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MartianCactus
MartianCactus
7:00 PM
noice
ok i now got to go
gotta study for computer test :P
bye!!
 
user218912
bye
 
MartianCactus
MartianCactus
nice discussion!
the book is TOO constly tho
 
user218912
read a pdf of it.
 
Obliv
Obliv
@martian you can find it online for free if you look. Though, I preferred the physical copy of my calc book back in high school
brought it to my other classes that I didn't care about so I could study it
@iceL I did what you did but only with calc 1 & some of 2 senior year.
what made u want to read an entire calc book anyway? Was it your parents?
 
MartianCactus
MartianCactus
me?
 
Obliv
Obliv
7:04 PM
Talking to @ice
 
MartianCactus
MartianCactus
no i havent read it so
kewl
 
user218912
@Obliv no because I wanted to learn physics for real. and someone told me it required calc 1-3.
 
user218912
my parents don't like me reading ahead.
 
0celo7
0celo7
@Obliv To really understand Shankar you need a course on vector calculus, linear algebra, and PDEs.
 
MartianCactus
MartianCactus
what is "for-real" ?
 
0celo7
0celo7
7:06 PM
@IceLord what?
 
MartianCactus
MartianCactus
like understanding everything on the deepest lvl?
 
user218912
@0celo7 you don't need a full course on pdes. you can just learn the stuff as you go.
 
user218912
@MartianCactus yes.
 
MartianCactus
MartianCactus
i know linear algebra
its the linear equations thing right?
 
Obliv
Obliv
@martian wow you're smarter than @0celo7 then
 
user218912
7:06 PM
@MartianCactus no.
 
MartianCactus
MartianCactus
oh
@IceLord well I have the same problem
wont call it a problem tho..more like a gift
 
user218912
I can see that.
 
Obliv
Obliv
@0celo7 I don't plan on reading shankar anyway.
 
user218912
@0celo7 what?...
 
0celo7
0celo7
it's a problem because nerds never get girls @MartianCactus
 
MartianCactus
MartianCactus
7:08 PM
theres a calc course on KA hto
tho*
 
user218912
don't waste your time there.
 
MartianCactus
MartianCactus
khan academy
i dont look like nerd do
so I wont have a problem..sure that IceLord is handsome too :P
 
user218912
...
 
MartianCactus
MartianCactus
ok bye!
 
user218912
@Obliv why?
 
user218912
7:10 PM
I read shankar in 7 days.
 
user218912
it's really basic.
 
MartianCactus
MartianCactus
idk what vectors
are
will i still understand that book?
the calc one?
 
user218912
@MartianCactus yes there is a chapter on vector algebra so you'll learn.
 
0celo7
0celo7
@IceLord I learned Calc 2 and 3 from there.
I say it's a pretty good place to waste time on.
 
user218912
@0celo7 no you said you used paul's notes.
 
0celo7
0celo7
7:13 PM
I lied
I used KA
 
MartianCactus
MartianCactus
ok
 
0celo7
0celo7
I can show you my account if you don't believe me.
 
MartianCactus
MartianCactus
u learned calc from KA??
 
user218912
I can't tell if he's trolling.
 
Obliv
Obliv
@iceL I'd rather learn linear & abstract algebra first. Then maybe I'd learn some topology/geometry. What's the point in reading a physics book if I'm doing a physics degree that's going to teach me that stuff anyway
I'm not going to be taking hard math courses so I'd rather learn those on my own time if i can help it
 
MartianCactus
MartianCactus
7:14 PM
why are you calling KA a place to waste time??
 
0celo7
0celo7
I don't think you have what it takes to learn geometry
 
user218912
because KA is for n00bs
 
MartianCactus
MartianCactus
?
why?
its a good place
 
Obliv
Obliv
@0celo7 it'd be a very slow and arduous process so nothing in the next couple years probably.
 
MartianCactus
MartianCactus
they explain everything clearly
 
Obliv
Obliv
7:15 PM
actually maybe 2 years from now. who knows
 
user218912
@MartianCactus exactly.
 
MartianCactus
MartianCactus
??????????????
 
