« first day (2336 days earlier)      last day (2607 days later) » 

8:22 AM
@BernardoMeurer: hi, how is the 2048 project going?
 
@JohnRennie Morning John :)
Moving works perfectly
I implemented some other features like q to quit and n for new game
Today I will focus on the undo functionality
 
I was thinking about how to handle the different move directions ...
The elegant way to do it is to use an iterator. You define a struct with member variables to hold the current position and the direction, and member functions to get the next cell.
Then you just pass the iterator to your collapse function.
However the sensible way to do it is copy data from the board into an int[5] array, pass that to the collapse function then copy it back. The copy to and from your tempoirary array depends on the direction but that's only a few lines of code.
 
:o
I had to struggle to login
fb login isn't working :/
had to turn on 4 computers hoping that my acc stayed loggedin
 
9:05 AM
constructing the one page of handwritten notes we're allowed on this statistical physics exam
even my undergrad course didn't allow this :o
 
writes down internal energy and enthalpy and grand canonical potential and stuff
but these are the things I already have memorized 🤔
 
how confident are you with what you've memorized?
 
completely
have had that memorized for something like half a decade now
better write down this ensemble stuff though 🤔
 
user228700
10:15 AM
> "Communication does not exist anymore"
 
user228700
Wtf...
 
I did not say that. I just think it doesn't exist in the way we think it does.
 
user228700
And what is that way?
 
i have already expressed my opinion about this before in here and don't want to recite it
and some neighboring messages
 
user228700
I'll check it out, thanks.
 
10:28 AM
maybe i'm just biased because i'm onto surreal and artsy things but to me nonlinear, avant garde stuff convey more meaning that linear stuff nowadays
 
Suprematism (Russian: Супремати́зм) is an art movement, focused on basic geometric forms, such as circles, squares, lines, and rectangles, painted in a limited range of colors. It was founded by Kazimir Malevich in Russia, around 1913, and announced in Malevich's 1915 exhibition, The Last Futurist Exhibition of Paintings 0.10, in St. Petersburg, where he, alongside 13 other artists, exhibited 36 works in a similar style. The term suprematism refers to an abstract art based upon "the supremacy of pure artistic feeling" rather than on visual depiction of objects. == Birth of the movement == Kazimir...
 
 
1 hour later…
11:40 AM
@GPhys did you do Rabi oscillations from sakurai?
 
googles Rabi oscillations
yes we did
 
12:23 PM
@GPhys I'm supposed to solve the equation for the $c(t)$ coefficients directly, but how am I supposed to guess the solution
google gives me an Ansatz that's magic
@yuggib Yep, I already checked that. Thanks for confirming.
Yosida is really anti-beginner
It seems to be written as a reference, not a textbook
 
12:39 PM
@0celouvsky and what is the ansatz?
 
@GPhys putting in tex, one sec
@GPhys the $/2$ is the magic
Without the $/2$ it's a reasonable Ansatz
but I don't have enough experience with coupled ODEs to guess it
 
solving the ODE? why?
 
what?
 
I think I just did it with algebra in the appropriate basis
 
so diagonalize the perturbation?
I don't see how you can get around doing an ODE, the perturbation is time-dependent
 
12:48 PM
one sec
 
@0celouvsky ewwwww
 
@AccidentalFourierTransform ?
 
$\mathrm i$
also, $\hbar=1$
 
$=\sqrt{-1}$
@AccidentalFourierTransform no.
> Among the topics included that are not usually covered in a textbook are a relatively recent development concerning equations with VMO coefficients and the study of parabolic equations with coefficients measurable only with respect to the time variable.
lol
Who studies these horrible PDE
 
right, if you set $\hbar=1$ you cannot integrate over $\hbar$ in the complex plane
 
12:53 PM
do people actually do that???
 
@0celouvsky you are exactly solving the system?
 
@GPhys yes, part b) is to then use perturbation theory
I'm just gonna go with this Ansatz, yolo
need to study for measure theory
 
for exactly solving it you do need to solve it like that yeah
@0celouvsky doesn't it work without the /2 anyway?
 
@GPhys it does but then the $a_j$ aren't real
they have another phase
the algebra is horrible
I'm just going to say that $/2$ makes them real
 
is that not a good enough reason?
 
1:03 PM
I guess, but I didn't come up with it lol
the prof said the problem is trivial, just plug what Sakurai gives back into the ODE
but Sakurai gives $|c_j|^2$, which kills the phases
 
me and professors often have different definitions of trivial
 
I think those are crucial for solving the ODEs
 
is trying to think of things to add to the one page of handwritten notes he's allowed to bring into stat phys midterm for some reason
 
dude, your matrix commutes with its exponential
 
@AccidentalFourierTransform exponential solutions only work for constant coefficient ODEs
 
1:06 PM
the solution is just $U(t)c$, where $U=\exp\int A(t)$
 
fuck that, how are you gonna compute the integral
in any case, I've written down the solution now
 
$\int e^{at}=\frac{1}{a}e^{at}$
 
@AccidentalFourierTransform really??
 
