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2:00 PM
@Jim Wait, are you here?
In case you are: in a universe dominated by phantom energy, is the distance to the cosmic event horizon $$d_{eh}(t)\propto\frac{1}{a(t)}$$?
 
@BernardoMeurer Heeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeey!!!!!!!!!!!!!! :-)
So have you plugged it in and turned it on? What does it sound like?
 
@JohnRennie Oh, do you know if the distance to the event horizon in a Big Rip universe is $d_{eh}(t)\propto\frac{1}{a(t)k}$?
 
@JohnRennie It's in such good shape
@JohnRennie I DONT HAVE ANY RCA CABLES
I just realised this
 
Jim
@SirCumference I'm always around, but I frequently leave my computer for long stretches of time
 
:: Facepalm :: I could have put some cables in the box if I'd thought. I have a pile of old cables.
 
2:04 PM
I have a nice DAC for source, that has a line out, but it's coax so I need to turn that to RCA lol
 
But it should be easy to get any cables you need as RCA cables are such a common standard.
 
Yep, I'm going to the store as soon as it stops pouring
Might get my turntable too
Since it has headphone out!
Which I didn't know
 
Coax for line out?
 
Let me show you
 
That's an odd design decision. Normally coax is the optical output.
 
2:06 PM
Oh crap, the coax is for digital out
Well, I'll get a 3.5mm to RCA then
 
The Hermes tracking is pants. It still shows the amp as at the hub, not even out for delivery. Oh well, as long as it got there safely.
 
You need some batteries for the remote as well.
 
I got em :)
I keep batteries handy for my gameboy
 
Cool :-)
I have to dash out. Let me know when you've got the cable. It's worth getting a good cable. I have some cables with gold plated contacts that I use for stuff like this. How much difference it makes I'm not sure, but the gold plating means the contacts don't corrode.
 
2:09 PM
:)
@JohnRennie Yep, I saw a pack of bottom of the line Audioquest cables for 30 bucks I think, I'll get those maybe
I'm pondering
 
I'm ot familiar with that model but I'm a fan of Sennheiser headphones. I have a pair of Sennheisers.
 
Sennheiser is awesome :)
 
$30 ... maybe get a cheap cable to start with for a few $ and see how well it works.
$30 is more than the amp is worth :-)
Anyhow I must go. Back in a couple of hours.
 
It's for a RCA-RCA, a 3.5-RCA and a pair of speaker cables :P
I ain't payng 30 bucks for one cable!
@JohnRennie See you later!
 
Jim
2:22 PM
@SirCumference well, the hubble radius is usually a good approximation of the cosmic EH and is denoted as $\frac{1}{aH}$. A universe dominated by a cosmological constant has $H\propto const$, which makes $d_{EH}\propto\frac{1}{a}$, but phantom energy is not a cosmo. const. It causes more excessive expansion
so, you'd probably find it proportional to a function that decreases faster than $\frac{1}{a(t)}$
 
2:36 PM
@JohnRennie : Nice. Out of curiosity: Who suggested that?
 
2:48 PM
9
A: Choosing the name of the chat room

corsiKaHow has Schrodinger's Chat not been suggested? It's both alive and dead until you open it to observe.

@JohnRennie you know how that looks like under chatjax, right? =P
Oh wow, does this ever probe the depths of off-topic.
user image
5
 
@EmilioPisanty : Thx.
 
@Jim If, for a Big Rip universe, $a \propto e^{k(t)t}$, where k is increasing, will the event horizon's distance be $d \propto \frac{1}{a(t)k}$?
 
3:07 PM
@ACuriousMind Enjoyed solving that problem? :P
 
0
Q: Re: Downvoting with no feedback

FarcherI have tried very hard to comply with the spirit of this forum but obviously still have not got the hang of it. I write a short comment and then am told it should be an answer. I answer a question and it is down voted but no reason is given. Here is an example http://physics.stackexchange.co...

 
@BernardoMeurer Not really but after I had started I had difficulties to stop :P
 
@ACuriousMind Hahaha, how long did it take you?
 
Jim
@SirCumference That'd be a good approximation, but the actual event horizon would be a bit more complicated. After all, the Hubble radius is only a good approximation for the event horizon
 
@BernardoMeurer About half an hour of scribbling various pointless approximation until I found one that gave a better bound than $2\beta$
 
3:16 PM
@ACuriousMind How the heck was I supposed to solve that in an exam with no calculator or nothing?
:(
 
Hi @ACuriousMind
 
@BernardoMeurer The other new answer gives a way without a calculator, I think
@BalarkaSen hey
 
How's things? Still doing strings and holonomy?
 
