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00:00 - 16:0016:00 - 00:00

12:59 AM
@FenderLesPaul maybe tomorrow :3
 
1:25 AM
@GBeau what's tomorrow?
 
DEATH
 
yay
@GBeau we must stay hopeful!
inspiring music from Braveheart plays in the background
 
did u see the star wars movie @FenderLesPaul
 
Indeed
 
ooo ocool
 
1:32 AM
@FenderLesPaul I...have something for you
@FenderLesPaul I promise, it's worth your time
 
gimme gimme
 
@no_choice99 You'd judge me too harshly
 
lool
 
@FenderLesPaul a work day
 
1:50 AM
@0elo7 what is it
@GBeau ah
 
@FenderLesPaul Skype...it's a file
 
I just want it to be over....
 
@0celo7 gimme just a bit
@GBeau hang in there bud
 
 
1 hour later…
2:57 AM
@ACuriousMind I see, makes sense
 
3:53 AM
@EmilioPisanty Illuminati confirmed
 
4:03 AM
There are times when I would very much like to be able to cast a non-binding close vote.
I thought that
1
Q: Is a deviation from the equal flavor ratio of neutrinos ruled out experimentally?

LCFNeutrinos have a lifetime which exceeds the lifetime of our universe. Therefore we measure an equal ratio of all three neutrino flavors, 1:1:1. However, lets assume that the heavier neutrinos can decay into the lightest neutrino very fast, so that only the lightest neutrino is measured in detecto...

might just need clarification, but the OP hasn't returned to offer any.
@Danu Well, hmmmm. It's like this: grad students are included in the fraternity once they're doing research. Even masters candidates. As are industry researchers, including the few doing in with only a Bachelor's degree.
But, yeah, a large fraction of that culture is either doctors or (as a post-doc I knew liked to say) "future doctors".
 
 
4 hours later…
8:27 AM
@SirCumference : the Sun just doesn't move round the Earth. Or round Venus. Or Mars. Or Jupiter.
 
 
1 hour later…
9:37 AM
I am currently reading "The Clockwork Rocket"
It is one of Those books
Weird physics musing disguised as a story
It's about a universe with a Riemannian metric
The physics explanations are a bit crowbarred in
 
 
2 hours later…
user116211
12:07 PM
So silent....
 
user116211
Oh! Hi! @0celo7...
 
12:19 PM
@ACuriousMind It's snowing
And they closed the University
Damn southerners....
 
"Letting the radius of this cylinder approach zero, we obtain the disturbing conclusion that providing data in a, for all practical purposes, one-dimensional region determines the solution in a three-dimensional region. Such an apparent ‘free lunch’, where the solution seems to contain more information than input data, is a classical symptom of ill-posedness. "
Hm, free lunch
 
There's no lunch for me today
The People of the South cannot drive when there is White Magic on the ground.
No way for them to get to work and make me food D:
Also, tsk tsk ISIS. Don't you reach your recruits trigger discipline?
 
The blond guy seems to be higher than a kite
He has no idea how he got here
 
Upon closer inspection the high one has his finger behind the trigger.
So no one has their finger on the trigger.
So actually, GG ISIS. Props.
 
1:25 PM
@0celo7 They...closed the university? Because of a bit of snow? oO
Or are you in the middle of a blizzard?
 
Light fucking powdering
 
English prof sent out an email saying he's amazed
 
1:40 PM
@ACuriousMind I guess I can either: (i) Play Assassin's Creed, (ii) Do homework, (iii) Write my answer on indices.
(iv) Play in the quarter inch of snow.
 
Obviously you'll try to do (ii), procrastinate with (iii), and end up doing (i) ;)
 
After my long discussion with @DanielSank the other day, I'm starting to think this answer will not be so trivial...
 
