The h Bar

FenderLesPaul

12:02 AM

@0celo7 sorry back

@0celo7 yeah if you just add the diagonal elements then you get $\rho + 3p$

but what if I do $\eta^{ab}T_{ab}$?

0celo7

That's ill defined in 4 d

Ignore that

Misread the TeX

FenderLesPaul

ok

0celo7

Well that's just the trace, right?

FenderLesPaul

which?

$\eta^{ab}T_{ab}$ is the trace yeah

and if you do that you get $-\rho + 3p$

as opposed to $\rho + 3p$

so im just wondering what meaning $\rho + 3p$ has

oh nvm I see what it's meaning is

it just comes from taking $n^a \propto \xi^a$ in 11.2.10

I was asking because I get the a similar term $\rho + 2p$ in a calculation I'm doing but $\rho$ and $p$ represent the quasi-local energy and pressure of the gravitational field relative to a 2-sphere of observers

and I was wondering how to interpret that physically

0celo7

12:18 AM

In model UN

Will be back in a bit

0celo7

12:35 AM

runs home

opens Straumann

gasps

oh you think I'm retarded now

@FenderLesPaul I had the EM tensor wrong in my head

@FenderLesPaul the thing you're looking for is the trace reversed crap, right?

that's where I remembered that from

@FenderLesPaul Straumann has a section on stars

maybe he has something in there but you seem to have it figured out

Jim

1:25 AM

My reaction when my computer crashes and I haven't saved my work in a couple days

4

obe

2:09 AM

@Jim That's kind of scary.

0celo7

2:24 AM

@Jim does whatever program you use not have an auto save feature?

FenderLesPaul

3:02 AM

@0celo7 yeah trace reversed crap is it

the $\rho + 3p$ that is

and it's basically the Komar mass as per Wald

but in my case $\rho$ is the gravitational energy and $p$ is the gravitational pressure

so I'm not entirely sure how to interpret it

The Dark Side

6:52 AM

I have a freak question, in case anyone knows about this:

With APS journals, we have an option of Mobile Subscription, which means that I can log in to my personal APS account while in my institute,

and sign myself up temporarily for a 15-day access to the APS journals from anywhere else too, i.e. from home or elsewhere.

I didn't seem to find anything similar for non-APS journals though, like Elsevier, or IOP. Am I missing something?

Anyone knows how to get access to them from outside the institute, given that the institute is subscribed?

yuggib

7:07 AM

@TheDarkSide if your institution have shibboleth, or athens you can remotely login to elsevier and springer

The Dark Side

On a sidenote - WorldBuilding.SE continues its fine tradition of catchy question titles:

yuggib

maybe also iop

The Dark Side

55

Q: How many humans can I abduct without getting noticed?

Humans as Pets is now a thing. But not for AI (as in the linked question) but for the aliens. This celebrity was seen with their human pet and now every alien kid is begging their parent to get one human as a gift for their next hatching anniversary. Alien morals work differently from the human...

@yuggib Oh, is it? I'll have to look for that. Never bothered! Thanks :)

yuggib

no problem ;)

The Dark Side

@yuggib Ah! Looks like we don't have them. Any other way/crack?

DanielSank

7:16 AM

Anyone want to try a stats question?

@Jim wtf I don't even.

The Dark Side

@DanielSank Since I don't know much about stats, I'll say YES!

DanielSank

Days? I not only save compulsively, I push my work to a remote repo every half hour just in case my hard drive would die.

@TheDarkSide Ok cool.

Suppose I have two buckets.

Each bucket can hold N stones.

I start filling the buckets with stones, one by one. For each stone, I have probability P to put it in bucket #1 and probability 1 - P to put it in bucket #2.

Once a bucket hits N stones, I stop.

What is the probability distribution for the fraction of the total stones in bucket #1 at the end of the process?

The Dark Side

Hmm...

:: Looks around for pen and paper ::

:: Can't find it ::

DanielSank

Actually, I may have just figured it out.

