@Semiclassical flow around a rotating disk near a wall

@AkivaWeinberger I convinced myself it's a punctured double torus. I don't want to unconvince myself :P

Hmmm

V,T are the independent variables for the Helholtx free energy

Which makes me think you’d want to write U=F-TS and dF = -S dT - p dV

Oh

Is the dual element of a vector $X^\mu$ written as $X_\mu$?

I’m starting from the right, to be clear

Right. Let’s trade U=F-TS as well

Yeah

U=F+TS

Right

I more had in mind the U in the right hand side

And getting rid of that in favor of F

I mean in the right-hand side of the identity to be proven

Plug in U=F+TS

Into the derivative itseld

So (d(F+TS)/dV)_T

Split it up

T is constant so you can pull it out of the second term

And the first term is a derivative of the free energy

@Semiclassical Ugh. $\rho\ge \rho^n$ for $\rho$ small. That's so counterintuitive.

Yep. Now use the differential form of dF to compute the first term

At least when you're doing a huge computation and that just pops up

Yep. But you already had +P as well

So that simplifies a bit

Yeah

TBH I was just following my nose up to here

So while this looks better I’m not sure what to do next

Hmmm

Can we use a Maxwell relation for that second factor?

Second of the two derivatives

I like that S is in here so I don’t want to get rid of it

Hmm

So -T(dS/dP)(dS/dV), both at fixed T

That looks durn suggestive

I mean, the overall factor of T is definitely appropriate

It may be time to start manipulating the other side, though

@0celo7 pls

I suspect the right thing to do on the RHS is some chain rule application

But I’m not sure which one

@p

god damn it

So looking at the left may offer a clue

@Phase what

I’m forgetting the thermo definitions of the two heat capacities though

@0celo7 my understanding was that $e^\alpha$ was a 4 vector, and that $e_\alpha$ is it's dual, but i cant make sense of this

The superscript and subscript seem swapped around, and the left part of the inner product doesn't even seem to be a vector quantity

$e^\alpha$ is the dual of $e_\alpha$

what is the issue?

wait, so $e_\alpha$ is the regular 4 vector? and what about the quantity on the left of the inner product

only the quantity on the right has the vector arrow

which inner product

that angle bracket is the duality pairing

huh? But it says it equates to the Kronecker delta right?

since they're basis vectors

that's the definition of the dual of $e_\alpha$

Had to step away, sorry

it's the 1-form such that $\langle e^\beta,e_\alpha\rangle=\delta^\beta_\alpha$

1-form/covector

man fuggit I might just give up

thanks anyway

what?

Why would you give up

@Blue well. The same idea as before would suggest going to the free energy with T, p as independent variables

But let’s hold om

@0celo7 just seems arcane to me. + might be getting kicked off course again who knows innit

Did we have (dV/dT)_P earlier on the RHS?

@Phase what the hell are you doing that they keep trying to kick you out of school?

@0celo7 attendance is like 70% because I have atrocious sleeping patterns and stuff

Back in a little bit

Although apparently it's looking very likely I'll be kicked out this time

Keep working, though. You might see something I’ve missed

just fix your sleep pattern

doesnt matter at this point

Probably would get flagged

I don't know how to help you with that

And anything I say will be Not Nice

Fair, I'm not expecting pity or anything

at this point I'm just talking because I have nothing else to do innit

just go to class

Yeah but it's pointless to say that now

Die has been cast

Just gotta see what it lands on

@Phase Right now, getting (more) stressed about it will just make things worse and mess with your sleep. If your sleep pattern is messed up, that'll be making you more tired and even more stressed and so we get a vicious cycle. Also, it could be that that's making you say/think what you're saying/thinking. So, if it were me, the first thing I'd do would be to talk to whoever's there that you can talk to about this sort of thing (tutor/supervisor/whatever)

Tried

Even registered myself to the University counselling service for an appointment

but that was weeks ago and have heard nothing

are you failing all of your classes?

