12:30 AM
How do we know that we can decompose a representation into irreducible representations by symmetrizing and anti-symmeterizing accordingly?
So it seems like we are just projecting out invariant subspaces however how do we know that there are no more invariant subspaces left

@Pizza tell us what you did and what are your reasonings

4 hours later…
4:18 AM
is it true that a field in physics isn't the same meaning of field in math?

@Obliv obviously true.

To what limit? Surely when we speak of vector fields we're talking about the same fields in math as in physics?
This part of these lecture slides bother me: "The concept of a field in physics has nothing to do with what is called a field in mathematics. A field in physics is simply a quantity that depends on space and time. That’s it. That’s all that a field means."
Surely they're related..
I guess I'm too newbie to know the extents of fields in mathematics though.
I thought that maybe he wrote that to keep people from getting in over their heads and to keep people focused on some simple ideas from the start
so I didn't take it 100% seriously but since you said obviously true @naturallyInconsistent I wanna know why
Because math is inherently not physics?

In mathematics, a field is a set on which addition, subtraction, multiplication, and division are defined and behave as the corresponding operations on rational and real numbers. A field is thus a fundamental algebraic structure which is widely used in algebra, number theory, and many other areas of mathematics. The best known fields are the field of rational numbers, the field of real numbers and the field of complex numbers. Many other fields, such as fields of rational functions, algebraic function fields, algebraic number fields, and p-adic fields are commonly used and studied in mathematics...
@Obliv Under Peano axioms, we can modify the axioms so that 0=1. That is a perfectly valid mathematical system. It is just that it is useless. Maths is very necessary for physics, but it is not physics.

5:20 AM
@Obliv in physics language: field. in mathematics language: a section of a bundle.
in physics language: the real numbers. in mathematics language: a particular example of a field.

S C H W E G

schweg !
^ "section of a bundle" Lol
when the first page of a book is like either of these perhaps it's a book that shall be read later :-)

6:28 AM
@Obliv you're overthinking this, they just mean it's not the algebraic notion of field (like the real or complex numbers are); apparently they forgot that geometers use "field" in much the same way physicists do

7:05 AM
Hello Everyone...
In inelastic collision between two objects can we determine individual objects contribution elasticity?
Let say if object 1 is perfectly elastic and object 2 is perfectly inelastic. Does collision experiment can tell which object deform.

@ACuriousMind you're an impostor
The real ACM would never be awake so early
@lucabtz also @fqq (EDIT: Oh, fqq started that conversation)
By the way, there is an English edition of Fasano Marmi
I had to use it because my Boringhieri edition apparently had some blank pages

7:28 AM
a lot of formula references are scrumbled and there are some obvious typos here and there but it seems a good book to me

It's a nice book and it has a lot of content
Chapter 10 is my favorite (canonical transformations) but that belongs to an ancient past

for me it still is a remote future :)

8:17 AM
Time will heal any incomprehension, young lad

1 hour later…
9:19 AM
what do u think are the holes in this scientist's understanding of consciousness?

9:39 AM
@Relativisticcucumber HONKRACK

9:51 AM
S Q U A C K

10:42 AM
@SirCrackpot i didnt know before yesterday though
@SirCrackpot symplectomorphisms vs canonical transformation: which term is better?

10:55 AM
@SirCrackpot that's because of the internet troubles I have to commute to the office! -.-

@ACuriousMind you work from home otherwise?
thought id add some ACM emphasis to it

hi
I need some help regarding (PINN-Physics Informed Neural Network) to make an AI that solves a non linear differential equation. Someone with enough knowledge about this please DM.

@lucabtz usually I work ~3-4 days a week from home, yes
@SamyakMarathe you don't need AI to solve differential equations
there's well-established numerical methods for a large range of equations; an "AI" will not beat them

@ACuriousMind oh but its a trend now
even if its bad af people will try to do it with AI
anyhow i have a question about complex functions. say i have the function $(1-z)^a$ i have seen a paper say this is equal to $$e^{\pm i \pi a}(z-1)^a$$ depending on the choice of the branch
now i forgot the question though

@ACuriousMind I know. But this is my class project. I need to use ML in physics. I need some help. If someone who can atleast solve non linear differential equations, could also help.

