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00:00 - 13:0013:00 - 23:00

12:09 AM
@obe so you're an expert on the harmonic oscillator now?
@0celo7 almost finished learning all of it. (from shankar and griffiths)
I learned how to solve it with ladder operators algebraically.
@obe do exercise 7.3.3 in Shankar, p. 196
it's quick and useful
I'll look at it later.
ladder operators = QFT in a nutshell
that's not even totally wrong
12:11 AM
a lot of basic string theory is ladder operators too
@ACuriousMind You made me sad.
@ACuriousMind when you said "index of the Laplacian" I thought we were going to get into K theory
:( no such luck
@0celo7 really? like creation and annhilation operators?
@TanMath yes
@0celo7 I know QFT! yay! lol
12:13 AM
the fields are decomposed into sums/integrals of such operators
@0celo7 Oh, should I have said "subscript"?
@ACuriousMind Yes.
@obe Sorry :(
@0celo7 ah..
in String Theory you use ladder operators to make string states
12:15 AM
I don't know what that is.
I just jumped on that question because it was tagged , and after I edited that out, I figured I could as well answer it for the edit+answer badge
state vectors of the string
right @ACuriousMind
@ACuriousMind It was fit for me to answer, and what was the point of all the information prior to the question.
@0celo7 Yeah, that part is just like normal QFT. Surprisingly much of the intro to String Theory is "just" a bunch of somewhat unusual QFT
@0celo7 CFT is a QFT.
@obe In this case, completely superfluous, but the question is better this way when I think of all the questions where people just write down a formula and ask about the meaning of a symbol we can't have a clue about without context
@ACuriousMind Why did you put a transpose instead of writing it vertically?
12:22 AM
@obe I think the transpose way reads better for inline math - the vertical vectors make the line spacing irregular.
@TanMath @obe For instance, the string is essentially a Fourier transform, with operator "modes" $\alpha^\mu_n$ that can create states. In light cone gauge, we have, for instance, $$\alpha^i_{-1}\tilde\alpha^j_{-1}|0;k\rangle\sim\text{graviton}\oplus\text{Kalb‌​-Ramond}\oplus\text{dilaton}$$
Here $|0;k\rangle$ is the string ground state with momentum $k$.
i'll answer it anyway since I need more answers.
obviously useless though idc.
@0celo7 Don't forget the fun fact that it's a tachyon :D
@ACuriousMind true
no one said bosonic string theory is right
Is there a way to disable the chat notifications about new questions?
12:27 AM
I'm confused by my two stars...
@alarge No, unfortunately not. (If no one wants them, though, we could ask the mods to remove them altogether, I also think they're mainly annoying)
@0celo7 Presence of a tachyon is not as such disastrous, always remember the Higgs is a tachyonic field.
@ACuriousMind I know this...
But there's no good way of dealing with the stringy tachyon, is there?
And it's very nice and convenient that the superstring has a "normal" vacuum.
@0celo7 I'm not sure. People probably didn't really try because we don't have fermions, anyway.
@0celo7 tachyons exist? really?!
@TanMath Yes, the Higgs.
12:31 AM
Should stress Higgs field, though. The particle we can observe is not tachyonic.
@TanMath We're talking about a different tachyon; this one is likely just the artifact of bosonic string theory being a toy model.
@ACuriousMind Just checking: higgs particle is the excitation about the vev of the field?
@0celo7 Yep
@ACuriousMind you know what time it is
@0celo7 half past 2am, why?
@ACuriousMind Lern Deutsch mit 0celo7
@ACuriousMind so how do I say "state vectors of the string" in German
ACM is dead, he's not saying anything
this is awk
12:47 AM
welp, he's dead
I'm the king of this chat now
Master, Master...
He's preparing for his reign of terror.
omg his ghost called me
nothing is happening...
My mic is working, why can't you hear me?!
12:49 AM
uh did you see my face just now
because this is not a good angle, I don't actually look like that
welcome back master
@Rigor when did you change to Rigor?
that's an imposter
3-4 hours
12:51 AM
the real ACM is trapped in an orbifold
5 hours ago, by ACuriousMind
Hmmm...When I'm an evil overlord, I should call my servant Rigor, not Igor, as would be custom.
damn my PC froze!
@Rigor ah.. and to confirm @skillpatrol is you a well?
@0celo7: What the hell? I heard a minute of noise, then it lost connection.
yeah my PC froze!
complete freeze!
12:54 AM
@TanMath yep
I can hear you
You said "Holy shit" :D
"Dude, my computer doesn't work"
Ah, there goes the connection again
Yeah that's me hard resetting
12:55 AM
I break your computer with the power of my voice?
Am I Dragonborn?
@Rigor why?
@ACuriousMind ok that's crazy
Skype killed my PC again
Wat do
I have no idea why that would happen
it's crazy
I was talking with an old BF3 buddy on Skype while playing BF4
I called in the group chat. Froze.