::sleepily clicks on review button::
::jerks awake::
geesh
i don't think i've seen this many in the review queue since...well, i'm not sure i ever have. wow.
 
@BalarkaSen Basically yes
Not much interesting math lately though
 
3:26 PM
@ACuriousMind I can send you my exam to solve
 
@BernardoMeurer No, thank you :P
 
Gotcha. I have been trying to learn a thing or two about foliations now-a-days
 
@ACuriousMind It's great, I swear
Very nice limits to compute
 
@Jim So, my question is: if the scale factor constantly increases in a de Sitter universe as well, and $d \propto \frac{1}{a(t)H}$, then shouldn't the event horizon be increasing in distance over time?
 
@heather The reviewers seem lazy, we've only had three reviewers (including you) today so far. And that's the UTC day, i.e. within the last 15 hours.
It's an unusual state, usually the queue grows to around 30 items and then goes back down after the weekend
 
3:47 PM
@heather If ever the review queue looks bad, have a look at stackoverflow.com/review for an instant feel-good moment.
and/or a gawk-in-horror moment
(keeping in mind that it's currently at under 10% of its historical maximum)
 
@EmilioPisanty 8.4k!? under 10%?!
 
164
Q: Huge close votes review queue on Stack Overflow

AndreyToday, the size of the close-votes queue is 55k questions and growing. Is that a problem? Which action could be taken to clean it up? It seems to be growing faster than Stack Overflow members are capable to handle it.

61
Q: What can be done about the massive Close Votes queue on Stack Overflow?

MoosemanThere are (at the time of writing this; see edits at bottom of post) 54.2k questions with close votes on the review page on Stack Overflow. Unlike the other review tasks, which all usually return to 0 quickly, the number of questions with close votes continues to rise. According the this Meta Stack 

164
Q: Close Votes review: I'm going on a strike!

ShaiI know this question is going to make me unpopular here – but I feel I have no other options. I have been concerned by the size of the close votes review queue for quite a while. When I started reviewing (less than a year ago) this queue already had ~30K questions pending review. Time passes an...

 
vzn
4:03 PM
@Emilio, remarkable, was not aware of that. but have noticed that reviews are timeconsuming and generate no "gamification" incentive. now looks like a bigger problem than with one site, more like a SE architecture/ scalability glitch. but must say dont have huge sympathy because sometimes seems like SE makes it too easy to/ puts too much emphasis on closing questions (aka "FGITW")...
 
77
Q: Stack Overflow needz moar ads

Shog9This got me thinking... Not about a contest though. I don't want people reviewing questions so that they'll get something in return; folks should be doing it because they care about the questions, about their community. If folks don't care, then what's the point? But maybe folks do care, maybe...

 
Jim
@SirCumference sorry, my $\frac{1}{aH}$ is the comoving hubble radius. I'm so used to working in comoving coordinates. The proper hubble radius is $1\over H$
 
@vzn reviews generate no "gamification" incentive?
since when?
 
vzn
@EmilioPisanty ok, maybe some badges for it? ranking boards? but no points right?
 
Did they cancel the badges and the progress trackers and the public leaderboard?
 
vzn
4:06 PM
@EmilioPisanty ps hows your Phd going?
 
@vzn done and packaged
 
vzn
@EmilioPisanty way cool/ congrats :) ... have you done the defense
 
@vzn please do not edit messages that have a @ ping in them, it pings on each edit
 
vzn
@EmilioPisanty sigh, another SE glitch not my fault :(
 
so this is all about users being lazy reviewing right?
 
4:08 PM
@vzn just don't do it is all. I have music on and would rather not have the chatroom interrupt.
 
vzn
@Hey-men-whatsup no. because users are lazy in 1000 different ways :P
 
@Hey-men-whatsup no, the SO reviewing problem is a fair bit bigger than that
 
vzn
@EmilioPisanty so turn off the ping. :P theres a way to do that isnt there?
 
