Mathematics - 2017-04-02 (page 1 of 4)

Meow Mix

00:04

Not having music sucks.

nbro

00:27

how do you interpret this minimization function:$\min_x \phi(x) = \frac{1}{2} \| f(x) \|_2^2$? I mean, why do we have a $\frac{1}{2}$ in front and why are we squaring the norm?

Simple

01:07

think about differentiation

a minimum has slope zero

arctic tern

@nbro I happened to notice you didn't say anything whatsoever about who was considering that minimization or any context about it.

nbro

01:27

@Simple I know what's minimization or maximization of a function

my problem is related to that specific function

@arctictern the context is non-linear square problems

Simple

the $1/2$ just for convenient when you differential the $\Vert\cdot\Vert^2_2$

nbro

@Simple well, but that still doesn't make much sense because you can simply omit the square and the 1/2

Adeek

01:52

@arctictern are you familiar with triangulated categories ?

arctic tern

@nbro I take it you're trying to minimize $\|f\|$? If so, it's easier to minimize $\|f\|^2$, and the $\frac{1}{2}$ factor makes everything physicsy (energy is $\frac{1}{2}mv^2$, the antiderivative of $x$ is $\frac{1}{2}x^2$, etc.). Saying that making a problem easier "doesn't make much sense" is rather weird. Do you think it "doesn't make much sense" to have a remote when you can "simply" get up and click buttons on the TV?

Balarka Sen

lol

Yeah, so the point here is $\|f\|^2$ is easier to minimize than $\|f\|$. Think about the standard norm in $\Bbb R^n$, man.

You just kick the square root out from the definition.

Simple

lol

Brody

At first I was wondering how a seemingly innocuous question got 10 net downvotes! And then saw the comments haha

18 hours ago, by GPhys

check comments hahahaha http://math.stackexchange.com/questions/2212731/airthmatic-progression

arctic tern

op might be a troll making fun of OPs that come to MSE to get people to do their work for them.

april 1st and all

Brody

02:03

Hi all. Hi @Balarka @arctictern

arctic tern

hello

Brody

@arctictern Riiight. Maybe

Balarka Sen

Hi @Brody!

Brody

Makes a ton of sense tbh. Good trollzing

Hey, how's it going @Balarka? :)

Balarka Sen

probably my favorite april fool joke: i.sstatic.net/4o7F8.jpg

Well, no, it's horrible but the comic was a good read.

Brody

02:09

That's good humor

Funny art style though

Balarka Sen

Right? I really like that comic

Adeek

@arctictern I want to see if my understanding of exact triangles is correct.

share.pho.to/Af28Y

Balarka Sen

I think the usual batman community laughed at the idea when Grant Morrison told them what he's doing

Adeek

There is a class of exact triangles means there is some object in this specific category

which satisfies some construction ? or is it something different ?

Brody

@BalarkaSen Not too familiar with the subject tbh

Balarka Sen

02:13

@Brody It's just comic stuff :P

Brody

Question... Does non-rational number mean anything contrary to irrational? Encountered a poster who used this term

Balarka Sen

how's things going?

Brody

Not bad. Mental-emotional wellness is improving-ish and I'm sensing a renewal for interest in mathematics

Learned some kinda fun stuff recently in real analysis. Open, closed sets. Isolated, limited points

Balarka Sen

Nice

Brody

How about you?

Oh, nevermind about the non-rational thing. It was clearly just for emphasis

Balarka Sen

02:22

I'm alright. Still learning math, and doing stuff

So, can you give an example of subset of $\Bbb R$ which is infinite and every point is isolated? (PS: This is easy)

Brody

$\Bbb Z$

Balarka Sen

Can you make that uncountable?

Brody

@BalarkaSen Good to hear. What's your current study btw?

Mmm one sec

Set of harmonic numbers

Oh wait

Uncountable

Balarka Sen

Right.

@Brody some objects called "foliations"

Brody

I'm blanking atm. Is this trivial?

Balarka Sen

02:27

Nah.

Brody

Hmm

Is it a famous construction?

Balarka Sen

vOv. Note that the answer to my question can both be yes or no.

