The h Bar

0celo7

12:04 AM

@ACuriousMind You're about as mature as the average high school freshman. Congratulations, you've hit puberty.

(It's a great song, btw.)

ACuriousMind

@0celo7 Now that you mention it, I have noticed an increase in hair growth lately...

ᴇʏᴇs

Whenever I come in here, it's always ACuriousMind and 0celo7 only

0celo7

@ᴇʏᴇs Whenever I go to math, it's always Ted and Mark.

+20 other people

ᴇʏᴇs

Who is Mark

0celo7

Sorry, Mike.

ᴇʏᴇs

12:11 AM

Haha

0celo7

@ᴇʏᴇs So what brings you to our chat?

ᴇʏᴇs

@0celo7 I used to be a physics major so I'm still a bit interested in physics stuff

0celo7

@ᴇʏᴇs Do you want to get back into physics?

ᴇʏᴇs

@0celo7 Mathematical physics maybe

0celo7

@ᴇʏᴇs Define that please.

ᴇʏᴇs

12:20 AM

@0celo7 Like topological quantum field theory or something

0celo7

Surely you realise you must first learn quantum mechanics and then standard quantum field theory for that to mean much, right?

@ᴇʏᴇs Do you know measure theory, functional analysis and some differential geometry?

ACuriousMind

It's depressing how often I have to remove mathematical-physics from questions :/

3

ᴇʏᴇs

I already took QM and I can take a QFT course when I transfer

@0celo7 Yes, but I only know curves and surfaces, not comfortable with smooth/Riemannian manifold stuff

I'm taking that later

0celo7

@ᴇʏᴇs You could read a large part of amazon.com/Quantum-Theory-Mathematicians-Graduate-Mathematics/… then.

I have that on my ridiculously long to-read list, but I'll never get to it.

The parts on geometrical quantization (ironically the parts I can hope to understand) require quite a bit of smooth manifolds knowledge though.

@ᴇʏᴇs Once you learn basic differential geometry, you should look into general relativity. There are books on it suitable for mathematicians: Straumann, Hawking & Ellis, Sachs & Wu, to name a few.

ᴇʏᴇs

Is Wald good?

0celo7

12:33 AM

@ᴇʏᴇs Excellent, but I'm not a mathematician. Hell, I'm not a physicist either.

He uses notation that even physicists think is strange.

@ᴇʏᴇs Do you know special relativity?

Some basic things: energy-momentum relation, Minkowski metric, perfect fluid energy momentum tensor, tensor formulation of electromagnetism

Zach Saucier

Hello people

0celo7

Hello

Zach Saucier

I was wondering if anyone was going to respond :)

0celo7

We generally don't respond to hello, no clue why.

Zach Saucier

Pendulum is my favorite band

Hold Your Colour made my childhood, haha

0celo7

12:46 AM

Good eye.

Zach Saucier

where are you from in the US?

0celo7

VA

Zach Saucier

I'm in GA

ACuriousMind

@0celo7 Bars where people greet you when you enter are creepy. It implies they aren't serious about drinking.

0celo7

@ACuriousMind In here we all drink the string theory Kool-Aid.

Zach Saucier

12:47 AM

If you come to UGA for school let me know :D

0celo7

@ZachSaucier I'm going to UTK.

Zach Saucier

kk

0celo7

University of Tennessee at Knoxville

Zach Saucier

my mom grew up there

0celo7

Very good nuclear fusion program and Oak Ridge labs 20 mins from campus.

@ZachSaucier Crush is really good. Actually, everything Pendulum made is really good.

Zach Saucier

12:49 AM

Not everything IMO :)

Just a large portion of it

do you like Knife Party?

0celo7

Yes.

Zach Saucier

They are two of the guys from Pendulum

0celo7

You don't need to tell that to a guy who has a Pendulum album cover as his avatar ;)

Zach Saucier

I suppose so

0celo7

Do you not like KP?

Zach Saucier

12:51 AM

I do, haha

so different than Pendulum though

nearly as great though

0celo7

The production quality (KP) is phenomenal IMO.

Zach Saucier

Ya, agreed

0celo7

Abandon Ship is not even dubstep, but still great.

