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03:02
I am given the space $V$ of continuous functions $[0,2\pi] \to \mathbb{R}$ with a scalar product $\langle f,g \rangle = \int_{0}^{2\pi}f(x)g(x) \mathrm{d}x$, and the subset $U$ of $V$, which contains all the functions $f \in V$ with $f(0)=0$. I have to define the $U^{\perp}$.
So, I mention that $\sin \in U$, so maybe finding $f$-s with $\langle f, \sin \rangle=0$ will say me something about $U^{\perp}$. So, I search for functions with $\int_{0}^{2\pi}f(x)\sin(x) \mathrm{d}x = 0$.
Integration by parts: $\int_{0}^{2\pi}f(x)\sin(x) \mathrm{d}x = \frac{\sin (x) \cdot (F(2\pi)-F(0))}{2}$. This equals 0, if the antiderivative $F$ of $f$ has the same values at $0$ and $2\pi$. So, all functions with that property are orthogonal to $\sin$. Is that really true?
I actually wanted to show that $f$ should be $0$, but it does not look as such at the moment.
cosine has this property so you can't conclude that $f$ is $0$.
@EricSilva I cannot do that, but I wanted to test this hypothesis. $0$ has definitly an antiderivative with $F(2\pi)=F(0)$.
What do you think is a googol miles away
@EricSilva using the questions I asked you before I can say that $F$ should be differentiable in $(0,2\pi)$, so there must be either Minimum or Maximum in that intervall where $f(x)=0$. But then I lose argumentation.
@AkivaWeinberger what exactly?
@Akiva I think there may be fewer than googol particles in the observable universe
03:15
Which is to say, the observable universe is many orders of magnitude smaller than a googol miles.
@Daminark a googol miles away would be way outside of the observable universe
Damn
sniped again
Doesn't really help to go to different units either. Too many orders of magnitude.
i think there's another earth but like bizzaro tbh
03:17
That's worse than I thought
like maybe it's like the terran empire from star trek
That said, I can see one place where a googol would show up in the real world.
Namely: Counting configurations.
And yet log(log(googol)) is like, less than 10
Yeah that function is like, bounded
Which in physics would be the number of microstates; one usually measures the log of that, which is basically the entropy.
And log(googol)=100 is certainly a reasonable-looking number
@Daminark "Less than ten" C'mon, you can figure this out
03:20
idk man ive never seen him integrate something that wasn't 0
this is one case where log base 10 is actually nicer, lol
this might be too much computation for him
Yeah I had log base 2 in mind
Though base 10 makes it easy, it should be 2
oh dude i got it
03:21
a googol miles away there's a copy of earth where everyone uses log base 7
@EricSilva Yo hold up I recently integrated $\sum \sin(nx)/n$ so like
they grow up so fast
I think there's a small town in Alberta where they do that @EricSilva
oh god
Wai tho?
03:22
@Bram28 +1 for use of Hokus Ponens :P
Also answered the question rather well.
they're evil
like actual evil
and a googolplex miles away there's a copy of earth where "pi ends in 3" is religious dogma.
I read this argument in but I am not able to follow it. Can anyone help?
X,Y be i.i.d Normal r.v.s
Let L=Max(X,Y) M=Min(X,Y) then by symmetry (-X,-Y) has the same distribution as (X,Y) so Variance(M)=Variance(L)
@Semi isn't that already religious dogma here
Eh, "pi is exactly 3" probably is.
03:23
Starts and ends, $\pi$'s in $\Bbb Z$.
I know Indiana once tried to legislate $\pi = 3.2$ or something but I don't know much beyond that
"pi ends in 3", by contrast, requires a fine balance of knowledge and utter ignorance
It's a palindrome
im p sure it's implied in the bible that pi = 3
The Indiana Pi Bill is the popular name for bill #246 of the 1897 sitting of the Indiana General Assembly, one of the most notorious attempts to establish mathematical truth by legislative fiat. Despite its name, the main result claimed by the bill is a method to square the circle, rather than to establish a certain value for the mathematical constant π, the ratio of the circumference of a circle to its diameter. The bill, written by amateur mathematician Edward J. Goodwin, does imply various incorrect values of π, such as 3.2. The bill never became law, due to the intervention of Professor C....
