The h Bar

Jaime Gallego

00:00

The Architects Sketch - Monty Python's Flying Circus

David Z

@EmilioPisanty Seems like that could be unlocked but maybe you could make a meta post about it? Just in case there is some reason to keep it locked, I'd like to see people have a chance to make it known.

0celo7

Google is scary

I'm getting a bunch of PC videos in my Youtube suggestions now

I'm sure if I didn't have adblock all of the ads would be PC ads

Emilio Pisanty

@DavidZ don't think it's worth making a meta thread

but it looks like a standard res-recom now

David Z

Yeah, I thought so too. I just don't like to undo a moderation decision (like locking a post) without understanding why it was made and checking that the original reasons don't apply. Let me look into it.

Emilio Pisanty

@DavidZ sure

0celo7

00:10

Overclocking to 7GHz with Liquid Nitrogen | Hands-On | Computex 2017

►

@JaimeGallego I have an LN2 source...

Jaime Gallego

Cool

Literally

They also make PCs on mineral oil

0celo7

I heard about that

Jaime Gallego

I wonder if superconducting CPUs will be a thing in 50 years.

0celo7

we'll probably have brain chips by then

does one really need a case?

what if you just have everything laying out

Jaime Gallego

Wall mounted PC

0celo7

00:17

is that some rich kid?

who has money an time for that

Jaime Gallego

I suppose so

Desktop mounted

0celo7

smh

@dmckee what is with these national labs...they expect students to travel across the country, rent a place for two months without any assistance from the lab, and get paid $15 an hour?

where's the love

dmckee

@0celo7 I'm not sure I'm familiar with the situation you're asking about. But then when I did summer work at a couple of labs it was as a RA, so I was paid and housed by my department.

0celo7

Your school had money to pay for undergrad housing?

dmckee

@0celo7 No. I did it as a grad student.

The only program I know of that does a decent job of compensating undergrads is NSF's REU program.

$5000 plus they house you is the minimum compensation NSF will allow. But seats can be pretty competitive.

0celo7

00:30

What REU gives $5000

I never saw one above $4000

dmckee

@0celo7 KSU for one. It may depend on the field.

0celo7

Cornell's REU doesn't give housing or pay

dmckee

But perhaps I have misunderstood, because I thought that it was the going rate.

0celo7

Good way to find out who the rich kids are

Sir Cumference

00:53

Any spanish speakers here?

Jaime Gallego

Me no habla espanolo

0celo7

@SirCumference si

Sir Cumference

@0celo7 really?

Jaime Gallego

@SirCumference I am, why do you ask?

0celo7

@SirCumference yes

Sir Cumference

00:55

@JaimeGallego Well, I'm wondering which would be the correct way of saying "Learning is fun": "Aprender es divertido", or "Aprendizaje es divertido"

Jaime Gallego

That would be aprender

Sir Cumference

So when can aprendizaje be used

Jaime Gallego

Aprendizaje would need an el, as in el aprendizaje es divertido

Sir Cumference

So would that mean the same thing as "Aprender es divertido"?

0celo7

@SirCumference Lernen macht spaß

Jaime Gallego

00:57

Yeah, but I can assure you nobody would utter el aprendizaje es divertido unless it's some soulless Education Board program.

Sir Cumference

Huh

Ok, thanks

0celo7

02:23

-1

Q: Is it true the Michio Kaku has completed a unified field theory started by Einstein by making use of string theory?

This professor has a few documentaries available explaining science to the layman like myself and he showed an equation no longer then a sentence that he says unifies all the know forces and particles in the universe. How can this be possible? Maybe I should add a thought or two for clarity. ...

@BernardoMeurer ayy, DAMN didn't even make it onto the BET AotY list

Album of the Year
24k Magic – Bruno Mars
4 Your Eyez Only – J. Cole
A Seat at the Table – Solange
Coloring Book – Chance The Rapper
Lemonade – Beyoncé

Read More: 2017 BET Awards Winners - XXL | http://www.xxlmag.com/news/2017/06/2017-bet-awards-winners/?trackback=tsmclip

How did Amerikkka not get on there either

Damn, too much RnB

Just win baby

02:39

what do you expect from BET?

0celo7

better taste in rap?

Just win baby

true, but RnB dominates

0celo7

@yuggib Do you have a good understanding of parabolic PDE?

taper

Hi there, how do u guys get something useful out of a lecture that requires too much mathematical background? (I am here and they are talking about tensor categories, functors, braidings, etc etc, which I am very not familiar about).

0celo7

My protip is to avoid mathematics that involves tensor categories

taper

02:48

well, the problem is that they seem to associate everything I have some idea (boundaries, fusions of particles), into something mathematical (bdry -> modular category, fusion category, etc). And then the talk goes into math...

0celo7

Well, my advice would be to switch to math if you're doing that much math :)

Just win baby

^

0celo7

QFT seems to be strangely algebraic and I don't really know why

Way more algebra than many mathematicians ever see

taper

And in front of me there is a UCLA CS phd talking about physics in the language of math. What can i do.