@ACuriousMind I liked more your old style RPG portraits
this new RPGs are uninteresting (apart the ones like PoE that copy from the old-style)
 
@yuggib I've been getting progressively more modern. After this one I'll have to either regress or start anew from the ancients
@yuggib You have evidently not played The Witcher 3 :P
 
I WAS RIGHT
 
1:47 PM
@ACuriousMind ehm..no
 
@yuggib New? What is considered new?
2010+?
2005+?
1995+?
 
@ACuriousMind it is difficult to find an image of Zork's character...
 
@yuggib Haha...I can use Nethack's @, though
 
o.o
What are these people talking about
 
@0celo7 I would go with post-Baldur's gate/Planescape torment +
 
1:51 PM
Those words mean nothing to me...
 
@yuggib KOTOR is modern to you?
 
@ACuriousMind yes...it is not in isometric 2D
 
...that makes me notice I didn't use any portraits from NWN. Perhaps the next one.
@yuggib I see
 
I should play KOTOR
 
you should play BG
or Zork
 
1:55 PM
what's that
 
The chance of me getting a virus from that is way too high.
I'm not clicking your random internet links.
 
zork is open source now
it is all perfectly legal
so I don't see the reason for bad pop-ups or alike
 
For a question this broad, Physics Forums is probably a better place. I have my reasons for not pointing people to Physics Overflow. — David Z ♦ 15 mins ago
oooooo
 
:-D
the good ol' war
we should point JD to physics overflow
 
2:11 PM
@yuggib please define the tangent space as pedagogically and short as possible
 
I am no geometer...however it is the vector space of derivations, where the derivation is a linear map from the real-valued smooth functions to reals that obeys the chain rule wrt to product
 
I know that
but why should derivations be the "tangent vectors"
 
by definition?
 
@yuggib : I've seen physics overflow. And I have a job to do here. Teaching you guys some physics.
 
you're failing!
 
2:19 PM
@JohnDuffield you indeed take pleasure in annoying everyone
 
I'm pretty sure general relativity is caused by unicorns
 
@0celo7 If you embed the manifold into $\mathbb{R}^n$, then the derivatives (i.e. the gradients) of functions on the manifold are really tangent to it in the naive geometric sence.
 
@ACuriousMind I know that too
 
@0celo7 Good - so that's the answer why derivations are tangent vectors.
 
Did you also know that if you isometrically embed the manifold in $\mathbb{R}^n$ and restrict the ambient connection, you get the Levi-Civita connection?
 
2:21 PM
geometry is boring
 
agreed
 
@yuggib : you started it. If you can't take it, don't dish it.
 
not enough GDP
 
@JohnDuffield I just wanted to point you to physics overflow
 
@0celo7 Uh, yes?
 
2:22 PM
@ACuriousMind is there anything you don't know?
 
@0celo7 Uh, yes?
I mean, probably. If I knew what I don't know I'd know it, wouldn't I?
 
@ACuriousMind did you know that I have a mole on arm that's worrying
@ACuriousMind Uh, what?
 
@JohnDuffield and I don't give a damn about your "physics"...it's more boring than geometry
 
@ACuriousMind Did you know that there is a bijective correspondence between the set of $r$-th order bundle functors on $\mathcal{M}f$ and the set of smooth left actions of the category $L^r$ on systems $\mathcal{S}=\{S_0,S_1,\dotsc\}$ of smooth manifolds?
 
>functors
nooooooooooooo
[diagram chasing intensifies]
 
2:28 PM
@0celo7 I don't even know what that is supposed to mean
 
@ACuriousMind ah, good
 
@0celo7 is that a natural transformation?
 
@yuggib ...sure
let's go with that
@ACuriousMind Seriously, I'm screwed.
The library is closed
So I'll just procrastinate all day :(
 
@0celo7 Natural transformation has a precise definition
 
@yuggib I took it from that book on functorial diff geo which is all about "natural operations"
So, perhaps it is.
 
2:30 PM
@0celo7 you could always learn some analysis today
 
@yuggib Yeah, I need to do the reading
Archimedean property, density of $\mathbb{Q}$ in $\mathbb{R}$ and cardinality
Welp, mods are editing the stars.
 
but geometry is still boring
 
Yes, that's (the least of) what happens when people post inappropriate messages
and other people star them
 
@yuggib : my physics is just physics. And that ain't boring.
 
