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user228700
1:00 PM
Do you read all those books you need to read this time of day?
 
John Rennie
John Rennie
Good. On that note I'm off to get lunch, though not radioactive bananas.
 
user228700
Oh, it's lunch time. Okay, I'll catch you tomorrow. Bye!
 
ACuriousMind
ACuriousMind
@Danu I think becoming a moderator won't make anyone, personally, "more effective", except if you make very liberal use of the unilateral votes which is likely to upset people. But we don't elect moderators because we want certain people to be "more effective", we elect them because someone has to deal with the issues that aren't suited for community review. I think people get this impression that mods are supposed to be more "effective" because many mods are simultaneously high rep users...
...so they tend to believe there is some sort of intrinsic relation between the two, while they are just both results of spending enough time on the site to a) be popular enough to be elected and b) have enough answers/questions to gather a lot of rep
 
user228700
@JohnRennie There's a great video about this(somewhat...Vsauce tends to go off-topic in weird but wonderful and mind-blowing ways) by Vsauce:
 
user228700
 
user116211
1:06 PM
@DavidZ: The community Election post is featured, right?
 
user116211
But the sidebar is still showing otherwise.
 
user116211
I know the side-bar is pretty late sometimes too get updated...
 
ACuriousMind
ACuriousMind
@JohnRennie [smartass mode on] Actually, the proper intensifications of NB would be NM and NO
 
user116211
But this time, I've noticed in the morning, the post was featured, but in the noon, it was not; just quite an hour ago, it was featured in the side-bar; but just now, it is not there... it's bothering.
 
yuggib
yuggib
@ACuriousMind What I understood is that technically the salary is related almost exclusively to the teaching activity, and almost not to the research activity for PhD students and postdocs.
 
user116211
1:08 PM
 
yuggib
yuggib
In the usual contracts given by universities. If the funds come from the DFG or some other funding agency then it is different
 
ACuriousMind
ACuriousMind
@MAFIA36790 I think the sidebar is confused because it also instantly became a "Hot Meta post" in its own right, so it doesn't put it inot the featured column as long as it's still hot, but that's just a guess
@yuggib Hm. Maybe it depends on the university and how many people it has available to teach
 
yuggib
yuggib
@ACuriousMind It's possible. I know only about Stuttgart and LMU
 
ACuriousMind
ACuriousMind
Because I think the amount of mandated teaching activity for a PhD/postdoc here does not suffice to justify the salary (there are strict rules for how much public employees are paid)
Then again, I don't know how many of them are actually employees, and which ones have fellowships from a graduate college or other scholarships
 
yuggib
yuggib
I have no great experience either. Let's say that I also think that the salary is more than good enough to cover the teaching activity
But the PhD students I met there always complained they had too much teaching to do
(the ones who were not paid with DFG funds)
 
ACuriousMind
ACuriousMind
1:14 PM
@yuggib If I ever meet a PhD student who's not complaining about some aspect of their situation I'll know something is horribly wrong.
 
yuggib
yuggib
yeah, the PhD is usually made for complaining and being bullied by a professor :-D
 
user116211
@ACuriousMind ohh, maybe; but it was there both as the featured as well as the Hot Meta posts quite a while ago....
 
user116211
@yuggib Is the teaching part mandatory?
 
yuggib
yuggib
@MAFIA36790 in germany very often it is mandatory
in other countries it depends
 
user116211
okay.
 
yuggib
yuggib
1:21 PM
usually is optional, but people want to do it because it means extra money
 
user116211
ohh.
 
yuggib
yuggib
@ACuriousMind However you always complain in academia: we've already said of PhD students; then when you're postdoc you complain you can't find a tenured job; when you're associate professor you complain there is no money for research, and the students are low-quality; when you're a full professor you complain about the overall state of the world.
 
user218912
@ACuriousMind hello
 
ACuriousMind
ACuriousMind
heyhey
 
user218912
@ACuriousMind can you elaborate on this please?
 
user218912
1:30 PM
12 hours ago, by ACuriousMind
@IceLord 1. You can only impose gauge conditions on massless vector fields. 2. You impose it usually by adding a Lagrange multiplier for it.
 
user218912
I know what a lagrange multiplier is but I don't know how it imposes the gauge condition.
 
