought that you were insulting me.
 
We're being spectacularly patient while you make excuses.
Grow up.
 
I disagree.
You grow up.
 
6:15 PM
Bye.
 
this is not the best way to seek help.
 
You may object in a nice way. You don't need to be patient.
Apparently not because you guys can't be direct when you don't want to help.
 
there is a difference between helping and just giving you the answer
 
Instead you come with hurtful comments. What good does that do?
Yes. I don't say that you have to help me.
You could jus say that you think that I should figure it out on my own. Infinitely better than insulting me.
 
If I could help, I would. I had to teach myself topology last semester. All I did was just come in and make a comment about DS/computational education. That's all. I just finished venting to my department chair about the inadequacy of DS/computational education.
 
6:17 PM
@Clarinetist I don't have any problem with you.
I have problems with people that insult others just because they can.
 
literally no one insulted you. i dont really even understand what you are taking issue with. there were multiple people trying to lead you to think about the problem so that you could come up with a solution on your own.
anyway, thats all from me on this nonsense
 
Let's forget about it.
 
what'd i miss
 
I suggest that you just let people know if you don't want them to continue asking follow-up questions.
Nothing of importance.
People implying that I'm stupid and that I'm testing their patience.
Instead of just saying that I should ask less questions. It's not so hard.
What's so dangerous with giving the answer anyway?
 
i could answer that, but it's dangerous
 
6:22 PM
Sometimes maybe it's just better to get over an exercise you're working on. Right?
I haven't had so many problems with the other exercises I've come across in this course, but this one gets to me.
 
is just not doing it, or putting down what you were able to do, an option? that's what i did. i understand why you wouldn't go that route very frequently, but some of the time, sure.
 
no one is telling you to ask less, the conversation was going fine until the tangent, you're taking offence at a vacuum
 
Maybe so
Text is an awful way of communicating anyway.
There was probably some misunderstanding along the way.
 
@BrookTaylor I am asking purely out of curiosity, not at all asking with malicious intent: what was the prerequisite you were told to take for this class?
 
@Clarinetist Let me check the exact requirements
Simply Linear Algebra II and Several Variable Calculus
 
6:26 PM
Thanks.
 
Is that standard for a topology class?
 
To provide you some context, I have observed that many data science programs allow students to graduate with bachelor's degrees without any calculus (not even Calc I).
 
at one place i taught, the architecture department (?!) required students that it had specifically recruited for architecture only, to take calculus. most of the students did not pass. it seemed like requirement malpractice to me. but maybe the point was to let the math department whittle down the class a little so they could keep in-major gpa's up and people could blame the persnickety math department
 
i didn't resent the students, i did resent the department. i asked around about it. nobody knew what to do
 
6:27 PM
I don't know much about prerequisites for topology, but my alma mater had a prerequisite of real analysis (one semester).
 
i took the clarinetist route of taking my ball and going home
 
Right
So, I of course had no ill-intent with whatever happened. If I offended anyone, I apologize.
 
i apologize for using a metaphor involving a ball, i now see a ball was involved in the conversation
 
But, I feel hopefully lost, I kind of just want to beat this exercise and call it a day, so if anyone wants to help me out I would be very thankful.
What I don't get is exactly what we are mapping to. I felt like I was exactly starting to get it once things went haywire.
 
Why don't you go back and reread the things we suggested you do?
 
6:31 PM
I did
You said $(x,y)$ maps to $(x,0)$
 
And you can see that visually.
 
Yeah
But don't we miss two intervals then?
 
@leslietownes It's weird how some degrees work. I know that in Physical Therapy, I tutored several students who were required to take Calculus for graduate-level admission.
 
I also said to move a little ball along the left edge and see what the projections look like.
 
Precisely $(-1,1)$ and $[2,3]$
Yes you did
Then we should cover the intervals I just mentioned
 
6:33 PM
If you start with a ball way up high, it maps down to a whole open interval.
 