@yuggib because of GDP?
@DavidZ so why remove the stars and not the messages?
 
2:35 PM
@yuggib : you should check out electromagnetic geometry. That isn't boring either.
 
oh for the love of crap
@JohnDuffield Do you even know what a fiber bundle is?
 
@0celo7 because I'm lazy
 
@0celo7 I assume he thinks it is some sort of Dirac belt
 
@0celo7 and don't say things like that
 
@DavidZ as good a reason as any, I guess
 
2:37 PM
@0celo7 : Yes of course. But you don't know the difference between curved spacetime and curved space. So spare me for the love of crap. Note that "Examples of non-trivial fiber bundles include the Möbius strip".
 
What does the Mobius strip have to do with anything?
lol
 
Go and read the mathspages Dirac's belt article: "In this sense a Mobius strip is reminiscent of spin-1/2 particles in quantum mechanics, since such particles must be rotated through two complete rotations in order to be restored to their original state".
 
You have yet to tell anyone why that's relevant
soccer balls are reminiscent of spheres...spheres have to do with the inverse square law...so soccer follows an inverse square law
reminiscence has nothing to do with the real world!
 
@0celo7 Let's see if you have studied: what is the cardinality of the reals?
 
@yuggib $2^{\aleph_0}$
 
2:45 PM
@0celo7 very good
 
note: the book does not prove that one
they prove that the cardinality of the reals is greater than the natural numbers
and they state that result in a remark
along with the continuum hypothesis
 
that is....?
 
There is no cardinal number between that of the naturals and the reals
 
very well
however do you agree that real numbers are cauchy sequences of rationals?
 
No, we have not defined Cauchy sequence yet.
 
2:47 PM
T_T
 
We have the general notion that $\mathbb{R}=\mathbb{Q}$+limits
But we have not defined limits
 
damn
 
We're going to talk about limits...tomorrow?
@yuggib what?
 
they should not do the density of rationals in the reals before limits
it is counterintuitive
nevermind
 
@0celo7 : it's relevant because electromagnetic is associated with "the curvature of a fibre bundle", but there are no actual fibres bundled together. The fibre bundle is however a "space", and according to Einstein a field is a state of space. A gravitational field is inhomogeneous space, modelled as curved spacetime. An electromagnetic field isn't.
 
2:50 PM
yeah, tomorrow we're doing limits
Cauchy sequences are...a week from now
@JohnDuffield that makes absolutely no sense, sorry
 
and then maybe you will prove that the cardinality of the reals is $2^{\aleph_0}$
 
@yuggib can you explain what he said?
I'm just a dumb kid
@yuggib prob not
the prof seems wholly uninterested in set theory
 
@0celo7 : it makes perfect sense, and you know it. No wonder a whole lot of people have been calling you a troll.
 
@JohnDuffield and you don't say things like that
 
2:54 PM
doesn't matter
 
@JohnDuffield So you don't know the difference between space and spacetime either?
A fiber bundle isn't spacetime
In any case, that fiber bundle is curved regardless of gravity.
You can have curved fiber bundles over Minkowski spacetime.
 
@0celo7 and again, that was not necessary. Remember, we expect people to be civil here. These messages I'm pointing out are not civil.
 
@DavidZ I'm being civil. I'm pointing out that he doesn't know what he's talking about. I'm not the one going around shouting "kid" and "troll"
 
@0celo7 (1) when I ask you to be civil, what anyone else posts is not relevant
 
@DavidZ I'm being civil.
 
2:58 PM
and (2) I'm pretty sure you're not, though I am open to getting second opinions before doing anything serious about it
 
Well, I have seen much more heated discussions in the past
 
OK, looks like you're starting suspension procedures...not much I can do about that.
 
and @0celo7 you're too easily distracted, we were talking about cardinalities and stuff
 
@0celo7: Just ignore JohnDuffield. There's nothing to win for you by talking to him, you should've realized that by now. @DavidZ: I don't think anything's been said that warrants "doing anything serious about it".
 