ACuriousMind
ACuriousMind
Tell me what a Lagrange multiplier is, then
 
user218912
I only know it in the context of optimization and lagrangian mechanics.
 
ACuriousMind
ACuriousMind
That's not an answer.
 
user218912
okay so lagrange multipliers basically allow you to optimize a function with a constraint
 
user218912
1:34 PM
by writing out the lagrangian for the function and constraint and multiplying the constraint by a multiplier (lagrange multiplier)
 
0celo7
0celo7
@ACuriousMind Aha
 
ACuriousMind
ACuriousMind
@IceLord Aha. Now what is the difference between that and imposing a gauge condition?
 
0celo7
0celo7
What's this style of teaching called
I like it
 
ACuriousMind
ACuriousMind
@0celo7 A cheap knock-off of the Socratic method, I guess :P
 
user218912
@ACuriousMind a gauge condition is a constraint?
 
0celo7
0celo7
1:35 PM
@ACuriousMind Interesting. Who came up with it?
 
ACuriousMind
ACuriousMind
@IceLord Is that a question or a statement?
@0celo7 Some Roman, probably.
 
0celo7
0celo7
@ACuriousMind It's a quatement.
 
user218912
@ACuriousMind I see, but how does a lagrange density with a lagrange multiplier in it look like?
 
ACuriousMind
ACuriousMind
@IceLord I don't understand the question
@0celo7 ::faint chuckle::
 
user218912
you said You impose it usually by adding a Lagrange multiplier for it., adding it to what?
 
user218912
1:37 PM
the lagrangian?
 
Bass
Bass
@ACuriousMind So the $\xi$ in the $\int DA\,\mathrm{exp}((i/2\xi)\int dx (\partial A)^2)$ term is a Lagrange multiplier? Never thought of it in this way.
 
user218912
@ACuriousMind is the lagrange multiplier in the EOM or the lagrangian?
 
user218912
sorry i'm misunderstanding.
 
0celo7
0celo7
why are you doing gauge theory in week 2?
 
user218912
how is this gauge theory?
 
user218912
1:40 PM
(I am not familiar with gauge theory so idk)
 
ACuriousMind
ACuriousMind
@IceLord I'm not going to tell you what to write down. You know how to use a Lagrange multiplier to impose a constraint, and a gauge condition is a constraint. There's no trick here.
 
user218912
@ACuriousMind I'm not asking what to write down!
 
user218912
I just don't know where to write it.
 
user218912
it imposes a constraint on the lagrange density or the field equations?
 
0celo7
0celo7
lol prof straight up told a dude in class he couldn't read his handwriting
 
ACuriousMind
ACuriousMind
1:43 PM
@Bass It is.
 
0celo7
0celo7
@ACuriousMind Bad ACM.
 
ACuriousMind
ACuriousMind
At least I catch most of my errors within the 2 minute delete window :P
 
0celo7
0celo7
Even I knew that one was wrong
I think!
 
ACuriousMind
ACuriousMind
I confused myself because the gauge condition is $\partial A = 0$, not $(\partial A)^2 = 0$, I overlooked the latter implies the former :/
 
0celo7
0celo7
Huh?
 
user218912
1:45 PM
@ACuriousMind can you link me an article that describes how gauge conditions and lagrange multipliers relate?
 
0celo7
0celo7
Put in indices
 
user218912
please?
 
ACuriousMind
ACuriousMind
@IceLord What is the difference between "imposing a constraint on the density" and "imposing a constraint on the field equations"?
 
user218912
@ACuriousMind oh
 
user218912
idk
 
user218912
1:45 PM
should be the same then?
 