Here's another question. Can you even give an uncountable subset such it is dense nowhere? That is, for any $p \in X$ and for any interval $[p-\epsilon, p+\epsilon]$ around it the set of limit points of $X \cap [p - \epsilon, p + \epsilon]$ is no more than $X$?

Rationals (albeit countable) are on the extreme end; dense everywhere.

Brody

It's tough for me

Balarka Sen

Keep it at the back of your head and chew on it occasionally :)

Brody

Of course, it can't be an interval or union of intervals intersect the rationals, irrationals, transcendentals

Balarka Sen

02:40

mhm.

Brody

Well, forget the rationals especially lol. But segments of the continuum and alike things are the only uncountable subsets I can imagine atm, and these are all dense!

Balarka Sen

Yup.

Note that both questions are about how sparse uncountable sets can be. The first is stronger than the second; if it's isolated at every $p$, you can pick $\epsilon$ such that X cap [p-$\epsilon$, p+$\epsilon$] is just p.

So if you can answer the first affirmatively you have answered the second. The second can be true even if the first fails however

Of course, both can fail

Brody

Right

Brody

03:13

So every member of $\Bbb Q$ is a limit point, and the set is everywhere dense. But no member is an interior point. This is weird stuff

Or at least certainly, the terminology is weird

Anheuser

Hello everyone

Brody

Hi

Balarka Sen

@Brody $\Bbb Q$ being dense in $\Bbb R$ means every real is a limit point of the rationals.

Brody

@BalarkaSen Thought so, but idk formally how they're related. I need to work on denseness

Anheuser

I've been thinking about the sum of the numbers 10 to 1, and have come to a few conclusions, I'm trying to find more information on it but my idea is very abstract. I've never heard anything about it and see no applications of it, but it's real and it has clear patterns.

Balarka Sen

03:16

Yes, every member of $\Bbb Q$ is a limit point of itself (constant sequence $p, p, p, \cdots$ for any $p \in \Bbb Q$) - but that holds for any subset of R. Interior points of a subset $X$ are points a small neighborhood around which fits entirely in $X$

But any small neighborhood around any rational contains a lot of irrationls, so can never fit in $\Bbb Q$

Anheuser

This is basically it, I'll explain it here.

Imagine you're 5 feet from a wall, and you have to move 10 feet, 9 feet, 8 feet, 7 feet ....1 foot.

Balarka Sen

@Brody Formally how what are related?

Anheuser

and if you reach the wall you have to walk in the opposite direction the amount of feet left in the numbers.

Brody

@BalarkaSen Denseness and limit points. In reality, I know little of the latter and less of the former

Anheuser

Well, I've found for every number less than 55 you can reach the wall.

Brody

03:19

Wait, every point of every subset of $\Bbb R$ is a limit point of the subset?

Adeek

@BalarkaSen do you know what is an additive automorphism in a cateogory ?

Anheuser

For the series 10-1 the maximum amount of "moves" is 10.

Adeek

specifically in an abelian category ?

Balarka Sen

Every point of $\Bbb R$ is a limit point of the subset, @Brody. "of every subset" bit is rather unnecessary and doesn't make much sense.

Brody

Unless by "itself" you exactly mean a point is a limit point to the point itself

Anheuser

03:20

I've mapped out every number to 55.

Balarka Sen

@Adeek Maybe one which preserves direct sums?

Brody

I'm confused now

Adeek

hm @BalarkaSen that seems to make sense yeah I will take that.

Balarka Sen

If you can explain your confusion I can probably try to unconfuse you.

:)

Brody

The set of harmonic numbers contains none of its limit points, no?

Balarka Sen

03:24

Harmonic numbers being $\sum_{k= 1}^n 1/k$?

Brody

Those, yes

Balarka Sen

Pick any harmonic number $p$.

$p, p, p, \cdots$ is a sequence converging to $p$, right?

Brody

I'm sorry, wait

Ted Shifrin

Heya @Brody

happy non-sleep, @Balarka

Brody

Let's just do $\frac{1}{k}\,:\,k\in\Bbb N$

Adeek

03:25

hi @TedShifrin

Balarka Sen

Yeah let's just do those, @Brody

Ted Shifrin

hi Kareem

Balarka Sen

@Ted I woke up at 7

Adeek

btw can I talk to you about something @TedShifrin ?