I guess people have no time for that, they do have a lot time for the ratings tough
 
@vzn or you could also just review your post before posting it =)
 
4:10 PM
@vzn I try to keep it on in case people have interesting stuff to say, but that's obviously not the case just now
 
vzn
@EmilioPisanty yep youre always such a ray of sunshine
 
44
Q: Display the number of pending review tasks created in the past 24 hours for the Stack Overflow close review queue

Shog9This is just depressing: And I don't mean it's depressing that there are that many questions that might need to be closed. There are nearly 6 million open questions on Stack Overflow - if under 2% of those are crap, we're doing great. Realistically, that number is probably going to get a lot b...

dammit, where is it.... I can't find the cleanup one
 
@vzn can we tone it down a notch? there are children in here =P ::clears throat::
 
vzn
@heather so everyone jump on me for using a built in chat room editing feature
 
@vzn sorry, it was a joke =)
 
vzn
4:12 PM
@heather emilio started the sarcasm if you didnt notice. oops, he has 50k more points than me. rats, lost :(
 
::shrugs:: i just don't think that we need to argue over the noise from pinging, that's all. besides, as a member of SE, you know that rep doesn't necessarily decide problems.
 
vzn
@heather right, so whoever is complaining about SE pinging (upon entering a chat room) can listen to you, you have some real wisdom there
 
sorry, i don't want to argue today, i'm still early-morning tired =) @vzn
 
vzn
dislikes arguing too o_O ... maybe should go somewhere other than cyberspace... or where people hang out :P
 
please understand i'm not trying to be rude or anything like that, i apologize if i came across that way.
 
vzn
4:16 PM
@heather youre surely one of the least rude ppl in here ;) ... sort of a ray of sunshine yourself! :P :)
 
ah, here it is
436
Q: Let's burn down the close queue!

Shog9 Stage 2 completed: The initial phase of the burndown was completed on 2014-03-03 10:48:49; the second phase completed on 2014-03-08 at 19:41. Detailed statistics on how these played out can be found on Phase 1 results and Phase 2 results. There remains much work to be done! You can find r...

last one (& best one), I promise
 
"Kill it with fire!" - lol
 
vzn
@heather so what are you working on these days?
 
@Jim Oh, that makes a lot of sense!
 
@vzn well, I'm sick right now, so I'm taking it easy.
 
vzn
4:29 PM
@heather bummer ok. :| get well soon. :)
 
@vzn, thank you. =)
 
vzn
4:41 PM
 
4:58 PM
@EmilioPisanty What the hell did I just read?
 
@BernardoMeurer: so did you get a cable?
 
@JohnRennie I'm waiting for my neighbour, she needs stuff too and she has a car :P
 
Senheiser only makes amazing stuff
These HD 650's are my best purchase of all times, I payed 200ā‚¬ for them about 2 years ago
They were in the box as I got them, half the asking price!
Worked flawlessly ever since
 
I can't remember what the HD475s cost - it was about 25 years ago :-)
 
5:03 PM
The guy had gotten it as a gift and didn't care for it
@JohnRennie 25?!
 
The past has faded into a blur, but I think I bought them while I was still working for Unilever and I left there in 1997.
 
Jesus, those are some long-lasting cans!
Interesting thing I just noticed, it's been 2 years since I got hit by a car, and only know is the difference in muscle on my right and left calves evening out
 
@uhoh Just saw this. I deleted the rest of our comments. We can definitely return to this later if you like.
 
Wow, I didn't know you'd been ina fight with a car and lost. What happened? Broken leg?
 
The car looked at me wrong so I attempted a round-house kick on it
Tore all the ligaments on my right foot
3 months without walking plus 4 months walking with an ankle support thing
 
5:09 PM
Ouch!
I guess the car won then :-)
 
Yep, lol
In my defence the guy was speeding in a school zone and had gone over a red light
I was just going cross the street to have lunch
I'm heading out to get cables! brb
 
Go, go, go!
 
@BernardoMeurer you're asking me?
or do you mean the Stack Overflow Closevote Review Queue Saga?
 
0
Q: Upload word document as answer

JensThis might seem as a stupid question but I would like to upload a word document as an answer to a question. I can convert the document to html and copy its contents but most of the formula disappear when pasting into the stack exchange answer box. I dont have a website, which could refer the inte...

 
obe
5:40 PM
@EmilioPisanty I don't like how you're talking to vzn.
 
is electromagnetic radiation influenced by electric or magnetic fields?
 
@JohnathanRalls no, or at least not under normal circumstances.
 
under what circumstances would it be influenced, and what would the influence be?
 
Electromagnetic waves combine linearly with other electromagnetic waves, and the linear combination means they do not scatter each other.
 
collimation?
 