Yeah
If we're on the top of the rectangle.
So we are just above $(-1,1)\times (-2,2)$
 
Right. So now look at little balls centered on $x=-1$ and let the $y$ coordinate go from $2$ down to $0$.
What do you see happening?
 
@Clarinetist Biomechanics.
A faculty member audited my multivariable calc years ago for that reason.
 
Why?
 
6:37 PM
For the physics in her research.
 
Hmm, I feel like I almost get it
Yes, what does happen when you go down like that
 
You go from open intervals to ….
 
closed ones?
 
Not quite.
 
Neither??
 
6:38 PM
Open on the left and where does the interval go on the right?
 
$-1$?
As in that's where the edge is.
 
Including that value or not?
 
It's not removed from $\mathbb{R}^2$ as the set $(-1,1)\times(-2,2)$ is open
 
So you get an interval like $(-1.2,-1]$, right?
 
Yeah
Damn
I drew it wrong
I drew it as the set which we remove looks
I drew it like the closed set was open and the open one closed.
Yikes
 
6:42 PM
As long as you sort it out now, you get it.
 
So on the left we have $(-1-\epsilon,-1]$
 
Right.
I mean, correct.
 
and on top we get $(-1-\epsilon,-1+\epsilon)$
Ohhh...
Sigh...
 
Above the top, yes.
 
Yes
I stared myself blind at the fact that I had drawn it wrong, and that there were two cut-out regions.
Well, I studied since 8 am this morning so...
I owe you an apology, and a big thank you, Ted.
So all of that just because I drew the set wrong. The devil truly is in the details.
 
6:49 PM
OK, glad you got it. Apology accepted.
 
Thank you!
I'm also sorry I spammed the chat for a while.
 
The room will forgive you in a day or two. :)
 
Most of us are actually good teachers at heart.
 
Being a teacher is infinitely difficult though.
As a student you don't get that though. You think it's easy.
At least I did before I started working as a TA at the IT department.
It's amazing seeing how difficult the students have with any programming, and how they can't tackle problem shooting.
 
6:55 PM
I did it 40+ years, so I know.
 
What do you think about flipped classroom?
 
with the desks on the ceiling? i'm for it.
 
Not that way
 
i don't put them on the walls
 
The professor should be on the wall.
Sounds more like Voodoo than teaching to me though.
 
6:57 PM
or do you mean when i flip off the classroom with both hands. controversial teaching technique. i'm not even sure it is a teaching technique.
 
Haha
Seriously though
Mustn't it be so boring to lecture the same thing every year for 40 years?
 
First, we teach different things. Second, I always engaged my students and had lots of interaction. So little things can be very different.
I tried to get students figuring things out in real time — not all, of course.
 
Like a blend of lecture and a problem-solving session?
For me, it's this stuff that I need help with: Not getting a lecture or lecture notes. I can watch or read that just fine on my own. I need to fight with some exercises and then get some instruction on how to proceed when I'm stuck.
 
If the lecture does nothing but regurgitate the text, then it's not a good lecture.
A good lecture teaches you how to think and develops intuition.
 
7:24 PM
what is an easy way to compute the homology of all simplices of $\Delta^d$ (a standard $d$-simplex) of dimension $\leq k $ for some $k \leq d$ (i.e. the $k$-skeleton of $\Delta^d$ viewed as a CW complex in the natural way)? For instance if $d = 3$ then the $1$-skeleton deformation retracts onto $S^1$, when $d = 2$ the $0$-skeleton is three points, is there a general way to figure out the homology group, or even better what the $k$-skeleton is homotopy equivalent to?
for $k = d-1$ its clear that this is $S^{d-1}$
perhaps in general for $1 \leq k < d$ it is homotopy equivalent to $S^k$
perhaps this justification works: Assume inductively it holds for $d=1,2,3$, now suppose $1 \leq k < d-1$ (the case $k=d-1$ has been proved), there is a deformation retraction of $\Delta^d$ onto one of its $d-1$-dimensional faces. This deformation retraction sends the $k$-skeleton , where $1 \leq k < d-1$ onto the $k$ skeleton of this face, and so by induction, we know it is homotopy equivalent to $S^k$
what does the room think?
 