I think they just went nuts and made whatever they felt like.

Zach Saucier

Most of KP isn't dubstep (at least what I consider dubstep is)

it's more electro-party, haha

0celo7

My EDM genre detector doesn't have a resolution that high.

Zach Saucier

12:54 AM

I DJed electronic music for a while, so I think I'm on the high end of that, haha

0celo7

The overwhelming majority of my music is hardstyle or hardcore.

Zach Saucier

but genres are very mixed/opinionated

0celo7

Some rap, dubstep, DnB and house mixed in.

Zach Saucier

I have a fair bit of all of those :P

0celo7

Do you know if any good hardstyle compilations have been released lately?

Zach Saucier

12:55 AM

college has gotten me more non-electronic in addition of electronic though

0celo7

I don't like buying individual songs, I go for festival packs and whatnot.

Zach Saucier

I stopped listening to hardstyle compilations a year or so ago. I like to diversify a bit more now

0celo7

Too bad.

Zach Saucier

I only get individual songs these days :P

I've gotten pretty picky with music choices because of how much I have

0celo7

I should focus my funds on getting more string theory textbooks.

Zach Saucier

12:56 AM

haha

have to enjoy life sometimes :)

0celo7

I have more music than I can ever listen to in one (or many more than one) sitting(s).

Zach Saucier

I'm currently at 12+ days of music I really like currently xD

0celo7

Well that's just ridiculous.

Zach Saucier

I like music :w

listen to it constantly

makes it so that I can continue working

0celo7

I like to listen to music when doing computations.

Zach Saucier

12:59 AM

same thing

0celo7

I can't read advanced material with music playing though.

Zach Saucier

I turn it off occasionally if I have to do really really deep thought

anyway, if any of you guys have improvements for my answer please let me know. I'm quite inexperienced at physics and it's a non-standard topic. I know I've got to be wrong on some parts of it

it's the only question on Physics.SE I've tried answering besides my own question (could probably also use a review) xD

0celo7

I could answer a technical general relativity question better and more accurately than a circuits question ;)

Zach Saucier

ya, I figured as much

but I was hoping someone in here may have some feedback

not very active this time of day, I see

0celo7

Do you know how to work iTunes?

Zach Saucier

1:03 AM

roughly

0celo7

I can't find the length of my library.

19.1 days.

That's crazy.

Zach Saucier

lol

0celo7

I think that's including DJ mixes of albums.

54 GB.

So that's where my HDD space is going.

Zach Saucier

my ~12 days is 32gb :P

must have higher quality on average

0celo7

I have 256 on everything.

Oh shit, look at the time. Blacklist is on.

Cya

Zach Saucier

1:06 AM

o/

0celo7

I don't know why I said that. I'm sitting in front of the TV with my laptop, still here.

ACuriousMind

lol

0celo7

@ACuriousMind You have class tomorrow?

@ACuriousMind You never did say what classes you are taking this semester.

ACuriousMind

@0celo7 Nope, no classes on Friday for me

0celo7

@ACuriousMind Explains being up at 2/3am.

ACuriousMind

1:09 AM

Just the semester opening party :D

@0celo7 Algebraic geometry, functional analysis, group theory, quantum fields on the lattice, constructive fermionic field theory and a seminar on QFT in curved spacetime

0celo7

@ACuriousMind Any lecture notes I could use?

Group theory? You're pretty much a god in that already.

ACuriousMind

@0celo7 No, the functional analysis guy updates his only after the lectures, and none of the other courses has any

0celo7

:(

I could use some on algebraic geometry.

Nakahara gave me a bit, hopefully that will be enough.

Stan Shunpike

@0celo7 regarding the 19hrs, just for comparison, Mozart wrote 7.5 days of music all by himself

And died at 35

ACuriousMind

@0celo7 It's partly about finite groups, which I know nothing about yet, I like the lecturer and I can use the credit

@0celo7 Try the Stacks Project ;)

0celo7

1:14 AM

@StanShunpike Well Mozart was a punk.

@ACuriousMind Huh?

ACuriousMind

@0celo7 It's a gargantuan collection of all the mathematics that go into defining stacks: stacks.math.columbia.edu

0celo7

Stacks?

