#serious-discussion
1 messages · Page 472 of 1
I bought an abstract algebra book several years ago but I didn’t have the mathematical maturity to do the proofs
but how do you think we made an educated guess as to what that formula even is
huh
okay
good point
same for sum of i
Also, this allows you to (in theory) construct an explicit formula for sum_i i^n
Just iterate.
a slick way to make an educated guess on the formula is what gauss supposedly did when he was 8
(that was the case n=100 but doesn't matter)
\begin{align*}
\sum^n_{i=1} [i^4-(i-1)^4]&= n^3\
&=\sum^n_{i=1}(4i^3-6i^2+4i-1)
\end{align*}
There you go, from that you can get the sum of cubes.

Tesseract
You can also derive it using the crank above.
Gauss's way is a lot cleaner, though.
field axioms are NOT designed to be wieldy in everyday use. they're meant to give just enough to develop the algebra laws we took for granted in high school
\begin{align*}
n^2&=\sum^n_{i=1}[i^2-(i-1)^2]\
&=\sum^n_{i=1}(2i-1)\
2\sum^n_{i=1}&=n^2+n\
\sum^n_{i=1}&=\frac{n(n+1)}{2}
\end{align*}
Tesseract
I know, I understand why it was necessary. I just don't like that type of proof lol
Having to prove something turbobasic
I think I'm just being a baby
But I'm not going to stop :^)
its kinda fun
Yeah no no point lol just venting
When Rokabe brought up "How do you think they came up with that formula" that did a lot for my perspective on it
I still find it annoying but him and Tess are right, it's not pointless
Just annoying 
At the same time, there's a one-of-a-kind sort of feeling when you first prove that 2+2=4.
Yes. If you really dislike yourself, you can do it from ZFC itself.
I did not say it was a good feeling, just one-of-a-kind.
:^)
What did the folks in Principia start with?

indeed fields having quite a bit of structure makes other structures that depend on them quite nice. wieldy refers to having to go back to axioms every time when doing a typical manipulation in real analysis instead of prepping algebra laws beforehand
Would you have to take an abstract algebra course to appreciate that?
you can get a glimpse of it in linalg
With what? Noncommutativity of matrix multiplication?
That's not very nice
That's all I can think of though
sure you can compare the amount of structure fields have to rings (of which sets of matrices are an example)
Right
I hate when I want to complain about things but they make sense so my complaints don't make as much sense -.-
idk how to word it
specifically the comparison you may have in mind is that multiplication in fields commutes but multiplication of matrices (type of ring) may not
Yup that's what I thought too
This is funny.
within the first few days of an AA class, an even bigger difference can be seen in comparing a field to a group (which has just 1 operation unlike fields)
I want to take AA but it doesn't interest me as much as analysis so I'd rather take analysis classes first but then all anyone talks about here is algebra stuff >.>
wtf is this
"It is used at least three times in ..." lul
Well I guess they're not wrong about it being occasionally useful
Finished the problem too, this was good
analysts are too busy working to waste time on discord
Fields are just places to do arithmetic

funny part is that people think it's some sort of complicated nonsense
but it's really just if you union two disjoint one-element sets, you get a two-element set
my brain machine is broke rn
trying to do a cool computer thing
Say you have a 4d parametric curve p(t) = (p1(t),...,p4(t))
how would one "step through" slices of that using a 3d plotter to see a region the curve passes through
if you plot the projection (p1(t),p2(t),p3(t)) it's almost like taking the whole 4d curve and just smushing it into 3d
is there any nice way to represent the 4d curve in 3d over time?
You can do it with volumes more easily like if you have a function w=f(x,y,z) you just plot the volume you get from fixing w to some constant c and plotting f(x,y,z)=c
but what about parametric curves?
I was thinking maybe you do the same thing kinda but instead set p4(t_c)=c some constant, solve for t_c and then plot (p1(t_c), p2(t_c), p3(t_c)), would that work?
then do a lil animation like -10<c<10 or something
oh and even better, swap the functions around so that p4 is the simplest to invert of them all
and just rotate your 3d graph later if necessary
Huh, neat!
Have you read through the Principia?
I have read enough introductory chapters to get through the notation
map one of the coordinates to color?
or to time
the latter will give you a moving point
TRUE THANKS SO MUCH
bruh
why
expanding my horizons
the foundations they use are quite different from what's popular nowadays
staring at badly designed cramped notation until you go shortsighted
who cares about the notation
I'm talking about the foundations
some notation is just better than others
again I can see mathematical content through the notation
looking at the different style behind the notation is v. valid
but it just sounds like a pain
eh
it uses a ramified set theory
the "historical" connections between ramified theories, predicativity, and russel's paradox are quite interesting
Wtf is ramified set theory
because nowadays it all just boils down to "U : U is inconsistent because girard's paradox, therefore let's use levels"
some historical perspective on why we do this is important
it's like where you have a general category of sets, right
and then you apply a battering ram
a levels
One more level mom
is this not ramification
Ultra what is your favorite area of math?

