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Leonhard Euler
Leonhard Euler
7:00 AM
@Mystic, Test=examination
 
Anonymous
You should ask your school teacher what he/she expects for an answer
 
John Rennie
John Rennie
@LeonhardEuler it's an odd question and I don't think it has any sensible answer
 
Leonhard Euler
Leonhard Euler
@Mystic, the school has been closed already . And we have holiday for preparaing for exams so
 
Anonymous
@LeonhardEuler Which board are you in ?
 
Leonhard Euler
Leonhard Euler
@JohnRennie, ??
@Mystic, Secondary Education Examination Board
 
Anonymous
7:03 AM
@LeonhardEuler Hmm, so this should do ncert.nic.in/ncerts/l/jesc102.pdf
 
Anonymous
Look up the salts section in the pdf
 
Anonymous
I am so fed up of the rote memorization based questions these board exams ask :P
 
Leonhard Euler
Leonhard Euler
Ok.
@JohnRennie, @Mystic, During electrolysis of water,hydrogen is collected at cathode and oxygen at anode, why?
 
Anonymous
Phew man. Use GOOGLE!!!
 
Leonhard Euler
Leonhard Euler
There is no answer for it in google.
 
John Rennie
John Rennie
7:08 AM
@LeonhardEuler Do you understand the basic principle of electrolysis?
 
Leonhard Euler
Leonhard Euler
@JohnRennie, means?
 
Anonymous
@LeonhardEuler That's not possible. You clearly haven't searched.
 
John Rennie
John Rennie
@LeonhardEuler Do you understand what happens in the process of electrolysis?
 
Leonhard Euler
Leonhard Euler
@JohnRennie, I didn't read this under elwctrolysis and ionization. I read it under chemical effect of electric current
 
John Rennie
John Rennie
@LeonhardEuler OK, so do you understand what happens in the process of electrolysis?
 
Leonhard Euler
Leonhard Euler
7:13 AM
@JohnRennie, yeah.
 
John Rennie
John Rennie
@LeonhardEuler OK, so tell me what happens in the electrolysis of water.
 
Leonhard Euler
Leonhard Euler
@JohnRennie, h2o decomposes into H^+ and OH^- ions
 
John Rennie
John Rennie
Yes. So what happens to the H+ ions?
 
Leonhard Euler
Leonhard Euler
H+ ions move to cathode,@JohnRennie
 
John Rennie
John Rennie
Correct. And what happens to them there?
 
Leonhard Euler
Leonhard Euler
7:19 AM
@JohnRennie, h+ ions gain one electron and gets converted into hydrogen atom
 
John Rennie
John Rennie
Correct. You asked During electrolysis of water,hydrogen is collected at cathode and oxygen at anode, why?, so can you now explain why hydrogen gas is produced at the cathode?
 
Leonhard Euler
Leonhard Euler
@JohnRennie, not still
@JohnRennie, I explained you the reaction that takes place at cathode
 
John Rennie
John Rennie
Well, what do you think happens to the hydrogen atoms produced at the cathode?
 
Leonhard Euler
Leonhard Euler
@JohnRennie, but not why hydrogen is collected at cathode
@JohnRennie, H+H---->H2
 
John Rennie
John Rennie
Correct. So H2 is produced at the cathode, and your question asked about hydrogen is collected at cathode.
So you've answered your question.
 
Leonhard Euler
Leonhard Euler
7:25 AM
@JohnRennie, so why is hydrogen collected at cathode, not at anode?
 
John Rennie
John Rennie
Ah. That's because in electrolytic cells the definition of cathode and anode are different from in batteries. The cathode is the negative electrode i.e. electrons are produced at the cathode and flow through the cell towards the anode.
The anode is the positive electrode.
It is a slightly confusing terminology and you aren't the first to be mislead by it.
 
Leonhard Euler
Leonhard Euler
@JohnRennie, actually my teacher too could not answer this ques.
 
Anonymous
Just remember that in electrolysis "cat"hode attracts the "cat"ions (positive ions) while "an"ode attracts "an"ions (negatively charged ions). @LeonhardEuler
 
Anonymous
@LeonhardEuler Haww? =P That's funny
 
Leonhard Euler
Leonhard Euler
@Mystic, since H+ ions are positive they go to anode, yeah?
 