I'll reinstall.
This is definitely not good for the OS
1:49 AM
I am now proficient in technical German
I am actually not sure when I last talked about a technical thing in German :D
Oh, wait, that functional analysis lecture was in German
I guess "Sobolev" is the same in every language :/
2:07 AM
@ACuriousMind I thought that was in Denglish
Only the notes. But right, that was odd.
2:19 AM
@obe Can I skip the chapter on variational principle? which chapter is that
2:40 AM
Found on the site: "The electron is an electromagnetic wave going round and round.".
3:23 AM
@FenderLesPaul hola
@FenderLesPaul I read the preface of that GR in matrix form book
he says it's for scientists and engineers who don't know advanced math
that's really sad that he thinks the average engineer cannot read 20 pages on abstract math to grasp tensors
4:01 AM
@FenderLesPaul you should learn the rains of castamere
4:12 AM
@NeuroFuzzy is that a Celtic piece?
@0celo7 heyo
noooo it's the game of thrones red wedding song!
and it sounds really good on guitar
any book that does GR using matrix mechanics should just be burnt
@NeuroFuzzy I'll give it a go!
hopefully it works :)
@FenderLesPaul yeah this! youtube.com/watch?v=POiqCHeeQvg
ooh that
yeah that would be fun to learn for sure
I'll get on that
right after I learn how to sing and play Kathy's song
4:33 AM
@FenderLesPaul oh, just listened to it. That sounds like fun guitar.
5:06 AM
@FenderLesPaul Is CMT interesting?
5:20 AM
hola hola hola
I need your opinion, but that means I need constant feedback too
I was thinking about the topic of why we see in visual light only
hmmm...sounds biological
5:25 AM
So I will write a detailed explanation, it will take a minute or two
Yea, I asked the biological community and they told me it's simple physics
Still up for a little bit of abstract thinking?
Sorry, I gotta run :(
:( alright then
You could ask on main.
5:27 AM
Like you mean a question?
@obe yes
It's a question that would be considered to have no actual answer
CMT is very interesting
imo by far the most interesting part of physics is CMT
what does CMT stand for
5:29 AM
@NeilGraham condensed matter theory
@obe if you're interested on basics
check out "Condensed matter field theory"-Altland and Simonds
Is there a simple concept to CMT that can be understood easily?
it's more of a discipline than a theory in the formal sense
it encompasses an extremely large portion of physics
Like electromagnetic effects?
EM, QM, QFT, statistical physics
@NeilGraham I don't like to understand Physics by it's terms, I would rather have experimental data presented to me in which I can interpret it myself.
I don't think that's a good idea.
5:36 AM
it's awesome
@obe Why is that?
It is inefficient.
Like are you going to take all the data from CERN and derive QFT and the Standard Model from it?
I still need to understand it's terminology to understand it's concepts but I like to break things down to the actual physical characteristics
You should first learn physics by its terms then do the other thing when you are at the frontier, if you want.
It will be a lot faster and effective.
I am only 17, and am planning to major in physics, so I am up for different interpretations
5:39 AM
Lol there are a lot of 17 year olds here including me.
@NeilGraham I guess that is a proper mindset though.
@NeilGraham just read the Feynman lectures
the rest will follow suit
@obe Oh that's pretty cool, but do you believe that it is almost necessary to actually not always be fully convinced by these concepts?
and do lots of problems in mechanics and EM
worry about the big picture and interpretations and viewpoints of physics later
@FenderLesPaul I was actually thinking about doing that
before you form interpretations and mindsets about physics
it's good to have a very good intuition for the subject
and Feynman lectures are the best for that IMO
along with doing a lot of really hard problems
like from Irodov's general physics problem book
5:42 AM
@FenderLesPaul Are they any bit out-dated?
or any IPhO type problem book
they're all on mechanics, thermodynamics, EM, relativity and such
which haven't changed at all since then so it's fine
plus Feynman's intuition is unparalleled
@FenderLesPaul You're sending him to the IPhO route?
yes I believe that's the most effective way to get really good at physics before jumping into more advanced stuff
What does that even mean
because it involves solving a lot of conceptually difficult mechanics and EM problems
@NeilGraham international physics olympiad
5:44 AM
The effort required to get IPhO absolute winner is about the same as learning GR, QFT, ST... to an advanced level.
no it isn't
Solving problems is boring though.
IPhO requires solving conceptually difficult problems and requires building really good intuition for down to Earth concepts
GR and QFT problems are not conceptually difficult at all
they're just tedious
solving problems isn't boring in IPhO
So it's a competition?
those problems are insanely fun brain teasers
@NeilGraham yes but the contest isn't my focal point
I just meant focus on being able to solve problems at that level
and you'll be golden
5:46 AM
I did that last year.