You don't have anything you particularly like to do or learn?
Should've picked ultrafilters
which math had worst notation
rn im being filtered by a geometry question
is geometry worst notation wise?
like bloated
);
im talking about for reading and clarity
Well, there's this crown thing here

talks oct 23

tell me something interesting
@narrow rock we may be on different armies but at least we're not fencey fencertons.
okay but unironically handwriting mathcal characters is hell
if you choose a field specifically to avoid that i dont blame you
"pretend" LOL
My symbols are better than your symbols.
also btw i'm also better than people who write L_p 🙂
easier to explain what you do to your relatives
hey mom can you pass the butter? anyway so back to discussing pseudodifferential calculus...
"I study how complicated systems evolve as variables change, such as how a drumhead vibrates when you strike it with certain force at a certain spot"
Just lie to your relatives.
it doesnt reflect anything beyond undergrad pdes but like
compare that to an algebraist
hey mom i study how to solve rubiks cubes 
"I study 2, other mathematicians study 3 and 4, we haven't gotten to 5 yet."
15 puzzle 
what is this ramsey theory
"i study symmetry"
"oh so like aesthetics?"
"
"
"what the fuck does 'sully' mean and why have you said it 3 times this conversation"
"
"
2-theory
bruh moment
Wat
everyone here gives too much attitude and is sassy and express it via sully
im working on it but its harder than youd think
itd probably be easier if i didnt file life insurance first
Oh I did not realize that was a real thing.
less paperwork
this is like a visual novel plot...
???
everyone here gives too much attitude and is sassy and express it via sully
no one would choose to pursue higher mathematics except to bolster their massive superiority complex
tf you expect
math is an inherently sassy field
Sass-theory
How do you feel about the "you dont own it" only have a license to use it.
first time I’ve heard of this
do you learn this in pdes too
much later on
i thought that also neeed a limit
are you given it equals e^-2
or did you just already look at the answer
(1+1/n)^2 = 1+2/n+random stuff no one cares about
do a substitution n = 2m
then move ^-2 out of the limit
no?
in the other one
?
🚀
$$\lim_{m \to \infty} \left(\left(1 + \frac{1}{m}\right)^m\right)^{-2} = \left(\lim_{m \to \infty} \left(1 + \frac{1}{m}\right)^m\right)^{-2}$$
mniip
because $x^{-2}$ is continuous at $x=e$
mniip
Is there a notion of how close two finite groups are to being isomorphic?
Things off the top of my head include the number of homomorphisms between them, the largest possible image of a homomorphism from one to the other, but neither of them are perfect
How about this: the closeness of G and H is the size of their largest shared subset?
Subgroup* then that could be an imperfect one too
No, subset
the problem I can see with that is G and G/H for small H should be "close" but could have no nontrivial shared subgroups
I wouldn't agree with subset, if you remove the group structure, then you can just take the smaller of the two sets and associate each element arbitrarily with something in the other group
giving that the largest shared subset is just the entire smaller group
Not quite
I assume you want equal elements then?
Then there's a problem; isomorphic but not equal groups have no shared subset...?
If A, B, and C are in the subset and AB=C is true in one group, it must also be true in the other.
That’s the only restriction.
Hmm...
Sounds ugly
It could potentially in some cases be a game as to the largest independent set in A
a subset of A with no two things in A multiplying to another thing in A
that's not a very group theory-esque thing to consider
that's not a meaningful notion?
a group theoretical property does not depend on the underlying set of a group
i.e. should be invariant under a group isomorphism
an isomorphism-invariant notion would be to consider various groups K with monomorphisms K->G, K->H
and find the largest K
this can be turned into a universal property, but then existence of such universal (rather than largest) K is doubtful
but it would be kinda required to extend the theory beyond finite groups
maybe you have to consider not triangles but rather squares 
I forget the term but can't every group be "factored" into simple groups?
Something with the normal series
But then isn't uniquely defined by it's factorization since you can "put things together" in different ways
jordan holder and composition series
iirc the composition series aren't "natural" in a sense?
oog solvable groups
the factor groups are unique but the order is not
so like the groups in the sequence can be different but you end up with the same simple factors
or something like that
sure but what I mean is that the decomposition doesn't upgrade to a natural transformation
or a functor I guess
oog
This is
Did you read what I said after that?
this?
Yeah
my point still applies
How?
for disjoint isomorphic groups the set would be empty
What does disjoint mean here?
but it is a different element in every group
But you can pretend it isn’t.
what about all other elements then?
What do you mean?
I could take the set {apple, banana} and define f(apple, apple) = f(banana, banana) = banana, f(apple, banana) = f(banana, apple) = apple
this would be a group
Yes, C₂
it is isomoprhic to C_2
but as sets, they are (likely) disjoint
because C_2 likely contains integer numbers or equivalence classes of such
We’re dealing with abstract groups here, so that doesn’t matter.
abstract groups don't have underlying sets
But they do have elements, so you can make a set.
and hence given g in G, it is meaningless to ask whether g in H
Yes
they do and they don't
Without the restriction I gave, the largest shared subset would just be the entire smaller group.
you can't talk about both "abstract groups" as if they're invariant under group isomorphisms, and their exact underlying sets (for the purpose of intersection) -- as if they're not
However, I gave it, so choosing what g is in H forces other elements.
how do you "fix" any elements?
(also note that what you're doing here sounds more and more like constructing a monomorphism from another group, than talking about underlying sets)
You say “this element of G is the same as that element of H”.
there are many ways to do that though
Yes
how do you pick one?
Any two groups will probably have many shared subsets, but I’m only interested the largest possible shared subset(s).
ok so translating what you said
you have a set K with injective functions p : K -> G and q : K -> H
such that for all x y z in K, if p(x)p(y)=p(z) iff q(x)q(y)=q(z)
and you're looking for the largest K?
Yes
that's similar but also slightly different from my version
ok but note that if there's x, y in K such that there's no z with p(x)p(y)=p(z), (and also by definition no z such that q(x)q(y)=q(z))
How can that happen?
we can always take K' = K + {★}, with p(★) = p(x)p(y) and q(★) = q(x)q(y)
so the largest K will be "closed under multiplication"
So it’s always a group?
if K is infinite, then K' will have the same "size" as K
I’m more interested in finite groups.
but I think there's always gonna be a K of the same cardinality that is a group
so yea
in some sense there's always a largest K that is a group
so really you're looking at subgroups of G and H that are isomorphic
Are you sure?
kinda
What if p(x)p(y)=p(a)p(b), but q(x)q(y)≠q(a)q(b)?
hmm
good point
then this sounds real ugly not gonna lie
it's kinda reminiscent of group objects in the category of partial functions?
which I don't think is a very well studied topic?
at least it seems that most of group theory tools break down there
hmmmm
there's a forgetful functor U from Grp(Set) to Grp(Set*)
and you're talking about objects over U
xy might not be defined in K, but when it is, we have p(x)p(y)=p(xy)
ah but no, that still fails to describe this structure because xy and ab are either the same point in K or not
I guess I'm out of ideas regarding what tools you might recover here
I was literally asking myself the same question this morning, hoping there might be some sort of associated metric on finite groups or smth
@leaden torrent you mentioned some time ago in #math-pedagogy that Lockhart advocates for bourbakism-with-pictures. Could you expand on that? From what I know, Bourbakism might refer to an approach to mathematical pedagogy in which the subject is treated very abstractly and hyperrigorously
lol what would this mean tho
the closeness part
like their subgroups are similar?
that's the thing idk how one would do it otherwise there wouldnt be a question lol
there is probably a way but idk if useful
is there an "expiration date", of sorts, for GRE scores? Like, if I take it senior year of undergrad, then take a year or two off and get a job not in academia, is it still okay to use those scores in my applications?
funny man
Yes, I do t know them off the top of my head but it’s stated somewhere on the GRE site
I think it’s in the range of like… 2-5 years???
It’s quite a lengthy time IIRC
dudeee getting the integral using the limit def is so cool idk
just the fact that it works out like that
I mean it's supposed ot work like that
but you kinda just get lost in the symbol crunching after a while lol
feelsgood to go back to the roots and see it work out