ACuriousMind

@0celo7 I don't really know what they are, but they are structures which encode information about spaces, like a generalization of schemes

0celo7

...

Schemes?

ACuriousMind

@0celo7 ...the basic object of algebraic geometry?

Spectra that are glued together (but I guess that's not more informative :P)

0celo7

1:17 AM

4715 pages.

Yeah, I'll start on that right away.

ACuriousMind

@0celo7 Hence the ";)" behind my suggestion ;)

0celo7

@ACuriousMind I read that as algebraic topology. I know nothing about algebraic geometry.

@ACuriousMind Do I even need to know any algebraic geometry?

ACuriousMind

@0celo7 Uh. Need? Probably not, but it captures geometrical aspects of strings, for example, the spaces of moduli that appear there are algebro-geometric objects in nature.

0celo7

@ACuriousMind God damnit, I should have expected The Bear.

@ACuriousMind Ok, those words are scary. I know I can't get to that level before school begins.

ACuriousMind

@0celo7 Heh

@0celo7 I probably agree with that, it is a huge field. My lecturer said he could probably give ten lecture courses on it and still only teach "introduction to...".

0celo7

1:31 AM

@ACuriousMind "Probably"? I'd be impressed with myself if I finish BLT before school begins, not to mention BBS and GSW.

How many people can actually understand Urs?

ACuriousMind

@0celo7 I think some people from MO like Todd Trimble do understand, but yeah, very few, I guess

Stan Shunpike

What's Urs?

0celo7

@StanShunpike ACuriousmind's spirit animal.

2

alemi

anyone familiar with the data query thing

or rather, more directly, can you give bounty to an answer without posting it on a question first?

Stan Shunpike

@0celo7 lmao

ACuriousMind

1:38 AM

@alemi No, a bounty must be open on a question for at least one day before you can award it.

alemi

I'm trying to write a query to see which questions had the largest bounties posted that were not awarded

and I'm getting some strange results

ah, nevermind

I was forgetting that half the bounty is awarded automatically

0celo7

@ACuriousMind I love how you offer no objection to my definition of Urs.

ACuriousMind

@0celo7 Well, if I objected, you'd probably dig out the chat message where I said that verbatim myself, so there's really no point to objecting :P

0celo7

@ACuriousMind I wouldn't know how to do that.

ACuriousMind

Oh. Well. Then, the theoretical possibility of that would at least make my objection hypocritical.

NeuroFuzzy

1:47 AM

@0celo7 there's a search thing in the top right corner though!

0celo7

@NeuroFuzzy TIL

ACuriousMind

@NeuroFuzzy Shhhhhhhhh, dammit! :D

0celo7

Mar 8 at 3:07, by ACuriousMind

I'll let my SE spirit animal speak:

Mar 8 at 3:07, by ACuriousMind

33

A: The Role of Rigor

Rigor is clarity of concepts and precision of arguments. Therefore in the end there is no question that we want rigor. To get there we need freedom for speculation, first, but for good speculation we need... ...solid ground, which is the only ground that serves as a good jumping-off point fo...

;DDDDDD

ACuriousMind

Good. Now you can reference everything everyone ever said in here

NeuroFuzzy

@ACuriousMind oh... oh dear what have I done?

ACuriousMind

1:52 AM

@NeuroFuzzy You've given great power to the masses. Whether that was a wise choice only time will tell

NeuroFuzzy

@ACuriousMind not the masses. They'd have to search to find it, and, well...

alemi

2:09 AM

looks like another bounty is going to time out soon

how often does that happen?

JamalS

7:44 AM

@DavidZ Do you know if and when physics SE is being updated to the new profile?

David Z

7:56 AM

@JamalS I presume it will be at some point, but I don't know when. I think it will be a while. (weeks, perhaps, just as a guess)

JamalS

9:16 AM

@0celo7 So I know BBS and GSW, but what's BLT?