How is the $1$-skeleton of a $3$-simplex deformation retracting to a circle? Maybe a $2$-simplex?
Or is my numbering off?
 
7:40 PM
by 3 simplex i mean tetrahedron
oh sorry, im dumb, it does not deformation retract to a circle
i was ignoring the apex...
also it isnt true that the deformation retraction of the simplex onto one of its faces sends the $k$-skeleton to the $k$-skeleton of the face
gah
 
I found some proof that proves 1 = i
i = i^1 = i^{4/4} = (i^4)^{1/4} = 1^{1/4} = 1
 
its weird that the $k$-skeleton of a simplex should be so elusive..
well you need to select the right branch of $z^{\frac{1}{4}}$ so that $i = (i^4)^{\frac{1}{4}}$ is true, and if you do then you won't be able to say $1^{\frac{1}{4}} = 1$ any more
 
It was a joke
 
@TedShifrin okay, what about this, the $1$-skeleton of a $3$-simplex is homotopy equivalent to the circle with three points identified?
@love_sodam oh I know, i was mostly just typing it to remind myself why its false
 
Is that algebraic topology that you are discussing?
 
7:56 PM
yeah, more like its what im currently fumbling :(
 
Hang in there.
 
Question: are there exponential functions involved in the definition of a cardioid? I'm asking because someone added a comment on this post stating that there aren't any.
 
@leslietownes bruh.
 
8:13 PM
@cpiegore You can use complex exponentials in the parametric representation. See en.wikipedia.org/wiki/…
Ah. It appears that you already know that. ;)
 
i should have been an actuary. my wife's work just offered some kind of 20-year term life insurance option. she asked what would be reasonable to pay for that in X amount. i pretended to think for a minute and said "$50 a month," just because it sounded like an amount you might pay, and it turned out to be what they were offering. i told her to demand a discount.
 
@PM2Ring Yes and I replied to the person who added the comment, attempting to inform them of that information, but they have not replied back.
 
@porridgemathematics i don’t see that.
You can compute annuities and future values, @leslie.
 
but can i pass a P exam.
 
8:32 PM
@Ted Any thoughts on:
yesterday, by PM 2Ring
Yesterday, I was messing around with $(1+1/n)^n \le e \le (1+1/n)^{n+1}$, and I noticed that $\pi$ is very close to the fixed point $n=(1+1/n)^{n+1}$.
yesterday, by PM 2Ring
I suppose there might be some deep analytic significance to this, or it might just be an interesting coincidence, in the vein of https://en.wikipedia.org/wiki/Strong_Law_of_Small_Numbers
> $(\pi+1)^{\pi+1} \approx 359.7956379$ and $\pi^{\pi+2} \approx 359.8670909$
 
@leslietownes Better you than me, but I completely despised actuarial work
 
No clue.
 
no, seriously, can i pass it. i think my parole officer is due to come around again, it's been a while.
 
I guess it's just one of those weird coincidences.
 
Well, back in the day, I worked for one of the leading study-material companies doing stuff for exam P
I would say if you understand my answer here, you can probably pass it
2
A: Are there independent random variables $η_1 = ξ_1 + ξ_2, η_2 = ξ_1 - ξ_2$ if $ξ_1,ξ_2$ are independent?

ClarinetistMethod of Jacobians You need to use the method of Jacobians to find the joint density of $(\eta_1, \eta_2)$ and then use the joint density to conclude independence. Observe that due to independence of $\xi_1, \xi_2$ that their joint density function is given by $$f_{\xi_1, \xi_2}(x, y) = f_{\x...

This one too:
7
A: Expectation and variance of $Y=\max(X_1,\ldots,X_n)$, where $X$ is uniformly distributed.