Yes, I don't understand why this kind of trends (going into category theories) is so popular.

0celo7

Category theory is something I'd like to learn just to know it, but I can't see any reason to learn it.

Maybe if I got into Frechet-type geometry.

taper

02:56

what is a Frechet-type geometry?

0celo7

@taper Infinite dimensional manifolds.

The standard introduction is heavily categorical.

I don't know why, and I can't see myself getting to interested in that field.

taper

why is it related to physics?

0celo7

I think my advisor has done work in $C^{k,\alpha}$ convergence of manifolds, he should know something about it.

@taper It's not (maybe it is), I don't do physics.

taper

Oh... :)

0celo7

I just like talking to some people here and ranting, so...

I guess I like general relativity and quantum mechanics.

DanielSank

04:45

Hi, everybody.

0celo7

@DanielSank Evening.

Sid

05:18

Morning all!

The Dark Side

06:09

@SevenSidedDie - Somehow I am very amused by your profile picture.

That's a pentagon.

On the top face.

The face in front is a trapezium.

How does this dice roll fairly?

SevenSidedDie

@TheDarkSide It's a perspective projection of a pentagonal prism. :)

@TheDarkSide Not as bad as I expected. I haven't done extensive rolling with mine, but it seems to be about as fair as cheap platonic solid dice sets (which isn't saying a lot, because the manufacturing tolerances of standards sets is actually pretty low).

The Dark Side

mathworld.wolfram.com/PentagonalPrism.html

Ah. Well on second thoughts, saying that feels too much like an accusation.

The Seven Sided Die does not roll fairly.

:: gets suspended ::

SevenSidedDie

@TheDarkSide 😇

The Dark Side

^ There's some character over there which did not display correctly for me. I hope it is not an angry emoji !!

SevenSidedDie

06:29

@TheDarkSide Not angry at all; it's as innocent as an angel!

The Dark Side

:P

Meanwhile ...

2

Q: How much Shannon entropy is there in people voting for Trump?

What I mean is: a voter choosing Trump or Clinton had a simple binary choice (I'm simplifying by 'forgetting' other candidates). Yet, would it not be unfair to state that all voters' votes contained the same, small, amount of entropy? After all, much information has gone into forming the final ch...

entropy probability information

^ Waiting with bated breath for an answer

JokelaTurbine

06:58

Some real stuff from Turbulence;

Turbulence vs. Laminar flow. Filmed in real water on low head dam.

►

At certain velocity the falling water hit's the still water without any disturbance. I consider this is macroscopic quantum phenomenon; Similarily like the reflection of light depends on material thickness, the viscous force depends on velocity difference, and at certain velocity it might be zero -> cause of Turbulence.

user228700

07:28

@JohnR: Morning :-)

John Rennie

Morning :-)

You've caught me just when I need to work for half an hour or so ...

user228700

No problemo :-) Carry on!

Just win baby

Kansas - Carry On Wayward Son

►

Wayward son: Any individual who thinks for themselves, and laughs in the face of authority. Someone who goes against the gain...

Avantgarde

07:51

hm kansas

fortunate son

JokelaTurbine

Here you have a high (~40 000) Reynolds's number flow, - in big scale. and it's still Laminar;

Laminar flow and turbulence on river, with color dye, filmed underwater

►

JokelaTurbine

08:07

Texas - The Conversation

►

conversation; exchange of sentiments, observations, opinions, or ideas

Dawood ibn Kareem

@TheDarkSide There must be a ratio of pentagon-side-length to other-side-length which makes the die roll fairly. I don't know how to calculate it, but presumably the people who make these things do know. Seems like a good question for a physics-based Q&A site, if anyone knows of one.

Qmechanic

08:31

I would appreciate it if someone could explain-to-OP/mediate/step-in/vote-to-reopen/vote-to-close here.

Slereah

09:08

@0celo7 How do we define bump functions, there's so many bloody definitions

Qmechanic

0

Q: How is the Falcon 9 aerodynamically stable while ascending?

How is the Falcon 9 aerodynamically stable while ascending? The rocket doesn't look like it should be able to fly straight. With the large, largely empty fairing at the top and the heavy engines at the bottom and no fins, it looks like it would want to flip around. Is it simply really well contro...

aerodynamics rocket-science space-mission

Off-topic as engineering?

Slereah

If you have to ask it's probably fine

@0celo7 basically do we assume that $f(p) = 1$ for some neighbourhood

John Rennie

10:17

@ACuriousMind @Qmechanic any (European time zone) moderators around? I'm assuming the Americans are all asleep. If so this needs moving to the meta.

Emilio Pisanty

> Space is equal in all directions, regardless of speed

> That is until you start traveling against the expansion of space. That takes a lot of energy

> Not even black holes manage that feat, unless you think you're Steven Hawkin

???

Slereah

Who is Steven Hawkin

Emilio Pisanty

@Slereah dunno

John Rennie

@EmilioPisanty :-) Link?