Anonymous
7:31 AM
@LeonhardEuler No. They are cations.
 
Anonymous
They go to cathode.
 
Leonhard Euler
Leonhard Euler
What are cations? --> positively charged ions,aren't they?
 
Anonymous
@LeonhardEuler H+ is a cation (+ve charged ion) which goes to cathode.
 
Anonymous
@LeonhardEuler Yes.
 
John Rennie
John Rennie
7:55 AM
@LeonhardEuler yes, but remember that in an electrolytic cell (and only in an electrolytic cell) the cathode is the negative electrode. So cations like H+ are attracted to the negative cathode.
 
 
1 hour later…
Anonymous
9:06 AM
Does anyone know the answer to this : physics.stackexchange.com/questions/316728/…
 
Anonymous
0
Q: Should we consider the temperature of the cavity's wall as surrounding temperature when a black body is kept inside it?

MysticA black body solid sphere is inside a cavity with vacuum inside. The walls of the cavity are maintained at a certain temperature say $T_o$ ($T_o < T_{\text{solid}}$). So which would be the correct (more appropriate) equation to write for the spherical black body? $$\frac{dQ}{dt} = \sigma A (T^4...

thermodynamics radiation
 
Anonymous
I actually saw two similar problems today. One considered the $T_o$ as surrounding temperature and another did not consider $T_o$ as surrounding temperature. So I am pretty confused. Although the other problem described a situation like a solid black body (initially at 327 degrees Celsius) is suspended inside a box whose temperature is maintained at 27 degrees Celsius...
 
ZeroTheHero
ZeroTheHero
@DavidZ Yes I had done this, but thought there was a mod here (Ocelo7).
 
Anonymous
@ZeroTheHero Ocelo7 isn't a mod.
 
Anonymous
Mods have a diamond symbol on their profile.
 
skill patrol
skill patrol
10:17 AM
...and the color of the letters of their usernames are light blue.
 
Leonhard Euler
Leonhard Euler
Hello
 
user400188
user400188
anyone know the latex for a particulrly long title?
I have a tile for a document but it wont show up. I suspect this is becuase it will not fit in a single line.
 
user400188
user400188
10:52 AM
Never mind. I figured it out
 
Leonhard Euler
Leonhard Euler
11:19 AM
Hello @Mystic
 
Anonymous
hi
 
Leonhard Euler
Leonhard Euler
@Mystic, Newly made quilt is warmer than old one. Why?
 
Anonymous
oh my god :(
 
Leonhard Euler
Leonhard Euler
@Mystic, why?
 
Anonymous
you really need to learn to use google
 
skill patrol
skill patrol
11:22 AM
Tighter stitches.
 
Anonymous
just search it and see what comes up
 
skill patrol
skill patrol
^
 
Anonymous
these are very very very standard questions
 
Leonhard Euler
Leonhard Euler
@Mystic, ok
 
Anonymous
 
Leonhard Euler
Leonhard Euler
11:24 AM
@Mystic, earth has gravity to pull objects towards it but an aeroplane flies in the sky. Give reasons
 
Anonymous
I can see atleast 20 links which contain the answers.
 
Leonhard Euler
Leonhard Euler
@Mystic, Yeah. I got
 
Anonymous
@LeonhardEuler I am not going to answer such questions unless you tell me what you have got after google search and what you cannot understand even after reading up the articles from google.
 
Anonymous
 
Anonymous
This link has the explanation.
 
Anonymous
11:31 AM
Obviously it won't fall down because there will be an upward lift too!
 
Leonhard Euler
Leonhard Euler
@Mystic, the article talks about lift and drag, (::::)??
I couldn't get
 
Anonymous
Yeah, a lift and drag forces act on a plane too.
 
Anonymous
Not only gravity acts on them.
 
Leonhard Euler
Leonhard Euler
@Mystic, what are those forces? I haven't read them
 
Anonymous
If only gravity was acting then it would have "fallen" down.
 
Anonymous
11:38 AM
@LeonhardEuler Then go and read about them from your books or from the net.
 
Leonhard Euler
Leonhard Euler
@Mystic, I don't have those in my book
 
Anonymous
Then read it from Wikipedia.
 