ClarinetistNotice that $$\mathbb{P}(Y \leq y) = \mathbb{P}(\max(X_1, \dots, X_n) \leq y)\text{.}$$ Now, note that if the largest of $n$ numbers is less than $y$, it follows that each of the $n$ numbers must be less than $y$ as well. So, $$\mathbb{P}(\max(X_1, \dots, X_n) \leq y) = \mathbb{P}(X_1 \leq y \c...

Those two topics are usually the toughest for exam-P students
 
8:41 PM
this was well within my capability about 10 years ago. i don't know about now.
also, my wife would kill me if i changed careers again.
 
I taught probability but I don't know this anymore.
 
my wife's MS homework was like this.
 
I personally didn't appreciate probability until I learned its foundations are in analysis
 
her instructor may have sensed something was up when her homework had triple integrals and measures in it instead of an application of Theorem 6.2(b), but he never said anything about it.
 
My last talk as an undergraduate was showing the connections between actuarial science, analysis, probability, and differential equations. Barely anyone bothered to attend. Lol.
 
8:47 PM
0
Q: Types of connectedness for $L_n:=\{(x,\frac{x}{n})\mid0\leq x\leq1\}\subset\mathbb{R}^2$ for $n\in\mathbb{Z}_+$

Brook TaylorExercise: Let $L_n:=\{(x,\frac{x}{n})\mid0\leq x\leq1\}\subset\mathbb{R}^2$ for $n\in\mathbb{Z}_+$. Then consider $X=\{(1,0)\}\cup\bigcup_{n=1}^\infty L_n\subset\mathbb{R}^2$ together with the subspace topology. Is this topological space path-connected, connected, and/or locally connected? Explai...

 
Ah, crud. I'm going to have to learn topology properly. It was ridiculous - but very necessary - to learn topology over a month.
 
I'll say
Usually just do programming and now this haha
 
Had to do it before my second semester of probability with measure theory over the Winter break. It was brutal.
On the first two weeks, I could tell my classmates were weak with their topology background too - some people asked why a union of open sets were open. I didn't understand it myself at the time either, but when I finally learned the definitions, well, it was trivial.
 
Why would a function be constant just because the preimage is clopen?
 
My favorite - but most difficult - programming class was in my master's degree, when a professor started us off on the very basics of C (i.e., variables, data types, and the like) and took us all the way to numerical optimization, Horner's method, Gaussian quadrature, FFTs, and parallel programming at the end.
None of us were programmers - we were all MS/PhD stats candidates
 
8:55 PM
Ahh I see
 
Not to mention, we also had to conform to a coding style which had to be verified via a Perl script, and we had to also push all of our code to GitLab. Thankfully I already knew version control from industry work, but I didn't envy anyone who didn't.
Oh, and we did everything in a Docker environment lol. That class was insane.
 
Haha, I have no clue about that stuff!
 
Every computer science program should honestly teach basic version control in the first semester. It is an injustice that it's not the case IMO.
 
Yey
I think I figured out one part of my question
The self-esteem is really low since I goofed up and made a fool of myself a while ago
 
9:27 PM
Everyone makes mistakes. You never stop making mistakes, but you do (should) learn to recognise and recover from them quickly, and gracefully. And hopefully, you recognise them before making them public. :)
 
i nevur maake mishtakes.
 
Yeah
 
Yeah raight @copper.hat
 
:-)
 
Does anyone have a clue about this?

https://math.stackexchange.com/questions/4131069/types-of-connectedness-for-l-n-x-fracxn-mid0-leq-x-leq1-subset-math
Otherwise, I might just go to bed
 
9:35 PM
I know the proof of irrationality of e
And it seems to me that the idea for proving a number irrational is the same
 
do you mean (0,1) in the first half of the definition of X?
 
Somehow showing that an integer lies between 0 and some fraction less than 1
Thus getting contradiction
 
it seems like a less interesting problem if (1,0) is there.
 
About Euler Mascheroni, I only know that it’s a limit of difference between Harmonic series and log. Why is it not yet proven though whether Euler Mascheroni is rational or irrational?
 