5:48 PM
@obe Constructive criticism is okay, but please don't tell people to "fuck off".
 
@JohnathanRalls at very, very high energy densities quantum electrodynamics predicts there will be some interaction and scattering. However I think the energies at which this happens are experimentally inaccessible at the moment.
 
bums my gums
 
Aha!
44
Q: Scattering of light by light: experimental status

Keenan PepperScattering of light by light does not occur in the solutions of Maxwell's equations (since they are linear and EM waves obey superposition), but it is a prediction of QED (the most significant Feynman diagrams have a closed loop of four electron propagators). Has scattering of light by light in ...

 
obe
@ACuriousMind oh well
sorry xd
 
i wonder if passing through a medium with a high refractive index would increase the influence of a surrounding electric field?
thought process is "slow the light, give it more time to shift"
 
5:50 PM
The energies involved would vaporise any dielectric medium the light passed through!
 
that is assuming that the same high levels of energy would be required for the interaction/influence while passing through the medium, correct?
 
Yes, but the energy densities involved are astronomically high. Even if you could increase the interaction by a factor of 100 or 1000 you'd still be talking about vast energy densities.
Actually you do get non-linear effects in some dielectrics. This is called non-linear optics. However it is the interaction of the light with the medium that is non-linear not the interaction of light with light.
 
@obe That's your prerogative
 
I suspect feeling are running a little too high for comments from bystanders to be helpful, but Emilio I wonder if you weren't a bit harsh.
I agree that it's annoying to be pinged over and over again, but there are worse things in life.
 
I asked him/her as a favour to stick to a standard procedure on this chatroom and s/he refused, so I withdrew from the conversation and indicated I was doing that .
 
5:59 PM
more to the point, i think both sides got a tad too annoyed over it.
 
Well yes, but it was an ill humoured exchange. Neither of you emerged with enhanced karma.
 
i mean, it's a buzzing noise from an internet chat room.
 
I don't think it is a big deal and I do not think it particularly warrants further discussion to be honest.
 
there are some pretty interesting phenomena involved there. would you happen to know of any tabletop experiments to attempt low-energy self focusing?

regarding the tension in the room: https://www.youtube.com/watch?v=wvNFiAVl-b0
 
@EmilioPisanty I second that
 
6:01 PM
3 messages moved to Trash
 
obe
what?^
 
@obe: that isn't helping.
Just let the dust settle and move on.
I will start mass deleting posts if this exchange continues. You have been warned.
 
btw re this meta post, has anyone even heard of news360 before?
 
@ACuriousMind that's sort of the point.
I for sure hadn't
 
4 messages moved to Trash
 
6:07 PM
@EmilioPisanty I asked a few people I know and neither of them had either - I'm kinda puzzled how it might generate so much traffic for us if no one really knows it.
 
2 messages moved to Trash
 
thank you @JohnRennie
 
obe
sorry my message lagged didn't see the trashed posts
 
1 message moved to Trash
 
6:08 PM
@JohnRennie Well, but who uses it?
 
@JohnRennie precisely. So why is a news app linking to us?
 
@JohnRennie how does that send anyone to PSE?
 
Seems pretty popular on Android. Assuming that's the same thing.
 
@JohnRennie i feel i need to apologize for the nonsense going on, and would request to steal some of your attention towards an inquiry you may have knowledge about.
 
6:10 PM
I just made a profile
 
@JohnathanRalls Yes?
 
politico, washington times, mashable, physicsworld, two phys.org pages
 
do you know of any experiments regarding low energy self focusing?
 
@JohnathanRalls Using a dielectric medium?
 
that seems to be the only way i've found so far, but if you know of another that'd be superb information
 
6:13 PM
and there it is:
 
@JohnathanRalls There is lots of stuff on self-focussing of lasers in plasmas. But that's still just the interaction of the light with the medium not of light with light.
 
http://physics.stackexchange.com/questions/308700/sign-of-feynman-diagram-with-‌​single-propagator-closed-loop#-/web/-1485886410829-trackingCode-Rcj8V7t6fy2TF2QYf‌​kzD8WyL6zhWoPvDGatnvKBKsdI=-articleId-388503845-vv-a30ec2ab-128f-4f52-80f3-5c5301‌​c28aee
0
Q: Sign of Feynman diagram with single-propagator closed loop

user2582713On p94 of Fetter & Walecka's Quantum Theory Of Many Particle Systems, it is stated that since propagators with both arguments at the same time such as $G^0_{\alpha\beta}(x, x)$ arise from contractions of field operators in the 2-body potential, which always appear in the order $\psi^\dagger_\beta...