03:24
Lol @Semi my friend has a shirt saying "My password is the last 8 digits of $\pi$"
3.141592653589…9853562951413
@EricSilva Only because people have no idea what a sig fig is.
@Akiva true true
i love ancient math
hilarious stuff happens somtimes
There's a circular thingy that's like 30 around and 10 across, and everyone somehow reads it as "pi is exactly three" rather than "they're rounding"
a lot of people think everything is literal man
I think the Pi Bill more indicates the fact that legislators don't need to be experts to introduce laws.
03:27
No, I don't think my computer is a literal man
@Eric
i meant in the bible @Daminark
Wait merp
We may laugh at the Pi Bill, but there's a hell of a lot of bad legislation nowadays that is just as ill-informed and yet doesn't get nearly this attention.
@Semi and in fact legislation is full of nonexperts making bad laws
I dunno if that comment was really interpreting what you said as "literal" per se
03:27
so sad
Indefinite articles are hard @Daminark
'tis true
@Daminark i was saying that a lot of people think that EVERYTHING in the bible MUST be taken at face value
no room for any interpretation
Someone was saying we should get a white-hat hacker to legislate stuff concerning encryption and stuff
even sensible shit like "they're rounding"
03:29
@Eric I dunno much about Christianity so I'd rather not weigh in on that too much
The other aspect of the Pi Bill is that it was not so much about "defining Pi" as proclaiming the successes and brilliance of a certain amateur mathematician
I mean, all numbers are finite, and can thus be considered to be 3
this isn't really about christianity and more about the social dynamics of religion in america
"The text of the bill consists of a series of mathematical claims (detailed below), followed by a recitation of Goodwin's previous accomplishments:
'... his solutions of the trisection of the angle, doubling the cube and quadrature of the circle having been already accepted as contributions to science by the American Mathematical Monthly ... And be it remembered that these noted problems had been long since given up by scientific bodies as unsolvable mysteries and above man's ability to comprehend.'"
@Akiva $\langle 3 \rangle = \mathbb{R}$ so like, yeah gg
03:30
esp in the south
@Eric I mean, if Christianity says that the Bible should be taken literally, believers are supposed to do precisely that
And, well, pseudo-experts getting press is another thing which hasn't gone away.
Lol wtf @Semiclassical
@Daminark "Christianity" means different things to different people so
Depends on which version of Christianity you mean, though.
Of course, that's something which literalists would also debate.
03:32
Mathematical nihilism: Everything rounds to zero
Or I mean, whichever sect of Christianity it is, the point stands that if a given sect dictates that the Bible is literal, then as far as they are concerned it's literal
"You might think there's different versions of Christianity, but really there's only one (which happens to be mine."
@Semi i have actually heard someone say that almost verbatim lol
there are certain groups that believe that anything that isn't specifically the king james version of the bible is profane
Are the different versions just different translations or are there actual differences?
If the latter, then does the King James version proclaim to be the verbatim word of God?
@Daminark my point was that people in america being christian literalists often has less to do with ideology than it does with social dynamics
03:34
Just read the original Hebrew, geez
btw have you read durkheim @Daminark
I think that the concept of 'different translations' wouldn't necessarily make sense to a religious literalist.
(Or JPS I guess)
he has interesting things to say about the sociology of religion
@Semi it often doesnt
But the different version of the Bible certainly do make a difference as far as how certain verses are understood and applied.
03:37
The reason I bring this up is that in Islam at least, the Quran is the verbatim word of God, and if anyone tries to change from that, it's automatically illegitimate, no questions asked. Similarly, the dominant sect also just dismisses the others.
@Daminark having read a few christian bibles in different languages they do frequently say different things
Well, keep in mind that the Quran was produced around 630 CE.
And it's because the others made claims that weren't backed by the Quran or by any verified authentic narrations of the prophet, so the sunni sect is just like "You guys are making shit up so what you say has no value"
With Christianity there's also the impact of the fall of the Roman empire and the first Schism to consider.
For this reason, I don't want to weigh in much on the dynamics of how other religions operate wrt their book
03:40
i think very few christians have read the new testament in its original form
With Islam, I think the continuity between the Quran of today and the Quran of 1400 years ago is a lot tighter than it is for Christianity.