$e^{ax}$ is an eigenfunction of the integral operator
 
i think so, yeah
you can also write $\int e^{at}=e^{a\partial}\delta(t)$
or some bullshit like that
 
1:08 PM
exponential series expansion of dirac deltas?
but isn't the powers of dirac delta not well defined since distributions cannot be multiplied together without a test function?
 
@AccidentalFourierTransform ...
@Secret he's referencing a stupid physicist paper
bad math by physicist standards
 
I really think physicists need to be a bit more careful on how they use distributions. It is easy to derive wrong results when misusing distributions
 
@Secret I'm meaning to ask a question on the main site where that has actually caused issues
most of the time physicists just carry on with completely wrong things and it works out fine
 
there was a very simple derivation of $\frac12=\frac13$ using $\delta(x)$ and $\Theta(x)$ that seems totally legit
 
lol
 
1:12 PM
Ill try to find it
 
In computational chemist terms, I suspect that most of the time stuff they did that works out might be because of error cancellations
 
@JohnRennie It's on GH already, you can go see how I did it
 
that is, you have two errors of similar magnitude, but opposite in some way, their effects then cancel out in the overall calculation
 
@BernardoMeurer I need more books, right
 
1:19 PM
too bad for you I'm getting a book today
I got it used, don't worry
pseudodifferential operators for BVPs :D
 
Meanwhile I need to revise a bit of behaviorial economics in order to understand how active choice can nudge them to increase vaccine usage
It's a good thing though, nudging is indeed very powerful
 
1:37 PM
"9/11 was an inside job" - ACM
 
Historic recurrence is the repetition of similar events in history. The concept of historic recurrence has variously been applied to the overall history of the world (e.g., to the rises and falls of empires), to repetitive patterns in the history of a given polity, and to any two specific events which bear a striking similarity. Hypothetically, in the extreme, the concept of historic recurrence assumes the form of the Doctrine of Eternal Recurrence, which has been written about in various forms since antiquity and was described in the 19th century by Heinrich Heine and Friedrich Nietzsche....
Unsolved question in history: Why does history repeats itself and we failed to learn fully from past mistakes
 
you are not the first one to wonder that
one may say that that question repeats itself over and over
 
I wonder, if our whole reality is actually a groundhog day loop with a period of roughly a few millennia
 
Eternal return (also known as "eternal recurrence") is a concept that the universe and all existence and energy has been recurring, and will continue to recur, in a self-similar form an infinite number of times across infinite time or space. The concept is found in Indian philosophy and in ancient Egypt and was subsequently taken up by the Pythagoreans and Stoics. With the decline of antiquity and the spread of Christianity, the concept fell into disuse in the Western world, with the exception of Friedrich Nietzsche, who connected the thought to many of his other concepts, including amor fati....
any latex expert around?
 
But if that is true, entropy should have been maximised ages ago (since everything is basically stuck in a loop). If it is not, it means the whole universe is a far from equlibrium system, then we could ask, why are those dissipative structures tend to be periodic
(perhaps I should not hastly generalise nonequlibrium thermodynamics to the whole universe without further justification)
 
1:45 PM
However, an even more interesting question is: If the cycle can be broken, what will happen, do we just settle into a new equlibrium
 
looks at time
 
0.5-1.5 hr before the main h barers pop into the chat
 
The only things I will want on the note sheet to take into exam are exactly the things I can't think of anyway
 
@Secret who are those?
I'm here
I'm the heart and soul of this place
 
1:57 PM
so am i
 
you're just the main trol
 
You guys are. But there are also others like kaumudi and acuriousmind and johnrennie and slereah
 
ACM ain't shit
@Slereah is cool
Cow smoothie is too involved with the JEE for my liking
 
Slereah's activity is strongly correlated to 0ceo's activity
 
JR has a sheep girlfriend, I can only trust him so much
 
1:59 PM
whats JEE?
 
