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12:01 AM
okk
Let me just do $[\bar H , S]$ and $[\bar H, L]$
i think i mean "hat"
 
12:28 AM
ha took some time to put the matrices together. Let me proceed
still calculating hehe
hmm should I write the matrices here? might take some time
$ \begin{bmatrix}mc^2 & c \sigma p \\c \sigma p & -mc^2 \end{bmatrix} \begin{bmatrix}\sigma & 0 \\0 & \sigma \end{bmatrix} - \begin{bmatrix}\sigma & 0 \\0 & \sigma \end{bmatrix} \begin{bmatrix}mc^2 & c \sigma p \\c \sigma p & -mc^2 \end{bmatrix}$
something like this errors due to blah. .
at any rate some similar stuff an simplifications . . . life's to short for expansions
and simplifications
ok let me move on
presumably one is interested in J and it's conservation
intermidiary steps were to play with commutation rel of H, S and H, L
cool
what does "covariant form" mean? Let me check on the interwebs and think in the context of the Dirac equation
 
12:57 AM
let me just redo that Hamiltonian first something is off
 
1:09 AM
looks fine
ok where were we
yes covariance
 
1:24 AM
let me get another slice of pizza
 
1:41 AM
right so covariance of dirac eq
Ok great one introduces some new matrices to put that donkey on blast
. . . . . basically we have gammas
scale left and right by $\frac{\beta}{c}$
. . . and redefine
all fun and nice, but does this make it obvious ? really ? hmm
let me see
 
2:28 AM
ok quick break.
 
2:45 AM
on a break
will be back and will go hard
 
3:28 AM
Just watched this . . . . after I was done laughing, I realized that she had more money than me
Als bhad bhabie makes more money than me in her sleep
fascinating times(btw, they make more than probably anyone who uses this site except for few peeps)
 
3:43 AM
Ok back to studying
let me grab some water
 
3:54 AM
I waked from an uneasy dream and can't fall asleep again though I still feel sleepy.
 
Were you dreaming about theta functions?
did you see esoteric looking renditions of meromorphic functions
?
they have a way of keeping people up at night
@CaptainBohemian jokes aside, are you ok? what happened? What did you dream about?
cool so I'm done with p.23 hehe
Let me now take some time and think about plane wave solutions
Why are they called plane wave solutions?
Let me just solve it then think about nomenclature later
 
4:09 AM
Because when you write them down in 3D, you get planes of constant phase.
 
Because the surface of constant phase (the wavefront) is a plane
Damn, sniped! :-)
 
hey, you invoked Huygen's
 
hehe :) awesome!
 
that's one better than me :P
(well, not invoked so much as mentioned something in that direction. but close enough)
 
You are most welcome to drop by the Problem Solving Strategies chat room sir @Semiclassical

 Problem Solving Strategies

General chat for high school physics. For MathJax see [here](m...
 
4:18 AM
@Cows I dreamt of I was just reminded that next class (just several minutes later) is the turn for my partner and I to make a presentation. This is a class in which all classmates are grouped (each group includes 2 to 3 people) to make presentation.
But we had not make any preparation at all, so I asked whether there is any group gladding to exchange presentation time with us so that they can make presentation in the upcoming next class and we present some time far later. But no group is glad to exchange presentation time with us, so my partner and I were trying to improvise to compose some material in order to present in the upcoming class. I was in panic during the process. Then I waked up understanding that’s just a dream.
 
@CaptainBohemian yeah presentations can be nerve racking
 
@Cows I often make dreams of this kind scenario, namely failing to prepare (well) for an upcoming presentation.
 
@In my youth, the disciplinary master at my boarding school said proper planning prevents failure. It's not true. Failure can always be an option. Don't stress out. Just give it your best shot and believe in yourself.
 
4:35 AM
@Cows when I was in middle school, in a class called "life counseling", there was a time which was assigned for my group (including 7 to 8 people) to make presentation. But none of us made any preparation. So when the teacher asked us to go to the podium to make presentation, we couldn't present anything. The teacher was very angry and asked us to go to stand in class for punishment. That's really an embarrassing experience.
 