The Dark Side

You have a total of N stones too?

DanielSank

7:22 AM

I have as many stones as I need.

Note that I could possibly put N-1 stones into bucket #1 and then N into bucket #2, so the total number of stones used is variable.

The Dark Side

Ah. I should've figured. "Once a bucket hits N stones, I stop."

DanielSank

@TheDarkSide Warning: this may be really hard.

The Dark Side

@DanielSank No problem. We always have the log out button. :P

DanielSank

You can log out any time you like, but you can't never leave.

:: guitar solo ::

The Dark Side

Lol. "can't never" = two negatives. => can always.

DanielSank

7:27 AM

@TheDarkSide You know the song, right?

The Dark Side

Nope.

DanielSank

zomg

@TheDarkSide Where are you from?

The Dark Side

As the profile says: Earth

The Dark Side, Earth

2.1k 4 12 26

homework-and-exercises newtonian-mechanics quantum-field-theory quantum-mechanics particle-physics kinematics waves

:P

DanielSank

@TheDarkSide sigh

@TheDarkSide youtube.com/watch?v=7tJ0I2J954A

The Dark Side

Even though sometime in the past, one overly aggressive user of this site dubbed me a Martian, when we had a small discussion.

@DanielSank Thanks :)

DanielSank

7:31 AM

@TheDarkSide This is a very, very famous song.

The Dark Side

@DanielSank Famous on which planet? :P

DanielSank

@TheDarkSide The really famous part starts at 1:19.

@TheDarkSide All of them.

These guys are on the intergalactic rock circuit.

yuggib

@TheDarkSide I don't know other cracks...do your university have a proxy service?

The Dark Side

@yuggib Yes it does.

yuggib

or, for the harder way, an ssh remote machine you can connect to?

DanielSank

7:32 AM

@TheDarkSide It's also easy to play, so if you have a guitar you can learn it and attract mates.

The Dark Side

@yuggib I think they don't allow the latter option of late.

yuggib

if you set up the proxy, you should be able to have all the subscriptions as if you were at the institution

for my old institution at least worked that way ;-)

now I have shibboleth

The Dark Side

@yuggib No, but they allow proxy internally, not remotely. Remote access to my institute is only for faculty, and even that requires extensive permissions :(

DanielSank

@TheDarkSide I highly doubt that.

The Dark Side

@DanielSank :: Gulp :: "Attract mates"

DanielSank

7:35 AM

Does your department seriously block all listening services from within?

@TheDarkSide eh?

yuggib

@TheDarkSide :( then I do not know how to do

DanielSank

@yuggib There is a 0.001% chance that the uni actually blocks traffic in such a way that you can't use an ssh tunnel.

yuggib

you have a very secretive institution... o.O

@DanielSank as I said ^

The Dark Side

@DanielSank It is sanction capital. Plus, there are rumors that it was taken up for discussion in the institute senate, and got turned down.

DanielSank

@TheDarkSide What does "sanction capital" mean?

The Dark Side

7:37 AM

@DanielSank Sanctions on everything. except possibly PSE and the likes.

DanielSank

@TheDarkSide PSE?

The Dark Side

Physics.SE Ahh...

DanielSank

@TheDarkSide Wait, what?!

You can't access pages on the internet from your uni?

The Dark Side

I just added possibly for fun.

DanielSank

@TheDarkSide I do not understand you.

yuggib

7:39 AM

@DanielSank You have to concentrate

DanielSank

Obviously you can access physics.SE.

The Dark Side

@DanielSank Some of them. This ain't China so not that intensity of blocking.

DanielSank

@yuggib What does that mean? Are you talking in riddles on purpose?

The Dark Side

One example is Codeblocks. Banned from within.

yuggib

@DanielSank I was referring to that university policy: "you have to concentrate"

DanielSank

7:40 AM

@TheDarkSide What the hell? You mean the programming IDE's website is blocked?

@yuggib Ah.

The Dark Side

And this poor bloke was only trying to obtain an IDE for C, C++!