Mostafa
Mostafa
Today, one day after I submitted my Masters thesis proposal on a topic related to topological insulators, the founders of the field got their Nobel prize!! :)
 
0celo7
0celo7
IceLord is an edgy teenager, don't listen to him @MartianCactus
 
user218912
wow.
 
0celo7
0celo7
7:17 PM
@MartianCactus I highly recommend KA.
 
user218912
@0celo7 I believe you're lying about using KA, because if you got spoonfed like that then how did you get the maturity to read advanced books on your own right after?
 
0celo7
0celo7
@IceLord See above.
 
MartianCactus
MartianCactus
80k points not bad
 
Obliv
Obliv
How do I solve $\mid \sqrt{16^2 + x^2} - x^2 \mid = \frac{1}{2}$
 
Mostafa
Mostafa
I was jumping all over the room like I won the Nobel prize!!
:)
 
0celo7
0celo7
7:19 PM
@Obliv You...don't. Why would you?
 
MartianCactus
MartianCactus
 
0celo7
0celo7
@IceLord So, anything to say now?
 
Obliv
Obliv
@0celo7 the phase difference between imgur.com/a/aHiGl the two points as $P$ approaches some $x$ is $\frac{\phi}{2\pi} = \frac{\Delta L}{\lambda}$ is this right
 
user218912
@0celo7 no i'm dumbfounded.
 
0celo7
0celo7
I don't know anything about EM @Obliv
 
Obliv
Obliv
7:21 PM
If I'm looking for the point $x$ at which the phase difference is half a wavelength (given $d = 16m$ then it's the hypotenuse of the triangle formed by $S_1,S_2,P$ minus the side right?
oh my original eq. would be $x$ not $x^2$
@0celo7 it's not EM it's algebra
so it's $\mid \sqrt{(x+16)^2 - 32x} - x\mid = \frac{1}{2}$
aw man I think I'm doing this wrong
 
MartianCactus
MartianCactus
so thers calculu 1 , caculus 2 and calculus 3?
 
0celo7
0celo7
@IceLord Why?
We can't all be as smart as you and learn calculus from a book...
 
user218912
@0celo7 don't troll me.
 
0celo7
0celo7
How am I trolling you?
 
user218912
I used online lectures and books, but not KA, and you learned most of what you know from books.
 
0celo7
0celo7
7:26 PM
I'm not clever enough to have learnt calc 2 and 3 from books
 
Obliv
Obliv
KA is very good @iceL for starting out
 
user218912
@0celo7 but you learned everything else which is 500x harder from books?
 
Obliv
Obliv
to build a foundation anyway
 
0celo7
0celo7
this ^
KA built the foundation
 
Obliv
Obliv
I did it for calc 1
got a 5 on my ap exam
 
user218912
7:27 PM
I used mit ocw for calc 1-5.
 
Obliv
Obliv
1-3*? @iceL
 
user218912
@Obliv including ode's and linear algebra.
 
Obliv
Obliv
oh
 
user218912
I never liked KA because it's slow af.
 
user218912
I watched my lectures in 3x speed.
 
user218912
7:28 PM
maybe that's why my foundation is bad.
 
0celo7
0celo7
agreed on points 1 and 3
 
user218912
if you agree on point 1 then why did you use it?
 
0celo7
0celo7
I wonder if @IceLord could do my ODE final
 
user218912
@0celo7 I'd have to study.
 
user218912
for a few days.
 
user218912
7:30 PM
but sure.
 
user218912
all the ode's in physics are trivial so I forgot all the methods.
 
0celo7
0celo7
ha!
trivial!
 
user218912
what?
 
0celo7
0celo7
sounds like someone didn't read Shankar properly
 
user218912
maybe.
 
Obliv
Obliv
7:33 PM
@iceL that's why you don't listen to all the lectures. I just used it for practice problems and clearing up certain concepts
 
user218912
@Obliv I wish KA had QFT.
 
user218912
I would use it.
 
Obliv
Obliv
Lol don't we all. If sal could explain QFT with as much ease as the other subjects we'd be very fortunate
 
Slereah
Slereah
Bloody hell
Apparently there's two different definitions of continuity for hyperreal functions
 
yuggib
yuggib
Well there are plenty of topologies
 
Slereah
Slereah
7:50 PM
@yuggib are you knowledgable in non-archimedean fields
 
yuggib
yuggib
I read something about non-standard analysis
but I am not so knowledgeable
 
DanielSank
DanielSank
@Qmechanic Indeed. This is probably a very good thing.
 