No

then I don't understand what the issue is

I have a spotty hand in rate because of my attendance but what I hand in tends to be in the 90%'s

so you're not turning in homework

Haven't really got a metric to judge failing or success by yet. hasn't really been that much set work

so that's like 10% of the grade

how are they kicking you out?

Attendance

over the weeks its been like

so you're literally getting kicked out for not showing up?

50, 65, 0, 70, 65, 70

yeah

1) That's incredibly stupid of the school. 2) Shame on you.

That's all I can say.

Yeah I know. I tried though

I've pulled two straight all nighters before

in a row

to make some of my lectures

What the hell does that have to do with attendance?

Why would you need to pull an all-nighter to get to class? That's literally the opposite of what you need to do.

Because I'm really bad at sleeping

@Phase have you gone to a (college?) doctor for insomnia

@Phase 1. Do you know this for a fact (as in, do you have an e-mail or similar saying "you will be expelled if...") or do you just think this is the case? 2. Don't do all nighters like that. Seriously, marks are much, much, much, much less important than mental health

I can't switch off, if I go to bed I just spend a lot of my time thinking and cant stop. I have to wait until I'm barely conscious from sleep deprivation to get a good nights sleep

@bolbteppa haven't gone to anyone yet, no appointments are being made by the system

@0celo7 what is difficult about having to stay up all night to make class the next day

@bolbteppa not everyone is as smart as you.

@Mithrandir24601 I was told by my course leader that I'll be meeting with someone much higher up, who has a reputation for removing people like me

@Phase Honestly this sounds like some 1984 shit.

@Phase It's usually up to you to make an appointment at all Unis I've experienced

I'm probably explaining it poorly

"Course leader" "meeting with someone higher up" "has a reputation for removing people like me"

@Mithrandir24601 I tried

I used the systems in place

What the hell, is this a university or a boarding school?

Idk, the UK

@Phase Have you called them? Have you physically gone to them and been like "I desperately need help"? Have you been to your GP?

Thankfully here no one gives a shit about you

@Phase if you are getting in trouble in the real world because of a sleep problem then it is generally advisable to go to a doctor if you can and talk about it and especially get a note if it's affecting things that badly

They can't remove you if they don't know your name

@Blue okay, back on my laptop now (was on mobile before)

If I get kicked out though that will by far be the worst week of my life. @bolbteppa @Mithrandir24601 again, at this point that won't be in time

I either am gonna get kicked out or a final chance that is apparently very rare

actually, in the interest of not interrupting

@Phase you should probably talk to your personal tutor straight away about this if things are bad and tell them you wont have the note in time but will get one etc

@Phase You think that you won't be in time. Universities in the UK are not remotely like that in my experience

I'm just going off of what I've been told

It's all my fault anyway

I'm not trying to demonise any institutions

@Phase Again, how do you know this? Rumours are probably there to scare you

It's from my course leader

@Phase you should let your tutor know and explain the situation to them asap that way there is a record you did your best

What is a "course leader"

what is a "tutor"

Universities in the UK don't even care about attendance unless you're doing something like medicine where it's a legal requirement

Like someone who's in charge of a year in a course

@Mithrandir24601 not true at mine.

I dont know why you're saying that when I've literally just said that I'm going to be kicked out over it

@Phase this kind of thing is literally what a personal tutor is there for

@Phase Your course leader said that. They're just a lecturer

@Mithrandir24601 yeah but they also have the power to remove me

as does the higher up he's referring me to

as an American, this seems extremely strange

It's possible they said that because they got out of the wrong side of the bed or they want to scare you into attendence

Nope

It's happened multiple times before

Someone else has already been removed

@Phase Then go to the higher-up and be like "I need help" and if they still kick you out, chances are it's a bad place to be

@Phase Starting tomorrow, you cannot miss a single class.

Idk. I messed up my A levels anyway, it's not as if I can go to anywhere that's like cream of the crop. If I get kicked out I'll probably just give up

If you keep missing classes you deserve it, honestly.

