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5:00 PM
i dont care about lagic
 
@ACuriousMind I am of course probably offending many people by splitting analysis into PDE vs. Operator Algebras, but that's a pretty fair splitting
 
@BalarkaSen That surprises exactly no one, I think ;)
You don't even care about spelling it right
 
I cracked up on that
 
@ACuriousMind pfffft
 
@Semiclassical My school doesn't have anyone who does logic, are there really people like that?
 
5:01 PM
I mostly have in mind a certain commentator
 
I must say everyone I've met in math and physics has been very "accepting" of what I want to study
It's the engineers who wonder why the fuck I care about math
 
@Semiclassical do i know this commentator
 
vzn
@0ßelö7 lol understood but you seem to "care" more about math than engr... o_O
 
@BalarkaSen yep
 
mmkay, i think i know whom you mean
 
5:03 PM
:)
 
@Semiclassical I feel about complex/algebraic geometry the way you feel about fluid mechanics
ACM is a girl vampire AI. Everything is possible on the internet.
 
@vzn you want my opinion? okay: sod off from telling me how I should conduct my business on an internet forum.
 
tbh the death metal ACM links here are pretty sappy
so might as well be true
 
@vzn That sounds vaguely sexist. (Also vaguely anti-ACM, but I don't care) "Anything goes" is not a good description of SE chat.
 
see, this right here is a good example
 
5:07 PM
@BalarkaSen :P
 
of stuff which I don't think it's necessary to flag over, but which I'm not interested in listening to. hence...ignore button
 
:40257102 lol
@ACuriousMind WHY DO YOU CENSOR
suspended for an hour
 
That wasn't ACM
 
dauym flagged
 
I flagged the two messages
 
5:08 PM
>.>
 
I didn't flag them, but I found them pretty tasteless
 
@Semiclassical agreed
 
Someone else clearly agreed with me so bye bye vzn
 
this flagging fetish needs to stop
 
and sufficient cause for me not to be interested in listening to them anymore
 
5:09 PM
And good riddance frankly. That was a crass thing to post.
 
oh well
 
For the record I've never flagged you
 
@0ßelö7 Responding with ridicule and another tasteless implication to a reprimand is inappropriate, and flagging was entirely justified.
 
are you saying I'm being inapproprite?
what ridicule
 
not his point
 
5:10 PM
@0ßelö7 No, I mean vzn's second message, not you
 
I didn't see any ridicule
 
> "lol thx for the reminder"
 
???
 
I think that's a bit of an overreaction
but then I'm a bit of a doormat, so
shrug
 
0celo7's capability of perceiving ridicule or irony or snark is absolutely 0
It's useless to try to explain him
 
5:13 PM
it's the difference between content which I find tasteless versus content which I find obscence
I don't consider anything in the foregoing conversation to have been obscene
 
@Semiclassical I agree. I don't think what vnz said was good, but I will never understand the obsession with cleansing the chat.
And that completely killed whatever discussion we were having, so good job @JohnRennie
 
i wouldn't call the flagging wrong so much as just unnecessary
 
@Semiclassical Yeah I didn't think it was tasteless as in obscene but tasteless as in a really unnecessary attempt at unsuccessful snark which ended up being not more than a cringe for me
But I don't complain about not having to see those messages anymore
Or anything of the like for the next hour
 
@ACuriousMind Mind explaining enthalpy? asking you after going through the Physics.SE answers and my book.
 
Doing unnecessary things is wrong. Increasing entropy for no reason.
 
5:15 PM
well, I put ignore up
soooo
 
New user shows up after someone gets banned? Interesting.
 
@Abcd Sure, if you can be a bit more specific about what you want to have explained about it
The Wiki article is passable, imo
 
@ACuriousMind "energy required to create room for the system". Does this also include a view that initially the system didn't exist and then it came into existence because of enthalpy provision?
@ACuriousMind Went through it too.
I don't like this definition "energy required to make room for the system". the formal definition is more intuitive: " It is equal to the internal energy of the system plus the product of pressure and volume."
 
@Abcd Not so much "because". The idea is that you consider the hypothetical that there was no room for the system (e.g. a piston with the piston fully down) and the "energy required to create room for the system" is then the work necessary to raise the piston to the current volume at the current pressure. But there's no causality implied.
 