Brody

Hi @Ted!

Ted Shifrin

03:26

ok, Kareem

Anheuser

@TedShifrin Ted, what would I type in to google to read more about adding up the numbers from 10-1 and any conclusions that can be drawn from the series?

Balarka Sen

@Brody So it is true that $S = \{1/k : k \in \Bbb N\}$ has a limit point, $0$, outside the set. But every point in $S$ is a limit point of $S$: trivially so, because $1/k, 1/k, 1/k, \cdots$ (the constant sequence) converges to $1/k$.

Adeek

@TedShifrin can you see facebook message?

Ted Shifrin

Yeah, Kareem

Balarka Sen

Any point in any set is a limit of the set, in fact.

Ted Shifrin

03:28

@Anheuser: I don't understand your question yet.

Balarka Sen

(Just take the constant sequence)

Brody

@BalarkaSen Oh, well I see the procedure, but this is a new definition to me. Think I was taught otherwise, which is an issue...

Let me check my notes

Ted Shifrin

To me that's not a limit point, @Balarka.

You have to have a sequence of other points converging to it.

Anheuser

@TedShifrin take your time to answer this.. But:

I've been thinking about the sum of the numbers 10 to 1, and have come to a few conclusions, I'm trying to find more information on it but my idea is very abstract. I've never heard anything about it and see no applications of it, but it's real and it has clear patterns.

This is basically it, I'll explain it here.
Imagine you're 5 feet from a wall, and you have to move 10 feet, 9 feet, 8 feet, 7 feet ....1 foot. and if you reach the wall you have to walk in the opposite direction the amount of feet left in the numbers. Well, I've found for …

Balarka Sen

That's strange, @Ted.

Ted Shifrin

03:30

You're talking about adding up the numbers 1,2,....,n, @Anheuser?

Balarka Sen

Brody probably has that definition.

Anheuser

Yes.

@TedShifrin And lets say I say you're 1 foot away from a wall, you first step forward 1 foot and backwards 9 feet, the next "move" is 9. So you step forward 9 feet, and the sequence is done. it has taken two moves. So 1 would be equal to 2.

any number less than 55 can reach the wall in 10 of these "moves"

if we then do 1+ 2 + 3... + 20 then the maximum number of moves are 20.

Ted Shifrin

@Balarka: No, your definition is strange. You would say that every integer is a limit point of $\Bbb Z$.

Check Munkres :P

Brody

Can't find my handwritten notes. It's something like Ted's version. Checking the electronic handouts...

Anheuser

@TedShifrin Am I just talking nonsense?

Balarka Sen

03:33

@TedShifrin Yeah, I would. I would say Z is isolated because there aren't other integers which clutters to an integer.

@Brody Sounds like a terminology issue on my side.

Ted Shifrin

Yeah, @Balarka. I think you've forgotten :)

Balarka Sen

Sorry 'bout that. I can only remember pictures, not definitions, it seems.

Ted Shifrin

To be honest, @Anheuser, I don't completely understand. There's a famous story about Gauss's figuring out that 1+2+...+n = n(n+1)/2 ... But what you're doing seems to have + and - in it and I don't totally understand — granted, I'm talking to 3 people at the moment.

Anheuser

In mathematic notation I guess you would be x units away from a limit, and if you reach the limit you must count backwards from the limit.

I've written notation for it and it looks something like:

B1, A1B9, A9.
B2, A2B8, A8B1, A1B7, A7.

Ted Shifrin

But you could do infinitely many different sequences of things, @Anheuser.

Balarka Sen

03:36

@Brody The definition you have in mind is not so hard. You just stop thinking about constant sequence. $p$ is a limit point of $S$ if there's a sequence in $S - p$ converging to $p$.

Brody

Okay, found my hand notes...

Balarka Sen

Of course, when $p$ doesn't belong to $S$, $S - p$ is the same as $S$.

Brody

$p$ is a limit point of $E$ if every neighborhood $N_{\varepsilon}(p)$ contains $q\in E$ such that $q\ne p$.

Ted Shifrin

Yup.