11:07 AM
@SamyakMarathe i can solve them analitically but i will keep how to to myself /s

@lucabtz can u help me. I have made the AI, I used the FDM to solve it. Unfortunately both the solutions are different. I need help

@SamyakMarathe no no i was just kidding, i know nothing about these PINNs
it is the first time i hear this acronym tbh

u don't have to. Can u atleast solve it for me analitically
using whatever numerical method suitable
the equation is called allen cahn equation. I am at UG level and this project has this equation which is unknown to me

@SamyakMarathe it was a joke based on the fact that the analitical solution of those equation is at best hard at worst impossible

ohh yess, because it's non linear. But can u do it using any numerical methods, say FDM
if u know how to solve non linear equation, even with python, that would help

11:11 AM
@lucabtz "symplectomorphism" is a flex

CAN ANYONE SOLVE NON LINEAR DIFFERENTIAL EQUATION USING PYTHON!!!???
I NEED HELP TT

@ACuriousMind I haven't seen that emoji in a decade and yet it conveys your displeasure

I wish it does, I am in serious trouble

@SamyakMarathe Please, do not yell. Some of the users here have sensitive ears.

I hate this AI I made, and Idk if it works or not
@SirCrackpot shatapppp

11:22 AM
@lucabtz I know, I spend a lot of time dissuading people from trying to plug ML into unsuitable use cases :P
@SirCrackpot My old person trait is that I think ASCII emoticons are superior to all the new-fangled emojis

@ACuriousMind for a while miao miao didn't know if you meant HTML, XML, MathML, kind of ML, or OCaml kind of ML...

11:39 AM
@ACuriousMind We've entered a new era where the new emoji are considered cringe by most
Also, you can write old-fashioned emoticons on paper

@SirCrackpot technically, you can draw anything you want on paper...

@naturallyInconsistent not if you suck

11:54 AM
No, if you suck, you can still draw stuff, it is just that they might be... interpretative

12:22 PM
What's the point of an emoji conveying wrong emotions, though?

12:50 PM
@SirCrackpot HONKBAH
ditto returns

1:36 PM
H O N K B A H

2:00 PM
@ACuriousMind yeah, people think neural networks are some sort of magic box and you can get anything from them

2:11 PM
also quantum computing
Such was also the case for a variety of things through history
ie. electricity, magnetism, radioactivity, nuclear power, etc
If you look at early 20th century pop science boy did people love electricity
Chemistry was also fairly magical

2:36 PM
@Slereah yeah also
or the combination of the two: quantum machine learning
how do i get mathematica to expand Log[(t^(1/2 + [Lambda]0) e[0])/(1 + 2 [Lambda]0)]

2:54 PM
But then I'm not gonna complain about people funding QM

@Slereah yeah i mean quantum computing is interesting, also quantum machine learning
but its just weird that people try to use it in ways that make no sense sometimes

You just have to remember that most people in charge of the important parts of society do not know anything

As you may remember in this Feynman anecdote :
> The Army told me everything, all the weapons they had, and all the gadgets, everything and they asked me all kinds of questions. Then they had cocktail parties, meeting generals and so on; informal things. A general would tell me that what they need is a tank that uses sand for fuel, because it would be great if you could just scoop up the sand and turn it into power, because they could keep on going.
The problem is refueling the damn things when they go too far, and so on and so on. They apparently thought that science could do anything. There probably is a way of solving this tank probl

1 hour later…
4:13 PM
@Slereah I think the attitude towards science has completely changed now though
The inventions coming from science now are mainly just a slightly more refined iteration of something that already existed. The inventions from science especially in the first half of the last century were completely revolutionary
Just think how crazy radio is

Things certainly have changed although I wouldn't say we don't innovate now

My point is that the innovations now are not entirely new things. They are just incremental improvements to an already existing invention

You could argue that about most things

I would say the radio and powered flight is something completely new
even television

I don't think it matters much as far as their impact goes

4:21 PM
Powered amplification

Which is just the electric version of the optical telegraph

@Slereah Yes but imagine how crazy it would have been when it first came out. You would think that anything is possible with science

Yeah but the same is true of modern tech, as we can see
AI is certainly feeling like that to a lot of people

Yes but we don't notice the effects because it's an incremental improvement of an already existing product