Of course! Blumenhagen, Lust, and Theisen

0celo7

9:49 AM

BLT

A BLT (Bacon, Lettuce, and Tomato) is a type of bacon sandwich. The standard BLT is made up of five ingredients: bacon, lettuce, tomato, mayonnaise, and bread. The BLT evolved from the tea sandwiches served before 1900 at a similar time to the club sandwich, although it is unclear when the name BLT became the norm. == Ingredients and preparation == While there are variations on the BLT, the essential ingredients are bacon, lettuce, tomato, mayonnaise and bread. The quantity and quality of the ingredients are matters of personal preference. The bacon can be well cooked or tender, but as it "carries...

@JamalS IDK what you're on about ;)

JamalS

11:53 AM

I've never liked sandwiches, but I'm tempted to try that...

Danu

1:11 PM

@ACuriousMind Mukhanov just told a funny anecdote about the Henneaux & Teitelboim book

ACuriousMind

@Danu Do tell!

Danu

2:11 PM

@ACuriousMind I'll get back to you tomorrow, because I'm going drinking after this lecture ends ;)

Zach Saucier

@0celo7 how do you like this? youtu.be/V6Efpz9Zz_0

ACuriousMind

2:59 PM

@alemi Anecdotal evidence: 2 of my 4 bounties have timed out without any answer elegible for auto-awarding, where I admittedly chose not to award one of them.

0celo7

@ACuriousMind So how about that first excited state of the closed string, eh? Why is the graviton the symmetric traceless state. (I get why symmetric, but not why traceless.) I suspect I missed something back when learning rep theory.

ACuriousMind

@0celo7 The trace is the scalar part of a symmetric tensor.

And the graviton is pure spin-2

0celo7

Oh, because it's massless?

@ACuriousMind Actually, why is it symmetric? Methinks it's because the metric is symmetric, but that logic might be incorrect.

ACuriousMind

nvm

0celo7

Mobile, which post did you link?

Confus

@ACuriousMind what does that "nvm" mean? Am I wrong?

ACuriousMind

3:17 PM

@0celo7: Alright, second try: 1. The graviton is the symmetric state because the metric is symmetric. 2. The graviton is traceless because the symmetric tensors decompose into spin-2 (symmetric traceless) and spin-0 (trace), and we do not mix the spin description of particles. The spin-0 part is the dilaton, not the graviton.

And "nvm" meant that what I wrote and then deleted was potentially more confusing than helpful, and possibly even wrong, so nevermind.

0celo7

I know what "nvm" means, I just thought nvm after a deleted post was strange

ACuriousMind

Btw, asI understand it, you should not think the graviton as the particle associated to the metric directly, rather as the thing associated to its perturbations, the gravitational waves.

0celo7

What is the spin of the Kalb-Ramond field?

@ACuriousMind Of course I know that :P, but brevity is key on a phone

ACuriousMind

@0celo7 I...don't think it has a spin

Since we are in 10D, there appear rep of the generalized Lorentz group that are not classified by spin like in 4D

0celo7

Slow down, I'm still in 26D.

ACuriousMind

3:25 PM

Holds also there :D

0celo7

Armed with this knowledge, I'm no longer convinced a symmetric traceless tensor has spin 2.

ACuriousMind

Hahahahaha

Yeah

0celo7

You should have pulled a lie to children.

ACuriousMind

Well, I think you can still say that the symmetric tensors of rank 2 decompose into the trace and the traceless part, and both are irreducible. Just call the symmetric traceless rep the spin-2 rep in analogy to 4D ;)

After all, you can only talk about spin in 4D at all because of the $\mathrm{SU}(2)$ hocus pocus that goes on with $\mathrm{SO}(1,3)$.

0celo7

That doesn't resolve the spin of the Kalb-Ramond field.

(Lack thereof)

Do I smell an SE question?

ACuriousMind

3:34 PM

@0celo7 What is there to resolve? You simply can't talk about spin in higher dimensions the way we are used to

0celo7

Then I'm no longer convinced the symmetric traceless tensor is the graviton.

ACuriousMind

@0celo7 But, think of this: When you quotient down to 4D, the symmetric traceless rep stays the symmetric traceless rep, hence any symmetric traceless field in higher dimensions will, in the final 4D theory that we want, give us a spin-2 particle.