Slereah
Slereah
Do you know what the benefit of using $^\rho \Bbb R$ over $^*\Bbb R$ is
I have hunches but I'm not so sure
 
yuggib
yuggib
what is $^\rho\mathbb{R}$?
 
Slereah
Slereah
Asymptotic numbers
It is $= M_0 / M_1$
$M_0 = \{x \in\ ^* \Bbb R | \exists n \in \Bbb N. |x| \leq \rho^{-n} \}$
$M_1 = \{x \in\ ^* \Bbb R | \forall n \in \Bbb N. |x| \leq \rho^{n} \}$
I think that's supposed to be a restriction of hyperreals to a certain scale of infinitesimals and infinites
From perusing I think the benefit might be that you can write asymptotic numbers as taylor series of infinitesimals
 
yuggib
yuggib
7:58 PM
I don't see why that should be useful
 
Slereah
Slereah
But I'm not convinced
Well most people seem to use it for various applications
So there has to be something there
 
yuggib
yuggib
"various applications"??
 
Slereah
Slereah
Most embedding of distributions in non-archimedean functions seem to be done in that
 
yuggib
yuggib
I am not sure that is useful
the point with non-standard analysis is that there is the transfer principle
so statements about starred things do not give "more information" than statements about usual stuff
 
Slereah
Slereah
Well there is also the transfer principle in asymptotic numbers
Also do you know how to write $^*\Bbb R$ properly in latex
I'm using ^*R but it fucks up if it's next to another character
 
yuggib
yuggib
8:03 PM
no I don't know
anyways, the idea that I got is that non-standard analysis may be useful for pedagogical purposes but not much more than that
 
Slereah
Slereah
It has its benefits
You can build an algebra of distributions in it
 
yuggib
yuggib
it has also its drawbacks
@Slereah maybe, but you can't do much with that algebra
 
Slereah
Slereah
Why not
 
yuggib
yuggib
because either you can't transfer back or you already could manipulate the original distributions in some sense
 
Slereah
Slereah
That's a generic feature of algebras of distributions, though
Colombeau's algebra forms a non-archimedean space as well
But, unlike $^*\Bbb R$, it's a ring, not a field
It's part of the reason why you get infinities in QFT
 
yuggib
yuggib
8:08 PM
bah
 
Slereah
Slereah
"In a sense the field $\Bbb R$ suffers from the disadvantage of being archimedean, ie, it has neither infinitely small nor infinitely large numbers. The field $^*\Bbb R$, on the other hand, suffers from a surfeit of infinitely small and infinitely large numbers. We propose in this chapter to construct and investigate a field midway between $\Bbb R$ and $^*\Bbb R$, which is nonarchimedean, but does not contain infinite numbers of unrestricted size, nor infinitesimals that are arbitrarily small"
Ah yes, there we go
I suspected as much
 
yuggib
yuggib
if you want to solve perturbative divergences there are plenty of standard tools
 
Slereah
Slereah
Well yes, but those already exists
What I want is write a paper :p
 
yuggib
yuggib
well, I have the impression that it is not the most promising subject
 
Slereah
Slereah
Psh, promising subjects have all been done way long ago
 
yuggib
yuggib
8:10 PM
even if I agree that singular perturbation theory of operators is intriguing from the QFT point of view, even non-perturbative
 
Slereah
Slereah
Do you have any ideas how many time I found a great topic only to find some jerk did it 40 years ago
Promising topics are all way too complicated to do by my lonesome
 
yuggib
yuggib
you need an advisor
that is supposed exactly to avoid that
 
Slereah
Slereah
Well yes but I had one
And he couldn't find me a grant for my thesis topic
So there I am
 
yuggib
yuggib
you should look for another advisor if you are genuinely interested in that career
 