 
The light-light interaction is many orders of magnitude too weak to cause and significant self-focussing at everyday energies.
 
closed as a duplicate
 
oh that's fine. i'm not all that interested in light on light interaction, but was curious. if i am able to reproduce a self-focusing effect through a plasma that'd be sufficient
 
6:14 PM
@JohnathanRalls Googling will find you loads of articles on the subject.
@EmilioPisanty Wow, Lubos dupe hammered it!!
 
i understand, was hoping that someone on here would be able to share some experience with the subject for a more interactive learning situation
 
@JohnRennie yeah, I'm surprised too
 
@EmilioPisanty Hmm...who wants random questions in their newsfeed?
 
but yeah, there's a ton of PSE on that feed
 
Perhaps now that Trump is in office he feels there's no longer any need for him to spend time on climate change denial :-)
 
6:16 PM
I think I'd click on a few questions and then uninstall the app when I realized the "news" feed isn't news :P
 
@JohnathanRalls I don't know of anyone in the site who does experimental work on light-plasma interactions. To be honest we tend to the theoretical end of the subject.
 
@ACuriousMind well, people are clicking through, so presumably there's people that like it
 
am i being a bother? if not i have another question :D
 
No, go ahead. The chat is intended for questions of this sort.
At worst you won't get an answer :-)
 
6:20 PM
sweet. lets say i'll use an induction coil to create a spark gap. would it be possible to make the generated plasma more dense?
 
@EmilioPisanty Hmm, those questions don't look terribly exciting ...
 
@EmilioPisanty That doesn't look as if it's targeting anything specific.
 
obe
it's probably a random selection of questions using a few key words.
 
@ACuriousMind Yeah, I think the only thing they've got in common is that they're new
 
@JohnathanRalls No. The density of ions in a spark is pretty small and they recombine almost instantly. I'd be surprised if the density were anywhere near high enough to affect light significantly.
 
6:22 PM
So...that referrer doesn't seem to tell us anything useful about what's attractive about the site
 
would a sealed container of argon be a better choice to pass the light through?
my concern with that is the light refracting from the argons container
 
@JohnathanRalls how would you ionise the argon?
 
@ACuriousMind seems so
I think it says something about the internet, though: you can top facebook at something it doesn't care about if you actively push it.
 
what would be the difference in using an electrode embedded in the container to make contact with the gas as opposed to using an electric field through a coil?
the latter being outside the argon's container
 
Putting the electrodes inside creates a discharge tube. But these only work at low pressures where the plasma density would be too low to do much to the light. I can't see how putting coils outside would do much.
 
6:28 PM
how would you ionize the argon for this scenario?
 
@Jim Oh sorry, one last question
 
@JohnathanRalls Creating a plasma with any significant density is big science not a tabletop experiment.
 
If the Hubble parameter truly changes with time, will the event horizon's proper (and comoving) distance be time variant in a de Sitter universe, considering $d \propto \frac{1}{H}$?
 
@SirCumference in a de Sitter universe H is constant.
 
do you know if ionized liquid would be easier to work with then?
 
6:33 PM
@JohnRennie Right, because the deceleration parameter is -1...
 
@JohnathanRalls The problem is the massive amounts of energy required. Ionisation energies tend to be 5-10 electron volts per atom. Multiply that by Avagadro's number to get the molar energies required and the results are scary.
@SirCumference I can't remember the details I'm afraid.
 
@JohnRennie Nah don't worry, I figured it out using the formulas
 
@JohnRennie God darn it! I want to, but a class is about to start...
 
@SirCumference Oh well, have fun. I'm going to settle into my armchair with a beer :)
 
6:38 PM
And it's a pretty basic question... ;-;
 
@oswald i would love to, but i dont have the required reps — yogi rajput 1 min ago
 
@JohnRennie could you point me in the direction of some literature? something more directed than bouncing from article to article would be ideal, if you don't mind.
 
-4
Q: Am I too late to be a Physicist?

yogi rajputI am 21 years old and in my 3rd year of b.tech. Though I have a huge interest in Computer science but from previous 5 months I want to pursue Physics and want to become a Physicist. so is it too late for that? Can i still pursue physics and if it is possible then how should I learn it from basi...

could we upvote this question so as to give OP the minimum rep to join chat?
 