Leonhard Euler
Leonhard Euler
Hello @Kenshin
 
Kenshin
Kenshin
12:01 PM
Hello
 
Alex
Alex
12:12 PM
Quick QM question. Does $| \psi(t) \rangle = \hat{U}(t,t_0)| \psi(t_0) \rangle = e^{-\frac{i(t-t_0) \hat{H}}{\hbar}}| \psi(t_0) \rangle$ hold only if $| \psi(t_0) \rangle$ is a energy eigenstate or does this hold generally for any solution $| \psi(t_0) \rangle$ of the time dependent Schrodinger equation?
 
Bernardo Meurer
Bernardo Meurer
@Alex Sorry, I only answer questions written on Comic Sans
 
Slereah
Slereah
@0celo7 wot
 
Anonymous
@BernardoMeurer Written "on" ? =P
 
yuggib
yuggib
@Alex It holds for any initial datum $\psi_0$
 
Bernardo Meurer
Bernardo Meurer
@Mystic Yes. You must scribe your question on the individual characters of the font using Photoshop
 
yuggib
yuggib
12:20 PM
(provided that, as usual, $H$ is a self-adjoint operator)
 
Bernardo Meurer
Bernardo Meurer
and they must be inscribed using Comic Sans of course
 
Anonymous
@BernardoMeurer mwahaha =D I wonder if you get your examination questions written on Comic Sans!
 
Alex
Alex
@yuggib Okay thanks.
 
Bernardo Meurer
Bernardo Meurer
@Mystic I write my lab reports in comic sans for the profs I don't like
 
Anonymous
Comic Sans is still legible. My Vernacular handwriting is illegible!
 
Sir Cumference
Sir Cumference
12:44 PM
@BernardoMeurer Comic sans gets undue hate
I happen to like it
 
Anonymous
@SirCumference Me too 8)
 
Anonymous
It is not suitable for official documents perhaps
 
Sir Cumference
Sir Cumference
It's like chalkboard writing :)
 
Anonymous
But I like it in books ! And in comics too!
 
Anonymous
@SirCumference Exactly!
 
Sir Cumference
Sir Cumference
12:54 PM
@Mystic high fives
 
jyotishraj thoudam
jyotishraj thoudam
Hello guys
 
Secret
Secret
O cool, so memory correlations DOES have an official term:
Free association (psychology)
Free association is a technique used in psychoanalysis (and also in psychodynamic theory) which was originally devised by Sigmund Freud out of the hypnotic method of his mentor and colleague, Josef Breuer. Freud described it as such: "The importance of free association is that the patients spoke for themselves, rather than repeating the ideas of the analyst; they work through their own material, rather than parroting another's suggestions". == Origins == Freud developed the technique as an alternative to hypnosis, because he perceived the latter as subjected to more fallibility, and becau...
Pretty sure vzn and Bernardo will be interested in this as they talked abour Freud and Jung alot
Unlike what is said here, we ADHDs don't need a therapist to initiate free association, we free associate all the time
 
0celo7
0celo7
1:20 PM
@SirCumference Of course you do
@Alex Any solution. For an eigenstate you'd replace $H$ by $E_\psi$.
 
Secret
Secret
My rotten joke
New category of hazard
Document hazard
Any non public peer reviewed journals printout and its associated electronic copies must be treated with caution.
All unused printouts must be shredded before disposal to avoid leakage of research material to the environment which can lead to an academic misconduct
All unused electronic copies must be destroyed after use
 
FrancescoS
FrancescoS
1:56 PM
Hi guys! Why does an Hamiltonian have discrete spectrum in a finite volume?
 