Slereah
Slereah
I did
 
yuggib
yuggib
8:13 PM
and try to get a grant
 
Slereah
Slereah
For two unemployed years
Three, counting that year I did a math master
Couldn't keep at it for much longer
Following your dream doesn't pay all that much
 
yuggib
yuggib
I understand
 
Slereah
Slereah
Since I'm not getting paid I'd rather do a fun topic
 
yuggib
yuggib
yes that's true
but then don't even bother for (pseudo)-mathematical topics
 
Slereah
Slereah
What is pseudomathematical about it
If I wanted something promising I'd do something boring like semiconductors or graphene
 
yuggib
yuggib
8:15 PM
don't know the details of what you have in mind
 
Slereah
Slereah
Hyperreals get a pretty bad rap
 
yuggib
yuggib
but if you want to do mathematics, and you're not used to write formal proofs is much more diffcult
 
Slereah
Slereah
I know plebs talk about it a lot but it's real math
Eh I've done plenty of formal proof
I was way into formal logic back in 2008
I did the first 13 chapters of the Principia Mathematica by hand
Fun~
 
yuggib
yuggib
No offence meant, but I don't think you're used to write formal proofs at a professional mathematical level
 
Slereah
Slereah
Probably not
We'll see how things turn out
 
yuggib
yuggib
8:18 PM
I hope well for you; but I can tell from experience that mathematicians are extremely more picky than physicists when it comes to refereeing papers
 
Slereah
Slereah
Well I'm not looking to write too mathy a paper, either
Just want to attempt to write a renormalization method using non-archimedean functions as distributions
And then the physical constants as aymptotic numbers
It has been kinda done already but using Colombeau algebras
I'd like to start it from the Hilbert space
But then I must build a non-archimedean Hilbert space
Which requires a field
 
yuggib
yuggib
Hilbert space of what?
btw, it has already been done (the construction of nonstandard Hilbert spaces)
 
Slereah
Slereah
Hilbert space over $^\rho \Bbb R$ instead of $\Bbb R$
Yeah I know
I have Toka Diagana's book opened too
On nonarchimedean Hilbert spaces
 
yuggib
yuggib
@Slereah I mean, Hilbert space of which quantum theory?
 
Slereah
Slereah
QFT
Don't really need it for QM
 
yuggib
yuggib
8:23 PM
which one? there are inequivalent representations of the ccr
 
Slereah
Slereah
Probably something simple to start with
Just free scalar field or something
To renormalize the vacuum energy
 
0celo7
0celo7
what's going on peeps
 
Slereah
Slereah
not much
Valter!
I had a question for you
Like 18 months ago
 
0celo7
0celo7
@ValterMoretti is that really you?
 
Slereah
Slereah
15
Q: Do tachyons move faster than light?

I Studied At HogwartsI am trying to understand whether or not tachyons travel faster than light. The linked Wikipedia page shows some seemingly contradictory statements, and they are confusing. For instance, the first sentence states that tachyons "always travel faster than the speed of light" whereas, in a later se...

special-relativity faster-than-light tachyon
" The fact causality is not violated no matter the sign of m2 is trivial: Causality properties of solutions of linear PDEs are always described by the principal part of the equation. It is gμν∇μ∇ν here, in all cases. The sign of m2 is irrelevant. – Valter Moretti Sep 26 '15 at 21:32"
What theorem is that
Couldn't find it
 
0celo7
0celo7
8:33 PM
Did you check Evans?
 
Slereah
Slereah
I don't know what Evans is
unless you mean
Rich Evans
 
0celo7
0celo7
no
the PDE book
I have it on my shelf, like any respectable person
 
Slereah
Slereah
I'm hoping @ValterMoretti will answer my question because I'm not sure I'll still be alive for his second coming
 
Obliv
Obliv
@0celo7 the mean free path of a gas is greater when the velocity of the particles are greater?
 
0celo7
0celo7
how would I know
 
user218912
8:46 PM
@Obliv yes.
 
Obliv
Obliv
The free path of a single particle is shorter when it's moving faster relative to the other particles, though @iceL
kind of strange to me.
well no the second part makes sense
the first part doesn't really.
 