Why are you sullying bruh
There’s multiple constructions of the integral
disgusting
I learned Darboux
I haven't worked with any of the other types yet
Which is via like… upper and lower sums and like
Not sieves
I forget
It was similar enough to Riemann sums
What is the difference between Darboux, Riemann-Stieltjes etc
i think riemann is like you pick the left or the right end of the interval
Yeah
or center or w/e
darboux is you pick the sup over the interval, and the inf over the interval, and these need to converge to each other as the intervals get small
ANd Lebesgue is just supremum of the measure? I haven't looked into it enough no sully ty
riemann-stiltjes is where you have a function alpha and the sum is f(x_n)(alpha(x_n) - alpha(x_(n-1)) instead of just x_n - x_(n-1)
so if alpha is like, a step function
this gives you a dirac measure
if alpha is some kinda bendy thing it gives you the gaussian weight
some kinda bendy thing 
it's very nice
alpha needs to be nondecreasing
and like
right continuous or something
basically it's just a weight
that you put on different points
so that each part of your partition is weighted differently

based on how steep alpha is when you go over that part of the partition
Would you learn about this in a normal undergrad real analysis text
i think rudin defines the riemann integral with riemann-stiltjes
some books do
i mean it's no extra work
it's all the same exact thing basically
wait what? the wikipedia article says riemann-stieltjes is a generalization of riemann integral, why wouldn't riemann come first?
i mean if it's no more difficult
why not just teach the more general one
and then tell people to pretend alpha(x) = x most of the time
you see these a lot in probability
there, alpha ends up being the cumulative distribution function of your probability distribution
’s biceps