ACuriousMind
ACuriousMind
@IceLord Then what did you mean by that question?
 
user218912
constraint on the action = constraint on the density = constraint on the eom?
 
ACuriousMind
ACuriousMind
I don't know what either of those terms mean, that's why I asked you what the difference between them is supposed to be.
 
user116211
@ACM was right; the sidebar was confusing between the featured and Hot Meta Posts:
 
user116211
 
user218912
1:49 PM
hey that's me!
 
user218912
:D
 
user218912
@ACuriousMind alright so is the lagrange multiplier in the density a field or a number? idk if this is a dumb question.
 
user116211
@IceLord yeh; for sure ;)
 
ACuriousMind
ACuriousMind
@IceLord Why don't you try whatever you think is right?
 
user218912
@ACuriousMind if my lagrange density is $\mathcal{L} = -\frac{1}{2}(\partial_\alpha A_\beta (x))(\partial^\alpha A^\beta (x)) + \frac{1}{2}(\partial_\alpha A^\alpha (x))(\partial_\beta A^\beta (x)) + \frac{1}{2}\mu^2 A_\alpha (x) A^\alpha (x)$ is the last term a lagrange multiplier?
 
ACuriousMind
ACuriousMind
1:58 PM
It's usually called a "mass".
 
user218912
yes
 
user218912
but is it a lagrange multiplier too?
 
ACuriousMind
ACuriousMind
Well, what do you think?
 
user218912
since my prof never talked about how lagrange multipliers work for fields.
 
0celo7
0celo7
@ACuriousMind Whoa.
TIL QFT is Catholic.
 
user218912
1:59 PM
@ACuriousMind no.
 
user218912
is the field $A_\alpha (x)$ a lagrange multiplier then?
 
ACuriousMind
ACuriousMind
@IceLord why not?
@IceLord why would it be?
 
user218912
nvm.
 
ACuriousMind
ACuriousMind
that's not an answer.
 
0celo7
0celo7
@IceLord I'm jealous, you're getting all of ACM's attention
:(
 
user218912
2:03 PM
I know and I'm not using it effectively.
 
user218912
@ACuriousMind just ignore me, I'll look at this problem again when we do field theory in class.
 
ACuriousMind
ACuriousMind
@0celo7 You should be proud you don't need it that much these days anymore instead :P
Or proud that you often do stuff where it wouldn't help you anyway, if you prefer
 
0celo7
0celo7
@ACuriousMind I do need help, but you can't give it :/
 
ACuriousMind
ACuriousMind
@0celo7 Yeah, that's my second variant, then
 
0celo7
0celo7
Kobayashi-Nomizu quote Steenrod but the definitions are different.
I need to read the original paper
 
ACuriousMind
ACuriousMind
2:05 PM
@IceLord Okay, but let me say that it's a bit frustrating that every time I ask you a question you either answer it without giving any reasons for why that's your answer or you don't answer it at all. I'm trying to get you to do the steps yourself instead of just telling you, but you're making it rather difficult.
 
user218912
@ACuriousMind yeah... it's because I haven't learned it yet and don't have a feel for it. though I really appreciate you doing that.
 
0celo7
0celo7
@ACuriousMind I would still like to discuss things with you, but if you don't find it interesting I understand.
Me a year ago would be bored by me now.
 
ACuriousMind
ACuriousMind
@0celo7 If it's more Riemanian geometry/isometry groups, I'm indeed not really interested :|
 
0celo7
0celo7
Right now it's group actions on metric spaces. Isometry group is a long way away.
And compact open topology. Not very fun, I admit.
 
ACuriousMind
ACuriousMind
Mhhh, I don't know much about general group actions, and nothing about the compact-open topology.
 