@ACuriousMind That piston example is great! Then why do we include the "internal energy" term too?
 
5:22 PM
@Abcd Because enthalpy is supposed to represent the "total" energy of the system, and the internal energy belongs to that, too.
 
@ACuriousMind In the piston example, how does the gas gain internal energy?
Oh, so we would have to work against the internal energy too while raising it?
 
@Abcd By heating it up. In the hypothetical, the gas would start at absolute zero and the internal energy is the energy required to heat it up to its current temperature
Or, well, we start with a gas at absolute zero with zero pressure and zero volume (not that such a thing actually exists), and the enthalpy is the total energy required to get that gas to its current temperature, pressure and volume
Some of the energy goes into "raising the piston" and some of it goes into the thermal motion of the gas particles
 
@ACuriousMind To get there we would also have to work against the pressure of the gas?
pressure exerted* by the gas.
 
@Abcd We're not working against the gas - we're heating up the gas, getting it to exert pressure and thereby raise the piston.
 
@Semiclassical Oh, he wants me to prove $(a\times b)_i=\epsilon_{ijk}a^j b^k$. That's only like the 5th time...
 
5:29 PM
Could you represent this piston example mathematically @ACuriousMind. (I know the first law of thermodynamics)
 
@Abcd Ah, yes. We supply heat $Q$ to the gas, causing it to have non-zero pressure. This pressure pushes the piston up, doing some work $W$ in the process. The first law now tells you that the difference between this work and the heat supplied is the internal energy - if you did this experiment (starting from a very cold gas at very low pressure/volume), you'd find that the work done is much less than the ehat you supplied -
the reminder has gone into internal energy, i.e. the thermal motion of the particles.
 
3 hours of color sorting done
(Please ignore anything on the upper right corner, they are some random naming thingy and will be edited out later)
 
@0ßelö7 ...ugh
that's just boring
 
@ACuriousMind can you derive enthalpy's equation from this? (the one that fits its definition - "energy needed to make room for the system")
 
@Semiclassical otoh the rest of the hw is interesting. If you take real/imag parts of a wave function the resulting equations are like a potential flow and you can develop energy conservation, etc. for it.
 
5:35 PM
H= U + heat supplied to gas? @ACuriousMind?
 
where U is internal energy of the gas. and H is enthalpy.
 
@Abcd Well, the definition is just that it's the sum of the internal energy and pressure times volume. The interpretation is that it's the energy needed to make room for the system at its current temperature, which comes about because it's equal to the heat you have to supply to a gas at absolute zero and zero volume to get it to the current temperature and volume, as I just argued.
 
@0ßelö7 that sounds like it could also lead to kramers-kronig stuff, though perhaps what's what you mean
 
@Semiclassical You'd have to remind me what that is. I've heard the term.
 
5:39 PM
@ACuriousMind Yes. Perfect. I just want you to write these words mathematically.
 
@Abcd Uh. Mathematically it's just $H = U + pV$, no?
 
@0ßelö7 it's something annoying, tbh. I remember the words but not the content
@ACuriousMind as ever in thermo, i always like to think in terms of processes. so $\Delta H = \Delta U+ \Delta (pV)$.
If pressure is held fixed but volume is varied, the last term is just the usual $p\Delta V$ work.
 
@ACuriousMind My interpretation as per that piston example. Heat supplied by us is the enthalpy = current internal energy of the system + the work done by the system.
Please verify^
@Semiclassical I saw wiki use this notation for first law: $dU = \delta Q + \delta W$
 
but $\Delta U=Q-W=Q-p \Delta V$
 
@Abcd Yes, exactly
 
5:43 PM
Anyone knows why opposite sign conventions in physics and chemistry?
I have to study thermodynamics in both subjects.
And I might often mess up the +ves and -ves!
 
The sign of work is an annoying convention indeed
 
so $\Delta H = Q$ if the pressure is held fixed. But if the volume is held fixed and the pressure is varied, then $\Delta U = Q$ and $\Delta H = Q+V \Delta p$.
that last term doesn't have a nice interpretation in terms of pressure-volume work.
 