💪
chmonkey looks in the mirror every morning and calls himself a good boy
He knows he’s a good boy

the lebesgue integral doesn't handle conditional convergence in improper integrals well
so maybe you could come up with some way to patch that up
people use the "cauchy principle value" to do this but it doesn't always make sense
for example, the lebesgue integral of sin(x)/x from 0 to infinity is not defined
even though it is riemann integrable
this is because |sin(x)/x| has integral infinity
and like
technically if you reorganized the order of the intervals
that you're integrating on
you could make the value whatever
(this is from riemann's rearrangement theorem)
so the lebesgue integral doesn't like that, since the reason it exists is to let you reorganize countable numbers of things without changing the value
whereas with the riemann integral you can just do the usual integrate to M, take the limit as M goes to infinity, and that's fine and converges
some would say this is actually a benefit of the lebesgue integral
but
knowing the integral of sin(x)/x is useful, it's used all the time
so like int -inf to -2 + -2 to 0 + 0 to inf? I don't think I'm understanding this right
something like that
but like
an infinite series
so if i was to be like "oh, let's integrate this by first integrating the interval [0, pi], adding on the integral from [2pi, 3pi], then from [4pi, 5pi], then let's go back and do [pi, 2pi], then keep going on with the evens a bunch more, and do another odd, and back to a few more evens, and then add up all these results"
the lebesgue integral says "it shouldn't matter that you did this! you should get the same answer"
just like what absolute convergence for a series says.
but this is not true for sin(x)/x. if you do what i said, you'll get a different value from what you're supposed to get.
So for an improper integral to be Lebesgue integrable do you need its series representation to be absolutely convergent?
I don't think I worded that right
to integrate over infinite bounds using Lebesgue integration do you need its series representation to be absolutely convergent?
yes
or
a simpler way of saying this is
f is only lebesgue integrable if |f| is too
wait so what even are people here
like are people here mathematicians, students or just people who do math for fun?
that seems trivial
probably because im asking an imprecise question
well nevermind
ty

