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5:08 PM
Hello. Do have a look at this name suggestion. Vote up if you like and vote down if you don't like the suggestion. meta.physics.stackexchange.com/a/9506/102705
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A: Choosing the name of the chat room

anonymousI vouch for the name The h Bar BQ I like it because of the three "puns": "h Bar" -> The Reduced Plank's constant. "Bar BQ" -> A barbecue (we all know that a significant portion of the discussion in the Physics Chat room is related to food and cooking! ) "BQ" -> Bottom Quark! Another major re...

 
@anonymous I'm afraid the pun will be mostly lost among people
 
@SirCumference Maybe. But at the same time I don't think many people understand the pun behind "The h Bar" also. If they want to know the meaning they will get to know it. :)
Also, I guess newcomers will be curious to know what BQ stands for.
 
5:41 PM
The h bar is the obvious choice of name, and everyone with the remotest knowledge of physics should get the joke. None of the other proposed names have come close to the elegance and simplicity of the old name.
I quite like David's suggestion that name could be temporarily changed for fun then changed back a few days later. That allows us to play without causing any long term annoyance.
4
 
5:54 PM
@JohnRennie I think you are right John. We never know who might be uncomfortable with moving on to a new name!
 
@JohnRennie I don't understand why there's such a kerfuffle. Since links to the room aren't invalidated when the name is changed, can't we just change it whenever we want, i.e. whenever one of the room owners decides to?
I'm surprised that the old link still works, but it does!
 
@DanielSank Well, some people might feel uncomfortable with a new name. Personally I would love to see the name being changed time to time, but then again some people don't like it.
@DanielSank Indeed it does. It is a dynamic url.
 
Can't we just call this the "Break everything bar" ?
 
@DanielSank A couple of people have expressed displeasure at the name change. I think they just consider it naff. Since I have no personal preference changing the name back seems a reasonable course.
@BernardoMeurer not stunningly witty :-)
 
@JohnRennie Neither are we
 
5:57 PM
@DanielSank The text at the end of the url is usually irrelevant on SE, that's also the case for questions and user profiles: It's the number after rooms/ that uniquely identifies the room, not the name.
 
rob
I'm a little uncertain, but perhaps big changes to the room name should be briefer than small changes.
 
@BernardoMeurer that's not true. I'm witty. I think farting is funny :-)
Can we call it $|\Omega\rangle$ i.e. interacting but vacuous? :-)
 
rob
We could call it Virtually Excited
 
@ACuriousMind Great, so let's have fun with the name.
 
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A: Choosing the name of the chat room

John RennieUpvote this if you want the name changed back to the h bar. Using my superpowers as a room owner I will change the name back if this gets ten upvotes (provided no competing suggestion gets more upvotes).

 
6:02 PM
@JohnRennie So we're going to do a meta post every once in a while?
 
@DanielSank I think changing the name if and when someone suggests something witty seems a fun idea. Exactly how we decide on the names changes I'm not fussed.
1 message moved to Trash
 
@JohnRennie Damn you
 
@BernardoMeurer that was funny for a bit
It has ceased being funny now.
 
Tsc, Thatcherette
 
I did in fact vote for Thatcher in 1979 when she first came to power, then again at the subsequent election. However I came to my senses after that :-)
 
6:10 PM
Dammit, you're too old for my insults to work
At least it means you get them :P
 
:-)
 
I don't know what's up with Thatcher, she just seems like an angry lady who doesn't like fun
She's the British David Z :P
 
In 1979 the UK was in a shocking state. Thatcher promised to bring order and indeed she did. But then she seemed to lose it and became something of a right wing lunatic.
Maybe after too long in power you lose your sense of perspective.
 
Ah, so she's a lunatic? I like her already
 
@BernardoMeurer Be careful about what you wish for :P
 
6:14 PM
There's entertaining lunatics (you for example :-) and there are scary lunatics
 
This reminds me I need to measure the temperatures of my fridge
I think it got the flu from me
it has a fever
 
@BernardoMeurer It's vitally important the beer temperature be maintained precisely!
 