JEEhad = devil worshiping
 
Also whenever my sydney clock strikes 1:00+, the chat is suddenly loaded with converations
sorry typo: gradually
 
how do I get the graph to start at 4 E14 Hz?
 
easy: dont use excel (or whatever shitty software you are using)
 
You should be able to click the x axis and go to axis options and set the min there
 
2:02 PM
@AccidentalFourierTransform don't say anything if you're not being productive
 
Is downvoting an answer just because it adds additional content after answering a question justified? -,-
 
NB: Chemists love to use excel for most of their data analysis. It is only when they need something of higher maths level and for generating publishable graphs they will use python scripts, matlab, mathematica and so on
 
@Secret yep, thanks
@AccidentalFourierTransform because you think $\delta(\mathrm i\partial)$ is a legitimate operator
 
@JohnRennie Going to replace all my statically allocated stuff with calloc
 
2:05 PM
I would never ever write that
 
PITA but worth it
 
$\delta(i\partial)$, on the other hand, is mostly ok for me
 
I will allow me to loop over columns and stuff
 
look at that beauty
 
2:13 PM
dude that looks awful
 
I said to shut up unless you have constructive comments
 
Every Microsoft-produced scientific content looks bad
 
second order and opposite side does not look significantly different. Does it means the opposite side have mainly second order effects?
 
Even people at microsoft research team use other tools in scientific papers
 
@Secret I don't know
I think second order and opposite side give better values for $h$, so those are probably correct
I don't know why first order is so bad, we did the experiment three times
it's like a clean 100% error
@yuggib no?
 
2:17 PM
The thing that I will say in praise of excel: even very weak students can be taught to use it.
 
such as me
on the other hand, I have a really long table that I can't seem to fit in my lab report in portrait mode
 
My department teaches students in general chemistry to use it for labs, and they remember how when they get to intro physics. Some of them are even able to interpret the R^2 value the fitter provides in a rough and ready way, which is great.
Every last thing about beyond that is awful, of course, but they can use it.
 
@0celouvsky you told me to shut up unless I have something productive to say. You said nothing about being constructive.
 
@AccidentalFourierTransform ಠ_ಠ
 
@BernardoMeurer we are discussing proprietary software. Wont you say anything?
 
2:19 PM
@0celouvsky ಠ_ಠ
 
@ACuriousMind ?
WORD
JUST LET ME RESIZE THE DAMN TABLE
 
Latex: don't mind about a table and get it beautifully looking
 
@0celouvsky dude, use Latex
 
@yuggib lab reports will only be graded if done in word and excel
 
2:22 PM
holy fuck this table
 
@0celouvsky what
that makes zero sense
 
Much of practical LaTeX is "Wait, which package was it that would do the right thing with that table, again?"
 
@0celouvsky T__T
 
I can't figure this out
the table is stuck off of the page
 
Every regular LaTeX user has their own collection of 'standard' packages.
 
2:23 PM
I can't bring the right side of the table onto the page
what do?
 
@0celouvsky You're using too many horizontal and vertical lines in that table, btw
 
@dmckee yes, but unlikely office everybody can have all the packages for free
 
what does that even mean?
 
oh please
the table is fine
how do I get the right side onto the page
 
2:24 PM
Indeed. All praise the mighty and generous CTAN!
 
@0celouvsky It means that professional table-making people (think newspapers) say it's bad for information processing
 
I'm not doing professional grade table making
I'm making a lab report to turn in by 2:30 PM
 
Which is no reason to do "not ever amateur grade" table making.
 
^
 
I just need this damn table to fit on the page
 
@dmckee then I would fail your class
but luckily I don't give a shit about that
 
"Professional table-making people" - are the table-making people professionals or are they making professional tables?
 
I just need to fit the table on the page
 
@ACuriousMind the former
 
And what does a non-professional table do for a living?
 
2:27 PM
@0celouvsky I don't actually grade students on typography or page layout. Just physics, communication and technical writing.
Which is more than enough.
 
Got it!
I made the sizing really small in Excel, then copied it over
 
you hand in a low quality report, you are sending a message about yourself
you a low quality bich
 
I am a basic bitch, I know
I love it
lol it's broken now
I can't make it larger
 
10 PRINT "I am your B***H."
20 GOTO 10
Uhg. The things my apple ][+ did to me.
I've never really recovered.
 
2:29 PM
Maybe there is a support group.
 
hahaha
 
> copying excel data into tex
YOU'RE ASKING FOR TROUBLE :D
 
"use latex ffs", whispered AFT
 
I'm copying it into word!
@AccidentalFourierTransform I can't take a zero on my lab reports, sorry
 
oh, whaat?
> using word for assignments
 
2:30 PM
@Danu I do all my math/physics in word
 
@Danu frankly,
12
A: Comprehensive list of tools that simplify the generation of LaTeX tables

E.P.Direct spreadsheet editing I've been handling data tables from Excel into LaTeX for lab reports for some while and I have tried several tools. I would like to make the case that unless you consistently require formatting of the same style, then quite often the simplest answer is to direct copy-p...

easiest way all told
 
9 mins ago, by 0celouvsky
@yuggib lab reports will only be graded if done in word and excel
 
@Danu that should read
> using words for assignments
perfectly reasonable practice
 
@ACuriousMind Oh god
time to burn the university down
 
wtf is this
 
2:33 PM
Excel 1 - 0celouvsky 0
 
I did it.
::throws down bloody sword::
 
I'm not sure if this question suits this forum but worth a try . I have searched a lot for the physics behind Coaxial feeds in antennas to launch EM waves and couldn't find anything apart from just the final equations . Does anyone know any sources/links ?
 