Plus the Christian bible isn't just the New Testament, but also the Old Testament.
And I suspect that the latter is even more challenging to properly translate than the former.
probably
i spent a while translating the new testament with a reading group and it's fucking hard
The Old Testament was written in Hebrew, and the New in Assyriac, right?
Or was it Aramaic?
I think it's also worth noting that while there are definitely people who read the Bible very literally nowadays, historically I think that's not the dominant trend.
@Daminark greek
03:44
Wait what?
For one, appealing to the Bible in a literal way more-or-less presupposes that everyone involved is capable of accessing that text.
the consensus among biblical scholars is that the new testament was originally written in koine greek
I've never understood that. Do you not actually have the original?
@Daminark It's less surprising when you think about the titles of the epistles in the New Testament.
How do you not know what language it was in?
03:45
They were literally letters among various Christian communities that emerged after the death of Jesus. I'm pretty sure a lot of them were Greek.
@Akiva the oldest greek and aramaic copies of the "original" text are from around the same time
and the reason the consensus is greek is because the language of the oldest texts seem to presuppose the audience isnt hebrew usually
We know the Old Testament down to the letter. The only dispute is a single vowel mark somewhere in the middle 'cause they're not usually written, and the two options are pronounced the same in Modern Hebrew anyway
I mean to be fair I've read nothing of the New Testament so I wouldn't know, but I was thinking that Christ and the people of his time who transcribed it were more likely to speak something like the Syrian language or Hebrew
and like @Semi said most of the stuff is literally addressing greeks usually
03:47
Which I guess says something about the influence of Paul versus Peter.
I thought Jesus spoke Aramaic
@Daminark a looot of people in the region spoke greek
(which is very, very close to Hebrew)
Just a reminder about the composition of the New Testament
Yeah likewise with the Quran, people transcribed it immediately and it is known perfectly
03:49
@Akiva greek was actually a common language in Galilee around the time of jesus so it's not improbable that he also spoke greek in addition to aramaic
(there's basically no way he didn't speak aramaic though)
The four Gospels, the acts of the Apostles, 21 epistles, and the book of revelation
One thing I know about the Quran, I think I heard it's arranged in length order rather than chronological order? Or am I completely wrong @Dami
(What's an epistle)
So a lot of the New Testament is not "what did Jesus say" but "how was the Gospel spread".
@Akiva not exactly, I don't know how the order goes
The second "chapter" is the longest one
That's very different from the Quran, for instance, which is understood as the literal testimony of Muhammed.
03:54
And in general the first few ones minus the first are the longest ones, I think
therer were also a lot of debates over canonicity of various books in the christian bible but honestly i know way less about that
yeah.
lots of apocrypha
so much fanfic
literally dan brown makes a living off of jesus fanfic
03:56
I also wonder: In which language was the Quran recorded?
@Semi Arabic
I figured.
classical arabic is pretty
Compare that with Christianity, where the dominant translation for hundreds of years was Latin.
my personal bible was recorded in russian
03:57
it was like relatively recently when roman catholic masses stopped being served in latin
Wait they're not anymore @Eric?
no
usually not
Is it Italian?
That meant that, despite the dominant role of Christianity in medieval Europe, the number of people who could actually read the Bible was much much smaller.
no it's local language usually
03:58
If it's English-speakers doing Mass, it's usually in English now.
Oh you mean, worldwide
but like i think my local church didnt start doing english masses until i was like 3
In the Vatican I imagine they'd still do it in Latin, or maaaybe Italian
Back then the whole notion of "reading the Bible literally" was a bit silly.
in the vatican they do latin usually
03:59
@EricSilva My dad was raised Catholic, and the switch from Latin to English mass occured when he was a kid.