@yuggib I need to get out of bed or else I will get nothing done today
brb shower
 
3:04 PM
@0celo7 You know, one of my pet peeves is when people take something I say and interpret it to mean something else. So I don't appreciate the assumption that I'm starting suspension procedures.
 
@0celo7 You do realize that's meant as a humorous exaggeration of a bad trait, yes? :P
 
only in mathematics, and not always, you can tell whether a statement is right or wrong (i.e. true or false)
 
@ACuriousMind Really?
 
Really. At least that's how I interpret the comic.
 
I thought it was Mr. xkcd explaining the anger of reasonable folks.
 
3:05 PM
It portrays an annoying, but common personality trait of the typical xkcd audience.
 
@ACuriousMind indeed, I didn't say that I was planning on doing anything serious
 
@DavidZ You've suspended me twice (?) over JD stuff?
 
@DavidZ I know, but you did ask for second opinions. I gave mine.
 
@0celo7 We're talking about what's happening now, not in the past
@ACuriousMind well, I didn't really ask for second opinions.
 
@DavidZ Past behavior is the best predictor of future behavior.
 
3:07 PM
Though it doesn't hurt to have yours, I suppose.
 
(As evidenced by the constant JD-0celo7 arguments.)
@ACuriousMind I know. I've tried blocking him before but I just can't do it.
I see him spouting some very wrong thing on an answer and then it leads back to chat.
 
@0celo7 whether it is or not, that doesn't matter for what I was saying. I was saying that I find it really irritating when people take something I say and interpret it to mean something else that I didn't say. So when you (apparently) assumed my comment about doing something serious meant I was starting suspension procedures, it doesn't help my mood. I didn't say that.
I'm already in a bad mood for other reasons too (IRL reasons). Which, incidentally, is part of the reason I'm not inclined to suspend anyone or go on a message-deleting spree or anything like that :-P
 
Anyways, back to "analysis" (US first year version of it at least)...how did you define reals without the notion of limits? did you do Dedekind cuts, or introduced some ad hoc axioms?
 
3:31 PM
God made only the integers, yuggib
(Kronecker slam!)
Are there any other completion of rationals except the reals and the p-adic numbers?
Well obviously yes but are any of them famous
 
the surreal numbers (even if they are technically not just a completion of the rationals)
 
@yuggib we did not define them...the prof says it's better to define them at the end of the course
 
What metric does it use to complete them
 
@0celo7 a "reasonable" compromise I guess..
 
@0celo7 ...how are you reading about the density of $\mathbb{Q}$ in $\mathbb{R}$ if you didn't define $\mathbb{R}$?
 
3:36 PM
@Slereah: Such that the rationals are dense? No. Not that any other ones are not famous, but that there are no others.
 
@Slereah he essentially uses a version of dedekind cuts
 
@MikeMiller whaaaat
 
@ACuriousMind we shall see...
 
You just blew my mind
 
you people are distracting me
and I have a thing at noon, so I won't be doing any analysis until later
 
3:37 PM
@Slereah: I don't have a proof off-hand but the name is Ostrowski's theorem.
 
@yuggib Basically, we define R intuitively as Q + other numbers so that the resulting field is complete
(in the axiom of completeness sense)
Dedekind cuts are in the book, but we're not covering them until later, when the machinery will be more natural
 
@0celo7 I see
but if you use the axioms for defining the reals, I think it would be reasonable
@MikeMiller what if you have a metric that does not come from an absolute value?
(maybe it is not possible in this case, just guessing)
 
@yuggib yeah, as an ordered field + axiom of completeness
 
I assume that your axiom of completeness means dedekind-complete
well, that uniquely identifies the reals
 
If $A\subset\mathbb{R}$ has an upper bound it also has a supremum.
 