@DanielSank yes.

DanielSank

@TheDarkSide why?

The Dark Side

@yuggib Exactly!

DanielSank

Why the hell would they block an IDE?

The Dark Side

@DanielSank No idea. In fact there is a separate funny story:

DanielSank

7:42 AM

@TheDarkSide Is it the whole uni or just your department?

What country is this?

How do the students stand for that?

My whole perception of reality is falling apart, unless you live in China or maybe Russia.

The Dark Side

@DanielSank Whole univ AFAIK, otherwise, you would at most need to walk a mile. It ain't China or Russia, but that's just two examples.

DanielSank

@TheDarkSide you are unable to say?

The Dark Side

The story I'm talking about makes more sense though. An old prof told me, that some years back, even arXiv got blocked, and it took protests and permissions to be eventually allowed.

The reason was quite silly.

yuggib

@DanielSank I think that in some countries university is just like a common working place, you are supposed to be there only for studying/working

so no slacking off

DanielSank

@yuggib How is downloading a programming IDE "slacking off"?

The Dark Side

7:47 AM

As the arXiv info page says, "arXiv.org (formerly xxx.lanl.gov) is a ...". No way they were going to allow a site which began with xxx :D

yuggib

@DanielSank don't know...I am not saying I agree with those policies ;-)

DanielSank

@TheDarkSide hahaha, really? They probably had some simple URL filter in place which auto-rejected it.

The Dark Side

So, the old guy couldn't access his own preprints :P

DanielSank

@TheDarkSide How did he submit them if he couldn't access?

The Dark Side

@DanielSank Seems like.

DanielSank

7:48 AM

Story is suspect.

The Dark Side

@DanielSank He had moved from elsewhere, and was fresh to this nonsense.

DanielSank

Maybe he uploaded at home.

Ah.

The Dark Side

Could be.

DanielSank

@TheDarkSide Why won't you say where this is?

I want to know where such ridiculousness exists.

The Dark Side

I'll tell you and then remove it, to preserve my anonymity:

(removed)

Alright?

DanielSank

7:50 AM

Ok, remove it.

The Dark Side

Done.

DanielSank

Very interesting.

In my country (USA) I think many universities are less strict. This may explain why there is an abundance of highly proficient xxx in technical fields here :-)

The Dark Side

@DanielSank Codeblocks could also be blocked on the based of download behavior, or maybe the name!

DanielSank

@TheDarkSide Seems strange. How are students expected to learn to use modern tools?

The Dark Side

@DanielSank That's ruining my anonymity. You will have to remove that bit, please.

@DanielSank They manage. it is only the institute.

DanielSank

7:53 AM

@TheDarkSide sorry about that.

@TheDarkSide Still, it is counterproductive for the institute to deny access.

The Dark Side

@DanielSank Codeblocks is not banned in the country. I myself got it from my personal ISP.

DanielSank

@TheDarkSide Right. It's just weird to me for a uni to block access to a programming tool.

Very weird.

The Dark Side

@DanielSank it is. But still, it is easier to manage a work-around in this case, than fight some stupid authority.

DanielSank

@TheDarkSide Indeed. However, I would note that the general strategy seems less than useful. In my experience, the benefit of given young people free access to information is quite large.

The Dark Side

@yuggib You didn't see what Daniel's xxx in that sentence stood for either?

DanielSank

7:55 AM

I estimate it outweighs the possibility of people squandering time on Youtube.

yuggib

@TheDarkSide Yes maybe, but the institution seems to be governed by people that do not know (part of) what the university teaches...

@TheDarkSide yes I did, thanks ;)

DanielSank

@TheDarkSide let me give an example.

The Dark Side

@yuggib You are very maturely diagnosing the problem. And correctly too I guess.

DanielSank

As a graduate student, I had a computer on a desk in the physics department.

One of my colleagues wished to download movies etc. to watch at home.

His internet connection to the outside world from home was of limited bandwidth.

So, he learned to tunnel the traffic through our computers in the physics department.