Only time will tell

4:26 PM
gps is completely revolutionary but it's also pretty old now

Also you have to remember that you only think that from your perspective living in the future
Things didn't change that fast for most people

i cant think of a "completely new" invention in recent times

Plenty of people didn't have fridges up until the 60's

VR is a potentially revolutionary thing from recent times

The biggest hyped thing I can think of is chatgpt
I swear it barely does anythign that couldn't be done before
I'm more impressed by google translate translating pictures

4:30 PM
gpt certainly isnt a slight improvement from what we had earlier
VR and AI are the "science magic" stuff from recent times

VR has been a gimmick for like 40 years

Tbf I am impressed by how it can write code

@Slereah yeah, but it will take over in a few decades
it has been shit so far

Chatgpt can mostly adapt copy pasted code from the internet
Which makes it as competent as many people employed as programmers, but still

i cant think of big innovations in travel beyond airplanes. maybe in the far future, u cud hav portal travel. but thats all fiction for now

4:32 PM
The biggest thing I take for granted without realising how amazing it is is YouTube

The thing is that I don't think a technology being original is that important
Plenty of technologies are very old but were pretty useless for a long time
Incremental improvement is important

I agree but you can see why people in the first half of the last century thought that science could do anything like make fuel out of sand in your example

Yeah but you're focused on specific examples
I have seen the magazines, people were also impressed by the incrementals
The development of medicine and chemistry was a huge deal

the extent to which all fields got revolutionised in the last century is hard to match up to

It's like, going to the moon in the 60s is a big deal but it's not that big of a stretch to see that it's just the technology of already existing missiles on steroids. It's not like radio where something you can't see is travelling through the air carrying what appears to be your voice. Nothing like that had ever existed

4:38 PM
i agree. wireless is the most magical thing to come out of science
it's the sort of thing fantasy stories wrote about
flying is also up there
the new equivalent of wireless would have to be something like portals. the bar is too high
i would say VR is really close to magic if it gets perfected, but people wont notice it as magic as VR got perfected over decades
wireless is more a binary thing. u hav wires, and then u hav wireless. so people noticed it as magic

Maybe some new technology will come out far beyond the atomic scale

Hello!

vaccines are exceptional too
last century progress is hard to match up to
u had incremental progress in science and meds till 1800s and in 1900s it all blew up

The gas mixture of N1 moles of one gas and N2 of another has additional microstates compared to (N1+N2) moles of one gas, the additional microstates are given by (N1+N2)Na!/(NaN1)!(NaN2)! ?
How is the number of microstates computed, I am new to statistical mechanics?

if u go far back in history, societies that are 500 years apart may not have tons of changes. but society is changing extremely fast now

5:01 PM
@Relativisticcucumber ditto returns !
someone is giving a talk at my school today about the category theoretic formalism of classical mechanics :D. what a coincidence (though, geographically not really...) since slereah (I think) recently posted Baez's post about this

It is the cool modern thing to do for theorists
Never trust people who would have you believe that physics is dead :p

hehe i wish to know more about treating physical systems as categories

a theory as a category

oh right yes a physical theory as a category

i wasnt correcting u. im just somewhat interested too
i think of a theory as axioms
oh but it can just be axioms for a category

5:17 PM
you can try here

do u think this has benefits

> A youth who had begun to read geometry with Euclid, when he had learnt the first proposition, inquired, "What do I get by learning these things?" So Euclid called a slave and said "Give him threepence, since he must make a gain out of what he learns."

5:41 PM
Anyone wanna give me a tough but doable electrostatics problem

@Obliv Probably not electrostatics but can work out how to do the lifetime of positronium calculation

Okay, where would I learn how to do that lol @Dirac1930

It's in L&L 4
I think you just need coloumb interaction
So it is kind of electrostatics
lol
It is under "The relativistic equation for bound states"
On 2nd thoughts I wouldnt bother lol

well I'm taking an electrostatics exam in like an hr so after that I'll look into it for fun lol

GL with the exam
I used to love electrostatics and electrodynamics
Might look into it again some time

5:48 PM
QFT really got u lost huh :P

Yes lol

what's your background? Maybe trying a diff resource besides L&L might help
I recall thinking about trying L&L years ago but then realizing it's way beyond my level
I was like, I'll just casually read bourbaki & LL