Balarka Sen

Right. So you work with deleted neighborhoods, $N_\epsilon(p) - p$.

Brody

03:38

And my professor supplemented that we could think of these as "attractors" onto which points of E tend to bunch up.

Balarka Sen

Sure.

Brody

iirc, it is then a consequence that there are indeed infinitely many $q\in E$ in any sufficiently small (deleted) neighborhood around a limit point

so the "attractor" bit makes visual sense

Balarka Sen

That is true. If there were finitely many in some deleted neighborhood you could scale the neighborhood to miss them all

And that'd become isolated: boo

Brody

And so, they are mutually exclusive by this definition, no?

i.e. isolated and limit points

Balarka Sen

Being isolated and being limit points? Yes.

Anheuser

03:42

@TedShifrin
http://imgur.com/a/hEMj2

Here is a graph

Ted Shifrin

I'm not exactly sure what I'm looking at there, @Anheuser.

Brody

So, every member of $\Bbb Q$ is a limit point of $\Bbb Q$, but every point of $S=\{1/n\,|\, n\in\Bbb N\}$ is not a limit point of $S$.

Anheuser

I guess I'll just have to wait until I see an application of it, or see something where it could be useful.

Balarka Sen

@Brody Agreed. (You could approximate rationals by other rationals arbitrarily close)

Brody

So it would seem denseness and limit points are intimately linked?

although, just realized I actually do have a definition for denseness too

Ted Shifrin

03:45

So if $S$ is dense, what can say about the limit points of $S$, @Brody?

Anheuser

I feel stupid now.

Ted Shifrin

Why, @Anheuser?

Brody

A subset $D$ of $\Bbb R$ is dense in $\Bbb R$ if $\bar{D}=\Bbb R$, where $\bar{D}$ is the closure of $D$

Adeek

@TedShifrin btw I started reading some papers by Paul balmer on tensor triangulated geometry

seems very fun

this topic I will be working on

Ted Shifrin

Interesting, Kareem. I don't know precisely what that is.

Indeed, @Brody. So can you answer my question? :)

Jaynot

03:51

Hi guys,  I have successfully proved that if  $p: (E,e) \rightarrow (B,b)$ is a covering map of connected and locally simply connected spaces and $B$ is a topological group with neutral element that $E$ can be given a structure of a topological group with neutral element also such that $p$ is an epimorphism of topological groups(The proof is very interesting)

I have the second question from the HW which says that show that Ker p is a subgroup of the center of $E$, Center of $E$ defined as $\{ e \in E : ex =xe \forall x ]in E\}$. I can always argue comfortably that the kernel is a subgroup.…

Brody

@TedShifrin The limit points comprise all of $S$

arctic tern

nice typewriter

Adeek

me neither so far but it is a category and you have some bilinear map which you can use to extend theory of scheme to non-commutative settings. That is how far I understand from it so far

Brody

and perhaps more?

Balarka Sen

@Brody Limit points are all of R

Ted Shifrin

03:52

LOL @nice typewriter.

arctic tern

@Jaynot yes, if f:G->H is a group homomorphism, of course ker(f) is a subgroup of G. the exercise is asking you to show it's contained in Z(G), the center of G. that is not automatic, and not generally true of homomorphisms f.

Jaynot

@arctictern Thank you.

Brody

@BalarkaSen Agreed.

Fruitful Approach

Is this result known?

0

Q: Conjecture: the set of all permutations of primes such that the first $3$ solve $XY + Z$ forms a group.

The group law is given by function composition. Let $G = \{\sigma \in S_{P}: \sigma(2) \sigma(3) + \sigma(5) \in P\}$ is a subgroup of $S_P$, the symmetric group on prime numbers (their permutations). Firstly, is this known. And secondly, how could I prove it? More info

Brody

Can't do much from the denseness definition though.

Ted Shifrin

03:54

What do you mean, @Brody?

Brody

@TedShifrin So $D$ is dense if its closure is $\Bbb R$. And I only know that the closure is $D\cup D'$, where $D'$ is the set of all the limit points of $D$

Ted Shifrin

Right. Do you know the definition of continuity yet?

Brody

fixed

What can be gleamed from this?

Ted Shifrin

For example: If you know the values of a continuous function on a dense set, then you know the function everywhere.