Would have been quicker to just make the table in word instead of copying it
 
@Aakusti what is it you actually need?
 
2:35 PM
i need a paper or link to a book to understand how they work
 
@Aakusti how what works? the join between a coaxial feed and an antenna?
 
now it's time to put the table in Word
 
yes
 
oh god this is gonna hurt
 
@Aakusti not sure this is the best place to ask for that. Sounds like ee.se material.
 
2:36 PM
okay , thank you
 
I mean, you can ask for it
 
done
 
particularly if you're really interested in first-principles
 
30 mins gone
time to actually write the lab report now
 
but I suspect it'll be better received by the engineers
 
2:37 PM
oh nooooo I have to do the percent error table
 
the stuff in electronics.stackexchange.com/questions/tagged/coax+antenna might be a bit too practical
but at least they have both a coax and an antenna tag
Anyways, @ACuriousMind, I had a question for you
on symmetries and generators and stuff
 
and stuff
 
I love stuff, shoot
 
units of action are just J*s, right?
 
yeah
 
2:43 PM
@ACuriousMind for the classical electromagnetic field, you expect the statement "the linear momentum generates spatial translations" to make sense on some level, right?
 
@0celouvsky the action is dimensionless
 
how does that actually work?
 
through Poisson brackets
just like in point-particle mechanics
$$E(x+a)=E(x)+\{a\cdot P,E(x)\}+\mathcal O(a^2)$$
 
^what AFT said
 
I'm always weary when physicists taylor expand
 
2:44 PM
@0celouvsky weary?
 
wary?
I'm not a native speaker
$\delta(x)=\infty +\delta'(0)x+\frac{1}{2}\delta''(0)x^2+\cdots$
 
@AccidentalFourierTransform OK, next question. Within that setting, how are plane waves special?
@0celouvsky you probably meant wary
 
^
I'm weary
(of Taylor expansions)
 
@AccidentalFourierTransform i.e., in what sense do plane waves "have definite momentum"?
 
@EmilioPisanty They're eigenstates of the operator $\{p,-\}$
 
2:47 PM
a plane wave $E(x)\propto \mathrm e^{ikx}$ satisfies $\{P,E\}=ikE$, so they are "eigenvectors" of $P$ I guess
^^
 
OK, so here's the thing. That works on the level of complex amplitudes, for monochromatic fields.
What if my field is not necessarily monochromatic, and I don't want to talk about complex amplitudes, and instead I want to keep it to the real fields $\mathbf E(\mathbf r,t)$?
 
then you've got photons with all sorts of $\hbar\omega$s flying around, why should it have definite momentum?
 
As an example, say I want something that's a plane wave along $k_z$ but without any restrictions on its behaviour on $x$, $y$
 
Then...you can have that, but that's nothing "special", I think
 
you cant do whatever you want to $k_z$ while keeping $x,y$ unrestricted, because of e.g. Gauss equation
 
2:50 PM
@0celouvsky because I can have something that has definite translation symmetry about one dimension without imposing any additional conditions
 
@EmilioPisanty I don't think translation symmetry implies that the momentum is sharply peaked in momentum space
 
@AccidentalFourierTransform there's the transversality condition, sure, but that only makes a small dent in the degrees of freedom I have available
 
but a plane wave is not physical anyway so who knows
 
Im not sure thats "small". It is a constraint for each point in space. You cannot have eg focusing in one direction without causing the opposite effect in the other two directions
but anyway, thats not really relevant right now
so nevermind
 
2:54 PM
@AccidentalFourierTransform if it really bothers you, have it polarized along $y$ with no dependence on $y$, but unspecified dependence on $x$
 
Okay, so you have this field configuration - what's the question?
 
So here's one way I can make sense of that setting - for a classical plane wave, spatial translations (along the defined direction) are equivalent to time translations.
I mean, that's what $\hat T_a f = e^{ika} f$ really means, right?
 
>putting hats on operators
 
in terms of the physical fields
 
for any wave, a spatial translation is equivalent to a time translation
 
2:57 PM
so, I guess the question is, can that be brought into Poisson-bracket language?
 
no need for it to be plane
 
@AccidentalFourierTransform not true
cf. Bessel standing waves
 
a wave is $f(x-vt)$
lol right, I forgot about the boundaries
 
$J_0(kr)\cos(\omega t)$ is also a wave
 
I was thinking of infinite volume, the d'Alembert solution
 

« first day (2336 days earlier)      last day (2607 days later) »