@JohnRennie I know!
Now I have to drink all my beer today before it gets warm :(
And I have a linear algebra exam tomorrow
so sad
 
That's ... just terrible :-)
 
TOO BAD I ALREADY PASSED THAT CLASS LOSERS
::chugs beer::
::punches liver::
@JohnRennie Since you've been through all the ages of man, how to I get rid of static on my records?
 
6:17 PM
Ah the pleasures of vinyl.
The best way to deal with the static is throw the record away and buy a CD instead.
 
:(
Dude, digital is no fun
too easy
Look, if it doesn't take a bathing in holy water by virgins in the moonlight to sound good I don't want it
 
Breathe on the record? Buy an anti-static gun?
 
Those pesky anti-stats cost 50 moneys!
 
Breathe on the record. The moisture in your breath will allow the static to leak away.
 
Is carbon fiber conductive?
 
6:20 PM
Pass
 
Lemme google
Yep
It is
 
There's no good way to make records sound perfect. You always get some crackles. That's part of the vinyl experience.
 
SO
I could get one of those carbon fiber brushes, and wire it to the mains ground
Ta-daa
Suck it Edison
 
You don't need to wire it to the mains earth. Your body is sufficiently conducting that you can just hold the brush and the charge will leak to earth through you.
But the static soon builds up again.
 
But then it doesn't look cool :P
Well, at least I don't have a pesky felt mat
You can power a small family with the static from those things
Heck maybe a large family
 
6:24 PM
Cool = armchair, beer, listening to prog rock on CD
Uncool = hunched over your turntable swearing continuously
 
Digital audio is too easy, you can buy any CD, it doesn't matter, the bits are the same (assuming the mastering is the same). You can use a 9.99 CD player on your computer with some delta-sigma DAC and it's all good
Sure, get a $99 DAC and it's even better, but it's just easy :P
Records? Search through all the 78 pressings of that album you like, find the good ones, scramble the world for one in good shape, buy it from a guy in Vietnam, receive a brick instead, repeat
 
You young impetuous fool :-)
 
Also I never saw a CD get anyone laid
maybe in the 80s
 
That's a lot of Radiohead ...
 
I like Radiohead
 
6:32 PM
Disraeli Gears, now that's a good album.
 
and Talking Heads
YES
Come on, Sunshine Of Your Love is too good to be true
 
I've got several of the albums on your wishlist in my box of old vinyl records in the attic.
Though they've been played a lot so they're probably not in great shape.
 
How much beer do you want :P
 
It's getting the records to you. They're surprisingly heavy. And like I say they're probably not in great condition.
 
::ponders::
How many are they?
 
6:35 PM
Actually, you're not having my copy of Paranoid. I'm keeping that for sentimental reasons even though I'll never play it again.
Electric ladyland is a bit crap, you can have that
 
Ay
It's a nice album :P
Paranoid is an AMAZING album, I understand :P
 
You can't have my Pink Floyd albums either - sentimental reasons again.
 
I still can't believe I managed to get all of Black Sabbath's albums in DSD
 
Or the Led Zeppelin
Actually I want to keep them all :-) Just in case I decide to buy a turntable one day.
 
Bahaha
There we go
My mother got rid of all my records the week I moved out lol
 
6:39 PM
c'monnnnn, rep cap, sooo cloooose
 
Thankfully my Pat Metheny records are safely guarded
 
182 today
 
Anyway, I'm going to crack open a beer, slump into my armchair and play Disraeli Gears (FLAC)
@EmilioPisanty 192!
 
@JohnRennie thanks
that's a really nice paper btw
 
@JohnRennie I have it in FLAC too
 
6:40 PM
@EmilioPisanty which one?
 
@JohnRennie the physics of mosh pits one
 
@JohnRennie How far up the frequency range can you hear?
 