Slereah
Slereah
Mean free path
In physics, the mean free path is the average distance traveled by a moving particle (such as an atom, a molecule, a photon) between successive impacts (collisions), which modify its direction or energy or other particle properties. The following table lists some typical values for air at different pressures at room temperature. == Mean free path in radiography == In gamma-ray radiography the mean free path of a pencil beam of mono-energetic photons is the average distance a photon travels between collisions with atoms of the target material. It depends on the material and the energy of ...
 
0celo7
0celo7
> Jennings, S (1988). "The mean free path in air". Journal of Aerosol Science.
interesting journal
 
Slereah
Slereah
apparently doesn't depend on it
 
user218912
@Slereah well temperature is related to kinetic energy which is related to velocity right?
 
Slereah
Slereah
8:49 PM
But it doesn't depend on that
Just the density and cross section
 
Obliv
Obliv
@slereah the derivation of that formula is from $\frac{\text{total distance}}{\text{number of collisions}}$ where the total distance is the avg. velocities of the particles in the gas multiplied by the time
 
user218912
@Slereah yes but read further down there is a formula for it with temperature. using ideal gas law.
 
Obliv
Obliv
and the number of collisions is the # of collisions one particle has on its path thats relative to the other particles
i.e $$\frac{v_{avg}\Delta t}{v_{rel}\Delta t \frac{N}{V} \pi d^2}$$
 
user218912
lol you have an extra curly brace
 
user218912
nvm
 
Slereah
Slereah
8:53 PM
"An important feature of our field $^\rho \Bbb R$ is that, putting it paradoxically, its infinite numbers are small and its infinitesimals are large."
heheheh
 
Obliv
Obliv
i'm going off of what the book said since Idk what that $\mathcal{l}$ is
 
user218912
@Obliv mean free path...
 
Obliv
Obliv
lol
 
Valter Moretti
Valter Moretti
@0celo7 Hi, what's the matter?
 
0celo7
0celo7
@Slereah needs you desperately
 
Obliv
Obliv
8:59 PM
huh.. the molar specific heat of a gas changes depending on the process it's undergoing. Less heat is required to raise the temperature if the process is constant volume. When volume changes and pressure is held constant then slightly more heat is required to change the temperature. This makes sense because the gas uses some of that energy to change the volume
(thinking to myself)
 
Valter Moretti
Valter Moretti
please here is quite late, I am tired, I should go to sleep
 
0celo7
0celo7
27 mins ago, by Slereah
" The fact causality is not violated no matter the sign of m2 is trivial: Causality properties of solutions of linear PDEs are always described by the principal part of the equation. It is gμν∇μ∇ν here, in all cases. The sign of m2 is irrelevant. – Valter Moretti Sep 26 '15 at 21:32"
He is wondering about this statement you mad
 
Valter Moretti
Valter Moretti
YES
 
0celo7
0celo7
Specifically if you know of a reference
 
Valter Moretti
Valter Moretti
WALD
the book on GR
 
0celo7
0celo7
9:00 PM
I know it, chapter 10?
 
Valter Moretti
Valter Moretti
it is easy
I think so
 
Slereah
Slereah
Lemme get my Wald
 
Valter Moretti
Valter Moretti
PDE od 2nd order in Lorentzian manifolds, all causal properties are fixed by the principla part of the operator
 
Slereah
Slereah
Thanks
 
0celo7
0celo7
Speaking of Wald and PDEs
 
Slereah
Slereah
9:02 PM
I'll look up Wald for that theorem
 
0celo7
0celo7
@ValterMoretti Do you have Wald right now?
 
Slereah
Slereah
I'm wondering if it means phantom fields are not causal
 
Valter Moretti
Valter Moretti
unfortunaltely I have not
I am home
 
Slereah
Slereah
My Wald is in my home
 
Valter Moretti
Valter Moretti
"phantom" fields?
 
Slereah
Slereah
9:03 PM
Always good company
 
Valter Moretti
Valter Moretti
I have about 200 books in my office, too many for home
 
Slereah
Slereah
Get a big ol' book case
 
Valter Moretti
Valter Moretti
However, tomorrow I will give you some more precise reference
 
Slereah
Slereah
Thanks
 
0celo7
0celo7
@ValterMoretti I might ask a PSE question on Wald Prop. 11.1.1.
There's a line in the proof that's blown my mind since I first read the book
 
Valter Moretti
Valter Moretti
9:05 PM
I do not know :) I do not remember all statements in Bob's book
 
0celo7
0celo7
Maybe I should pick it up this weekend and give it another shot
@ValterMoretti It's about asymptotic behavior of massless KG fields along geodesics.
 