While you can call this a frivolous waste of his time, the fact is that he learned some practical skills regarding networks and internet protocols in doing this.

The Dark Side

True.

DanielSank

7:58 AM

He had a goal, he achieved it by self-learning. This is a Good Thing.

Another example:

I can access Youtube etc. from work. This means I could waste my day watching videos.

I don't do this though, because my work is demanding and I like it.

However, a few minutes each day I can laugh with my coworkers. This builds a good feeling and we like going to work.

In my opinion, to restrict access is treating people like children with no self control. It is not productive.

That's just my opinion.

The Dark Side

I agree. But I have to live with it, and it is just the institute.

DanielSank

Right. I'm just criticizing whatever bureaucrat made the rules.

@TheDarkSide and don't get me wrong; there are some fantastically stupid things here.

I owed my uni several hundred dollars when I graduated due to various insane fees.

yuggib

@DanielSank Nevertheless, I think it is a rule more widespread than you think

in various countries

DanielSank

@yuggib Even so it's counterproductive in my opinion.

yuggib

@DanielSank Yes, of course. But probably they could make a good case for themselves when discussing those policies

you know, addiction to social media, etc...

DanielSank

8:04 AM

@yuggib The funny thing is that those cases are probably made without data.

I wonder if you can just proxy the outside internet from your home...

yuggib

@DanielSank If they were scientists, and knew the data analysis, probably there would not be the problem at all :-D

DanielSank

@yuggib The hard part is probably getting data. Controlled social experiments are really hard.

@TheDarkSide can you proxy from home?

The Dark Side

@DanielSank I can access internet there, privately, but not using the institute's LDAP credentials etc.

DanielSank

Oh, wait, are you trying to get banned pages from within uni or journal subscriptions from at home?

The Dark Side

Lol. Journal subscriptions from home. What were you thinking?

That's why no IOP and Elsevier remotely.

DanielSank

8:09 AM

@TheDarkSide I thought you were trying to subvert the uni's ban on some sites, but that's just because I was distracted by my criticism of restricting access by your uni.

The Dark Side

@DanielSank OK. :)

DanielSank

@TheDarkSide Are you sure you can't leave an ssh server running on a computer at the uni and tunnel your traffic?

Or heck, just ssh into a machine, download what you need, and email/ftp it to yourself.

Hmmm, actually that may not be legal.

The Dark Side

@DanielSank I think it is restricted on purpose. It is for the "fair use of the educational resources", as yuggib was hinting at.

DanielSank

@TheDarkSide I understand that it's unavailable from off campus, and I understand why.

However, since you are a student it might actually be perfectly legal for you to access the journals through a computer on campus.

Have you tried that?

Do you know what port forwarding is?

The Dark Side

@DanielSank I get around by sending the URL of the article to any friend who is on campus, and requesting him to download and email it to me.

Works fine, but it introduces a restriction.

DanielSank

8:15 AM

@TheDarkSide Hahaha. Ok.

yuggib

gotta go...

DanielSank

If you want to improve your routine (and learn some stuff) look up "port forwarding" and see if you can use it to access journals from home!

The Dark Side

Same with me too. Hungry.

DanielSank

@TheDarkSide I love food.

I made a stew of chick peas and tomatoes yesterday.

yuggib

see ya

The Dark Side

8:17 AM

@DanielSank Thanks for your time. Will do.

DanielSank

@TheDarkSide Have fun.

The Dark Side

@DanielSank Great, cya

:)

Slereah

9:06 AM

Hey

Back from the holidays

And boy am I sick

0celo7

11:24 AM

@Slereah too much liquor?

user54412

12:36 PM

@DanielSank $P(k) = \operatorname{Binom}(k; p, N+k)$, $0 \leq k < N$; $P(N) = \sum_{m=0}^{N-1} \operatorname{Binom}(N; p, N+m)$?

Slereah

1:11 PM

@0celo7 Also not enough sleep

And I have a cold

skill patrol

must have been a great holiday :P

Slereah

good thing I took this week off too

skill patrol

recovery is important...