Brody

But to answer your question earlier, I mean

Ted Shifrin

03:58

Oh, you mean Balarka's answer?

Brody

Yeah

Ted Shifrin

Well, every point of $\Bbb R$ is either in $S$ or a limit point of $S$.

You made the statement, in addition, that every point of $S$ is likewise a limit point.

Brody

It makes sense intuitively/visually, but what can be done with "If $D\cup D'=\Bbb R$, then $D'$..."?

Balarka Sen

the hell's going on in imgur

Ted Shifrin

So every point of $\Bbb R - D$ is a limit point.

Now you claimed that $D\subset D'$.

Brody

04:04

@TedShifrin I missed this question. No, not yet in analysis

Ted Shifrin

OK ... I gave you a typical application of density, anyhow. :)

Did you have an argument in mind for why $D\subset D'$? This is not true for general subsets.

Balarka Sen

@Ted I gave Brody two exercises, one asking whether uncountable sets can be nowhere dense and the other asking whether uncountable sets can be isolated

Ted Shifrin

I guess a YES to the second answers the first.

Brody

@TedShifrin I just popped that off as a guess

Balarka Sen

True

Ted Shifrin

04:07

So can you give me an argument for it, @Brody?

Balarka Sen

@Brody It is true for $\Bbb Q$, but is it true for all dense sets? That's what Ted's asking

It is interesting to think about clutterings which happen within a set, instead of which happen outside

Brody

that $D\text{ dense}\;\Rightarrow\;D\subset D'$?

Ted Shifrin

Yeah, this is starting to remind me of a problem in Rudin that drove me absolutely nuts when I took analysis six centuries ago.

Right, @Brody. We're discussing subsets of $\Bbb R$ here, nothing super general.

Hi @Fargle.

Fargle

Hi @Ted.

BAYMAX

six centuries @TedShifrin ha ha :)

Ted Shifrin

04:11

Note that it can be false if our universe is a proper subset of $\Bbb R$. Let $X = [0,1]\cup \{2\}$. Then $X\cap\Bbb Q$ is dense in $X$, but $2$ is not a limit point.

Brody

Informally, I'd claim denseness implies between any two distinct members of the subset there exists another member. Indeed, infinitely many then. So, every point of $D$ is a limit point.

Ted Shifrin

Note what happens if I take $[0,1] \cup \{\sqrt2\}$. :P

Balarka Sen

@TedShifrin It is true in $\Bbb R$ though.

Ted Shifrin

I'm aware, @Balarka.

So the proof should make it clear where it fails for my example(s).

Brody

These are a lot of definitions and weird terms to remember

And they're in fact not that many tbh

Balarka Sen

04:15

I agree. I just try to remember the pictures instead.

The ten million definitions are confusing

Especially when they are not that different from each other

Ted Shifrin

In many of my courses (e.g., linear algebra and the multivariable math class, and even abstract algebra) the first page of the final was usually 10 definitions from the course.

They didn't have to be stated verbatim, but they had to be correct.

For example, omitting nonzero from the definition of eigenvector was -2 points out of 5.

Brody

At first, I thought you meant as a cheat/help sheet

Ted Shifrin

You know me better than that!

Brody

Like elementary stats courses that list all the random variable pmfs, cdfs, etc. on exams

Ted Shifrin

In differential geometry I did provide a lot of formulas, of course, but not all.

Semiclassical

04:18

It's a different sort of course, but

Brody

@TedShifrin I suppose :P

Balarka Sen

Reminds me, I should start learning some differential geometry

Ted Shifrin

LOL, sure, sure, sure, Balarka.

Semiclassical

for the intro physics course I'm TAing, the prof doesn't provide an equation sheet of any kind but rather expects students to bring a notecard with equations on it.

Balarka Sen

Maybe I want to start at holonomy :)

(In your notes I mean)

Brody

04:20

Regardless, these notions (despite the clusterfuck of definitions) are pretty cool. Just how the very structure of numbers we deal with has all these remarkable properties

Semiclassical

I'm not really a fan of that approach, though. I'd much prefer everyone to have access to the same set of equations on a quiz, since it's still up to them to interpret each equation correctly.