@ACuriousMind Thankss a lot seriously! Understood very well!! Now, last question: why is change in enthalpy of endothermic reactions +ve and that of exothermic reactions -ve?
 
@Semiclassical Yeah, sure. I didn't want to spawn a different discussion about different kinds of processes where differnt things vary, but maybe that would have been good to say
 
i should probably stop talking, my brain isn't work-ing right now
 
5:46 PM
i see what you did there
i wish i hadn't
 
20
Q: Why do chemistry and physics have different sign convention in thermodynamics?

A---BIn physics class, we write the first law of thermodynamics as $\mathrm dU =\mathrm dQ - \mathrm dW$ and in the physical chemistry class, we write the same law as $\mathrm dU =\mathrm dQ + \mathrm dW$. The reason being the sign convention is different in both the cases. In physics we take work...

 
I personally feel that the physics convention is more intuitive.
 
the sign conventions are more merciful when you start writing in terms of T,S, p,V
 
@Abcd "endothermic" means you have to supply energy to get the reaction, "exothermic" means the system releases energy when it undergoes the reaction. Since enthalpy is the total energy of the system, the sign of its change tells you of which kind the reaction is.
 
5:48 PM
then you just have $dU=TdS-pdV$
 
@Semiclassical in both physics and chemistry?
@ACuriousMind Nice, understood.
 
6:09 PM
If I have a bucket of water and stick a hole in the side of it of area, $A$, the rate of flow, Q is calculated by $Q=A\sqrt{2hg}$, right? Where $h$ is the height of water above the hole? Just from $Q=Av$ and $v^2=2gs$.
 
I haven't read a recent physics thermo book that uses the "-" version (well, Reif actually defines two symbols so that whe and his readers can have it both ways).
(I've read several introductory tomes that use the "-" version, but I figure that's because more engineers take that course than physics majors).
In short the "-" version is not the 'physics' convention at all: it is the engineering convention and in at least some engineering contexts it is the obvious one.
 
vzn
nonlinear, succumbed to wiped off blackboard by strong sponge(s) :(
 
Nov 5 '16 at 2:17, by dmckee
user image
 
@BalarkaSen About 35% of it. I'm not in the mood to listen to GY!BE post rock. Did you like it?
 
6:25 PM
@dmckee that's horrifying
 
@Avantgarde I have it on my to-hear list
I'm still recovering from Bish Bosch to listen to even slightly upbeat anything lol
Need more dark shit like that
 
haha okay
 
@dmckee maybe it's a matter of what texts they were surveying, but
 
@BalarkaSen Try this. youtu.be/aiDNf8trWn8
 
No Kittel, Schroeder, Huang, or Landau-Lifshitz
Reif is the only one of those I recognize
 
6:40 PM
@Avantgarde So this band is also from 4AD I see
Not the record though
I'll bookmark this. I hope the lyrics are not corny
 
I just got reminded of this. Listened to it a couple of months ago. Was nice.
 
6:58 PM
@Semiclassical I actually improved that table after posting that previous image. The new version includes Kittel, but not any of your other suggests (it's what I could lay hands on that week).
@EmilioPisanty I actually put it together to prepare my students for just how bad the stat-thermal notational landscape can be.
I adopted Reif's notation for my prepared notes and usually show the 1st law in both forms when I reference it.
 
7:13 PM
@dmckee ah, kk
@dmckee lol at Kittel using Z for all three partition functions
 
@Semiclassical Yeah. I guess he figures it's clear from the context.
 
It usually is tbh
Though, I think there's one context where he would write the differently: the grand partition function can be written as a sum of N-particle canonical partition functions
I think he had that as a problem and denotes the latter as Z_N
though what always made me crazy was stuff like activity / fugacity / chemical potential
 
The table is full of interest. I mean look at Goodstein (good book, BTW). Why $R$ for the work? Why $W$ for the enthalpy? Seriously, David? What were you thinking?
 
using A for the Helmholtz free energy has always seemed weird to me. but I chalk that up to all the sources I was educated with using F
but using $\Phi$ for the Gibbs free energy is just weird (another Goodstein idiosyncrasy)
 
@Semiclassical I've never understood that choice, but it is surprisingly common.
 