@leslietownes Yeah! I do
Wait no
Do you have any idea about path-connectedness?
 
9:43 PM
i do.
koro this more of a vibe than a mathematical principle but when you have something is very quickly approximated by rational numbers (it takes thought to formalize this) it is often easier to deal with in terms of rationality/transcendentality than when it was not.
i don't know of good representations of euler-mascheroni other than things that involve limits of differences of things where the convergence is very slow.
 
We don't even know if $e+pi$ is rational, despite De Moivre's & Euler's formulae.
 
more importantly, we don't know why anybody should care if it's rational. :)
 
OTOH, $e^{\sqrt{163}\pi}$ is almost an integer...
 
i do like that how we know that e+pi and e pi can't both be algebraic. that's a good concept.
 
pure algebra
 
9:59 PM
Ahh so that seems to be the reason: no good approximations to that constant are known @leslietownes.
 
good approximations really help. a lot of the early (constructive) results in transcendentality
the liouville number, e, stuff with particular types of continued fraction expansions
are like that
 
this reminds me of how I once wanted to read a proof of Lindemann-Weierstrass, but in the end was too lazy
a riveting story, I think
 
you wanted to read a proof of lindemann-weierstrass, but you got better
you recovered
 
I thought this was Lindeman-Weirstrass law: if a is algebraic then e^(a) is transcendental
But I was so wrong
I looked up more about it
It had something to do with linear independence
 
that's reminiscent of gelfond-schneider
what you wrote
in terms of the form. it's definitely not a statement of that result
 
10:06 PM
Then same story as that of Thorgott
 
@Koro that's a corollary
 
I know that but didn’t know that when I’d first encountered the law.
 
Lindemann-Weierstarass is a theorem that basically says "e is reaaaaaaally transcendental"
 
During set theory while proving countability of algebraic numbers
 
the best version control is no version control
unless ur getting payed to code
in which case :/
 
10:29 PM
it really isn't, even if you're all by yourself. but if you're playing the role of the devil on the shoulder, play on.
 
IDK I think it's super nice to be able to say "I wrote XYZ line of code on this day because of ___"
 
I have a general question with regards to multivariable analysis that is causing me quite some angst.... so we have a bunch of techniques to either establish that a limit exists or doesn't exist. And if need be we can be formal to find necessary $\delta$ and $\epsilon$.

What do we do when we are in higher dimensions? Even in two and three dimensions things get very messy vary quickly.......I can't imagine trying to bound a function of 25 degrees, even keeping track of the variables would be a nightmare.
 
@dc3rd You generalize your idea of what a "distance" is in higher dimensions. In one dimension, it's $|x - y|$. In higher dimensions, it's the Euclidean norm $\|\mathbf{x} - \mathbf{y}\|$ for vectors $\mathbf{x}, \mathbf{y} \in \mathbb{R}^n$.
 
so all we really have is the idea of magnitude to use then? I'm just going off of what I've been doing recently, but it even get's tricky to extract a magnitude to use to control things from certain functions in 2 and 3 dimensions.
 
10:45 PM
Suppose I have a convex quadrilateral with vertices on the unit circle.
Now suppose I have another convex quadrilateral with vertices on the unit circle
I am going to place them in $\mathbb R^3$ such that one is at height $0$ and the other at height $1$.
Can I use these vertices to build a convex cuboid?
 