0celo7
0celo7
@FrancescoS It's probably automatically a compact operator.
Your underlying measure space will have finite measure
 
yuggib
yuggib
@FrancescoS Confined particles, i.e. operators of the form $-\Delta +V$, with $\lim_{\lvert x\rvert\to\infty}V(x)=\infty$ have automatically discrete spectrum (i.e. compact resolvent)
@0celo7 there are unbounded operators "in a finite volume", so it is not true that the operator is automatically compact
 
FrancescoS
FrancescoS
@yuggib Thanks for your answer. Can you give me some references please? :)
 
Alex
Alex
2:11 PM
@yuggib Do you maybe know why the transition probability given as $$P_{if}(t) = |\langle \psi_f| \hat{U}_{I}(t,t_i)| \psi_i \rangle|^2,$$ where $| \psi_i \rangle$ and $| \psi_f \rangle$ are the unperturbed eigenstates and $\hat{U}_{I}(t,t_i) = e^{\frac{i t \hat{H}_0}{\hbar}}\hat{U}(t, t_i)e^{-\frac{i \hat{H}_0}{\hbar}}$, I'm assuming it's related to the postulate that the porobability of being in the unperturbed state $|\psi_n \rangle$ is given by $|c_n|^2 = |\langle \psi_n| \psi_n \rangle|^2$?
 
yuggib
yuggib
@FrancescoS Reed-Simon, vol.4 ; theorem XIII.67
@Alex it looks a lot like scattering theory (S-matrix), but there should be limits $t\to\infty$ and $t_i\to -\infty$ or something like that...
 
ACuriousMind
ACuriousMind
@Alex Looks like standard Born rule to me: $U_I\lvert \psi_i\rangle$ is just the time-evolved state, and taking the overlap with the final state $\lvert \psi_f\rangle$ gives the probability amplitude to detect it in the final state.
 
yuggib
yuggib
@ACuriousMind it is the evolution in the interaction representation
not the standard evolution
and the interaction representation is usually used in scattering theory
 
Alex
Alex
@ACuriousMind What is the general form of the Born rule that you are quoting?
 
ACuriousMind
ACuriousMind
@yuggib Sure, but need not be scattering, could just be ordinary perturbation. Still, the expression is just the overlap of the time-evolved initial state with the final state, no?
 
Alex
Alex
2:27 PM
This is just basic perturbation theory, no scattering mentioned in the text thus far.
 
ACuriousMind
ACuriousMind
@Alex Given two states $\lvert \psi\rangle,\lvert \phi\rangle$, the probability to measure one as the other is $\lvert \langle \phi\vert\psi\rangle\rvert^2$
 
yuggib
yuggib
@ACuriousMind not exactly, the factors $e^{\pm itH_0}$ are not there in the overlap...
 
ACuriousMind
ACuriousMind
@yuggib States in the interaction picture evolve implictly with $H_0$, no?
 
yuggib
yuggib
@ACuriousMind As it is written, it is the probability that the (full) time-evolution of $e^{-it H_0}\psi_i$ is detected in $e^{-it H_0}\psi_f$
 
Alex
Alex
@ACuriousMind That's really what I thought it was but I have only been exposed to the form of the Born Rule where $|\langle \psi_n
\psi|^2$ gives the probability of being in state $| \psi_n \rangle$.
 
ACuriousMind
ACuriousMind
2:34 PM
@yuggib Well, what I meant is that the $\psi_i$ here, if they are interaction-picture states, already contain an evolution by $H_0$, so when going to the Heisenberg picture we would really be left just with $\langle \psi_f \lvert U(t)\vert \psi_i\rangle$ since the $H_0$ factors cancel out
Maybe they're not interaction picture states, though, not enough information to decide
 
yuggib
yuggib
Of course if you define $\psi_i = e^{it H_0}\phi_i$, and $\psi_f=e^{it H_0}\phi_f$, then $P_{if}(t)=\langle \phi_f, U(t)\phi_i\rangle$
but then you are taking the transition amplitude with respect to two different states ;-)
 
0celo7
0celo7
@yuggib you never gave me a reference for the elliptic Neumann problem
 
yuggib
yuggib
@0celo7 I gave you csato etc. book, I don't know anything else
maybe you can find something in Hörmander as well
 
Alex
Alex
@yuggib I understand Acuriosminds answer so let's agree that it is correct :)
@yuggib Thanks for the assistance.
 
ACuriousMind
ACuriousMind
2:52 PM
@0celo7 Ew :P
 
Alex
Alex
@ACuriousMind It states further that the transition probability can be given in terms of expansion coefficients as $$P_{if}(t) = |c^{(0)}_{f}(t) + c^{(0)}_{f}(t)+...|^2.$$ Not sure if that makes things clearer in your discussion.
 
yuggib
yuggib
@0celo7 linear operators are indeed linear objects...
 