I regret it a lot.
I recommend Irodov or Morin "Classical Mechanics With Problems and Solutions"
Can I explain this one idea that I derived myself, and ask you if this is at least decent problem solving done?
the latter has quite a few very fun problems
lol Irodov, I have a copy on my desk.
@NeilGraham I mean you can
but really if you're at the stage of learning physics you should hold off on the personal idea building for a while :)
5:48 AM
@FenderLesPaul Well this idea is backed up pretty well
go for it
@FenderLesPaul I was looking at a glass of water and was thinking about why we see water as completely clear. For some reason, I delved more into this idea. I began to think that it may be an evolutionary advantage that we were able to see 'clean' water as clear and 'dirty' water as murky, but to be honest this was not significant and only led me onto more in depth thinking. I then understood that all biological life originated in the ocean's, full of mostly water, and that sight was developed..
by these biological organisms. The main thing I understood finally was that the light that could perfectly go through water, aka visible light, was the only light that could be perceived by these organisms, and that is simply why we see in visible light only.
Other organisms that can see ultraviolet (which is not many) and ones that can see in infrared light use antennas and other methods, but the eyes developed from early organisms in the oceans
Light doesn't perfectly go through water though. The reason we see visible light only is because the spectrum of the sun is focused in the area that we call visible light.
This is a biological theory, not a physical one.
Yes, I understand that, but then again I am interested in all of science, not specifically physics. I find that kinda hard to get around, to only be focused on one science subject.
5:56 AM
I have to agree with obe here
Science is too large now to do that, polymaths are becoming more and more rarer.
we mainly see visible light because the sun's spectrum is focused mainly there within the Earth's surface
Even if you focus on one topic, it's still too large to explore completely.
What do you mean the suns mainly focused on the visible light spectrum exactly?
and as obe noted, light does not perfectly go through water
5:58 AM
Well the error in what I explained for one is that the ocean is not made fully up of just water.
@NeilGraham The light produced by the sun is mostly in the visible range of the spectrum.
That is how we defined visible light.
@NeilGraham it doesn't have to do with other substances
@NeilGraham Right, and are you forgetting the most obvious thing? Air.
this is an intrinsic property of water
it absorbs certain frequencies and reflects others
Yes, I understand that light had to go through our atmosphere before it went through the water and was perceived
6:00 AM
Therefore even in that case it's more likely that eyes evolved on land by your theory.
I don't know if that's right though.
Yes, it had to of, because our atmosphere is obviously more forgiving to light.
@0celo7: You know anyone who has a MacBook 12?
The main idea I'm trying to portray is that the only information that organisms underwater who developed eyes could interpret was the light that could be seen through water, and that has influenced the spectrum in which we can see in overall.
@NeilGraham It did not because we would have evolved to see this spectrum regardless of whether water is transparent.
And that is why some animals developed antennas and such
6:05 AM
There are a lot of documentaries you can watch on this
To be able to see a larger spectrum of light
Those are extra-sensory organs that formed due to evolutionary constraints.
to learn how and why organisms developed eyes, even primitively underwater
they're pretty laid back documentaries too
Check out David Attenborough's series on the origin of life
they're my favorite
Where can I watch something like that
there are also some papers in AJP that were published many years ago
that explain optical phenomenon in water using harmonic oscillators
let me see if I can dig those up
6:08 AM
@NeilGraham See, this is why your approach to science is flawed. If you had bothered to do some research and reading in the origin of life, eyes, and formation of the oceans and atmosphere by well established facts, you would not think of these theories and instead learn a lot more.
screw it I'm watching it again
You have to be infinitely intelligent to be able to decipher all of science from data and observation.
not to mention it takes away a significant beauty of physics
and takes away a very crucial reason so many people love physics
starting from the ground up, building a theory using concepts and mathematics, and then using calculations to make predictions that experiments verify
That is the problem that you have, you think that you need to be a genius to be able to understand how things work. Physics isn't understood by geniuses, it's understood by the curious.
By the way, that is @obe
6:12 AM
no one's saying you have to be a genius to understand physics
if you do it the way physics is normally done a la Newton
or Galileo
you do have to be infinitely intelligent to however start from experimental data on pulleys and inclined planes
and derive Newton's laws just from the data
Can you define infinitely intelligent
without even thinking about concepts like force
or mass or acceleration
there's some abstract thinking that you have to do in the end
you can't just bootstrap experimental data into a physical theory
@NeilGraham Infinitely intelligent is a kind of abstract term.
@NeilGraham Why would the curious waste their time coming up with theories about things that have already been explained before by someone else, rather than learning about things that already exist?
@obe That is where you are true
I wish David Attenborough was my grandfather
6:18 AM
I google search though, and I stupidly believe that is enough.
The benefit that theory has over experimentation is that it can make predictions within its own framework, and that is where experimentalists fall behind theorists.