Balarka Sen

@Brody There are crazy weird subsets just in $\Bbb R$

Ted Shifrin

@Semiclassic: I would much rather decide what belongs on the cheat sheet, thank you.

Semiclassical

Agreed.

Brody

i.e. basic stuff like nested interval property, denseness of rationals and irrationals, Cantor set properties (which we haven't learned yet)

Balarka Sen

04:21

Not to say in higher dimensons.

Cantor set is my favorite ;)

Brody

speaking of, I believe the Cantor set is related to an earlier discussion ;)

Balarka Sen

I believe your belief is correct

Ted Shifrin

So, for example, I expected my students to know how to compute the fundamental forms, know the definitions of line of curvature, asymptotic curve, etc., but I gave them all sorts of ridiculous formulas that no one could memorize (and nor should one). Equations for parallel transport, geodesics, Codazzi and Gauss equations, etc. But they had to know the Gauss Bonnet theorem.

Brody

but didn't want to shoehorn it since I don't actually know anything of it from my own merit

Balarka Sen

start discovering. that's math: you can just discover stuff instead of knowing them

Semiclassical

04:24

I'd be more on board with the notecard thing, though, were it not for the fact that the problems on the quizzes are often HW/discussion problems they've seen before.

Brody

I feel like trying to work around the continuum intervals was getting me somewhere along the idea of Cantor sets though

Semiclassical

So I very much suspect people end up writing down solutions to such problems on their notecards.

Which....ughhhhh.

Secret

I tend to learn maths by ramming two or more mathematical objects together

Ted Shifrin

@Secret: That's the sort of thing that happened to my car and the garage wall, and it's costing me a bundle to repair. So be careful.

Brody

I have a _____; I have a ______. Ugh

BAYMAX

04:26

there must be something like a portable small digital board in hands of every one doing mathematics ... ?

Semiclassical

uhh

Ted Shifrin

@Brody Huh?

BAYMAX

where they can do calculations , sketcches even when they are travelling sleeping when ever they want!

Brody

@TedShifrin It's a silly meme-ish thing.

PPAP（Pen-Pineapple-Apple-Pen Official）ペンパイナッポーアッポーペン／PIKOTARO(ピコ太郎)

►

Semiclassical

@TedShifrin Here's a question for you. What's the worst way in which a quiz can go wrong?

Ted Shifrin

04:29

Well, I know that I wrote an impossible Lagrange multipliers question for my final when I was extremely ill with cancer. I only realized when I started grading and realized the class had wasted oodles of time on what should have been a 10-minute problem. You mean like that?

Balarka Sen

It rains forever in here / Here the clouds graze the skies like mute animals / The eager green weeds press their faces upon the door / "Abani, are you home?"
Half-dissolved, within my heart, weary / Amid great pain, I fall asleep / Suddenly I hear, a knock at the door / "Abani, are you home?"

Semiclassical

Eh, I mean beyond that. Stuff like cheating for instance.

What's the worst-case scenario?

Ted Shifrin

Oh, not in quiz writing.

Cheating on any quiz or test can get someone thrown out of the university.

Semiclassical

Right.

Ted Shifrin

If one establishes it before a judiciary board, etc.

Ugh @Brody.

Semiclassical

04:32

Here's a rather different scenario (bad, but not worst case) which has become apparent in the last quiz.

Ted Shifrin

I guess I don't know the point/intent of your question, @Semiclassic.

OK.

Semiclassical

Yeah, I'm fishing a little I suppose.

Secret

We once had an exam in a hot summer day indoors and then the power went out

Ted Shifrin

So everyone melted?

Brody

@TedShifrin It's a good formula in exposition when conflating/combining two objects. Everyone should use it.

Secret

04:33

Well, almost, lol

Semiclassical

A quick note on the format of the test. There are two long problems and some multiple choice problems; they are supposed to write answers for the first two on the sheets for them, and submit the MC questions via bubble sheets.

For this last quiz, the other proctor and I had them turn in the entire (stapled) test packet; we brought those back to the front office, counted them out, then separated out the two answers into two stacks. (150ish papers).

Ted Shifrin

This sounds like an hour exam, not a quiz.