@BernardoMeurer 8 kHz. No kidding. My top cut-off is 8 kHz now I'm old and decrepit. I used to be able to hear 19 kHz as a lad :-(
 
@EmilioPisanty 202 now :) The video looked interesting (OK 200 :P)
I'm watching
 
6:42 PM
@JohnRennie And here I was thinking badly of myself for cutting off at 18kHz
@JohnRennie Also, if you do end up getting a turntable, Rega makes amazing tables in the UK
@JohnRennie Also, what speakers have you got?
 
@BernardoMeurer Heybrook HB2. They are older than you are but they still work fine and I love the sound from them.
 
@anonymous it's actually given me the extra +2, from the accept on Kyle's answer there
 
@EmilioPisanty Eh, how? Isn't the cap 200 per day?
 
I don't think I'll ever make the legendary badge
but at 26/50, maybe I do have a shot at the silver within the next four years
 
@BernardoMeurer there is no chance of me ever getting a turntable. I grew up putting up with flipping turntables and I hate them with a vengeance.
 
6:52 PM
@anonymous accept +2s and +15s are exempt, as are bounties
 
@JohnRennie Oh, that's a nice pair of speakers! Do you have a power amp or an integrated receiver?
 
@EmilioPisanty Oh I see. (BTW when is +15 awarded? I know only about +2 for accepting answers)
 
@anonymous as in, your answer gets accepted
 
Where they 300 a piece or the pair? I remember something like that in cost
 
The amp is a Marantz PM6010. It's nothing special and you can buy them on eBay for £200 or so, but again I really like the sound.
 
6:54 PM
Ha, we had a shitty turntable at home that skipped and screamed like hell. I loved it :P
Marantz made really good stuff
 
I paid about £200 for the HB2s in 1981. I don't know what they would cost to buy second hand these days.
 
Also, I have a question, why is it super common to see tube headphone amps, harder to see tube speaker amps?
 
@BernardoMeurer I've got a Marantz CD player. I forget the exact model but it's a special edition and it sounds absolutely brilliant. Really, really, nice.
@BernardoMeurer Don't know.
 
Sweet! I just rip everything to CRC match since my player is shit
 
I'm not a mega hi-fi buff these days. I have an old hi-fi that sounds really good to my ears so I stick with that. Every time I've tried replacing a bit I've decided I don't like it as much and I've gone back to my old amp and speakers.
I use a Mac Mini running Kodi to play the FLACs with audio from the Mac's analogue port.
 
6:59 PM
Is the DAC on that any good?
I guess Apple computers have decent DACs in general
 
Anyone here tried the new Apple Airpods ? How are they?
 
It's pretty good. It's better than any PC I've owned. I keep wondering about buying a Dragonfly USB DAC or something like that, but never got round to it.
 
@anonymous Bah, for their price I could get some really nice IEMs
I've hear very good things about the Dragonfly, I'm dying to know how it actually sounds
Since my cans are 300Ω it takes some power to drive
But this Dell does surprisingly well
I have a portable player that doubles as a USB DAC, I use that sometimes too
but it has issues with xHCI USB controllers on Linux, so I haven't used it much for that lately
xHCI == USB3
I actually have gone borderline insane trying to fix the issue, but I gave up after some 3 days
 
Sorry, phone call. Where were we?
 
We were talking 'bout DACs
 
7:07 PM
The last I heard if you wanted a £200 DAC the Dragonfly was the standard recommendation.
But I'm not sure if it will drive headphones directly.
 
@BernardoMeurer I think the price is justified as it has an internal computer which can recognize voice commands. It claims to have a good battery life as well.
 