@NeilGraham You need to read more books instead, or learn to research from the internet properly.
@obe I'm backed up on learning programming or learning this, so it is a hard decision.
I guess I can learn both
@NeilGraham You can, it's better to.
I'm off, bye.
peace dude
@obe bye
So @FenderLesPaul, do you believe that a good start for me would be to start off on the Feynman Lectures and do background research along with that?
6:24 AM
Uhh I wouldn't just stick to Feynman Lectures
they don't have problems
there is a companion problem book but it's not that great
you should somehow find a good problem book or a textbook with good problems
in regular classical mechanics for example
I am taking AP physics this upcoming school year, so classical mechanics is essentially covered for me.
AP Physics problems are a joke
you need to go beyond those
it pays off trust me
the harder the problems in classical mechanics you can solve
the much better honed your problem solving skills and intuition will become
Okay, would you know where I could possibly find these more advanced problems.
and your ability to intuit in more advanced areas of physics will greatly improve
Irodov, Morin, Kleppner are three that I like in particular
these are books
these would do the trick coupled with your AP Physics C class
side note: is it still called AP Physics C?
iirc they changed a lot of the terminology after I graduated high school
No, straight up AP Physics
6:30 AM
ah ok
well anyways I hope that helps
So do these books teach as well
the second one does
first one doesn't
it's just a problem book
this is a lot of material by the way
definitely take your time with it
no rush whatsoever
And does this go all the way to thermodynamics and possibly even relativity?
Morin includes some relativity but no thermo; irodov has some thermo problems iirc
but don't worry about thermo or relativity for now
just focus on mechanics
and EM
Okay, thanks a lot by the way.
6:33 AM
no problem broski
btw I would recommend watching as many David Attenborough documentaries as you can
I have no working knowledge of biology at all so idk just how dumbed down these documentaries are
but they're soooo cool
especially the ones on insects
They are not dumbed down
well that's awesome
They are just sort of providing basic information, but I use them to get ideas about neural systems by learning more about the properties for unusual species
6:36 AM
That was a pretty cool abrupt confirmation right there
Anytime :D
6:49 AM
@ACuriousMind I was rereading my ballentine quantum mechanics book. I read about gauge transformations I finally now understand that they are a mathematical construct. But I dont quite get why. Could you try explaining it to me? I get the $\phi$ and $\mathbf{A}$ constitute the four potential but I am so used to thinking about E and B as fields in the vector sense, I am habing trouble imagining what the four potnetial is. Any help would be great :D
3 hours later…
9:39 AM
@StanShunpike you know the definitions of $E$ and $B$ as derivatives of the potential?
10:18 AM
Did you find a way to login to meta? @DavidZ
Yeah, it's a known problem with HTTPS on meta sites
Ok, interesting...
10:40 AM
Q: Can't log into some meta sites

Dan NeelyI'm logged into the main sites for Workplace.SE, Physics.SE, Money.SE, and Space.SE; but show as logged out when I go to any of the meta's for those sites. Attempting to log in again results in the page refreshing with my still being logged out. I am able to visit meta.StackOverflow, and meta.S...

11:21 AM
@dmckee : re your find, yes, that's what an electron is. In atomic orbitals "electrons exist as standing waves". Kick that electron out of that orbital, and it still exists as a standing wave. That's why you can diffract electrons. Standing wave, standing field. The Einstein-de Haas effect is for real. If I can expand on this please don't hesitate to ask.
Oh, and could you do something about the serial downvoting please? Somebody's going through my old answers downvoting them for no good reason.
11:41 AM
du u now interfernce of light?
12:18 PM
Following a conversation I had with Bosoneando, I thought I'd ask a question about why electrons and positrons move in opposite helical paths. Here it is. I couldn't find any duplicates. I'd be grateful for your answers and/or comments.
12:48 PM
@StanShunpike You'll have to tell me more specifically what your trouble is. The idea of a gauge transformation you can already see in the three-dimensional potential $\vec A$, because you can add any gradient $\nabla\phi$ to $\vec A$ and have the $\vec B$-field unchanged: $\nabla\times(\vec A + \nabla\phi) = \nabla\times\vec A$.
@Huy Not personally, no. I've seen them around campus, however.
@ACuriousMind conformal field theory?
@0celo7 huh?
@ACuriousMind What is CFT in German?
@0celo7 Konforme Feldtheorie, obviously ;)
@ACuriousMind never heard of Konforme before
I...can't stop looking
It's so beautiful
12:53 PM
It's not an usual word, but it is the translation of conformal - the conformal maps of complex analysis are konforme Abbildungen.
@ACuriousMind a usual
IDK if typo just FYI...
I have never come to terms with that rule looking at pronounciation and not spelling :D
It's to make speech flow better!
an usual just sounds wrong!
the worst is when you have a(n) (acronym)
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