@Semi there was also the christianization of a shit load of pagan stories which complicates the average medieval europeans relationship with christianity
yeah that's when it happened to my parents in brazil
but the church around here was weird
Christianity was very Roman in that regard.
ive read a bunch of christian stories in old english and that shit is weird
the interpretations of christian stories were decidely un-latin
04:00
I actually own a Quran in my house somewhere. It's all in Arabic, I can't read it
I think my dad got it back when he was studying Arabic (he remembers essentially nothing of it now)
Lol, I can read Arabic but with great difficulty
there's actually a poem i read (dream of the rood i think in modern english) where the cross was treated as jesus' warrior-retainer (in the germanic warrior tradition) and jesus as a warrior king
there was a lot of verbal gymnastics that happened to deal with the fact that he was executed and didnt die in battle
but kind of like spiritual battle?
I have to wonder how much Islam and Christianity have varied historically, come to think of it, as far as how much reliance there was on literal interpretation.
it was fucking weird
With Christianity I know that the focus on literal interpretation becomes significant once people could actually start reading the Bible for themselves.
04:04
Judaism is kinda strange when it comes to literalness of interpretation
So it says "Don't boil a kid in its mother's milk" three times in the Bible
But I don't know about Islam. There's always been fundamentalist versions of it, I'm sure, but I don't know how that worked under the Ottoman Empire versus after.
so what people decided was each time should teach us something new
so essentially the law expands with each time the phrase appears, until it became "Don't eat dairy and meat in the same meal, and also if you have meat don't eat anything with milk in it for a few hours"
The dominant trend is and has been that at least in principle, insofar as it is possible, you take the direct interpretation
i think one of the key differences isnt just how islam treats the text but how it subverted local religion @Semi @Daminark
obviously i think this is probably because of the direct interpretation thing
but other things probably affect it to idk
In the meantime, something must have gotten messed up because while we're so strict about the whole mother's milk thing, we have absolutely no problem shmearing it with its mother's liver!
(I don't know how much liver is used in non-Jewish cuisines. It doesn't taste too bad)
04:07
So, a lot of the specifics in Islam didn't come while it was subverting the local religion
The Prophet lived in Mecca before revelation, and 13 years after
Also, to be clear, kid = baby goat
Historically, Christianity tended to absorb rather than uproot the local culture.
yeah that's what im getting at ^
Which I again would associate with it going hand-in-hand with the Roman Empire in such times.
0
Q: Since the implied derivative is a derivative different only for piecewise constant functions, is there one that is the same for periodic functions?

TyphonThe definition of the implied derivative is given below: $$I(f,g) = g(x)\lim_{h \to 0^+} \frac {f(x+h) - f(x)}{h} + (1-g(x))\lim_{h \to 0^-} \frac {f(x+h) - f(x)}{h}$$ where $f$ is the function being differentiated and $g$ is an arbitrary characteristic function to encapsule the fact that the i...

welp
my geometry phase is over
back to differential equations
04:09
Mecca was rather hostile to the religion, but at the time the revelations were much more... I dunno, spiritual somehow?
@Semi a lot of it is cause the roman empire didnt wanna deal with barbarian germanic peoples and making them mad
It was about the one-ness of God (in contrast to hundreds of idols floating around), Mohammed being the prophet, heaven and hell, so forth
@EricSilva Right. The way Rome tended to deal with subjects was to give them citizenship.
and make their heroes into saints
@Typhon Welcome to the math chat, we're discussing Abrahamic religions and the contrast between Christianity to Islam
04:10
Also I think (though I'm less sure about this so don't take me on it) that a good number of stories of older prophets were revealed around this time
@AkivaWeinberger no thanks
Also very occasionally we discuss some math
...
I do wonder how much of it comes down to how Christianity versus Islam interacted with the relevant Empires.
@AkivaWeinberger do you not know me?
04:11
Roman Empire for Christianity, of course.
I'm just making a joke on how non-mathy the chat is right now
Of course I know you
But I'm not sure it works for Islam re: the Ottoman Empire, for instance.
yeah ik nothing of the history of the ottoman empire basically
or anything near the near east after like really early antiquity
Is $[0,1]$ the union of countable many disjoint closed sets? There's an MSE post on this somewhere but I lost it
(Countably infinite)
In Medina the religion was welcomed, and that's when a lot of the restrictive rules were revealed. Those are extremely specific in most contexts, like there's a verse which just says how you're supposed to handle debt
04:13
@AkivaWeinberger fair enough. for a second there i thought maybe I was having another freaky dream where I go like a whole day of working on stuff only to wake up and find out it was a dream and that now I have to actually do in real life all over again. In other words... a passive-aggressive nightmare... they are the worst.