@CaptainBohemian I can certainly understand. sometimes teachers are agnostic to the psychology associated with learning, and learning environments. Try not to think about it much. Believe it or not I am haunted by physics professors who've gone out of their way and made fun of aspects of my personality, and knowledge of the subject, at a time was I was quite lost and vulnerable.
It can be pretty hard, but remember that you have, time, and an opportunity to learn and explore as much as you desire , freely and without bounds
This is priceless
hehe
@CaptainBohemian Trust me you'll be ok. I went through similar things even in primary school in Cameroon. Except worse.
wow reading Huygens principle now
 
@Cows wow!You studied in a primary school in Africa?
 
@CaptainBohemian yes
Then I wrote the GCE
O'Levels
hehe good times
 
@Cows What's GCE?
 
@CaptainBohemian General Certificate of Education. It's quite useless unless you have the British one, or the French matrise, and or License or something along those lines
I meant maitrise
 
4:53 AM
I have learnt Huygens principle in high school but have never learnt it again in undergraduate and graduate schools. I guess it's just a way of picturing and may not have use in practical calculation.
 
a classic from 1978 for your Friday night listening pleasure :-)
 
@CaptainBohemian well quite honestly I'm not sure about the facts, although personally from looking at it i think it may help remember how to calculate
@skullpatrol hehe :P yay Friday
 
gotta love that polyester look/sound :P
 
hehe
 
hoho
 
4:59 AM
@Cows maitrise is not an English word and the dictionary gives explanation in a language I can't understand.
 
C'est un mot francais
It
is a french word
 
It's a long article so search for maitrise
@0celo7 Damn :-( I'm thinking chicken and bacon in white sauce for today.
 
@JohnRennie waste of good chicken.
 
Critics! I'm surrounded by critics! :-)
 
5:03 AM
I do like chicken in a creamy sauce, but on its own I find it a touch bland.
Adding a bit of chopped bacon or ham just adds a bit extra to it.
 
I like to baste it in Nando's peri-peri sauce. I assume you can get it outside of the restaurants in UK?
 
::sounds of crickets:: oops, you said critics :P
 
Or, if spicy isn't your thing, you can melt some butter, add a chicken stock cube and some soy sauce, then use that as a baste.
 
Chicken basted with jerk seasoning is a family favourite, but I don't think I've tried peri-peri.
 
I don't know what jerk is.
 
5:06 AM
It's a Jamaican spice mix. Very hot so you have to use it carefully!
 
OK, I'll look out for it. I don't think it's sold in my country though.
 
Jerk is a style of cooking native to Jamaica in which meat is dry-rubbed or wet marinated with a hot spice mixture called Jamaican jerk spice. == Etymology == The term jerk is said to come from the word charqui, a Spanish term of Quechua origin for jerked or dried meat, which eventually became the word jerky in English. Jerk is also derived from the action of jerking, which referred to poking meat with holes so that flavor could more easily be absorbed. The term jerk spice (also commonly known as Jamaican jerk spice) refers to a spice rub. The word jerk refers to the spice rub, wet marinade, and...
 
yup jerk chicken
there it is!
 
Jerk pork is very good too
 
ox tail is another good one
 
5:07 AM
To me, something just seems wrong about Cows eating ox tail.
 
@DawoodibnKareem lolz
 
lol
You missed my joke? @JohnRennie
 
@skullpatrol ::sounds of crickets:: :-)
 
:-D
 
And I was thinking willow on leather.
 
5:16 AM
Don't mention the cricket :-)
 
ok solved it
 
@JohnRennie Sore point is it?
 
I heard about a cricket scandal...
 
That's not the one John's talking about.
 
oh, sorry
 
5:23 AM
@DawoodibnKareem :-)
 
I keep thinking of Fawlty Towers - don't mention the war.
 
ok taking 2 hours off to correspond with someone will be back , actually make it 3 hours hehe
 
cya ltr
 
5:46 AM
^ This is what I mean when I say Brazil is a peculiar place
 
6:01 AM
*l8r
 
@JohnRennie Hi , good morning !
I have my exam tomorrow ( JEE MAIN ). Wish me luck ! :) Oh also give your blessings , teacher.
 
@Tanuj Good luck! :-)
 
@JohnRennie :)
 
Anonymous
6:26 AM
@Tanuj All the best
 
@Tanuj Best of luck.
 
6:56 AM
@Tanuj good luck!
 