Secret
Secret
> "While this question may be related to philosophy or occur in a philosophical context, the question itself doesn't seem to be about philosophy, and is therefore not a good fit for our site."
how is this not epistemology and the metaphysics of belief?
 
DHMO
DHMO
@Secret you might want to attend to the conversation in the math chatroom where I'm asking Alessandro about the intuition of an open set...
 
Secret
Secret
DHMO: Ok
 
DHMO
DHMO
3:01 PM
@Secret but the conversation is not quite fruitful yet
 
0celo7
0celo7
@yuggib Hörmander volume 3 looks amazing
Volume 2 not so much
@ACuriousMind Given an affine hyperplane $H\subset \Bbb R^n$, how might I go about constructing a linear functional with $[f=1]=H$?
We did this last semester in analysis but it's linear algebra so I forgot
Assume $0\notin H$, of course.
 
Secret
Secret
My view on metaphysics: Everything are objects, including nonexistence and nothingness
 
ACuriousMind
ACuriousMind
@0celo7 Take its displacement $a$ from the origin and the projector $P$ onto the subspace it forms when shifted to the origin. $\frac{\langle v-a, P(v-a)\rangle}{\langle v-a,v-a\rangle}$ should do the trick.
Oh, wait, that's not exactly linear
 
0celo7
0celo7
@ACuriousMind I know how to do it assuming $\Bbb R^n=H\oplus \Bbb Rv$.
Is there a way to shift that linear functional away from $0$?
 
ACuriousMind
ACuriousMind
3:17 PM
Wait, if $0\in H$, then you cannot have a linear functional doing what you want, since linear maps must map 0 to 0
 
0celo7
0celo7
Sorry, I meant that if $0\in H$, then I have a functional $g$ s.t. $\ker g=H$.
 
yuggib
yuggib
@0celo7 yeah, Chapter XVIII is essentially the foundation of pseudodifferential calculus, i.e. of what I do... ;-P
 
0celo7
0celo7
@yuggib I want Reed and Simon too. How is one supposed to have time for all these great books?
 
yuggib
yuggib
@0celo7 well, you read some, and use some as a reference
Reed Simon 1 is not so useful if you have Kato, Yosida, (and maybe dunford schwartz or the alike)
 
0celo7
0celo7
@ACuriousMind So I can take $H\not\ni 0$, and shift it to the origin, to get $K=H-x$
Then I have $g$ a linear functional with $\ker g=K$
So that's $\ker g=H-x$
$x\in H$, we can assume $g(x)=1$
I think that's it.
 
ACuriousMind
ACuriousMind
3:22 PM
Yeah, that works
 
0celo7
0celo7
If $v\in H$, then $v=x+y$, where $y\in K$.
So $g(v)=g(x)+g(y)=1+0=1$.
Ah, that should work in any NVS. Nice.
 
0celo7
0celo7
3:35 PM
@ACuriousMind So how about defining $g$ implicitly by $v=k+f(v)x$, where $k=P_K v$
We know that $x\notin K$
So project $v$ onto $k$, subtract that from $v$, and you have to get a point in $\Bbb Rx$
so let $f(v)$ be the number you need to scale by to get $x$
 
Slereah
Slereah
3:51 PM
The papers I was talking about
 
0celo7
0celo7
4:05 PM
Crap I can't find my professor
I won't get paid!!
I don't have money for the springer sale
@yuggib Is RS2 better than Hormander 1?
@Slereah can you recover the manifold somehow?
it would be neat if just assuming causality implies a manifold...although that's highly unlikely
 
Slereah
Slereah
Just from causal relations, I don't know
 
0celo7
0celo7
@yuggib Is it normal that Kato defines the dual as antilinear functionals?
 
Slereah
Slereah
I don't think you can define an open set just with those relations
 
0celo7
0celo7
@Slereah causally open?
one can define certain topologies via sequences
 
Slereah
Slereah
Although...
$I^+$ is an open cover
 
0celo7
0celo7
4:11 PM
@Slereah Do you know Alexandroff's theorem?
 