3:46 PM
yes
so you defined the reals axiomatically
 
I guess so!
 
it is not true that you didn't define them
 
Oh, ok
 
@yuggib: Not sure what the point is. It doesn't respect the field structure and there's no reason to believe that the completion will be a field.
 
3:47 PM
@Slereah you love that site, don't you
 
I do
 
So is $\sum_{n=0}^\infty\aleph_n$ the biggest number?
 
No it is that + 1
Also you can't sum cardinalities
 
@0celo7 that is not well defined
@Slereah yes you can
the sum is trivial, it is the biggest of the two
 
So 1 + 2 = 2???
 
3:48 PM
Oh, so it's $\lim_{n\to\infty}\aleph_n$.
 
@MikeMiller I see your point, I was just asking
 
@yuggib: Why isn't it defined?
 
@Slereah with infinite cardinals only
 
Also aren't some cardinalities not possible to compare without the axiom of choice :p
 
@MikeMiller $\aleph_\infty$ does not make sense
 
3:50 PM
Pick set representatives for each cardinal. Take a disjoint union of these. The cardinality of the new thing is the sum of the cardinalities of the old.
 
$\aleph_{\omega}$ makes sense
but it is by far not the biggest cardinal
 
@yuggib: But a sum of a number of cardinals, indexed by another set, does make sense.
 
Only 27 degrees out
 
Well of course that's true. But the written sum makes sense.
 
@MikeMiller it's an abuse of notation, I would write it $\sum_{n\in\omega}\aleph_n$
 
3:51 PM
Sigh...
PhD set theory again
 
the worst
 
Why does the physics chat always devolve into fucking set theory discussions?
 
mb you should do things of 18 years old
Like shots
And do the dew
 
Notation exists for the sake of communication. I don't see how what was written could be confused for anything else. But sure.
 
Play some Call of Doody
 
3:52 PM
I am not playing CoD
I do play Battlefield regularly
 
@MikeMiller It could have been $\sum_{n\in\varepsilon_0}\aleph_n$, or $\sum_{n\in\aleph_{1}}\aleph_n$
they all give different results
and $\omega$, $\varepsilon_0$ and $\aleph_1$ are all infinite ordinals, so you can index alephs with them
 
I do not think it could have been any of those but $\omega$, to be honest.
 
@0celo7 Because you always start discussions about fucking set theory :P
@0celo7 ...I thought you said there is snow? oO
 
@MikeMiller I immediately thought it is not good to have $\infty$ in a sum involving cardinals (that are useful as infinite numbers), so the notation was not communicating the same thing to two people
 
3:57 PM
Yeah, I got your point.
 
"Snow"
 
Oh
I realize now you probably used your barbarian "degrees" there.
 
@ACuriousMind These barbarians won the war, hush boy
 
What's the new avatar
 
user54412
-4
Q: From the zero-point energy ( E0=1/2h’v ) and Casimir effect of the smallest distance ( L ) can we conclude that E= h’c/L?

Riadh Boukratemnλ=L and L=2λ compared to E0=1/2h’v v = c/λ ⇒ λ = c/v ⇒ λ= L/2 ⇒E0= 1/2h’.c.2/L= h’c/L = 1/2h’v ⇒c/L= 1/2 v ⇒ v = 2c/L ⇒L = 2c/v ⇒ E= h’c/L when L = 2c/v when v = 2c/L Any comment?

 
user54412
3:59 PM
nλ=L and L=2λ compared to E0=1/2h’v..... v = c/λ ⇒ λ = c/v ⇒ λ= L/2..... ⇒E0= 1/2h’.c.2/L= h’c/L = 1/2h’v...... ⇒c/L= 1/2 v ⇒ v = 2c/L ⇒L = 2c/v..... ⇒ E= h’c/L when L = 2c/v when v = 2c/L..... Any comment? — Riadh Boukratem 39 mins ago
 
the temperature of horse's blood as the top of the scale
a (surely very replicable) mixture of ice and water as bottom
all defined by a veterinarian
 
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