@BalarkaSen Yeah, it's not bad
I don't like Judas Priest though
 
I have never listened to them before
 
That style of metal makes me cringe
 
I don't technically listen to mainstream heavy metal
 
I know too many manchilds who listen to Priest for me to be able to like it
 
7:27 AM
Lol
 
I'm in a Joy Division moment right now
 
Joy Division is 10/10
 
Yeah, it's so heavy
 
Unknown Pleasures is a great, great album.
 
Unknown Pleasures is really good, yeah
 
7:34 AM
Hello
 
@BalarkaSen After watching this I think I understand what the problem with flat earthers is
It's painful to watch, btw
But it's worth it
 
@BalarkaSen you just got flagged in the Math chat :-)
 
@JohnRennie I don't really care anymore
 
Lost the will to chat eh? :-)
 
I'm really just getting tired of pedantry.
Or maybe I just mean pretentiousness? I dunno, it's late
 
7:39 AM
It's better for me if I get banned for a couple hours and get work done
@Semiclassical I think I am correct in that there's too many smartassess in the chat
Let's leave it at that
That's just the appropriate adjective
 
I'm also just getting tired of people who seem allergic to the possibility of being wrong
 
@Semiclassical Maybe yer wrong about that
 
oooh
 
burn
 
7:41 AM
@BalarkaSen Category Theory is beautiful
So, so beautiful
 
i am subverted
oh noooes
 
@Bernardo No comments
;)
 
I'm starting a small article on Category Theory and Graph Theory
 
Nice, I'd read that
 
I want to remodel my Lacanian Graphs as categories ultimately
 
7:42 AM
The problem with category theory for me is that it seems pretty irrelevant for the kind of stuff I like working on
 
Also, my prof gave up on understanding that article, lol
@Semiclassical It serves me b/c of functional programming
 
Hi!
I've a textbook, which is physics for scientists and engineers by A. Serway
 
and my far-fetched dreams of the FUCC language
Functional Unicode C Clone
 
seems like this textbook didn't explain ''Water waves''
 
i.e. Functional C
@Morata I hate that book
 
7:44 AM
Is there any reason that the book didn't explain ''Water Waves'' on wave optics?
@BernardoMeurer Do you have any alternative?
Which explains every topic on physics?
 
@Morata John Rennie
 
@BernardoMeurer I didn't get what you mean?
 
it's an in-joke
 
^
But seriously
No book explains "all of physics"
 
ooh :/ yeah but
I'm high school
so wanna find everything on a book.
at least useful topics
 
7:46 AM
If you want a book on Mechanics, which IIRC Serway is, Kleppner & Kolenkow is good
Has really hard exercises though
There's a list of books somewhere on this website, I think
 
Those books didn't explain everything very well
 
For mechanics, those books didn't explain how to draw free body diagram when there are two boxes.
I mean action-reaction
 
@Morata If no books "explain everything very well" odds are:
1. You are the problem. You lack the knowledge required to read the book, or you need to work harder.
2. You have unrealistic expectations of how much a book should cover
3. You need to read more carefully, do more exercises
one of those
@Morata Most of those books assume you know how to draw an FBD, since that's not really all that hard
 
@BernardoMeurer Why?
 
7:49 AM
I learned how to draw an FBD from @JohnRennie and @dmckee, here on this very chat :)
@Morata For the same reason a Quantum Mechanics book doesn't bother to teach you calculus, you're supposed to know that already
 
I've got it perfectly ;)
u r too right
However, at least It should've explained ''Water Waves''
 
@Morata In any sense, if you have questions always feel free to ask here on the website, people are surprisingly nice, even if I'm a grump
The little physics I know I learned from bickering in this chat
 
@BernardoMeurer Indeed, am training for physics olympiads
 
@Morata I don't know what you mean by "explain water waves"
 
Reflection, Refraction of water waves.
 
7:52 AM
@Morata K and K should serve you well
 
yeah I downloaded its pdf.
a sec ago
 
Cool
I don't see why it matters that the waves are in water
 
reflection/refraction is geometric optics, not wave optics
 
@Semiclassical You mean for water waves?
 
@Morata What difference does it make if it's waves in air or in water?
 
7:54 AM
@BernardoMeurer That's what I'm searching for.
I've seen a lot of differences between them.
 