Slereah
Slereah
Vaguely yes
 
0celo7
0celo7
It says that $J^-(p)\cap J^+(q)$ generates the topology of spacetime
 
Slereah
Slereah
What this system lacks on the other hand is a metric
 
0celo7
0celo7
ah, but you see
 
Slereah
Slereah
There's no definition of distances
 
0celo7
0celo7
4:12 PM
causal structure defines a metric up to a conformal factor
 
Slereah
Slereah
So you only get equivalence classes of conformal spacetimes
 
yuggib
yuggib
@0celo7 I don't think they do the same things exactly; Hörmander is surely better to study distributions and fourier transforms, RS 2 to study self-adjointness problems (of importance in quantum physics)
 
0celo7
0celo7
@yuggib But isn't RS2 titled "fourier analysis"
 
yuggib
yuggib
@0celo7 and self-adjointness
@0celo7 it is not normal, but most of the time duality in TVS is considered, it is done for real TVS. And for complex TVS antilinear dual functionals may be more natural in connection with e.g. Hilbert spaces and Hermitian forms
 
Slereah
Slereah
I'm not sure how you'd define a euclid like distance for GR
You can't really say that one is positive and the other negative
I guess you'd need to define two different relations
One causal and one spacelike
 
yuggib
yuggib
4:21 PM
@0celo7 RS 2 has two chapters: one is Fourier analysis, and is essentially the basics of the theory of distributions and Fourier transform, and then some Fourier analysis in function spaces; the second is about self-adjointness, essentially for Schrödinger operators in quantum mechanics, and then time dependent Hamiltonians, and free (bosonic) quantum fields
interesting if you are a math.phys guy, less if you are analysis-oriented
 
Slereah
Slereah
How does Euclid define curves that aren't lines or circles anyway
Those are the only curves in the axioms
 
0celo7
0celo7
@yuggib ok, I think I'm the latter
 
Slereah
Slereah
And how do you span spacetime
Geodesics?
Do you also include circles for spacelike planes
It is sort of odd that mathematicians tried to check the consistency of Euclid for so long, and when they finally did, nobody bothered to update it
The continuity axiom might be a bit much for high schoolers I guess but why not Pasch
It's fairly self evident
 
yuggib
yuggib
@0celo7 I know
 
Slereah
Slereah
Also how do you actually prove SR theorems with that
I guess you pick a timelike line and define it as the observer?
and the important events are intersection of that observer line with other lines
Maybe we could try to define the axioms for Minkowski space and try to prove length contraction from it
apparently neither Tarski nor Hilbert define circles primitively
which is nice
 
0celo7
0celo7
4:42 PM
@Slereah my modern physics professor said the old "GR is used in GPS"
Should I correct him
 
Slereah
Slereah
Feel free to
I should buy Hadamard's geometry book
 
0celo7
0celo7
@ACuriousMind what's "tangent" in German?
@Slereah link?
 
Slereah
Slereah
There doesn't seem to be an english version
I read that book back at uni
it's a fun one
Proving Euclidian theorems from Hilbert's axioms
It's unfortunate I never know where to buy physical science books
There aren't a lot of book shops with a good selection of them above school level
 
0celo7
0celo7
@Slereah do you consider math to be a physical science?
 
Slereah
Slereah
I don't want to get into such a debate
Sounds like a dumb debate
 
0celo7
0celo7
4:50 PM
My advisor said Stanford has a good book store
@Slereah I'm asking if you're including math books in that list of books you can't find a store for
 
Slereah
Slereah
bit far for me
Yes
 
ACuriousMind
ACuriousMind
@0celo7 Tangente
 
Slereah
Slereah
I bought a few science books at book shops but they're mostly basic books for university students
 
0celo7
0celo7
@ACuriousMind for the function too?
 
Slereah
Slereah
Can't find a lot of good books
 
ACuriousMind
ACuriousMind
4:52 PM
@0celo7 No, we call that by its proper Latin name tangens :P
 
0celo7
0celo7
@ACuriousMind ok, that explains my physics prof's strange name for it
Fuck Latin, the romans died for a reason
 
ACuriousMind
ACuriousMind
They...did not so much die as become other people, no?
 