There are definitely more high schoolers than Ph.D. and above.
However, you can still get good answers.
good evening! If G a group and R is an equivalence relation and cl(x)= {a in G/ xRa}, can we safely say that cl(xy) = cl(x)cl(y)?
or is it only a special case for Z/nZ ?
nvm
I just proved it
but it's not true?
idk, I proved it only for a particular group that I needed
it will be wrong for this group too, just partition into {e} and {rest} then notice
{e} = cl(e) = cl(a*a^{-1}) != cl(a)cl(a^{-1}) unless your group has order 1, 2
yeah it has order 2
in fact, xRy iff y in {x, ax} such as a in G (a group)
so card(cl(x)) = 2
I should mention that every element in G is an inverse of itself
aka, x^2 = e
I used that in the proof
Am I missing something ?
i mean it will work in special cases, but for general equivalence relations it is really wrong
you essentially want to build a quotient group which works when the equivalence relation comes from a normal subgroup
Khan Academy has good videos on calc
I just need to sit through an actual calc thing
or you can push to spivak
they go to slow for me...
when you say actual calc wdym
explaining the basics of it
i suggest finding a good calc book and walking through it on your own pace
coursera, edx have some nice courses as well
redirect me to a better channel if there's a distinct subject this belongs in, cause i can't begin to guess how to go about this. these are some scribblings from a few months ago, i just got back around to them and i really wanna figure out if there's any way to explain why this relationship exists
this started with just the graph on the left, i had this idea that there would always be 3 points of intersection so long as the circle's lowest point was tangent to the parabola's vertex, and those 3 points would tend towards an infinitesimal distance apart as the parabola's coefficient would tend towards infinite.
but i messed around and found out that actually after c hits 1/(2r), the parabola only touches the circle at its vertex, and i have no idea where this relationship would have come from.
is there a taylor series that fits the curvature of a circle? my calc knowledge isn't strong enough to try and figure it out on my own, but if there is one then i wanna see if it has any correlation to 1/2r, otherwise i want to see if there's any other reason why a parabola fits the curvature of a circle so nicely when it's coefficient is a non-pi value
Yeah! They have the same 1st and 2nd derivatives at that point causing the circle to nestle into the parabola
oh my god thank you thats the answer ive been looking for
so i was on the right track with trying to find its taylor series but i just um haven't formally learned that much calc yet
Yup! In fact, try adding (x^4)/8 to your parabola and you’ll see it hugs it even more. That’s because we’re putting in more and more of the Taylor’s series at that point
For this, you could consider the function -sqrt(r^2 - x^2) and find its taylor expansion
But that sounds nasty
That's just the function for the lower half of the circle
i actually was going to take that approach if i didnt get any response, i'd already derived that function but i didnt wanna do anything with it
because spooky scary
idk if i could find the derivative of a function with 2 variables (edit: with my current maths capability)
but i mean i guess i could just say r=1
The other way to do this is to look at solutions to the system of the two equations as c varies. To do this, I would use the equation for the parabola to say r + y = cx^2 to sub in for x^2 and get (r+y)/c + y^2 = r^2. So we're looking at when y^2 + y/c + r/c - r^2 = 0.
Now we can solve for y, and see what the possible y's are given r and c. Well, one solution is y = -r. We know that from the bottom point where they both meet. What's the other? It's going to be reflected across the axis of symmetry, which is given by y = -1/(2c) (remember the axis of symmetry of the parabola ax^2 + bx + c is -b/(2a). here a = 1 and b = 1/c).
So then for there to be another solution ABOVE y = -r, we must have that the axis of symmetry reflects -r UPWARDS. i.e., it has to be above -r. Then -1/(2c) > -r for there to be more intersection points, and this simplifies to c > 1/(2r).
This is the algebraic way instead of the calculus based (analytic) way
Note that I took a shortcut using the axis of symmetry, but you could also just use the quadratic formula on our solution, find the two roots for y, forget about the -r root since we already know about that one, and then see what conditions on r and c make it so that r+y = cx^2 actually makes sense (since cx^2 cant be negative, so r+y must be positive).
r+y > 0 with y being the other root of y^2 + y/c + r/c - r^2 will imply that c > 1/(2r).
And then you can see that at c = 1/(2r), the two roots are equal.
After all, then the polynomial becomes y^2 + 2ry + r^2 = (y + r)^2
I think this para is misleading. It is of course true that this function is not Lebesgue integrable, but this is not really a distinction between the Riemann and Lebesgue integral. It is not Riemann integrable in the "basic" sense either, and improper integrals can be defined in exactly the same way for either. For things like this example of course, the value will depend on the choice of engulfing sets and it is just convention to take [0,M].
That makes sense
My point was mostly that there's still work to be done beyond defining the lebesgue integral
If you want to talk about the kinds of things people need to talk about
(in particular, conditional convergence and later singular/oscillatory integrals)
Most rigorous/advanced treatments of calculus I see (eg spivak calc on manifolds) first just define the Riemann integral for bounded things on boxes, and then extend using partitions of unity to the case of integrating locally bounded things over arbitrary say open sets, and this extension is usually only made for functions that satisfy that "absolute integrability" condition which makes this definition invariant.
yeah ofc
Yeah I think when people make that comparison it's because usually with the Riemann integral you define it on compact sets, and then the only way people seem to ever extend to stuff like integrals over R is improper integration
While in measure theory you often talk about the "non-improper" integral over unbounded things
So if you define improper Riemann integrals and get new stuff, you're strictly extending
While if you were to do the same with Lebesgue you'd be overwriting existing stuff
At least that's my impression
I had watched this recently: https://www.youtube.com/watch?v=ZYj4NkeGPdM&t=55s
And I don't think 0 and * are confused. I think one is strictly greater than the other but on a different axis. Imagine if instead of playing as red and blue, the players are the person who goes first p1 and person who goes second p2. If we choose the perspective of p1 * is strictly greater than 0. Then the blue and red lines would be confused with one another because this axis is color ambigious
A playful venture into the vast and mysterious forests of combinatorial game theory.
This one simple game will change the way you look at numbers forever! Hackenbush is easy to pick up, but exploring its strategy leads us down a fantastical mathematical rabbit hole, through which can be found the roots of our familiar number system, intricately...
it might be possible that there are more than 1 kinds of 0 using this perspective same way there is more than 1 *
This is too much work
And this is such a simple PDE too wtf
uh so I kinda have to draw this
is there an easier way to do this
What is this suppose to represent
Solution to a PDE
probably some waveform over space, and the other dimension is time
lul
exactly this

I think I’ll just leave some empty space on my paper and then Photoshop it into the scan
fourier method out the ass
Yeah that’s what the notes say too
but I still don’t want to do all this
Thankfully the initial velocity is 0 so that helps
But he gave such a dickwad initial deflection function -.- why couldn’t it have been something simpler
lol
@pale orchid just for fun I tried it
do you think this will work
like does it get the message across
of what the solution looks like?
that looks super cursed
sure i guess
idk if you can manage to label a couple of things on the axes
some period & amp
you can show the wavelength or wavenumber on the space axis for a fixed t
i guess that doesn't make much sense if you have several frequencies though
the periods should be linked via the wavenumber and propagation speed
but only in a straightforward manner for a single frequency
this plot is made through the fourier method, right?
so it's the superposition of a bunch of sines and cosines
what's the form of the sol?
Why wouldn't it just be 2pi in t and 2pi in x
they have different frequencies and the number C^2 there is doing something
spatial frequency depends on that C
ye
and the unit is radians/meter or whatever unit you're using in space
so that's the spatial frequency
anyway yes, it's 2 and 4, but don't forget the 2 pi factor
I think what I can do is
(to avoid all the mathy mess)
When I draw these lines to denote that the curve has a volume
the coordinate axes make it look weird
so I think I will color over the curves in pen and draw basis in pencil
let me try
you can always just ignore me and not indicate anything lol
or draw 2D cross sections
I'm sorry 😭 I don't get it enough
since the solution is the product of 2 functions that depend on a single variable each, you can easily draw cross sections
Oh
I see what you mean
Hm
I think I might do a 3d and two cross sections if I have space
Embarrassing but I'm kind of having trouble figuring out the traces 🥴
For cross sections
I think
Okay
Okay so on the y axis (right handed system) the x component is constant so it's gonna be cos(4y) and on the x axis the y component is constant so it looks like sin(2x) yeah?
geogebra just crashed so I can't check -.-
But it looks right on Desmos
bruh what
isn't that what you meant by cross section
hey i have a question for you undergrad students

do you learn topics such as dot product, cross product, vector sum in linear algebra?
Yes
don't you take analytic geometry before?