Semiclassical

Eh, we call it a quiz.

shrug

Two other TAs then each pick one of the problems, grade that stack of papers, and bring them back to the front office so that the other TAs can pick up the graded problems and hand them back in discussion.

Ted Shifrin

I'm guessing some papers got lost?

Semiclassical

There are some which appear to be missing, yes.

Ted Shifrin

04:37

So did the students not turn them in or did you guys mess up?

The students may insist that they turned them in when they in fact did not.

Semiclassical

To be precise, there are students who have scores for the first problem but not the second.

Ted Shifrin

Or maybe they really did and something got dropped somewhere.

If these tend to be good students, I would say it's likely you guys f***ed up.

BAYMAX

ohh

Ted Shifrin

This system is not a good system.

Semiclassical

Agreed.

Ted Shifrin

04:38

Way too easy for stuff to get dropped/lost.

Semiclassical

I see two scenarios.

Well, three.

Ted Shifrin

How many are missing?

Semiclassical

About seven out of 150, I think?

So not a huge amount, but not just one or two.

Ted Shifrin

You said you had stapled packets.

Semiclassical

Right.

So it would be unlikely that they'd have turned in just one of the two problems.

Ted Shifrin

04:39

Did you notice that when you pulled them apart to separate the problems that some had only one problem?

Apparently not, or you would have known.

Semiclassical

Indeed.

Balarka Sen

complicated situation

Semiclassical

One scenario is that there was a mixup between counting the packets and separating them.

Ted Shifrin

So it's pretty clear that the person grading problem #2 lost a bunch of 'em. This is clear to me.

Semiclassical

The front office saves -all- the papers we brought back from the test, so that's a scenario that can be checked on Monday.

Ted Shifrin

04:41

If you separated them, only two things could have happened. (1) You forgot to separate a few papers. Then #2 would still be attached to #1. (2) You didn't pay attention when there was only one of them.

BAYMAX

how about online quiz

Ted Shifrin

Or, most likely, some got lost.

Or fell on the floor while you were doing all this.

Semiclassical

(1) If it was still attached to #1, the grader for that would have noticed.

Ted Shifrin

If the students insist that they turned them in, I think the only thing to do is to have them do the problem for you again (orally? in writing?) ... Of course, if quiz solutions have been posted, that won't work. And of course you can't give them too much time to cheat and prep on this.

Brody

spontaneous evaporation

@BAYMAX so easy to cheat with those

Semiclassical

04:43

I could imagine some kind of mix-up where papers that were supposed to have been graded were instead put in a junk pile (for multiple choice problems, scratch paper, etc.) But the physics front office holds on to those papers, so that's a scenario that can be checked albeit tediously.

Ted Shifrin

I was expecting DogAteMy to come back here on April Fools Day and return my eyes to me ... :(

BAYMAX

jumbled up questions ... with limited time period with students sitting in opposite parity ...

@Brody

Semiclassical

Also, we did the separating in the area inside the 'lobby' of the office area.

Brody

@BAYMAX Oh, I was thinking in-home online quizzes (or online anything)

Ted Shifrin

Conceivably a few papers could have slid off to the floor and you didn't notice, @Semiclassic.

Semiclassical

04:45

Sure. But I find it hard to believe that other people going through that same area wouldn't have noticed them.

Brody

That would work though, with a secured assessment program @BAYMAX

Semiclassical

So I don't consider that a high probability.

Ted Shifrin

Are the papers put in a tightly closed manilla envelope, or did the TAs just walk around with a stack of loosely flopping papers?

Semiclassical

In transporting the papers back to the front office, they were secured in a carrier.

Ted Shifrin

I mean the next stage.

Brody

04:46

I'm a bit scared at the image of Ted sitting at his PC with empty orbits

Semiclassical

When they're given to the graders, though, they just get them in a stack.

Sometimes I'll ask for a manilla envelope, but it doesn't come by default that way.

Ted Shifrin

That's not a good system. Way too easy for something to fall out in transportation or even when the TA takes them home.

Secret

So that's the history of the name DogAteMy, as in DogAteMyEyes...?

Ted Shifrin

No, Secret, it was DogAteMyHomework.

But it's not really right.