0celo7
0celo7
@ACuriousMind he also kept calling a jolt "Ruck" and I don't think he realized that's not an English word
@ACuriousMind I'm pretty sure they all died
Read a book sometime
 
Jaime Gallego
Jaime Gallego
Greeks are weirder
They all read books full of equations
 
0celo7
0celo7
I'd be happy if he read one of those too
 
user228700
5:04 PM
@JohnR: Hi :-)
 
Bernardo Meurer
Bernardo Meurer
@JohnRennie Just got Black Sabbath's self titled album on Vinyl
on the title track the thunders at the beginning sound real AF on a good stereo
 
0celo7
0celo7
@BernardoMeurer I have a QM test today
 
Slereah
Slereah
Try correcting the questions
"First of all, this is not the correct definition of a hermitian operator"
 
Bernardo Meurer
Bernardo Meurer
@0celo7 How are you prepared?
 
0celo7
0celo7
@BernardoMeurer I memorized perturbation theory up to second order including normalization
 
Slereah
Slereah
5:12 PM
neeeeeeeeeerd
 
0celo7
0celo7
I know the selection rules for hydrogen transitions
Can anyone tell me why psychopaths comb over their hair?
It's a characteristic sign
 
Slereah
Slereah
Many people comb over their hair
Because baldness is looked down by society
 
0celo7
0celo7
All psychopaths
 
Slereah
Slereah
sure, but $(\forall x \in X, \varphi(x) \wedge A \subset X) \to (\forall x \in A, \varphi(x))$
 
0celo7
0celo7
What?
I'm saying it's necessary and sufficient
 
Balarka Sen
Balarka Sen
5:36 PM
@0celo7 I really like the Thin White Duke's hairstyle
 
Slereah
Slereah
did Ted Kaczynski have a combover
he did not
 
0celo7
0celo7
Is he a psychopath?
 
Slereah
Slereah
He did complex analysis, so obviously, yes
Also he lived in a cabin in the woods and mailed bombs to people
Apparently he's still alive
I wonder if he had any good math insight since
"On May 24, 2012, Kaczynski submitted his current information to the Harvard University alumni association. He listed his eight life sentences as "awards" and his current occupation as "prisoner.""
 
0celo7
0celo7
lol can you cite the guy unironically?
 
Slereah
Slereah
Let's see what papers he wrote
 
Secret
Secret
5:39 PM
[Topology] The rationals and the irrationals are neither sets in the open interval topology of the reals
 
0celo7
0celo7
what?
 
Slereah
Slereah
 
Secret
Secret
in Mathematics, 4 mins ago, by Secret
I still yet to fully comprehend the cantor set, but I will soon

Hmm, so that means...
Since the irrationals cannot be a countable union of open intervals, it is not open. Now the complement of the irrationals is the rationals which is also not open because any open interval contains an irrational so it cannot be a union of open intervals, and singletons are closed and pairwise disjoint thus. It is not closed either because it does not contain all of the limit points such as the irrationals. Therefore the rationals is a neither set. Therefore the irrationals are not closed thus the irratio…
 
Slereah
Slereah
lots of boundary function
 
0celo7
0celo7
@Secret your sentence is not correct
 
Slereah
Slereah
5:41 PM
does this seem like the paper of a madman
 
0celo7
0celo7
"are neither sets" makes no sense
 
Secret
Secret
neither is short for "neither open nor closed" because I want to save typing
 
0celo7
0celo7
...since when
 
Secret
Secret
really, they need a shorter name for neither open nor closed sets
 
Slereah
Slereah
His thesis
Oh man
Typewriter and pen equations
He really was a madman
Can you imagine how it was to write a thesis before printing was widely available
Handwritten thesis
I wonder if I can write to him about something in his thesis if I have questions
prison mail about boundary functions
 
0celo7
0celo7
5:45 PM
@Slereah Please don't talk about people who cannot respond
 
Slereah
Slereah
He's in jail, not banned from PSE
 
0celo7
0celo7
same thing, no?
@Slereah Kato uses $\boldsymbol{\mathsf{X}}$ for vector spaces
now sure how I feel about that
 
Slereah
Slereah
Slightly odd
 
0celo7
0celo7
maybe not that bold
 
Slereah
Slereah
I can sort of see why?
$X$ for spaces is standard and bold for vectors as well
 
0celo7
0celo7
5:53 PM
 
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