These are covered, but linear algebra focuses more on vector spaces, and linear transformations between them
oh
I took that in HS I’m pretty sure lol…
Yes
I figure most people will take geometry before, simply because it is an earlier class. But LA doesn't really depend on geometry
i mean i learned all that stuff in analytic geometry and it seems like in linear algebra we have it all again
i see
@pale orchid
I’ll take it
I’m not doing that for the next problem though 
actually it's not that bad
I assume you worked hard on it but other than looks how does one even read these graphs?
like without units or something idk. Unless it isnt required
but then again even using geogebra I couldn't read the plane graph really
hey
just a general question
how do i know whether math grad school is for me?
i want to study more, do research, get a PhD, yes
but i'm not sure whether i will eventually stay in academic math
this is not exactly a math question but could someone throw some light?
are you currently in a masters?
i got into a research oriented masters precisely to figure that out. the piece of cardboard was anyway gonna be a plus both in salary and job opportunities, and i took the chance to figure out whether i liked research or not and how academia works
cuz it might be you like research and not academia, or you like both or none
and one kinda goes from there
i'm currently in third year of undergrad, so i will apply next year
i see. have you already begun working on your undergrad thesis? that can also give you an idea
yep, sorta. i do enjoy research, and that's why i think doing a PhD would be a great idea
but like, academic math may not be something i'd want to do - since industry jobs get you more 💰
and also it takes so long to get a tenure track job tbh
my point being, if i don't continue in academia after, is the PhD "wasted"? is it a better idea not to go through with it in the first place? or are there industry positions that could benefit from a PhD
you can still do research, just not in academia
it'll probably influence the choice of things you specialize in
fair enough, so i probably should not worry rn?
like you might wanna pick up applied maths along the way
guys
also would the field i specialize in during my phd matter?
i have a question
listening
what no lmao
can u help me turn these into standard from
i mean algebra is probably not industry-oriented. i do analysis, pdes, geometry stuff so that might have applied directions? in any case i see that i'd have to pick up some applied math
Dirty little secret: most people who employ math PhDs don't care at all about what math you did
They just see it as an indicator of being "smart", in the sense of being adept at abstract thinking and problem solving
And are cool with you learning a lot on the job
There are exceptions ofc
friend of mine works at siemens mobility (railways and stuff) and has a math phd in their team
But in general I wouldn't sweat it TOO much
that math phd did research on graph theory
Hey that sounds kinda relevant to railways lmao
siemens hired her years ago and had no idea wtf graph theory is and had her work in random teams for years
before realizing that this is relevant to railway stuff
and moving her in that position which now fits really well
Sounds like it worked out pretty well
ye but it took like a decade
she apparently was a pretty early researcher in graph theory
Yeah that's my point, many employers don't really care
i think the hiring persons are now more aware of what it is
yeah in the age of google im sure theyd at least know the basics
graph theory is very, well, visual, so its easy to understand
if i told employers my research was in "algebraic K-theory"
theyd be like "idk tf that is but it works"
again, there are some more technical positions where you do need specific knowledge
some modelling gigs, security companies, etc
but these are in the minority
as long as you can program and can pick up stuff easily theyll take you
my (maybe bad) impression is that most employers think that a math phd (or just a degree) is a sign that this person can quickly learn whatever we throw at them
this also applies to physics phds for what its worth
physics phds are weirdly high-earning relative to physics bachelors

like obviously any phd is a pay jump but
why would anyone get a physics degree
its extra big for physics phds
since undergrad physics knowledge is like, utterly useless
but a piece of paper that "proves" youd be competent at basically whatever quantitative mess you inherit
thatll get you places
believe it or not, some people are interested in physics
(shock and awe)
though if youre saying this in the sense that "its smarter to get a math bachelors and then a physics phd", maybe i see your point? i know thats the advice for econ but idk about physics
all the physics majors i know started hating physics
and switched to a mathematical physics major
due to lab work
okay fair
labs are dumb
im sure they have pedagogical merit
but monkey brain dont care whats good for it
monkey brain drinks 3 coffees a day and gets into increasingly weird fetishes for dopamine hits
and monkey brain HATES labs