@LasVegasRaiders this discussion is less religion than it is history of religion tbh
I remember the answer is "no" but I forgot why
There was actually a dream I had last week where semiclasical was drunk, akiva spilt chemicals in their lab and the combination of the two of them being incoherent created hilarity.
My dreams tend to be like watching weird anime
At one point everyone freaked out caused akiva said they were going to post a bad photo only to have them post a picture of a baby donkey (kid)
because they threatened to send everyone [n]a kid photo
04:15
If I could remember what was going on, I'm pretty sure it'd make an interesting storyline...but nooope
even my dreams are filled with horrible puns
@Semi I'm not terribly familiar with the Ottoman empire, but I do know that the Safavid Persian empire was the main pioneer of the second sect of Islam, called "Shia"
oh and one time ted shifrin had a job in a kindergarden class.
I mean not pioneer per se
04:16
he said that "he was old too old for that sh**"
One thing we haven't even mentioned, of course, is the whole East versus West aspect of Christianity
and when he was asked further...
he meant that a kid literally threw poop at him
anyways...
fun stuff
The idea that sorta led to it was that there were 3 people considered "caliphs" (elected as religious/political leader for life), and the 4th was the Prophet's cousin
My dreams feel more creative than I do when I'm awake, which is always a bit disappointing
Now, some subset of people felt that the Prophet's cousin should've been given precedence, and there was some stuff that fell out of that, I think some notion of 12 saints, etc etc
But I think the Shia sect came to prominence only with the Safavids
I'd guess Ottomans probably didn't do too much to the religion
04:21
@Semiclassical nah. Opposite for me
if anything my dreams troll me
they once in a blue moon fool me into thinking im awake
then i do shit
XD
then I have to do shit twice
@Akiva i think the idea is that if $\{F_{i}\}$ is a countable disjoint collection of closed sets covering the interval you could find a descending sequence of intervals $I_{i}$ satisfying $I_{i} \cap F_{i} = \emptyset$. Then $\bigcap I_{i}$ is empty, but the unit interval is compact so it's not empty.
@Semiclassical it is amazing how many integrals I can solve trivially, yet wolfram alpha acts like they are confusing.
for instance
the integral of floor(x)^2
Yeah, not sure why it struggles with those.
It can do definite integration just fine for that, of course.
But symbolic integration of floor(x)^2 isn't something Mathematica is well-adapted for
it claims the integral of floor(x) is x*floor()
get on it stephen wolfram
04:34
^^^
Weirdly, Mathematica is happy with integrals like
Integrate[Floor[x]^2, {x, 0, t}, Assumptions -> 1 < t < 2]
It outputs -1+t for that which looks right.
And more generally it seems to work fine if I tell it which integers $t$ should fall between.
Huh, and actually it works fine if I replace that with something like 0<t<10 (it spits out a big piecewise function)
welll
because then it can break down into a finite sum of heavysides
but it cannot handle the big thing
It basically only knows how to do it in a brute-force way.
04:37
heh
I know the non-brute force way
;-)
However, the fact that it's not supported makes me suspect that the actual demand for such integration is pretty low.
i wouldn't say that
remember that difficulty with finding those continuous solutions?
regular integration yields the missing piecewise constant
Sure. I meant 'demand' in the sense of supply vs. demand.
i.e. if it's not supported after Mathematica has been around this long then probably it's because not a lot of people actually have to do those integrals.
but you miss my point
those integrals are useful for solving the ODEs
the ones you said had floor stuff
You mean ones with piecewise coefficients?
04:40
in practice people just need to numerically approximate solutions usually
yeah
which mathematica is very good at
@EricSilva ...
true, but an actual solution can be far more useful
Eh, depends.
well... it cannot be worse
04:41
actual solutions are frequently less useful to the people who need numerical solutions
it can
I mean, a lot of the time what I care about is the asymptotic behavior of the solution
and a functional solution tells you that by visual algebraic examination?