Slereah

I wish I didn't live both near a park and a construction site

Pretty hard to catch some sleep

FenderLesPaul

1:30 PM

@0celo7 thanks I'll check it out

0celo7

@FenderLesPaul what is the interpretation of a Jacobi field (this may sound dumb, there is a hidden question)

FenderLesPaul

for GR purposes it's supposed to represent a timelike or null congruence of worldlines

usually geodesics

so e.g. the vector field representing the timelike worldlines of a family of observers

caustics of the Jacobi field then represent the observers colliding

0celo7

Ok

but Wald says the existence of a nontrivial Jacobi field with conjugate points does not always imply that

but then he keeps on going

he says something like the existence of a Jacobi field does not always imply that two geodesics actually meet

p.224

I don't get the part starting at Note, however until the end of the para

FenderLesPaul

just a sec

he's just saying that the Jacobi field itself need not be geodesic

0celo7

Why would you think that

Isn't the Jacobi field the separation vector?

Conjugate points

In differential geometry, conjugate points are, roughly, points that can almost be joined by a 1-parameter family of geodesics. For example, on a sphere, the north-pole and south-pole are connected by any meridian. == Definition == Suppose p and q are points on a Riemannian manifold, and is a geodesic that connects p and q. Then p and q are conjugate points along if there exists a non-zero Jacobi field along that vanishes at p and q. Recall that any Jacobi field can be written as the derivative of a geodesic variation (see the article on Jacobi fields). Therefore, if p and q are conjugate along...

hmm

0celo7

2:18 PM

Prof. Dydak has a 25 minute video lecture on "Philosophy of this class" :/

I have to ask my wife what they mean by some doohickey.

what is he going on about...

0celo7

2:38 PM

haha a Common Core rant

DanielSank

3:16 PM

@ChrisWhite Not entirely sure what that expression means.

Terry Bollinger

3:54 PM

Hello.

Hmm, I've seen chattier chat sessions!

Danu

Hey @TerryBollinger

They just miss me (and mostly ACuriousMind)

Terry Bollinger

Hi Danu.

Is ACuriousMind out today?

Danu

I guess so...

I just got back from a holiday in Prague

Terry Bollinger

Sounds nice!

Danu

How are you doing? Did you recover a bit?

Terry Bollinger

4:04 PM

Doing remarkably well, considering. Rate of recovery took all of my doctors off guard.

Danu

That's great!

Terry Bollinger

Any interesting physics going on?

Danu

Currently, in my life?

Terry Bollinger

Sure!

Danu

I'm mostly studying mathematics (I'm on summer break, so no courses to work on)---trying to get some algebraic topology going.

0celo7

4:07 PM

ACM has departed us

Danu

However, I decided to do all the exercises of my book and guess what... That takes ages!

Terry Bollinger

Hi 0celo7, how so?

@Danu Still, doing the exercises is still the best way to "ingrain" the ideas deeply...

Danu

@TerryBollinger It is, and I'll be doing a related course next semester so it'll be worth the effort.

Terry Bollinger

Algebraic topology always worries me a bit just because there are so many subtle ways that errors and assumptions can creep into that kind of edifice. A proof of consistency is not the same as a proof that the last turn taken was the right one to take.

You get very complex edifices, but not necessarily a good idea where to navigate.

And yes, for any math course with follow-ons, wow can practice ever make the next course easier!

Hi obe

Danu

@TerryBollinger What do you mean?

You doubt the usefulness of it within mathematics?

Terry Bollinger

4:17 PM

@Danu Hmm. Well, the simplest example of topological ambiguity that I can think of is this: When you take the product of a circle time a circle, what is the most natural and informative space in which to embed the result? You don't have to embed it at all of course -- that is the direction topology has taken in recent decades. But if you do decide that an embedding space is useful (it is), do you use 3 or 4 Euclidean dimensions?

Danu

@TerryBollinger I guess that depends on what you want to do/show...