0celo7
0celo7
2:13 PM
Me neither. I need an old fashioned general topology book like Kelley or Dugundji.
For some reason the newer ones don't discuss it.
Neither does Bourbaki.
 
user218912
brb class
 
0celo7
0celo7
@ACuriousMind I also have to figure out what things I know about group actions are about Lie group actions.
 
yuggib
yuggib
@0celo7 bourbaki discusses the compact open topology
simply it is not called in that way
it is the topology induced by the uniform structure of compact convergence
 
Secret
Secret
2:28 PM
@IceLord Don't ask me about actual QFT maths stuff yet, because I know basically nothing of it as I am still in quantum
 
John Rennie
John Rennie
@ACuriousMind you've made the mistake of confusing me for someone who isn't an anal retentive nerd :-)
3
Q: Emphatic form of nota bene

John RennieI suppose this is really about Latin, but since there is no Latin SE an answer using modern Italian would be welcome. In the days of my youth we had a Latin teacher who used the phrase nota benissime when he wanted us to take extra special notice. I may have misremembered the phrase, and in any ...

translation
 
ACuriousMind
ACuriousMind
lol
I bow before the master
btw, there is now a Latin Language
 
0celo7
0celo7
@yuggib Wait...do you know about the compact open topology?
 
John Rennie
John Rennie
@ACuriousMind it's really a Dog Latin Stack Exchange I need. I wonder if there'd be enough support to start one :-)
 
0celo7
0celo7
Dog Latin?
 
ACuriousMind
ACuriousMind
2:44 PM
Not to be confused with the much more aristocratic Cat Latin.
 
0celo7
0celo7
You and your cat superiority complex
@ACuriousMind The dog is clearly superior to the cat
@ACuriousMind I will vote for you if you change your avatar to a dog.
 
ACuriousMind
ACuriousMind
3:04 PM
@0celo7 I'm no sell-out :P
 
yuggib
yuggib
@0celo7 not so much
but I know that for all uniform spaces it coincides with the uniform structure of compact convergence
and that a thorough discussion of uniform spaces and induced topologies can be found in Bourbaki
 
Obliv
Obliv
@0celo7 what would the gm in $\frac{cal}{gm \cdot ^{\circ}C}$ mean
gm should be a mass since this is specific heat
 
0celo7
0celo7
@yuggib Ok...thanks.
I found a paper which says that what I need is "well known"
 
yuggib
yuggib
probably it is
 
0celo7
0celo7
"it appears in several texts on general topology"
 
Obliv
Obliv
3:11 PM
ok why would they use $gm$ to mean grams
that's just stupid.
 
0celo7
0celo7
@yuggib My topology prof had never heard of it
He's famous enough to have a wiki page, fwiw
 
yuggib
yuggib
@0celo7 in french school uniform spaces are well known
 
0celo7
0celo7
Which Bourbaki should I be checking?
 
Xasel
Xasel
Hey everybody here How was yar day
 
yuggib
yuggib
@0celo7 general topology, chapters 5-10, chapter 10 on function spaces
first section on the uniform structure of $\mathfrak{S}$-convergence
 
0celo7
0celo7
3:15 PM
How does one get that book
 
yuggib
yuggib
the uniform spaces in general are in General topology 1-4, chapter 2
 
0celo7
0celo7
it's not on Springer
 
yuggib
yuggib
I have only the french version of both
 
0celo7
0celo7
frig
@yuggib have you heard good things about Dugundji?
 
yuggib
yuggib
@0celo7 never heard of it/him
I have not an extensive knowledge of general topology
and I use bourbaki as a reference
 
0celo7
0celo7
3:20 PM
I don't need an extensive knowledge, I need something that's in English (or German)
 
Danu
Danu
@ACuriousMind The point for me, mostly is actually to realize that it will make one much less effective at helping out with certain aspects of the site. It was something I hadn't thought about much before I became a HSM moderator.
 
yuggib
yuggib
 
0celo7
0celo7
you said chapter 10
 
yuggib
yuggib
both are in english also apparently
your library should have them
maybe they're also on springerlink
 
0celo7
0celo7
I cannot download the second one
 
Obliv
Obliv
3:23 PM
holy crap how many pages is that book @yuggib
 
yuggib
yuggib
I don't have the subscription here
I can't try
 
0celo7
0celo7
They have the French version wtf
damn library
 
yuggib
yuggib
@Obliv not so long
 
0celo7
0celo7
@yuggib it won't even give me a springer link link
 
yuggib
yuggib
the first one is on springerlink right?
 