@Oswald I have added the user to the explicit write access list to this room for now; they should be able to enter and talk
 
Thanks @ACuriousMind
 
6:45 PM
in fact i think it'd be beneficial for me to work from the basics up. is there a recommended book to do so?
 
7:02 PM
Hi
 
@Oswald please no... for future reference, if you want someone to have access to chat, do it by asking a mod, don't upvote bad content
7
 
no recommended book? bummer.
 
7:27 PM
@DavidZ I didn't know moderators could do that
 
@JaimeGallego Yeah, it's not a very commonly advertised feature.
We do prefer to have people earn their access to chat the "normal" way, by getting 20 reputation. But not if it means upvoting a post that doesn't deserve the upvotes.
Incidentally, what @Oswald was proposing is technically full-fledged vote fraud - one of the cardinal sins of SE. (But we genrally don't punish it in cases like this because it's an honest mistake and we'd really rather just say "hey don't do that" than get into official warnings and suspensions and so on.)
 
I see. Thank you.
 
7:51 PM
@Jim Uh, quick question. Is the Big Rip considered a nonstandard cosmology by a lot of cosmologists?
Actually, are any universes with equations of state besides $-1$ considered nonstandard?
 
@SirCumference What does "non-standard" mean there?
 
@ACuriousMind I guess what it means here
A non-standard cosmology is any physical cosmological model of the universe that was, or still is, proposed as an alternative to the then-current standard model of cosmology. The term non-standard is applied to any theory that does not conform to the scientific consensus. Because the term depends on the prevailing consensus, the meaning of the term changes over time. For example, hot dark matter would not have been considered non-standard in 1990, but would be in 2010. Conversely, a non-zero cosmological constant resulting in an accelerating universe would have been considered non-standard in 1990...
 
@SirCumference So, given that the article explicitly mentions the $\Lambda$-CDM model as the currently standard model of cosmology, and that that model does not include the possiblity of a Big Rip, what's the question?
 
@ACuriousMind Somehow I forgot that the $\Lambda$-CDM model uses an equation of state of -1...
Never mind my idiocy
I'm finding ways to confuse myself...
 
Jim
8:18 PM
very well, I'll not mind it
 
Now, can anyone explain to me how this edit got approved?
4
 
8:34 PM
@ACuriousMind My guess is a disagreement between us and the reviewers over the extent to which editors should add original content to someone else's post.
 
9:18 PM
Hi, everybody.
@ACuriousMind What's wrong with it? Just kinda wacky?
 
@DanielSank Uh...I don't see any indication that the author wanted those pictures to be there and I don't really see what they add to the post.
I.e. I would have rejected both as "no improvement" and "conflicts with authorial intent".
 
Yeah, it's kinda weird.
 
vzn
9:47 PM
@DanielSank hi, question on QM/ weak measurements if youre around
 
vzn
10:07 PM
Dec 13 '16 at 17:45, by ACuriousMind
which is precisely why I'm sceptical of the claims that whatever they measured is actually the "wavefunction" because standard QM also has phase freedom, i.e. for any quantum state the real and imaginary part of the "wavefunction" is not actually defined.
@ACuriousMind ā†‘ question on that... do you know any refs that discuss this "phase freedom" esp wrt weak measurement(s)?
 
@vzn Every non-beginner quantum mechanics text should discuss that quantum states are actually rays and not vectors in Hilbert space, i.e. $\lvert \psi\rangle$ and $\mathrm{e}^{\mathrm{i}\phi}\lvert \psi\rangle$ denote the same state (which is what I meant with "phase freedom").
 
vzn
10:22 PM
@ACuriousMind ok. anyway, think your phrasing did get to the crux of the issue. the pt is, maybe there is something new here wrt weak measurement. std qm theory posits only |psi|^2 can be measured and not psi exactly. suppose weak measurements are giving statistical measurements on psi itself. that would not actually contradict std QM would it?
 
@vzn You can't "measure" $\lvert\psi\rvert^2$ either - best you can do is do a lot of position measurements and infer it from that. (There are ways to know $\lvert \psi\rvert^2$ exactly, but in that case you know the states of the system exactly and figured out what state the system is in, so you know its wavefunction, that's not what I'd call measurement). I don't know what a "statistical measurement on psi itself" is supposed to be.
 
vzn
@ACuriousMind ok, am not an expert on qm so this is difficult, but the general idea is that (to borrow some of your own framing) suppose a new theory removed the phase freedom, in such a way that it can measure phases, but not in a way that contradicts (std) QM. that seems to fit the bill of a "deeper theory"... & it seems like weak measurements nearly or precisely make that claim...
 