Conversely, the fields don't change reps when quotienting out the higher dimensions, so the graviton cannot come from anything that does not at least have the 4D spin-2 rep as a subrep

So calling the higher-dimensional field the graviton already is just suggestive naming because we anticipate what it will turn into in the final 4D theory

0celo7

So why can't we end up with a spin-x Kalb-Ramond field in 4D?

ACuriousMind

@0celo7 Since it is an antisymmetric tensor, it will not transform in an irreducible representation of $\mathrm{SO}(1,3)$, since the irreducible reps are the symmetric tensor reps. It will be a mixture of spin-1 and spin-0, and the precise decomposition will depend on the exact way we arrive at the 4D theory.

So it doesn't make sense to talk about the spin of Kalb-Ramond because it is 1. not in an irreducible rep 2. not clear from the high-dimensional theory what exactly it will be.

0celo7

Antisymmetric is reducible?

ACuriousMind

3:45 PM

@0celo7 For $\mathrm{SO}(1,3)$, I believe so, yes.

But I should probably think about that before stating it :P

0celo7

How the heck can you reduce an antisymmetric tensor?!

If it's self dual, I know you can.

ACuriousMind

Ha, yes. The antisymmetric tensors are $(1,0)\oplus(0,1)$ in 4D.

0celo7

Didn't we talk about this the other day?

ACuriousMind

See Wiki.

@0celo7 What other day? I don't recall that

Looking around a bit, it seems you mainly get spin-0 modes from the Kalb-Ramond fields, and spin-1 modes if you allow it to be massive. (Don't ask me how or why, I'm just reading abstracts)

0celo7

Representation theory is demonic

0celo7

4:18 PM

@ACuriousMind So if we reduce an antisymmetric tensor like that, it becomes a sum of a self dual and an anti self dual tensor, right?

ACuriousMind

@0celo7 Yep

0celo7

@ACuriousMind I'm struggling here. How does one show that?

Every time I think I've got this figured out, something like this comes about.

ACuriousMind

Uh...I'd show that the self- and anti-self-dual parts each have three d.o.f., and since the antisymmetric tensors have six, they exhaust all possible antisymmetric tensors.

...and with that, I'm off. Have a nice #TimeOfDay, everyone

user54412

6:19 PM

Here's a question: why are the equations of thermodynamics always written in such utterly useless forms?

Stan Shunpike

@ChrisWhite example?

user54412

Like right now, all I want is to remember the conversion $(s,p) \to (\rho, p)$ for an ideal, $\Gamma$-law gas

user54412

but everyone keeps writing down all these logarithms, not to mention the use of extensive variables (when has an extensive variable ever been useful to someone?!)

user54412

And I was just lamenting with a postdoc how there's no such thing as a good stat mech/thermo text.

Stan Shunpike

I know! I looked. I couldnt find a basic text everyone liked

0celo7

7:09 PM

@ZachSaucier I hope you didn't make that. I hate happy hardcore.

Zach Saucier

haha, no I didn't

0celo7

When I say hardcore I mean Angerfist, Hellsystem, etc.

Zach Saucier

ya, I meant to say happy hardcore

0celo7

Naw, hardcore needs to be dark and evil.

@JamalS How can you not like sandwiches? Is there something specific that you don't like about them?

@ZachSaucier Like this.

Zach Saucier

ya, I listened to that a bit more a few years ago

Depths of Despair was one of my favorites

0celo7

7:22 PM

Yes!

JamalS

9:31 PM

@0celo7 They just don't appeal to me. I don't like ketchup or mayonnaise either, so a sandwich without that is pretty dry.

Samuel Montgomery

9:55 PM

(removed)

NeuroFuzzy

(removed)

0celo7

@JamalS You need grease from flesh to moisten your sandwich. A sandwich that needs ketchup or mayonnaise is a poor sandwich. (Vinaigrette works well too.)

user1667423

11:44 PM

I have heard that the +--- sign convention for the metric in GR is more convenient for the treatment of spinors. Does anyone know why this is so?

0celo7

11:58 PM

@user1667423 Convenient? Not sure about that, but since the original references on spinors in physics are particle physics/quantum physics, it would explain why that signature is more common.

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