@JohnRennie Come save this soul
 
The key difference is the wavelength of the waves involved.
 
@Semiclassical How?
 
@Morata The fact that water is more massive will make the wavelengths different wrt. air, I guess?
 
If I drop a pebble in water and see the waves spreading from that, then the wavelengths will be on the order of cms.
The wavelength of light, by contrast, is on the order of hundreds of nanometers.
I'd be more precise right but my brain is not working.
Point being that, with light, you can do stuff about reflection/refraction of light rays.
 
7:57 AM
so they are same?
 
There's elements of that in water waves, but what matters more for water waves is stuff like diffraction.
I should note that i'm predicating this on the assumption that you're interested in water waves, i.e. water moving back and forth, and not light travelling through water.
 
However, It should've explained it.
It's nearly same with Light Waves.
 
I'll point out, i guess, that water waves usually aren't discussed in detail in an intro mechanics book
you're more likely to see sound waves or wave optics.
 
Exactly!
Those are what I've seen.
Then what kind of book should I read for water waves?
 
of the two, then, you should compare sound and water waves.
not sure tbh. it's not something I've looked at much myself. i'd suggest fluid mechanics/hydrodynamics but that's probably overkill
 
8:04 AM
What about geometric optics?
 
what about it?
you're more likely to see coverage of geometric optics in an intro mechanics book. for a fuller discussion, you'd want a book on optics
 
Indeed, I need too many books
 
but you probably won't see much discussion of reflection/refraction of sound/water waves, because that is by and large not so helpful
 
cuz this textbook didn't explain what to do when there are two cells connected in parallel or series
so there are too many mistake that book did.
 
8:05 AM
yeah thats what I'm delaying with
even if am training for olympiads...
@Semiclassical idk what to do rn
 
@JohnRennie @Cows I finally found "maîtrise" in the link JohnRennie gave. It's like a half-master degree conferred to students who have completed 60 credits while the master degree is conferred to students who have completed 120 credits.
 
yeah, the french have a different approach to education
 
@Semiclassical Is there any alternative?
 
@skullpatrol France has very complex education, too diversified without uniformity.
 
The alternative is that you look at books and see what you can find. There's not going to be any one reference you'll be able to look at that will work for everything.
 
8:15 AM
@CaptainBohemian well as they say, vive la différence :-)
 
@Semiclassical What about mechanics?
 
Same thing. Look at books, see what works.
 
@Morata if you're training for the olympiads, study old tests
check out "The Art of Problem Solving"
 
@skullpatrol Then I'll leave reading books
will be trying to find everything on wikipedia or something
Do you know any resource that can be used online?
 
8:25 AM
@skullpatrol I mean for other topics
 
this doesnt seem useful lol
 
@skullpatrol I think u didn't get what I've tried to mean ;=
For other concepts of physics
not for olympiads.
 
21 mins ago, by Morata
even if am training for olympiads...
 
8:28 AM
Yeah but no need to find any book for olympiads right now.
I'm struggling with waves.
 
the basics?
 
yeah
 
go back to your school textbook and build upon that
 
that is too bad
 
look for a similar textbook at that level
 
8:32 AM
I've looked for everything I could find
the thing is I wanna know everything about physics by just reading textbooks.
and solving problems
However, am not able to find the correct textbooks
or which explains the topics I want to know.
 
have you tried the library?
 
@skullpatrol Yes, I have.
 
any university library will have good textbooks
 
i wanna find them online
 
start with a real library
 
8:37 AM
@skullpatrol What's the difference between reflection of water waves and light waves?
 
@Morata are you familiar with the Huygens construction for calculating how waves diffract and reflect?
I ask because the Huygens construction applies to all waves, light, sound, water waves and any other kind of waves that I haven't thought of.
 
8:57 AM
Guys, should I read the history of Quantum Mechanics before starting to actually learn QM? Or maybe I should directly start learning Quantum Mechanics?
 
Anonymous
@Morata Heh. Looking at your profile picture, I thought you're Floris.
 
@NovaliumCompany how much time do you have?
 
Anonymous
@NovaliumCompany The latter is more useful. That said, knowing the historical background behind a subject is nice, too, if you are interested and have time.
 
I'm 15. Considering this, quite a lot :D
 

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