0celo7
0celo7
3:24 PM
> Title: General topology
Uniform Title: Topologie générale.
Author: Nicolas Bourbaki
Subjects: Topology
Description: [1] Chapters 1-4 -- [2] Chapters 5-10.
Translation of: Topologie générale.
Includes bibliographical references and indexes.
Related Titles: Series: Bourbaki, Nicolas. Eléments de mathématique. English.
Publisher: Berlin ; New York : Springer-Verlag
Creation Date: c1989
Format: 2 v. ; 24 cm..
Language: English
Identifier: ISBN 038719374X (U.S. : v. 1);ISBN 0387193723 (U.S. : v. 2);ISBN 3540642412 (softcover v. 1);ISBN 354019374X (2nd printing v. 1);ISBN 3540645632 (softcover …
 
Obliv
Obliv
It probably doesn't go very in depth in each topic, right? Still, just section 2 goes through a LOT of algebra
 
0celo7
0celo7
Aha!
They do have the English
@yuggib Yes.
 
yuggib
yuggib
@Obliv what book are you talking about?
 
Obliv
Obliv
the first link
 
yuggib
yuggib
mmmh, they don't do so much algebra on a topology book
 
Obliv
Obliv
3:26 PM
oh it's in multiple books
 
yuggib
yuggib
bourbaki are around 20 books
 
ACuriousMind
ACuriousMind
@Danu "Much less effective"? The only thing I see is being more cautious with close and reopen votes, and if a single user is that relevant for those processes the site has bigger issues to begin with.
 
0celo7
0celo7
friggin $75 for Bourbaki Vol. 2
Is it worth it @yuggib
 
ACuriousMind
ACuriousMind
In slightly related news, I think I just dupe-hammered a HNQ :P
 
Xasel
Xasel
Hey guys I have confuson
 
yuggib
yuggib
3:27 PM
@0celo7 I have all the bourbaki books, so for me they're worth ;-P
 
Xasel
Xasel
Weall have been taught about conservation of momentum
 
yuggib
yuggib
still better if you take it from the library first
and then decide based on your needs
 
Xasel
Xasel
but is there any proof regarding that momentum is conserved
 
0celo7
0celo7
@yuggib Yes...
 
yuggib
yuggib
all the convergence stuff is done by filters in bourbaki
 
0celo7
0celo7
3:28 PM
I need something better than Munkres for general topology
 
Xasel
Xasel
or why the momentum is conserved?
 
0celo7
0celo7
My prof recommended Dugindji
but I can't tell if they have the theorem I need in there
 
yuggib
yuggib
I don't know it
by the way which is the theorem?
just out of curiosity...
 
Xasel
Xasel
@ACuriousMind:you have any idea about it?
 
0celo7
0celo7
@yuggib I need: $X$ locally compact, then $C(X,Y)$ has a countable base in the compact-open topology iff $X$ and $Y$ have countable bases.
Can you please check Bourbaki?
 
ACuriousMind
ACuriousMind
3:30 PM
@Xasel Most physicists consider symmetries to be more fundamental than conservation laws and refer to Noether's theorem as the underlying reason, cf. e.g. physics.stackexchange.com/q/60021/50583
 
0celo7
0celo7
I have a paper that proves $\Rightarrow$, but I really need $\Leftarrow$.
I have a partial result from Dugundji, which I am trying to digest.
I don't care if this uses filters or nets or whatever.
I'm willing to learn all of that.
 
John Rennie
John Rennie
@Xasel conservation of momentum follows from a symmetry called shift symmetry.
 