@0celo7 I'll try

There's no excuse. You have to go to class.

@Phase a personal tutor + a doctors note or the promise of a doctors note to the tutor is how a genuine issue is dealt with in these kinds of situations

@0celo7 I've never missed a class while being awake / stable

and even when my relationship of over a year disintegrated yesterday I still went in

I try to attend

@bolbteppa thanks I'll try

(What kind of place cares about attendance :p)

oh my god

I like a lot of the lecturers though. A lot of them are genuinely nice people, like one will always entertain my dumbass questions, and even recommended some books for me etc

I just wasted 30 minutes of my life

damn integrals.

Btw how does one distinguish between genuine depression and just being unhappy

do you want to kill yourself?

Because I keep being asked by the course leader but I can't actually give an answer

@Phase I'd suggest that you go to bed now and set the alarm for plenty of time for tomorrow's lecture. Allow your work to suffer if that's what it takes. In my experience, if you feel you can't sleep because of stress or you're thinking about work/physics, then if it were me, I'd physically exhaust myself before bed - have a really long game of squash or something else as intense and draining. If it's actual insomnia, you need to see a GP

yes but that could just be circumstantial

If not, do you have the energy to kill yourself?

I have tomorrow off

@Phase maybe you need to take up running or something

@0celo7 I do, and I don't

probably inappropiate for hbar

I didn't see that

good

Conversation should probably shift back to something more hbar suitable

You're gonna get an email from shog

@Phase If you're even asking this, I'd strongly suggest going to a medical professional

If sleep issues are affecting your daily life it's not circumstantial, go to see tutor + doc asap

@0celo7 I'll get a bill from Shog, at the exact cost of 1 human soul

WHAT IS A TUTOR

@Mithrandir24601 seems a bit extreme though, besides Im not registered anywhere near here

@0celo7 Depends on the Uni :P

@Phase It's not extreme

depression sounds serious and spooky

@0celo7 lots of colleges around the world assign a 'personal tutor' to students, someone a student goes to with issues, problems, getting used to college etc

Go to the nearest GP practise and get an appointment - they can register you at the time - it's not a bother to them at all

Yeah I just dont wanna be unregistered from my home GP

@Phase They can also put you on the list temporarily (I've done this a couple of times when I've been at home over summer)

I guess that could work

I dont think I could really talk to someone about it though

Beyond it just being difficult for me to communicate with people in general, I tried talking a bit to the course leader but I ended up having to stop to avoid cracking

@Phase It's hard, but it'll make things better in the long run

@Phase Is it easier for you to send an e-mail?

I suppose, it's worth a shot at least I suppose even if for no other reason than a piece of paper to help me stay here

Well it's easier because it's no problem if I crack while writing it

I think I'd rather if we stopped talking about it though, I appreciate the care and advice and stuff, I just feel rather awkward commandeering hbar for a personal therapy session

@Phase Then it would be a good idea to send an e-mail to your tutor with the course leader cc'd

Thanks @0celo7 @bolbteppa @Mithrandir24601

@Phase It's OK :)

back to trying to understand what a Levi-civita tensor is

and generally spooky geometry

@Phase what they want to see is effort so that’s what you need to show them

@0celo7 i put a lot of effort into stuff it's just that it takes a while to be relevant

But nicely, today one of them actually did

Did Biot-Savart but did that a couple years ago as part of a challenge thing someone gave me

folks, question

can y'all access physics.org ?

it's stalling for me

@EmilioPisanty Doesn't look like it :/

In any case, @vzn, I realize now that my earlier defense of phys.org was based on a confused picture of the facts.

I was confusing phys.org with physics.org, which is an educational website run by the IOP and which used to have excellent content (though apparently they're not publishing much of late)

so my impressions of the average quality of phys.org are unreliable and need to be recalibrated

(they did have a much better piece than their competitors on this one, but I've seen several bad pieces too)

in any case, apologies for the mix-up