Not usually.
i mean not if the equation is complicated enough
I mean, suppose we're talking about some obscure special function
04:42
which in practice will happen more often than not
Sorting through the asymptotics of those is often not a trivial task.
fair enough
@Semi also depends on how much the person who needs the solutions knows
but still
@EricSilva Yeah.
04:43
if one cannot find the solution at all, and another can find a solution... why not?
And sometimes the exact arguments are complicated enough that it's easy to miss what they're telling you.
or rather, why not have a means to get a solution
Because a solution as such is usually not as important as understanding what that solution is doing.
again bc the actual solution might be more complicated than just getting numerics
it's like extra info you dont need
true
04:44
and numerics are frequently so blindingly fast nowadays
but being capable and not using it is a lot different than being generally incapable.
Do I really care if it's 1.61723 versus 1.61724? In some cases, maybe. But often times I don't care at all.
we might not care if we can prove the mean value theorem, but surely we care if it can be proven
numerical methods are so good now that you could basically get any precision you want really fast anyway
@Typhon sure but that's a different thing
true, but isn't the pursuit of actual solutions still worthwhile?
04:46
no one said it wasnt
or rather the pursuit of finding methods to find them
oh ok
just that mathematica is largely not built for that kind of people
i thought you were saying solutions is no longer useful
Also, if you're doing this in the context of an application to a specific problem, often times the extra info that the exact solution contains is just plain not trustworthy in the context of the motivating problem
XD
@Semiclassical heh
04:47
no just that most people using things like mathematica every day dont think they're useful
A model is never intended to capture everything about the problem
it's not the same thing really
i need to take a numerical analysis class tbh
im interested in knowing more about how that works
To be fair, what I find really interesting
is people using advanced ideas from exact solutions to motivate better numerical methods.
@Eric There's one this fall
@Daminark ik but im too busy
im taking at least rep theory and grad algebraic top and probably either algebraic geo or elliptic + parabolic pde
so ill be busy
04:49
Lol, makes sense
I could sorta consider doing it but it's lower on my priority list and I'm hoping to do a reading course so... likely not
Right now my hope is with Laci
oh that would be fucking sweet
Not sure on what yet, somewhat leaning toward this book I have on permutation groups by Mortimer and Dickson
The example I have in mind is people using Riemann-Hilbert ideas to develop efficient/stable ways to solve certain nonlinear ODEs.
04:51
But I've also considered going a bit deeper into graph theory
@Daminark you could also just ask him what would make an interesting reading course
and do that
he knows better
Oh, I was thinking that you were supposed to go with an idea already in mind. Yeah I'll prob do that then
i mean having taken a reading course that was basically "read this book" and one that was like "read a bunch of papers and talk to me about them", the second is better
By which I mostly mean stuff like this paper: math.uci.edu/~ttrogdon/publications/NNSD.pdf
On top of that I might actually do one this spring
04:53
@Semi that stuff is pretty cool honestly
brb
it is. Alas, I'm pretty well convinced I'll never properly appreciate it.
@Daminark with who
That, I'm more back and forth on
At least one aspect of it is pretty easy to understand, tho
04:55
If I think that taking atop outright would be too redundant, depending on who's teaching, but I still want to do a bit more before grad, I might try asking someone in that direction
The other side I'm thinking of is something number theory-related
In classical asymptotic analysis, one approach is to find an integral representation of a solution, and then do steepest-descent stuff
you mean the undergrad course in atop right? @Daminark
Yeah
ah i have 0 clue
The Riemann-Hilbert idea is in some sense a generalization of that, though not in an integral-representation way
04:57
@Daminark learn something you would never learn in a class here
But apparently it's a close enough comparison that there's a kind of 'nonlinear steepest descent' that can be applied to a Riemann-Hilbert problem in order to extract numerics/asymptotics.
So at least at the level of strategy it's very similar to the classical approach.
Of course, the devil is in the details...
ik nothing of classical asymptotic analysis
I mean, so if I do something atop related, ideally it'd be off the beaten path
At least wrt classes
So like, I dunno, k-theory
what's really the point of a reading course if it's not something you wouldnt learn in a class
I mean I never argued on that point
04:59
i wasnt arguing
i was just commenting
Oh, I mean, yeah

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