0celo7
0celo7
translation symmetry
 
John Rennie
John Rennie
A rose by any other name ...
See:
23
Q: How do we know that energy and momentum are conserved?

mathewHow do we know energy and momentum are conserved? Are these two facts taken as axioms or have they been proven by an experiment? This question has been in part addressed here: Conservation of Momentum but I don't see how translational symmetry implies conservation of momentum. If the reasoning b...

energy-conservation momentum
 
VenkiPhy6
VenkiPhy6
Does anyone know of good problem books along with detailed solutions? I would like the book to be organized by topic and include a list of equations required to solve those problems so that I can read the theory behind them from my textbook and then solve them...
 
0celo7
0celo7
3:33 PM
but they are not conserved in GR
@VenkiPhy6 We literally have no clue what kind of problems you're looking for.
 
VenkiPhy6
VenkiPhy6
@0celo7 I am undergrad preparing for entrance exams to graduate programs..so problems at that level...
 
John Rennie
John Rennie
@VenkiPhy6 get yourself a copy of Irodov's problems. There are numerous web sites with solutions to them.
 
0celo7
0celo7
Btw...what is it with Indians' obsessions with problem books?
 
Xasel
Xasel
@JohnRennie and @ACuriousMind : I couldn't make out what you guys mean by Symmetery in this conetxt lest the shift symmetery
 
0celo7
0celo7
They seem to always ask for them
 
VenkiPhy6
VenkiPhy6
3:35 PM
@0celo7 ENTRANCE EXAMS with very low pass percentages...!!!
 
ACuriousMind
ACuriousMind
@0celo7 I think it has to do with the large importance of standardized tests for admissions?
 
yuggib
yuggib
@0celo7 I think it is covered if $Y$ is a uniform space
 
Xasel
Xasel
@VenkiPhy6:Russian books are way to go like L SEna Pinsky
 
John Rennie
John Rennie
@VenkiPhy6 Hmm, graduate level? Irodov is probably too simple then.
 
Xasel
Xasel
wait a min
 
0celo7
0celo7
3:35 PM
@yuggib Even better, how about a metric space?
 
Xasel
Xasel
^Completely legal and in public domain
 
yuggib
yuggib
@0celo7 then it is covered since every metric space is a uniform space
 
VenkiPhy6
VenkiPhy6
@JohnRennie Exactly!
 
0celo7
0celo7
@ACuriousMind Ok, so you have noticed it too?
@yuggib Ok can you give me the theorem number?
 
Xasel
Xasel
@VenkiPhy6:See above link/website there you may find something of your concern
 
ACuriousMind
ACuriousMind
3:37 PM
@0celo7 Yes. It's the second most noticable thing right after the "doubts"
 
0celo7
0celo7
I don't understand the doubt thing.
When I translate "I have a question" in Google, it returns "I have a question"
 
John Rennie
John Rennie
@Xasel You need to understand Noether's theorem, and to be honest it is hard. I forget where you've got to in the educational system, but even most physics undergrads would struggle - at least first/second years.
 
0celo7
0celo7
Not "I have a doubt"
 
ACuriousMind
ACuriousMind
@0celo7 It's linguistic evolution, these things rarely make sense
 
Xasel
Xasel
hahaha...@0celo7:You guys are confuse by Indian english
many indian use words: doubt
for asking pupose
there are also other lingos like :prepone,etc..
@JohnRennie:well to say only at high school lvl..at par with Kaumudi
Hereby indian is being refere toSE Asia Indian rather than Native Indian of AMerica
 
John Rennie
John Rennie
3:40 PM
@Xasel In that case you'll need to take Noether's theorem on faith. To be honest I don't really understand it either so you're not alone.
 
0celo7
0celo7
@JohnRennie I can explain it to you later if you want
It's an integrability criterion for ODEs at heart
 
Xasel
Xasel
what space homogeneity 'relation with conservation of momentum
 
yuggib
yuggib
@0celo7 well, they use a slightly different language and so there is not exactly a theorem number to see that directly
 
DanielSank
DanielSank
@JohnRennie Noether's theorem isn't that bad is it?
 