i looked it up yesterday and 3 coffees is totally fine
your teeth probably won't like it, but it should be fine
yeah
why is lab work a bad thing 
people just dislike it
it takes up a LOT of time in dumb shit
it also hated the physics labs in my undergrad
it would legit take like 10~20 hrs to write a dumbass report that was worth like 1 point out of your final grade
but there's like 10 of them so they build up
i feel like maybe someone in chemistry might love that
you go 2~4 hrs to measure shit at the lab
and then write BS for hours on end
its all the extra shit
i did chemistry labs in undergrad
it wasnt super bad but i'd rather not have done it lmao
its like
yeah, the report
okay the worst part of any academic job is the emails
now imagine that sort of mundanity, but you have to have a calculator in hand calculating shit
and double checking everything since it counts for a grade
i know it sounds like major first world complaints but like
it really is such a monotonous task
i mean it does sounds tedious and repetitive and i would hate it but it might just be suited for some people unlike us you know
i know a couple people who love that enviroment
most bio/chem students
sure, but my impression is that most people dislike labs
even people who like their subject hates (undergrad) labs
ye i suppose thats true
I still would love to be a math proffesor
exactly me
i don't mind sticking my hand in a coil to measure fields and shit
but then they'd ask to compute verything by hand AND simulate, and compare the results
show propagated error
and write like 10 pages of shit explaining it, with tons of references
miss me with that shit
it takes more work than the class itself
we also had this ancient lab equipment
and it was super hard to measure things
you were never sure if you fucked up or the lab equipment did
there always was one digital of everything
and everything else was stone age analogue
writes down note:
possible lab failure or my failure but we cant know for sure
also lab booklets at my undergrad were like $80 per course
hunched over a breadboard for 2 hrs cuz shit wasn't working. turns out either the breadboard was an open circuit cuz it was too old, or the components were burnt and ruined by the previous group
which i hold to this day to be a scam
shit should be $15 max
it was like 40 pages of black and white text
bruh you just triggered war flashbacks
shortly after my undergrad i became a lab instructor
every single day... "measure current in series, and voltage in parallel"
5 seconds later, burnt fuses in all the multimeters
measure the current from the 12v source to ground, why don't you
lmao
relatable 😦
How was I suppose to assume the main gnd wire was broken and not properly grounded 😦
smh
no memes in #serious-discussion
well actually closer to this
but students managed to fry them
the uni was not happy
aha
yea these look more for like basic digital electronics tho
you threaded the wire through a little hole
and screwed it down
and i guess it was broken and not making proper connection
Then I also had a bad little cihp
chip*
was the bread board all attached
the thigns we have they just have like velcro
but seeing other people use the lab you can just take your crap and put it somewhere in the mean time
hopefully next semester math class is good :V
Do you study math outside of classes or do you get enough through classes?
my classes miss a lot of details and proofs due to the pace so most of the time i have to prestudy/overstudy to get the most out of a class im interested in
most work is done outside class
Looks like you started off as an EE/Physics person and then transitioned into a sig.proc. chad. Noice
and how much time are you able to dedicate and treat as if it was a full class
even busy semester i had < 20 hours per week of actual classes
so its kinda expected to spend at least as much time outside of class
i mean just a weekly homework sheet takes like 10 hours per week
like say you are interested in a some topic or subject
do you have enough time to study that while doing your actual scheduled classes
if im interested in something, i usually will try to take a class on it
makes sense
i tend to do things i cant do in college in summer
like studying philosophy/justice
mostly none-math
but it might be just me

make me mod so i can study justice
do you take summer classes also?
idk if that is common or not
started as telecom, a branch of EE, yeah
i know some degrees you might need to
good evening everyone, I found this statement in a problem: let (G, .) a group contained in Mn(R), we clarify that G is not necessarily a subgroup of GLn(R), which makes it possible that G contain matrices of r<n such that r is the number of linearly independent vectors
in the french notation we call r ''rang"
this statement doesn't make sense to me at all
if G a group then all of its elements are invertible
Because in order to G be a subgroup, every element must have an inverse
Don't they mean like
A subgroup of M_n(R) under addition?
Because that would make sense
But again
GLn(R) is not a group under addition too
Which makes this even worse
Yeah, that statement is totally flawed.
they said: if A in G then A has, for multiplication, an inverse A'
Oh, ok so it is a multiplicative subgroup.
wait
there's something crazier
in first line the wrote: let G a multiplicative group that is not reduced to {0}
shouldn't it be {In} ?
where In is the neutral element for Mn(R)
Yeah, it should be Id_n.
The identity
There's definitely some weird stuff in these problems.
Where did you find these?
I will give the benefit of the doubt and like
Just assume these are typos or misprints.
Or maybe mistranslation
maybe typos
I translated the problem to eng so we can discuss
here what it says in case there are french ppl
Damn, I have a french test tomorrow
Dont put the translation lol, let me try
"In this party, one considers a multiplicative group G non reduit â (0)" ok I stopped understanding
sure
close enough
"the multiplication of matrices, an inverse in G one notates A'"
in this part, we consider a multiplicative group non reduced to..
Aha
on <--> we
I guess I could have guessed reduced
ic, but don't you also use it for "you" in some cases?
nope
we say on for "they" in some cases and for "we" in other cases
confusing I know
It's said that the neutral element isn't necessary the identity matrix
We could imagine that with another neutral element than id, there could be matrix non invertible regarding to I_n, that is invertible for this convention
If $E$ is your neutral element and $M\in G$, then $M$ is invertible in $G$ if there exists $N$ in $G$ such than $MN=NM=E$
So the inverse of M has no reason to be the inverse matrix for the usual conventions, if it happens that the rank of $M$ is maximal.
Adrien
that makes total sense
What book is it from ?
but what makes us sure that E.E= E
just homework
It's by définition of E
then they should demonstrate its existence before defining it no?
You see, the notation for the inverse of $M$ is $M'$ and not $M^{-1}$ because there's no reason for them to be equal
do you want the full problem? (if you're familiar with french notations)
No, you suppose than there exists a group G and a neutral E such than ... (the usual properties of a group)
I'm French 
yaay
Adrien
Yeah why not
You have $E^2=E$ so E is a "projecteur" !
Adrien
I assume your problem studies which $G$ and $E$ can exists with these properties, and there will be not much
Adrien
I thought they supposed that their exist an E other than In, and then conclude a contradiction to demonstrate that E is unique
that was a good example
If it's not said, it's not supposed !
I see
If you have difficulties with problem 2 , try to review your lectures about projections
@candid oak
I will
@surreal sapphire How do you export your notes from the nova pro
that doesn't work well i think