Secret

ok

Semiclassical

04:48

The real kicker, though, is that all the TAs are supposed to count the papers at the front office, and sign a log while they're there.

Ted Shifrin

@Brody empty orbits?

Brody

@TedShifrin eye sockets without eyes

Semiclassical

We did count the packets, and I signed the proctor log to that effect. So that was documented.

Ted Shifrin

Could still get lost after that, though, @Semiclassic, although that would establish if everyone turned in #2.

Oh, thanks, Brody.

Remember that I have a number of extras.

Brody

True, it wasn't specified how many Akiva stole

Semiclassical

04:49

However, the other proctor was also a grader. So they just took their stack and didn't take the time to count them again. Additionally, they didn't sign the grader log.

Ted Shifrin

Balarka claims I've rolled as many as 12 to 14.

@Semiclassic: Sounds like a recipe designed to fail. The professor needs to do something about it.

Meanwhile, if it turns out that a few students actually did not turn those in [which you've already said didn't happen] then there's a question of their academic honesty. But ...

BAYMAX

ha ok@Brody

Semiclassical

In addition, they 1) got the scores in at the last minute (scores uploaded the night before the students were supposed to get them back), 2) when they brought the graded sheets back, they seemingly didn't bother to count how many they were turning in or sign the grader log.

Brody

not to interject, but on a related note, in high school I went through a whole math class not having any idea we were doing a quiz

Semiclassical

Now, want to guess which of the two problems they graded?

Ted Shifrin

04:52

I think that's self-evident, @Semiclassic, and those guys need to be reprimanded big time.

Semiclassical

Agreed. I'm not at all happy about the situation.

Ted Shifrin

It seems to me this is a question about TA responsibility and not about undergraduate cheating.

Semiclassical

Yeah.

Ted Shifrin

The professor in charge needs to take action.

Brody

and had to awkwardly explain to the teacher afterward how I had not done the quiz nor had been aware one took place until it was too late

Ted Shifrin

04:53

Or the undergraduate head of the department or ...

Semiclassical

I didn't intend to frame it as cheating, by the way. The reference at the beginning was simply to put it outside the context of just plain quiz-writing.

Ted Shifrin

@Brody: How can you go through a whole class and not have any idea there's a quiz? You mean you skipped?

OK, @Semiclassic, but you definitely misled me :P

Semiclassical

Yeah, I guess so.

I'm just really unhappy about it and needed to vent.

Ted Shifrin

You have my sympathy. If I were the professor in charge, I would (a) seriously disciplined the guilty TAs and (b) try to figure out how to reconcile things with the students affected.

Brody

@TedShifrin No, sat through the class session as usual but was apparently aloof during the administration of the quiz, thinking we were continuing the section's exercises in-class

Ted Shifrin

04:56

And the professor probably should report these folks to the graduate coordinator re dereliction of duty.

@Brody: After 40+ years teaching in some form, I cannot for the life of me figure how you could manage that.

Semiclassical

What really makes me think it's not an issue on the part of the undergraduates, though? One of the students affected was one of mine, and I watched them turn their test in. (They had forgotten to put their name down on their first quiz, so they made a specific point of doing so on this one.)

Ted Shifrin

@Semiclassic: But did you verify that both pages were turned in?

Semiclassical

No, I didn't. I remember her signing at least one of the pages, but I can't clearly remember if it was both.

Ted Shifrin

So I rule that as irrelevant and immaterial :P

Semiclassical

Yeah. :/

It's not an evidentiary thing, I guess.

Brody

04:58

@TedShifrin In retrospect, I can't make sense of it either. But it happened. And my teacher, though skeptical at first, accepted it and allowed for a make-up another time

Semiclassical

More just my sense of the student speaking.

Ted Shifrin

Ah, I see, @Brody. You're one of these fragile flowers we keep hearing about ... :D

@Semiclassic: I'm sticking with my original opinions.

Semiclassical

I believe the technical term is 'special snowflake.'

Brody

@TedShifrin Come now?

Ted Shifrin

Oh yeah, I misspoke.

Semiclassical

04:59

But yeah. My feeling right now is that the other TA f*d up.

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$Mathematics$ Mathematics