John Rennie
John Rennie
@0celo7 Let me get back to you on that one
 
DanielSank
DanielSank
3:41 PM
You need only calculus.
I think.
 
Xasel
Xasel
As described by PhysSE forum
 
0celo7
0celo7
@DanielSank Correctomundo
 
DanielSank
DanielSank
@0celo7 So what's the big deal?
 
0celo7
0celo7
It's trickier on a manifold
 
yuggib
yuggib
@0celo7 maybe it is better if you find a text that discusses the compact-open topology more directly
 
0celo7
0celo7
3:41 PM
@yuggib Probably. Any suggestion?
@DanielSank I didn't say there was one, did I?
 
DanielSank
DanielSank
nope
 
yuggib
yuggib
@0celo7 not really
 
0celo7
0celo7
It's @JohnRennie you should be talking to
 
John Rennie
John Rennie
@DanielSank From time to time I go through the maths and it all makes sense. Then I lose interest and in a few months find I've forgotten the details. The thing is that I only need the result not the proof of the theorem, so I have little motive to commit it to memory.
 
ACuriousMind
ACuriousMind
@DanielSank I think @JohnRennie is just afraid of Lagrangian mechanics ;)
 
John Rennie
John Rennie
3:43 PM
I've never been very action orientated
 
DanielSank
DanielSank
heh
 
John Rennie
John Rennie
God that's a rubbish pun
 
DanielSank
DanielSank
@JohnRennie Yeah, why bother memorizing proofs?
 
Xasel
Xasel
hahah..though youar into RAF
 
ACuriousMind
ACuriousMind
@JohnRennie Par for the course around here, then :)
 
John Rennie
John Rennie
3:44 PM
And I thought physicists were masters of wit and humour ...
 
0celo7
0celo7
Why would you think that?
Weird.
 
Xasel
Xasel
There are...thought their humours is a secret one
 
user116211
 
Xasel
Xasel
@MAFIA36790:Why are you telling me this?
ok I get it once I mistakeingly referred it to as forum
 
ACuriousMind
ACuriousMind
"once"...that was less than 10 minutes ago!
 
John Rennie
John Rennie
3:48 PM
Sigh ...
-2
Q: Is it a collisssion?

I HATE STACK EXCHANGE Q:if a boy is walking on road and see's a snake,he ran back , Now does collision occurred between snake and boy? I am so confuse can anyone please help?

collision
 
DanielSank
DanielSank
^ Great title.
 
John Rennie
John Rennie
@DanielSank Yessssssssss
 
user116211
@JohnRennie The body content is speechless ;(
 
David Z
David Z
ooh, it's almost chat session time
 
ACuriousMind
ACuriousMind
@JohnRennie Now that comment is a textbook example of "not constructive" :P
 
Xasel
Xasel
3:50 PM
@ACuriousMind:oh kindly spare me
 
DanielSank
DanielSank
@JohnRennie I really don't think you should have made that comment though.
 
Xasel
Xasel
I forgot about that
so lets say twice
 
DanielSank
DanielSank
@ACuriousMind flagged as such
 
Obliv
Obliv
I'm so mad @johnR I literally couldn't print-screen in time
 
user128101
@JohnRennie, Hi , did you understandmy concerns?
 
Obliv
Obliv
3:51 PM
as I pressed it the post was no longer viewable ;(
 
John Rennie
John Rennie
@DanielSank yes, it was a childish moment. DavidZ has now deleted my comment and indeed the question.
 
DanielSank
DanielSank
@JohnRennie :D
 
John Rennie
John Rennie
@Obliv it's been deleted
@user104372 Hi.
 
0celo7
0celo7
@ACuriousMind You're in luck
By book on geodesic balls has arrived
 
David Z
David Z
@JohnRennie it was a little funny though
 
ACuriousMind
ACuriousMind
3:52 PM
Seriously though, "I HATE STACK EXCHANGE" doesn't really make SE users extend goodwill towards you
@0celo7 Finally something so you can handle your balls!
 