6:01 PM
@Obliv given the case of a thick conductor with a cavity, within which a charge $\rho$ resides, suppose that the internal surface develops a surface charge density $\sigma_{\text{inside}}$, and the outer surface develops a surface charge $\sigma_{\text{outside}}$. prove that the fields due to $\sigma_{\text{inside}}$ and $\rho$ cancel out at all points outside the conductor, and also prove that the field due to $\sigma_{\text{outside}}$ cancels at all points within the conductor.
"hint; use the uniqueness, Luke"

6:30 PM
You know, sometimes I'm just glad the world agrees on a common unit of time
If there's one thing that ought to be consistent, it's probably that

6:46 PM
It's a huge mess

OK, sure. But imagine if some continents used the second as their unit and others used 0.6 seconds
it'd be a nightmare to adjust to

Me I am French
I proudly adhere to metric time
10 hours a day, 100 minutes of 100 seconds per hour

well so do most people who work in physics lol
I have no intuition for the imperial system, so it's always confusing for me
even though I live in the US

I mean metric time never caught on unfortunately

oh, thought you said "metric units"

6:52 PM
apparently they made a few clocks in metric time back then

7:31 PM
Ok people, I decided that I'll be ad interim ACM

8:03 PM
folks. what are your thougts about the "Kerr vs Penrose" thing? I am particularly curious if Penrose has ever commented last Kerr article...

8:38 PM
@Slereah is it feasible to work in physics without a phd? I'm okay being a pipette monkey equivalent for physics if there's room for growth?
btw i mean in research
@nickbros123 Need more info. Thick conductor is to mean a volume or some sort of shell? If it's the latter, $\sigma$ is the surface charge density for a given shell but if it's the former then $\sigma_{inside}$ might be the cavity's border and $\sigma_{outside}$ would be the conductor's surface

@Obliv Dyson did not have a PhD!

I appreciate you believing in me @SirCrackpot but I am not freeman dyson

well I guess it depends on what kind of physics
if you're doing mathematical physics then you really just need a pen and paper
if you're working on experiments then that's a different story

@SirCumference what were your options pre-phd like did you consider going straight into the industry?

8:53 PM
I just applied to PhD programs
granted i'm 50/50 at this point on whether I'm going to go beyond the master's

may I ask where you went to school? my school has a professional option geared towards phds but it would have taken an extra year of schooling which would be out of pocket for me so I didn't do it
but I wanna work at a cool place like cern but I don't think I could do anything more than custodian work with a bachelors

I'd rather not say, but in my case the PhD is paid for
or rather, I get paid to do TAs and RAs

my friend in bio works at a biopharm research place and he only has a bachelors (had to write a paper to complete his masters) i would like to do something equivalent for physics
he doesn't do the theoretical stuff obviously but still gets paid well (ya i know it's pharm, so funding is no issue I think)
@SirCumference No problem, I was only curious as to whether your school had multiple options for physics bachelors
and whether you did something that was specific to phd candidates

by school, do you mean undergrad university?

yeah

8:57 PM
not as far as I'm aware
they did have stuff like 5 year Master's programs in the math department

What do you think gave you the best shot at getting into a Phd program?

it mostly comes down to research and recommendation letters
I didn't have to take the physics GRE since it was waived during the pandemic, so I'm not sure how much it matters nowadays

lol that's interesting

most schools ask for 3 recommendation letters, so I'd say you should ideally have at least two be from professors you did research with

Idk, from what I hear about phds, they underpay and overwork so I wonder if it's even worth it. I guess it's necessary for some areas though

9:03 PM
some people do love it
IIRC @JohnRennie said it was some of the best years of his life
personally I'm not really a fan, hence why I'm thinking of leaving

what do you wanna do instead?

being underpaid and overworked are the main factors for me, plus not really knowing whether I enjoy research
programming is the only other thing I'm pretty good at, so probably something utilizing that
still thinking over my options

what does the work include for you? I know you're in astronomy but I have no idea what you're doing :P

most of my research has been analysis of data from surveys of galaxies
which largely boils down to creating a billion plots and explaining what I see

would you wanna do something tangentially related to astro research like something more applied maybe (I guess working at a space agency)

9:08 PM
I'm not 100% sure yet

I get the sense you really like astronomy though so I imagine you'd wanna stay in the field but move away from academia

at this point I still haven't figured out whether research isn't my thing or my projects have just been kinda boring so far

I see

learning physics is something I could always do as a hobby in any case

@SirCumference What areas have your projects been on and what are your main interests?