7:28 PM
yeah.
I think Schroeder uses $\Phi=PV$ in one problem, which seemed reasonable enough
 
@Semiclassical F and Phi are the same letter.
@BalarkaSen "we let g denote its positive definite fundamental tensor"
Oooooooold paper
 
eh, I guess Phi does preserve the F sound you have for F as the Helmholtz free energy
 
@Semiclassical that's why we say Phield
 
I still don't like it, though. If U,H,F are all latin then it's weird to me to have Gibbs be greek
 
vzn
8:13 PM
shrug
 
$N|(q-2)$?
 
Is that supposed to be just a quotient? :/
 
lol what notation is this
 
@BalarkaSen I don't know
elliptic regularity notation I guess
@Semiclassical There's a classic book in my field that doesn't have a PDF online. I have a library copy but would like to have a digital copy on my laptop. Can/should I use a library scanner to scan the whole thing? Will a librarian do that for me?
 
8:25 PM
no idea
 
vzn
@0ßelö7 what are you reading? d | n is used in number theory to signify d is a divisor of n.
 
@vzn Reading math, and I know what it means in number theory
 
context, as ever, matters
 
old PDE paper, clearly
 
@vzn point being that interpretation doesn't make sense here
 
vzn
8:27 PM
@BalarkaSen most authors will intro/ descr their notation at beginning...
 
old paper
 
In any case, I hope to not need the lemma. It's not clear to me what $r$ is supposed to actually be because there's a Sobolev embedding and Holder inequality involved.
 
so likely not
 
So it could be any old nasty thing
Nonlinear PDE is bad. I need a nap.
 
vzn
Aug 25 at 17:31, by 0celo7
Number theory is pretty boring
Apr 11 at 23:25, by 0celouvsky
I'm not, although number theory is on my list of things to learn
 
8:35 PM
@0ßelö7 That looks pretty weird, where is it from?
I've never seen the | used for something other than "divided by" or set-builder notation.
 
How old is it?
 
@ACuriousMind One of Trudinger's old papers on the Yamabe problem, 1968.
 
would it make sense to have $r=N/(q-2)$?
 
the Yamaha problem sounds interesting
 
sounds like...a trip
 
8:37 PM
Autocorrect
 
YEAAAH---awww
 
loooool
 
@Semiclassical Maybe. I have to work out the Sobolev embedding by hand. I'm in class and feel like death however
But I need to pretend to have done something before I see my advisor in 22 minutes
 
@0ßelö7 ...ugh, that hits waaay too close to home
 
I'm not even in grad school. Why do people already try to stress me out
 
8:39 PM
Because academia convinces people that stress is normal.
...ok, now I'm a bit annoyed at the prof I'm TAing for
 
@0ßelö7 Perhaps you're trying to stress yourself out and your lecturer/supervisor/whoever-deals-with-this-sort-of-thing actually would rather you be less stressed even if at the result of less work getting done?
(Yes, I'm serious)
 
Yeah I'm stressing myself out
Usually it works but I don't feel good today
The result is misery
 
second problem: "Find the solutions to the Schrodinger equation with the potential $V(x<0)=\infty$, $V(x\geq 0)=\frac12 m\omega^2 x^2$."
 
I feel icky. I need to eat something healthy tonight
And drink more water. Ah, I bet I'm dehydrated
 
i've always seen | to mean "such that", but then, I'm not in any sort of advanced study =)
 
8:42 PM
Perhaps you have forgotten your daily dose of memes
@heather Right, that's how it's used in set builder notation
 
This is a nice problem, one which requires the student to remember that a solution to the Schrodinger equation on the real line is also a solution on any subset of the real line (aside from boundary conditions).
 
@heather That's the set-builder notation I was talking about ;)
 
but also not quite applicable here
@ACuriousMind you have been sniped
you ded m8
 
@BalarkaSen Maybe he's also consumed an unhealthy meme.
 