Valter Moretti
Valter Moretti
I essentially mean the fact that the support of solutions is completely included in $J^\pm(S)$
where $S$ is the support of Cauchy data on a Cauchy surface
 
Slereah
Slereah
I think it might be theorem 10.1.3
 
Valter Moretti
Valter Moretti
this property only depend on the highest order of the differential operator
$\Box$
 
0celo7
0celo7
Lol
@Slereah cf. Leray
 
Slereah
Slereah
9:07 PM
Who
 
Valter Moretti
Valter Moretti
You may add any other term like \pm m^2 and the result does not change
 
0celo7
0celo7
the proof of 10.1.3 is not in Wald
 
Slereah
Slereah
Is it gonna be in HE again
 
0celo7
0celo7
no, it's in Leray.
 
Slereah
Slereah
And then not actually be in HE
 
Valter Moretti
Valter Moretti
9:08 PM
I think the same result, which is standard, can be found in Friedlander's book
 
0celo7
0celo7
Which book is that?
 
Valter Moretti
Valter Moretti
The one about wavefunction in curved spacetime, something similar
It is easy to find
 
0celo7
0celo7
Interesting!
@ValterMoretti Thanks for another senior project idea :)
 
Valter Moretti
Valter Moretti
That one!
OK, sorry I MUST sleep now. I have a lecture tomorrow morning
bye
 
heather
heather
I'm trying to figure out how Shor's algorithm (in quantum computing) is actually implemented; i.e., what gates are used in what order. Does anyone know a good resource to figure this out?
 
Slereah
Slereah
9:13 PM
bye
 
0celo7
0celo7
Ok @Slereah what book should I read next
 
Slereah
Slereah
any topic?
 
0celo7
0celo7
Math preferably
 
Slereah
Slereah
Can't go wrong with "A history of mathematical notations", by Florian Cajori
 
0celo7
0celo7
Did you read it?
 
Slereah
Slereah
9:23 PM
I have read parts of it
It's more of a reference book
Not much point in reading all of it
 
0celo7
0celo7
Some dude just stopped me and asked me if i wanted to come to "bible talk"
 
Slereah
Slereah
Please do
 
0celo7
0celo7
Why?
 
Slereah
Slereah
Ask them to read Ezekiel 23:20
 
0celo7
0celo7
Which one is that
 
Slereah
Slereah
9:26 PM
the best one
 
0celo7
0celo7
Is it the one with the donkey penises
 
Slereah
Slereah
it is
 
0celo7
0celo7
You damn weirdo
 
Slereah
Slereah
Are you calling the bible weird
You heathen
 
0celo7
0celo7
No I'm calling you a weirdo
 
Slereah
Slereah
9:29 PM
Did u know
The Bible predicted quantum mechanics
 
0celo7
0celo7
I believe it
It's written by Him after all
Lord Motl
 
Slereah
Slereah
"The order created by God is on a foundation of uncertainty. The Book of Genesis explains that the world was an abyss of chaos at the moment of creation. Quantum mechanics is predicted in several additional respects by the Biblical scientific foreknowledge."
Good news $^\rho \Bbb R$ is a complete field
with respect to its ultrametric
Also all Cauchy sequences converge
Which is nice
 
Obliv
Obliv
9:53 PM
whelp test time. hope this studying pays off.. ahaha..
 
user218912
good luck.
 
Obliv
Obliv
thanks. I just hope there aren't any carnot engine problems since that's the only part I didn't cover.
 
user218912
@Obliv what course is this?
 
Obliv
Obliv
physics 3
I also have a calculus exam tomorrow at 6pm
didn't study for that at all since I've been studying for physics.
tomorrow will be fun.
 
user218912
okay gl.
 
user218912
9:54 PM
bye
 
0celo7
0celo7
Guys I need help with calc 3
 
user218912
::asks super duper technical math question and calls it calc 3 because it uses ideas from calc 3::
 
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