9:13 PM
@DIRAC1930 It's mostly been data analysis for extragalactic astronomy
ideally I'd probably like to do some cool mathematical physics
but that's a pain in the ass to work in
it's just hard to get funding for those kinds of things

you don't really need funding for that.. you just need to not have to worry about living expenses :P

well to be more specific, it's a very competitive field with not a lot of job security or pay

Are you interested in condensed matter theory?

and given how I've always cared more about learning than research, I could probably just get a different job and study physics as a hobby
@DIRAC1930 nope, cosmology mostly

So you are more interested in GR than QM?

9:16 PM
I'd say so

i feel like that's an especially competitive area for theoretical physics research but that's just my gut feeling

the job conditions for being a physicist are just not great, which sucks
especially when you focus more on theory

@SirCumference I hear people say that but it blows my mind since physicists lead the way in innovation i think
in some cases at least

well the more you can convince the public that the research will be useful to their everyday life, the better off you are

At the end of the day, I think you should apply for the projects you are interested in and if you get offered a place, you can make a descision then

9:19 PM
it's hard to do that with GR, string theory, etc
@DIRAC1930 tbh I'm not really sure if I like research to begin with
it's a much slower process than learning new things

How so?

'new' to you but perhaps not new. good research fundamentally provides 'new' information no?

@user85795 papers can take years to get published
you need to dot all your i's and be very careful not to miss anything or make mistakes

right

Ok, I knew I liked doing research so it wasn't really a choice for me and as soon as I got to do my first research project, I loved it

9:21 PM
it's not really the same as just opening a textbook and learning something new each day
@Obliv in the grand scheme the paper should generally be something new, but getting that published takes a lot of small steps
it's hard to remind myself this is a cool, exciting new thing when the procedure is writing mountains of code each day
it just gets tedious tbh

pretty much
and when the job conditions kinda suck, it makes me wonder if I actually want to do that as a career

But now it's different and I prefer going through lectures

do you teach @Dirac1930

Nope
And thank god for that lol

9:26 PM
@DIRAC1930 amen

Wouldn't want to ruin peoples lives by showing them QFT lol

not for everybody i guess lol

i mean I like teaching but it would break my back to do that on top of all my other work (classes, research, etc)

if u could estimate your progres in QFT as a percentage, how far do you think you are @Dirac

it's already brutal grading 50 labs per week on top of everything else i gotta do

9:27 PM
And then doubly ruining their lives by wrongly showing them QFT lol

dang that's a lot of grading..

@Obliv Well I don't really understand it very well at all
But it's a lot better than how well I used to understand it

i'm afraid to take a peek at L&L

L&L are honestly perfect

does it just go through mechanics to QM non-rel then add rel and then QFT->QED->more QFT

9:33 PM
Mechanics, Classical Field Theory, Non-Rel QM, QED, Stat Mech, Some other ones, and then L&L 9 is QFT in cond matter
There is an electrodynamics book perfect for you
lol
I think it is L&L 8
"Electrodynamics of Continuous Media"
There is a joint 1st and 2nd volume called A Shorter Course in Theoretical Physics which I prefer since it has less information
However L&L 3 and L&L 4 are my main texts that I like (alongside L&L 9 sometimes)

9:52 PM
@Obliv not yet
@DIRAC1930 volume 9 is the second part of volume 5

1 hour later…
11:08 PM
@SirCrackpot L&L 9 is essentially the ideas of L&L 4 transfered to condensed matter theory
The full title is "Statistical Physics, Part 2: Theory of the Condensed State. Vol. 9"

11:20 PM
@DIRAC1930 lol the "probably" makes it even more fun
"hey somebody can recomend me a good movie?" "probably not a movie but the little prince is a great book"

It has the coulomb potential in it so I dunno if it's classed as electrostatics lol
quantum electrostatics
And then since the bound state is an eigenstate of $\hat{H}$, its a stationary state so it's 'quantum electro-stationary-states statics' which is almost electrostatiscs