@vzn Measuring the phases would contradict standard QM because it is an axiom of standard QM that vectors belonging to the same ray stand for the same physical state. If you could measure the phase this would mean they are physically distinct states.
 
vzn
ok. have to think more about what you mean by "the same ray"
 
@ACuriousMind You can "measure" $|\Psi|^2$ as much as you can "measure" anything else, no?
 
vzn
10:34 PM
let me try to phrase this another way. theory I proposes A, B can only be measured in combination. theory II proposes A, B can be measured separately but not ever in any way that contradicts measuring them in combination by theory I. therefore, the theories are not in contradiction. but theory II is "deeper" than theory I.
 
@DanielSank "Measure" in the sense of "figure it out to sufficient accuracy", yes. "Measure" in the sense of "there's a self-adjoint observable whose eigenvalues correspond to the possible measurement results for this quantity", no.
 
@ACuriousMind Ahhhhh, theorists...
 
vzn
A, B = real/ imaginary parts of psi.
 
@vzn You are misunderstanding the problem. (I assert that) standard QM asserts that the phase is not a property of the physical state. It's not "unmeasurable", it has no physical meaning and is only there because the mathematical description in terms of Hilbert space instead of projective Hilbert space (where all rays are collapsed to point) is more convenient. Anything that "measures" "the" phase contradicts standard QM because there is no unique phase associated to a state in QM.
@DanielSank :P
 
@ACuriousMind :P
 
vzn
10:39 PM
@ACuriousMind ok but think you are overextending the actual claims/ content of QM and getting more into the copenhagen interpretation with that assertion. what is the proof (from axioms) that measuring unique phase must be impossible? and plz dont cite bells thm. & dont think the no cloning thm works here either... what if there is a way to measure it that doesnt contradict any of the axioms of QM? that seems to me what weak measurement is getting at...
 
@vzn I already told you, it's an axiom of QM that states are rays (and by definition a ray is the set of vectors differing only by a phase and scaling). Please learn the basic mathematics of quantum mechanics before suspecting interpretational issues and Bell's theorem behind every little thing.
 
vzn
@ACuriousMind lol fine, ok, so posit (say) a "substate" then o_O :P
 
I think this discussion has gone off the rails a bit :)
 
There were rails?
 
vzn
@DanielSank maybe weak measurement will put std QM off the rails some day o_O
 
10:50 PM
@ACuriousMind is focusing on a correct, but I think tangential issue about the uniqueness of wave function representations of quantum states.
@vzn No.
 
vzn
@DanielSank lol fine, no train wreck, & the trains have to keep running on time, but maybe there will be new train(s) :P
 
@vzn I have to say that you have a bit of a habit of hearing about a buzz-topic and then coming here to ask if that new topic somehow revolutionizes our entire understanding of Nature.
This is extremely unlikely to happen, ever.
Science is more incremental than the fairy-stories might have you believe.
@ACuriousMind Well, no... who am I kidding?
 
vzn
@DanielSank think am actually sticking to the facts :| ... sometimes there are new facts that need sticking to though =D
 
@vzn Weak measurement isn't really that big of a deal.
@vzn True dat.
Weak measurement sounds amazing only if we start from the ridiculous assumption that wave-function collapse is instantaneous and magic.
 
vzn
@DanielSank it seems (to me) to be a bigger deal than (most) ppl currently realize.
 
10:53 PM
@vzn Can you explain why?
 
vzn
@DanielSank (to reiterate) for (key) reasons just outlined, it does appear to me to be verging on a "new/ deeper theory"...
 
@vzn Please believe me when I say that a large fraction of the quantum community already understands the new theory.
Weak measurement isn't new.
I think you might feel that weak measurement is revolutionary simply because you've been taught an archaic, and unfortunately present-in-textbooks version of QM.
 
vzn
@DanielSank abandoning phase freedom is new. whats the opposite of phase freedom? maybe phase measurement?
 