David Z
David Z
Anyway. Anyone have anything to put on the agenda for the chat session? We've already got heather's question about the goals of the site, and the upcoming election, as topics
 
John Rennie
John Rennie
@user104372 You're quite correct that an isolated neutron will beta decay into a proton, electron and anti-neutrino.
 
VenkiPhy6
VenkiPhy6
@0celo7 I always wonder why EVERYONE is NOT obsessed with problem books! Coz I will read a good standard text(Klepner, AP Frech, Zemansky...) then try to solve problems that are given there. But I will get stuck and will have nowhere to go!! Most times solutions manuals aren't available for these books. So the only alternative seems to be a problems book with solutions so that I can continue reading and not waste time. I wonder...what do you in such situations?
 
user128101
@JohnRennie, can the new proton be absorbet into a nucleus and beta decay?
 
John Rennie
John Rennie
And the mass of the proton is equal to the mass of the neutron minus the electron and neutrino mass and minus the electron and neutrino kinetic energy.
In principle we can take a nucleus and add the proton to it.
The mass of that nucleus will increase by less than the mass of the proton because we have to take some energy out of the system to bind the proton.
 
user128101
3:55 PM
@JohnRennie, right, now that proton is 2.5 Em ligher, if it beta-decays will it lose anotther Em +?
 
John Rennie
John Rennie
The resulting nucleus, with the extra proton, may or may not be to decay by electron capture or beta+ decay. It depends on the structure of the nucleus.
 
ACuriousMind
ACuriousMind
@DavidZ Only other meta kerfluffle I can think of is questions with an ulterior motive, but I'm not sure there's need for further discussion on that one.
 
David Z
David Z
Yeah, me neither
 
John Rennie
John Rennie
Ooh we have a chat imminent don't we?
 
DanielSank
DanielSank
@ACuriousMind Please no.
 
user128101
3:56 PM
@JohnRennie, right, suppose that proton now loses a positron, isn't it 3 Em lighter than the mother original neutron?
 
0celo7
0celo7
@ACuriousMind who said that?
 
John Rennie
John Rennie
@user104372: I'm afraid this is bad timing as we have a chat session from 17:00 to 18:00 and we need to suspend other discussions for that hour.
 
0celo7
0celo7
@VenkiPhy6 I'm not a physicist.
My problems nowadays involve a week of hell
I've got a stack of papers on my desk
 
ACuriousMind
ACuriousMind
@DanielSank Just bringing up options, I don't have any particular desire to talk about that either
 
0celo7
0celo7
I don't know when I got to the point where my work involved research papers
 
David Z
David Z
3:57 PM
@JohnRennie There is always the other room

 Backup Room – The h Bar

A backup room for when The h Bar is busy. (chat.stackexchange....
 
0celo7
0celo7
but it did
 
ACuriousMind
ACuriousMind
@0celo7 It was a username
 
user128101
@JohnRennie,OK, I suppose I clarified my dobt, leave a comment at your answer, thanks
 
user128101
I mean it is clear to you what I need to know
 
ACuriousMind
ACuriousMind
@DavidZ Suggesting to go to the meta room for a physics discussion while we have a chat session mainly about meta in the main room is a funny move ;)
 
DanielSank
DanielSank
3:59 PM
@ACuriousMind yes
 
David Z
David Z
@ACuriousMind The irony is not lost on me ;-) but it's a naming thing
 
DanielSank
DanielSank
Notation is hard.
 
ACuriousMind
ACuriousMind
Oh, the h bar is helpfully informing we we're starting in 27 seconds.
 
DanielSank
DanielSank
Wow, lotsa people show up for these chats, eh?
 
David Z
David Z
lol yeah me too
 
John Rennie
John Rennie
3:59 PM
Why have we just attracted an alien mod?
 
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