@ACuriousMind totally knew that =P
 
8:44 PM
@heather the fact that it'd read as "r=N such that (q-2)<n/2" makes that interpretation a stretch
 
oh...actually, that kinda makes sense
set builder
defining the set = building it
 
Yes, exactly
 
@Semiclassical well I guess it depends on the context; that doesn't sound dramatically weird to me.
but i know nothing =)
 
@ACuriousMind Lots of cancerous memes on the internet.
 
well, (q-2)<n/2 seems to be a condition entirely seperate from r=N
not impossible, but quite strange
Getting back to the question, it's a nice problem and one can reason to the solution without much difficulty once you see the idea. But there should be some reasoning
 
8:46 PM
If anyone wants the specific paper, the title is ~ remark deformation scalar curvature
 
~ is a strange symbol to begin a title with ;)
 
That means "similar to"
Should be enough to google
 
anyways. what the prof has in his posted solutions for that question: "The solutions are the odd harmonic oscillator solutions."
which is correct, but
no logic or anything, just "these are the solutions"
 
flayless lagic
 
oh, and for some reason the solutions for next week's HW are already on the course website...gonna check with him if that was intended or not :/
 
8:51 PM
@Semiclassical Maybe it's trivially obvious to him?
 
Dang, I like my logic Bolton-style. Lots of flaying.
 
given that he had to provide hints to the students, I don't think it should be considered obvious
 
Maybe the students are stupid
 
moreover, if someone gave me that as the entirety of their solution, I probably wouldn't give them credit
 
@Semiclassical Is the marking scheme for the markers or the students doing the questions?
 
8:52 PM
it's an upper-division quantum mechanics course.
 
@0ßelö7 Hm?
 
Did someone flag me
 
@Semiclassical As in, final year undergrad?
 
it's not a marking scheme. it's what he posts as solutions after the students turn in that HW set.
@Mithrandir24601 right.
 
My chat just crashed
 
8:53 PM
and final year physics undergrads
 
@0ßelö7 No, but I was about to remark that that wasn't very nice :P
 
so definitely people who should be using calculus a lot
 
@Semiclassical Well, then that's simply a horrible solution to post and you're right to be annoyed
 
right
 
What does calc have to do with anything?
 
8:54 PM
He also didn't post a solution to the fourth problem
 
@Semiclassical In this case, I would suggest that, given the answer (not full solution), final year undergrads should know enough to be able to figure how to get there and learn something in the process, while giving the full solution would mean that they wouldn't learn anything
 
@0ßelö7 Did you see the paper
 
No
Chrome crashed
 
lol
Gromov crashed your Chrome
 
@0ßelö7 eh, I'm just using that as a reference point of "people who know enough math to be in their fourth year"
 
8:55 PM
it's too much for your little browser
 
@BalarkaSen what about it?
Do you want me to read it?
 
you should
 
@ACuriousMind what mostly bothers me about it is that we're supposed to select some of their HW problems and grade them as if they were quiz problems
 
What does "grade them as if they were quiz problems" mean?
 
kinda hard to model that when the solution posted online is something I'd give a poor score on for a quiz
of the HW problems each week, we pick three of them to grade based on the correctness of the solution. the rest we just check if they did it or not.
 
9:00 PM
@Semiclassical That... Does not sound like a good idea - shouldn't the markers do that for all the questions?
 
shrug
keep in mind, though, the students don't know what problems are chosen ahead of time
and that the selected problems count as the majority of the points on the HW
it makes my job easier, tbh
even if it is a bit goofy
i like this prof, but he's been kinda frustrating this semester.
 
@Semiclassical Still though - I suppose it's not as bad if it's only upper years that get that sort of treatment as I'd hope that they could go through and correct their own work, but maybe I'm being unrealistic?
 
yeah, for the most part the students are expected to manage themselves
 
Oh dear I'm about to get ill
 
the test is how well they do on the quizzes
 
9:07 PM
@BalarkaSen ok
@Semiclassical QM quizzes?
 
ya
a few long-answer problems each time
 
Time to play the "do I have to vomit or is it the schizophrenia" game
 
@0ßelö7 Make chicken soup
 
@ACuriousMind I'm in a seminar
 
chicken out of there then
its either chicken soup or chickening out
 
9:13 PM
@0ßelö7 Order chicken soup then, I guess
 
go outside, breathe in some cold air, drink some water, and get un-ill
 
It's a sauna outside
The door is by the board. I can't escape
And Ive got a meeting afterwards
 
can you not skip meeting
if you're seriously ill you should
 
Puking on your advisor might convince him you're too stressed out :P
4
 
9:31 PM
@BalarkaSen no im fine now.
 