It will, at least the new ones will
@anonymous I don't think the voice processing happens in the earbuds
No Apple product has a justifiable price
With that said, they do make gorgeous products
So there's that
 
@JohnRennie Ah, I have mixed feelings about whathifi
I like head-fi forums
 
@BernardoMeurer Are you sure about that ? Someone told me otherwise
 
7:11 PM
@anonymous I'm not sure. That's why I said "I don't think ..."
Time for dinner folks, talk to y'all again in a bit
 
Yup, time for a beer, armchair and book.
See everyone tomorrow
 
@JohnRennie Good night :)
 
7:59 PM
In extrinsic semiconductors is Fermi level same as donor/acceptor energy level ?
 
::peeks out of den::
 
 
1 hour later…
9:24 PM
@ACuriousMind Potentially dumb question
Can phantom energy exist in a Big Crunch universe, but with its energy density incredibly small?
 
hello
 
@SirCumference I'm having deja-vu
 
@ACuriousMind I'm not learning about it now, but curious
 
I'm pretty sure I have answered that exact question last time we talked :P
 
Yeah, but it gets a bit more confusing when I think about it
You said yes
But if phantom energy's pressure becomes more negative, won't a Rip be inevitable?
 
9:28 PM
Why?
 
@ACuriousMind Well its pressure becomes more negative as its volume increases, and its volume increases as its pressure becomes more negative
Won't a feedback loop eventually cause it to become significant and lead to a Rip?
 
...you're once again ignoring all the other stuff in the universe
 
@ACuriousMind Yes, but phantom energy's pressure decreases more and more. Won't it eventually be too much for gravity to counter?
 
There is a point of expansion where that certainly happens, but I don't see why the universe would need to even expand that far. What's wrong about a scenario where the universe expands a little - far too little for the phantom pressure to become dominant - then contracts again?
 
@ACuriousMind Well, if it contracts and the scale factor reaches 0, will phantom energy's pressure still keep decreasing?
 
9:34 PM
I don't understand the question.
 
Probably because I'm confused
OK, lemme see if this makes sense
We have a closed matter-dominated universe with phantom energy
That universe contracts from a Big Crunch
Will phantom energy's pressure still continue to become more negative?
 
Wait a moment
Phantom energy has $w\rho = p$ for $w < -1$ and density $\rho$ and pressure $p$, right? Why do you keep saying "as volume increases, its pressure becomes more negative"?
 
@ACuriousMind OK, wait
I'm a bit confused
John Rennie said
Jan 7 at 7:15, by John Rennie
Anyway the point is that the equation of state determines how the pressure changes with volume. With a regular gas P is positive and decreases with volume. With dark energy P is negative and constant. With Big Rip stuff P is negative and becomes more negative with volume.
Jan 7 at 7:16, by John Rennie
So a negative P makes the volume expand, but as the volume expands P gets even more negative, which makes the expansion even faster and we get a vicious cycle.
 
Yeah, well...that's not really correct, in my understanding. The equation of state is the ratio between energy density and pressure.
 
@ACuriousMind Yes, by definition
OK, let me ask something. In dark energy's case, the pressure is negative and remains constant with time, right?
 
9:45 PM
For ordinary matter, you can interpret this directly as a relation between volume and pressure, because the energy density of ordinary matter in a FLRW universe scales with $a^{-3}$, which is a volume factor.
But e.g. radiation scales with $a^{-4}$, it is both diluted and redshifted, so the change in energy density is not the same as the change in volume
Finally, phantom energy scales with some positive power of $a$, meaning it gets denser as the universe expands more quickly.
 
Sigh, I gotta go. I'll try to meet back here in an hour or so
 
Because of its equation of state, it getting denser means it exerting more negative pressure
But I find talking about "volume" here confusing because in FLRW universes the energy density does not scale with volume except for non-relativistic ordinary matter.
(I also find it confusing to think about stuff that gets denser as the universe expands in the first place; I guess that's why I'm not a cosmologer ;P )
 
10:07 PM
Any progress on your "mooc" @dmckee?
 
 
2 hours later…
11:59 PM
Would anyone happen to have access to smf4.emath.fr/en/Publications/Asterisque/1990/183/html/…?
 

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