I mean, the question is in which context you actually want to compute concrete multivariate limits, which I would say happens very fairly
 
I'm just imagining a situation where I was trying to control the size of something Thorgott and the process that would have to occur to get a "nice" bound on my object.
 
also, in 'real life' nobody does limit proofs with delta and epsilon on the formulas for the functions themselves.
you develop a body of general and not-so-general theorems using epsilonology and apply those instead.
if you had a box of 20 theorems in your toolkit, and didn't have to worry about delta and epsilon, you could do quite a lot
there are counterexamples to my statement of course, some people make a life out of finding the best delta for the given epsilon, or asymptotically best, or whatever. but many problems do not require that
 
this brings me moderate relief Leslie......going to have to be more comfortable with the idea of not having the "best" approximation possible......that's a "me" issue though....shrug
thanks for the clarification.
from all
 
11:00 PM
it's the same in one variable analysis. a lot of the exercises are hard only because you don't have the theorems yet. once you have the theorems, you 'level up' and have the option of working at the level of theorems and only dipping into epsilonology when you really need it.
sometimes you have to be clever in applying theorems, or verifying the hypotheses of theorems, but it certainly isn't, "oh no, what's delta going to be." usually.
that becomes a last resort instead of a first resort. as it should be.
 
I just found out about something called hololive
apparently some of the people I know from competitive programming watch it
does anyone know wtf is up with this
 
11:18 PM
no. it appears to be an allegedly machine-generated stable of pop stars, akin to the human ones that many of us are familiar with. can't shake the suspicion that in a basement somewhere, a few dozen people in motion capture suits are working very hard for little money.
the same model but now there's pictures instead of people. how alienating
 
I am learning about Fsigma sets [ en.wikipedia.org/wiki/F%CF%83_set ]. Is the empty set an Fsigma set? I think yes, because the empty set is a closed set. But I am not sure since it's a bit tricky with "vacuous truth"...
$F_\sigma$ sets *
 
@leslietownes not allegedly machine-generated, its real people with virtual avatars realized via motion capture. there's lots of money in the industry.
@terrace indeed, the empty set is closed
 
yes terrace
 
OK, thank yo u
 
oh, if i were them i'd have gone all the way and said they were machine generated. by AI and also deep learning.
machine learning didn't want to participate.
 
11:31 PM
it looks like the whole thing with "vtubers"
seems kinda silly tbh but it's probably related to anime or whatever
 
the wikipedia page on the borel hierarchy is surprisingly good in terms of quality, but you can tell a set theorist really got their hands all over it. i've seen more accessible treatments in books.
you do get to goofy sets and ordinals pretty quickly.
i think i'm going to retire and become a vtuber.
or the pre-avatar of a vtuber. do we have a word for pre-avatar?
 
If you pick a "random" subset of R, what is the probability that it is F sigma?
Probably 0 because it seems like everything in analysis has the property that "almost all X are pathological"
 
this is a question that requires a specification of the desired notion of 'random'. it will have an answer but it needs more inputs.
the baire hierarchy is often useful in proving results of that type but it is somewhat distinct from any probabilistic notion.
 
like almost all functions are discontinuous everywhere, almost all continuous functions are nowhere differentiable, almost all real numbers aren't even computable
so probably almost all subsets of R are really pathological
@leslietownes what is normally used for a measure on the power set of R
is there something like the lebesgue measure, but for P(R)?
 
i've never worked too far outside the borel sigma algebra. or its completion.
 
11:42 PM
Hello I have a question if anyone can reply and tell me ill appreciate that. I have found this very confusing including my teachers are a bit confused. Is 0 a perfect square?
 
P(R), who knows. my guess is the measure would have to leave out a lot.
gabriel the usual answer would be yes, unless you have some meaning that it would exclude it from being one. it's not the square of anything nonzero. but it is the square of itself. which is fine.
1 is too, and that doesn't stop 1 from being a perfect square.
i just realized that what i've said would sound funny in a screen reader.
 
thankfully ted isn't here to tell us that 0 isn't a natural number right now
 
it isn't. but if you're talking about properties of 0 you're already outside of that unfortunate debate.
:)
 
time will tell that you stood on the wrong side on history
 
It ruined Leslie's week to agree again with Ted.
 
11:58 PM
i just got nervous because i realized i may have had reason to refer to natural numbers in my thesis. i'm afraid to go check
ha! i didn't. i had reason to refer to $\{0, 1, 2, 3, \dots\}$, which i appropriately denoted $\mathbb{N}_0$. i think that settles it.
 
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