9:53 PM
Does anyone have good example questions for the quantum computing proposal? It's a great idea, but so far, many of the questions are... Well... Let's just say that I'm very close to giving out a lot of downvotes and critical comments and I don't really want to do that :/
 
Going hardcore on code and smart water like a boss
 
At least a third or so of the questions with 10+ upvotes feel like the OP didn't think of using Google or Wiki first :/
 
vzn
10:09 PM
@Mithrandir24601 hey whats new with the qbits? did you see DSs new paper? any reaction? :)
@Cows srsly interested in solitons, or was that all just for fun?
 
@vzn He's published a new paper? Do you have a link? I actually need to sign up to some journals' mailing lists... And do some problem solving - my PhD has finally properly started :D
 
vzn
curious what you or your colleagues think about that, also IBM supposedly now has ~17qbits open science (since may?), wonder if anyones tried that
 
@vzn Ooooh, thanks :) I knew they had something like this somewhere (it's hard to not notice that they're planning to release a 49 qubit system...) but didn't know they'd uploaded the paper :)
 
@vzn I am serious about solitons
 
@vzn Aside from the fact that they used 'supremacy', I'm extremely excited :D
 
vzn
10:16 PM
@Cows so are you studying physics? in school? as you may have noticed, its a very advanced topic, very little at undergrad level
 
@vzn
I am out of school, but hoping to get back someday. Dropped out senior year of undergrad.
I am 99% sure I will be in school next year
 
I haven't tried the 17 qubit IBM one yet - I haven't been bothered to sign up to the beta, the 5 qubit one is enough to mess around on, run what I need to on an actual quantum chip and I can perform simulations of larger systems at that size anyway
 
vzn
@Mithrandir24601 yeah DS was saying it wasnt a great word either maybe, trying to remember
 
@Semiclassical meeting canceled ::eye twitch::
 
vzn
@Mithrandir24601 are you saying youve tried the 5qbit one?
 
10:18 PM
Jun 13 at 21:04, by DanielSank
@Mostafa The name "quantum supremacy" is generally disliked by everyone in the group.
 
vzn
@ACuriousMind what group?
 
@vzn His group, presumably.
 
So one paper has that strange |, another has a strange Green's function argument, and the other says it's trivial
I give up
 
@vzn I've done physics on the 5 qubit one, yeah :) Just simple operations that could be used to measure a certain type of fidelity, although IBM did this ages and ages ago, so this is nothing interesting or new - it was just to demonstrate a point on my project report. If I had lots more time, I would have used it to look at the effects of noise on t-designs, but never got that far, although I still want to if I get the time some day
 
vzn
@ACuriousMind lol his group incl leader Martinis just released a paper with it in the title. ?!?
 
10:23 PM
@vzn That they dislike the standard terminology in the field does not mean that they don't use it. Nothing funny about that.
 
vzn
@ACuriousMind have seen complaints over the terminology (a blog, maybe will try to find that again) but havent heard anyone proposing alternatives esp in literature...
 
@vzn quantum advantage
 
@vzn If you reread the conversation around the message I just linked, he says "We didn't invent it. Most of us really, really wish we had a better name for what we're doing.". But maybe you don't want to look too closely at that transcript.
 
@ACuriousMind No need for sass
 
10:43 PM
;_;
good guy libgen has it
what a beast
 
@0ßelö7 That's... :o What...
I would rather have a first edition LOTR book at that kind of price
 
who the heck writes math books in French in 1997
wow this is actually a fantastic book
how has this not been translated?
oh you dirty
@ACuriousMind what's an acceptable bad word for for french person
I don't need to look up what [214] is
 
10:58 PM
baguette
 
@3075 and you are?
@ACuriousMind I need help
 
@0ßelö7 I ask myself that everyday.
 
11:15 PM
J. Funct. Anal.
lol
 
11:49 PM
The media version: army.mil/article/194131/…
Probably one of the most illustrate version of what entangled systems look like in short range: A system where the basis of possible combinations of observable assigned to a probability distribution.
Had to read the actual paper in detail to see if the media version simplifies it correctly
Also need to revise how the correlations from non commuting observables differ from those of entanglement
 
@BalarkaSen proud?
 

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