Terry Bollinger

I'm not questioning the usefulness! The ability to find things that are particularly interesting. Every construction has parts that are more or less interesting, more or less powerful. Simply expanding on definitions does not necessarily address that aspect of building up mathematical edifices.

Danu

What I'm thinking is that (co)homology is super useful (as is homotopy)

Terry Bollinger

@Danu Very true, and a good goal can be marvelous for helping to focus on which parts of the edifices are most useful.

@Danu Hey, good topic and no debate with that!

Danu

I'm learning alg.top. in order to apply it to smooth manifolds, so I have a pretty concrete idea in mind, I guess.

In fact, the book I'm reading (Bredon) is specifically geared towards applications to smooth manifolds too :)

So I'm not too worried about getting lost in pointless abstraction ;)

Terry Bollinger

4:21 PM

I've seen cohomology and homotopy pop up in some of the most interesting and (to me) unexpected spots in some of the robotics and AI related research I've been involved in.

Danu

Also, I'm reading Grothendieck's memoir and it's so beautifully poetic it really makes me feel like all mathematics is worth doing, regardless of any use whatsoever :D

@TerryBollinger I heard diff.geo. is also quite useful in animation sometimes :D

0celo7

@TerryBollinger My dept. head does AI research...

Terry Bollinger

@Danu You know, that really is an excellent point, because frankly sometimes it's pulling on that one tiny annoying thread that makes something hidden and truly beautiful pop out. That memoir sounds pretty cool...

0celo7

Is Greothendieck the hippy?

Danu

@TerryBollinger If you can read french, I highly recommend it.

Terry Bollinger

4:23 PM

@0celo7 Really? Has he ever worked with U.S. federal funding? If so, I might know him.

@Danu Alas, some German, a little Spanish, sign language, but no French!

0celo7

@TerryBollinger engr.utk.edu/nuclear/hines.html

Danu

@TerryBollinger Merde :P

obe

@TerryBollinger Hi

0celo7

@obe PSE and work are mutually exclusive

Terry Bollinger

@Danu I know that one!

@0celo7 PSE?

Danu

4:26 PM

@TerryBollinger It's the cursing that counts.

@TerryBollinger Physics SE

Also, false @0celo7

0celo7

lol I thought "False" was like "even more wrong than false"

Terry Bollinger

@0celo7 I don't think I know him but I'm pretty sure I've seen his name.

obe

@0celo7 aw ;(

I'm reading ballentine.

Terry Bollinger

@obe I am soooo not getting the word refs today... :)

0celo7

you've gone through half a dozen QM books...

amazon.com/Quantum-Mechanics-A-Modern-Development/dp/9810241054

obe

4:30 PM

@0celo7 I'm still focusing on griffiths, I am only reading some pages of ballentine.

0celo7

ballentine talks about rigged hilbert spaces, which you don't need

Terry Bollinger

@0celo7 Not that one. Do you recommend it? What's its saving grace?

(More bluntly: I actively avoid books named "QM" in the title...)

0celo7

@TerryBollinger I haven't read more than a few chapters myself.

@TerryBollinger how else are you going to learn QM?

obe

@0celo7 Though is it skip-able or part of the entire book?

Terry Bollinger

Heh! Not by reading every different opinion on it, I'd say, because every one will be different. For concepts I've found Feynman's take on it very, very satisfying and many others not so much. For the maths, focus on the question at hand.

0celo7

4:33 PM

I think it's just in the first chapter, but it might make cameos later on.

For your purposes, the position vector is in the Hilbert space.

obe

@0celo7 What do you mean I don't need to know rigged hilbert spaces? Do you or ACM need to know?

0celo7

I don't.

obe

Is it bad to know?

0celo7

No, just more stuff to think about.

If you're trying to do this fast, no use learning advanced topics that won't come up in your QFT class.

obe

Ok, I won't.

Terry Bollinger

4:36 PM

@0celo7 Foundation concepts firmly first. Makes the elaborations so much more comprehensible later.

Hi John Rennie!