you can export them some way, but it wont look good
mostly size issues
and on pdf it doesnt work at all i think
the notes are stored separately from the pdf
i like using one note for notes because its synced to your account
if its available on the google play store it can be installed but no idea how well it would work as i personally dont use it
Any tips on how to not get bored during math class?
let me ask something instead
why do you think you get bored during a math class?
Its too ez
We do the same thing like 10 times while I already understand it after 1 time.
sounds like a chance to teach yourself new things
study harder mathematics ahead of your class
speedrun the questions then flip the sheet and fiddle with things by yourself
try and find interesting questions
and then try and answer them
for example, 'what are the differences between the square numbers? the cube numbers? the fourth powers?'
that's one i remember doing
by interesting questions i mean more like. open-ended exploration vs just specific problems from a competition or something
Good idea. I never thought about trying such problems during class.
I once tried finding out a formula for the maximum area of a right angled triangle when you have the length of the perimeter.
ah, that's interesting
It turned out to just be a proof of that the maximum area would be achieved with an isosceles triangle.
yes
But it was nice to use things I learned in class like the quotient rule.
Ok thanks for the idea.
@devout nacelle 👀
Manan likes to fuck a lot
I feel with a substantial understanding of the subject, one might be able to discover connections or perspectives that weren't realised before.
Sully back
I suppose that is the case with mathematics usually as well.
No I mean, the guy would have no creativity, like, he would be perfectly unable to create new knowledge, no matter how (seeing new links being creating new knowledge
)
Oh hurb
Hmmm
Then yeah, it's just a repository which can fetch information
Nothing more and nothing less
Yeah, I think too 
please dont
I feel with a substantial understanding of the subject, one might be able to discover connections or perspectives that weren't realised before.
How can I change the my nickname in this server?

Thank you
break the rules of math; do whatever the teacher tells you not to do in math and see how far you get until it does not make sense anymore
Can confirm this
😉
Lol
Should've added in the ""
I really think this server could use a “Venting” channel. With the amount of frustration people get with math, it’s not uncommon for people to want to vent, and often times they decide the math discord is the place for it. Sometimes however, this bleeds into other channels, so it’d be nice for people to have a specific place for them to just let things out with or without looking for people to really respond to it. I think chill is currently the best channel for that, but it’d probably be nice and I think a lot of people would enjoy just having a channel specifically devoted for being able to vent in. I’ve noticed some other servers have a Venting channel and it seems to benefit the server overall in many ways, including boosting bonding between community members
I feel like that would just make this place toxic 
How is that?
I mean, as you said, venting can leak into other channels and potentially cause disdain among community members if they say something a little shitty while venting
i suggest we just encourage deskslamming and moving on
I mean obviously expectations of being respectful to community members would still exist in such a channel.
Sure, but just by having a venting channel could increase said disrespect because thats typically what venting entails. Even if you put a rule in against it
le vent 🤓
How about #the-teapot
We can all post gossip toward others in the server there
If you enter the teapot, be prepared to fight off a million critiques.
We could make it so that you opt in with a role to see the channel. That way if someone doesn't want to see all the gossip about them, just dont take the role! It's that easy.
that's great. i've been looking for a fight recently
Give it a voice channel too for good measure
I propose a #galois channel for organizing pistol duels.
Lol, my school server was basically only ever active when there was a conflict. Otherwise it was practically dead.
I cackled out loud
crackled?

I have had an epiphany
the "dont pin anything in #serious-discussion " meme was never actually funny
therefore


i had pinned a good one at the beginning on the channel history and you removed it
such hurting of the butt right now
lol