@vzn Nobody has abandoned phase freedom.
I'll be you one chocolate chip cookie that nobody has abandoned phase freedom.
 
vzn
@DanielSank it is true, was not indoctrinated in the std way, & as they say in CS, it could be a feature instead of a bug :P
 
10:56 PM
@vzn Uh, "phase freedom" was my argument for why I would be cautious about the interpretation of the results of one particular measurment, weak measurement itself never "abandoned phase freedom", where did you get that from?
 
vzn
@DanielSank lol finally someone that isnt so emotional about all this :P
 
@vzn Take it or leave it.
 
vzn
@ACuriousMind think abandoning phase freedom may be the step toward Boldly Going Where No One Has Gone Beforeā„¢. maybe "abandon" is too loaded/ dramatic a word for some though :|
 
@vzn Perhaps you'd care to be more specific?
 
vzn
@DanielSank dont know how to be more specific. am basically proposing that (some) weak measurement experiments are actually statistically measuring/ sampling the real/ imaginary parts of psi. & that there is some currently hidden evolution ("mechanics") of these components that is not contained in std qm. ie/ aka maybe a quantum submechanics
 
10:59 PM
@vzn Yeah well unless you explain why you think that, there's not much conversation to have here.
Let me show you what I mean: "Hey, vzn, I think green jellybeans might prove that time travel is possible. I can't be more specific, I just think it".
See?
 
vzn
@DanielSank you can talk about jellybeans/ chocolate chip cookies if you want/ like. how about "trajectories"? what does std QM say about them? advances.sciencemag.org/content/2/2/e1501466.full
 
@vzn QM says a lot about them. You want me to type out a textbook?
(And yes, I do like cookies)
 
vzn
@DanielSank think some of the "trajectories" being measured by weak measurements have (physical) rules that are not predicted by (but dont contradict) std qm.
 
@vzn What do you mean by "std qm"?
If you mean "stuff in undergraduate textbooks", then you are quite correct.
 
vzn
@DanielSank basically, von neumann axioms
 
11:04 PM
However, the theory of trajectories is well understood and has not uprooted quantum mechanics theory.
@vzn I am not familiar with those.
 
...how can you know "von Neumann's axioms" but not what a ray is?
 
vzn
@DanielSank lol you likely are but maybe not under that name....
 
@vzn Link.
 
vzn
@ACuriousMind there are probably lots of QM textbooks that dont say much about "rays"...
 
@ACuriousMind Calmate, bro.
@ACuriousMind FYI, exclamations in the vein of "How can you not know X?" are very good at making people feel bad, and not good at much else.
 
vzn
11:08 PM
dont know a lot of things ... anyway can look up a favorite "more axiomatic treatment of QM" ref for you DS (not near my books right now) but the contents wont be any surprise to you...
 
@DanielSank I know, but I am genuinely curious how one might know the von Neumann axioms but not what a ray is, given that one of the von Neumann axioms is either "states are rays in Hilbert space", "states are vectors up to scalar multiplication" or something equivalent. It's like someone saying they don't know how to make dough and then casually referring to their experience baking bread later.
 
@ACuriousMind Meh. Wikipedia.
 
vzn
have very many QM refs of various qualities, havent read all of em yet
anyway the "new" (weak measurement) theory seems to be measuring points on a bloch sphere so to speak, something std QM has "nothing to say" about. aka trajectories
aka phase measurement...
 
@vzn listen to me.
What you are calling "std QM" is obsolete. Comparing modern experiments to an old theory is not particularly interesting.
Trajectories are very well understood.
Also, making a plot of points on a bloch sphere doesn't even require trajectories. You can do it with projective measurements in what is called "state tomography".
 
vzn
11:27 PM
@DanielSank what if the real/ imaginary parts of psi are the legendary "hidden variables"? staring everyone in the face since the very beginning? that looks more to me like the case, & weak measurement describes its "sub-"mechanics....
under construction/ some assembly reqd...
 
@JohnRennie DUDE
THIS AMPLIFIER
IS THE SHIT
 
11:44 PM
@BernardoMeurer nice
 
@DanielSank Almost tore my head open listening to Rhapsody on a Theme by Paganini just now
 
@BernardoMeurer I advise you not to do that.
 
@DanielSank I wasn't planning on it, but when Rachmaninoff dropped that base it hit me
 
indeed
Tests are running.
Entertain me for two minutes.
 
I'm writing a makefile
let's hope it doesn't crash earth into the moon
 
11:58 PM
hshahahaha
 
@DanielSank ALMOST deleted / recursively
Jesus
that was hardcore
 
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