And hi Hritik Narayan!

0celo7

@obe those QFT lecture notes didn't suggest to me that you need to know anything beyond Shankar-level material. What section in Ballentine are you reading?

Ballentine does stuff like axiomatic probability that bored me to tears.

John Rennie

@TerryBollinger Hi. Sorry for the late arrival. I've been doing proper work i.e. work I get paid for :-)

Terry Bollinger

@JohnRennie It happens to all of us... :)

0celo7

And I don't think he has the group theory twist that (old version) Sakurai has, so I'm not sure of what use he is to you.

John Rennie

@TerryBollinger £500 per day - I can live with that :-)

0celo7

4:38 PM

I think he does stuff like Bohmian interpretations and Bell's inequalities that you don't need either.

@JohnRennie I'd appreciate a donation to the 0celo7 College Fund.

Terry Bollinger

@0celo7 Axiomatic probability? Good reading for insomnia, mayhaps?

0celo7

@TerryBollinger hah

brb class

Terry Bollinger

@0celo7 Hey, Bell inequalities are very cool if you ask me!

@JohnRennie Sounds like a decent pay rate to me!

obe

@0celo7 3, 6.

0celo7

@ACuriousMind yay German Straumann came in

John Rennie

4:42 PM

@TerryBollinger Nuclear industry - they seem to be flush with money and eager to give it away.

Terry Bollinger

@0celo7 The 0celo7 College Fund, ah hmm...

John Rennie

I've been doing some work calculating corrosion rates in reactor cooling systems.

Terry Bollinger

@JohnRennie Times have changed there. I lived through the doldrums, from an alma mater that graduates a lot of nuclear engineers. Now things are hopping a bit, both in fission and (well maybe) fusion.

@JohnRennie That is good work! You are doing truly important work that could prevent a catastrophe!

HDE 226868

@ACuriousMind Now I'm a supervillain. . .

John Rennie

@TerryBollinger True, if a cooling pipe corrodes through the consequences wouldn't be pretty.

And my work helps prevent that ... erm ... do you live close to any reactors? :-)

Terry Bollinger

4:45 PM

@JohnRennie BTW, the Chancellor of my old university had my wife and me visit our campus nuclear reactor once. He didn't tell me it was open water and running full bore just for our visit. It's pretty eerie looking right at those blue cores with nothing but water in between.

HDE 226868

@TerryBollinger No safety barriers in between?

Terry Bollinger

@JohnRennie No, but Congress releases truly dangerous levels of hot gases pretty often...

@HDE226868 Nothing! Very few reactors of that type left. Open room, look in the pool, glow glow glow. Wow.

HDE 226868

@TerryBollinger Wow.

user54412

@DanielSank Binom(k; p, n) = (n choose k) p^k (1-p)^(n-k)

John Rennie

Goddamn daily close limit again.

Why the sudden upsurge in homework and plain incomprehensible questions?

Terry Bollinger

4:52 PM

@ChrisWhite Argh, this is my computer that I don't have MathJax links set up in advance.

user54412

@TerryBollinger I didn't MathJax that expression anyway ;)

Terry Bollinger

@ChrisWhite ... which I belatedly realized after tapping return... :)

John, we just didn't hit any particular physics today. Suggestions? I've been out (a bit of an understatement), so that's my excuse!

@JohnRennie Do you ever use octonions in your relativistic work?

John Rennie

@TerryBollinger I'm about to sign out (dinner, not more work!) so I'll leave you chaps to discuss physics. I'm about to discuss food!!

@TerryBollinger I've never used octonions.

Terry Bollinger

@JohnRennie I'm out too, good talking to everyone. I just got back on to computers yesterday, so no need to push it. Thanks John, it's used some, but rare.

John Rennie

I get the impressions they're a clever way to handle rotations that solves a problem no-one really has.

Anyhow, dinner calls. Bye all.

Terry Bollinger

4:57 PM

@JohnRennie Quaternions absolutely, and octonions link to E8. Bye!

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