Emilio Pisanty

same OP as in @JohnRennie's link

so it actually informs that thread too

@JohnRennie I don't know why you didn't close-vote to migrate, though

I do love the feedback tag, though

@Qmechanic it's got an answer, it's probably OK to just let it be

John Rennie

10:27

@EmilioPisanty I had forgotten the Meta was an option on the move to other site close reason. I generally only use that for suggesting migration to the Math SE.

Emilio Pisanty

also, anything that keeps Peter Kämpf contributing here is probably a good thing

@JohnRennie =P

Slereah

2

Q: How much Shannon entropy is there in people voting for Trump?

What I mean is: a voter choosing Trump or Clinton had a simple binary choice (I'm simplifying by 'forgetting' other candidates). Yet, would it not be unfair to state that all voters' votes contained the same, small, amount of entropy? After all, much information has gone into forming the final ch...

entropy probability information

Physics Meta

10:55

-1

Q: Is this community biased or it fulfilled all of it's negatory? ( Asked after 1hr40min of experiencing community)

As per title as this is the amount of time it took to evaluate legitability of forum which I now negate

discussion

Hritik Narayan

11:07

If an accelerating observer has an associated horizon, why doesn't the Earth?

John Rennie

11:18

@HritikNarayan Are you thinking of the horizon we get in the Rindler metric?

Hritik Narayan

Yes!, @JohnRennie (I've seen this horizon described as the "black wall" horizon, in some places)

John Rennie

@HritikNarayan the spacetime of the accelerating observer is equivalent to a spacetime in which the gravitational field is constant i.e. does not change with distance.

However the gravitational field of the Earth decreases with distance above the surface. That's why there is no horizon.

Actually, no, wait ...

While what I've said is true the black hole horizon in the Rindler geometry is below the observer i.e. you fall towards it. So in your example of the Earth the horizon would have to below the ground.

In the Rindler geometry there is a horizon above the observer but it is a white hole horizon not a black hole horizon. This white hole horizon doesn't exist for the earth because the gravitational field decreases with distance from the surface.

The Rindler black hole horizon is analogous to the event horizon around a black hole i.e. if you're hovering above a black hole there is a horizon below you.

yuggib

12:16

@0celo7 I would say so (if by stronger norm you mean that $\lVert \cdot \rVert_X \leq C\lVert\cdot\rVert_A$).

@0celo7 I would not say so

Slereah

@0celo7 Synge uses "world function" while Visser uses "geodetic interval"

what to pick

Just win baby

\o @yuggib

yuggib

@Justwinbaby o/

Just win baby

12:34

how's it going? @yuggib

yuggib

not bad...too hot

but it's not going to last

today is probably the last day of summer over here

Just win baby

cool :-)

yuggib

you?

Just win baby

Same too hot.

cooling down today

0celo7

12:56

@Slereah well, there are bump functions and there are plateau functions

The one that's constant on a neighborhood is a plateau function

A bump function is a nonnegative function with compact support and unit integral

Slereah

Not all are assumed unit integral!

although all bump functions can be normalized to one

I think I'm gonna pick = 1 on a neighbourhood of p and compact support

It seems to be the standard definition in diff geom

0celo7

Bump function is not a technical term then

Equaling one on some neighborhood means plateau or cutoff

Just win baby

13:13

Gaussian function

Slereah

13:25

Gaussians aren't bump functions >:|

Secret

0

Q: Why are composite fermions either bosons or fermions but not neither?

The question is getting at something subtle and not necessarily obvious to me. It is often claimed that an atom being composed purely of fermions is either a boson or a fermion itself. I interpret this as meaning that the atom can be treated as a fundamental particle (in the sense it can be put ...

quantum-mechanics

and then you have ${}^3$He being fermions while ${}^4$He being bosons

0celo7

13:39

@Justwinbaby lameo

@Slereah indeed they are quite famously not bump functions

@Slereah Here's a nice exercize... Let $M$ be a paracompact smooth fold and let $C\subset M$ be closed. Then there is an $f\in C^\infty(M)$ such that $C=f^{-1}(0)$.

Slereah

Is that just by reversing a bump function with support $M \setminus C$

Although I guess that may fail to be compact

Secret

Anti-Matter and Quantum Relativity | Space Time

►

Now googling: Fidget Spinors

3

Result: Not found

Bernardo Meurer

Lol

Hritik Narayan

13:59

Thanks @JohnRennie Mind boggling stuff. How are you doing?

0celo7

@BernardoMeurer pc pls

If this is gonna happen it needs to be before the steam sale ends

@Slereah no...it's actually very hard to prove

but it's very interesting because closed sets can be nasty

Bernardo Meurer

@0celo7 Alright, hop on Skype

0celo7

???

Secret

14:15

9

Q: Does entanglement not immediately contradict the theory of special relativity?

Does entanglement not immediately contradict the theory of special relativity? Why are people still so convinced nothing can travel faster than light when we are perfectly aware of something that does?

quantum-mechanics special-relativity entanglement faster-than-light

Re: 18 votes answer:

Do we actually know what causality violation phenomenon is predicted to like, what prevent a phenomenon that look causally violating simply because the way the information of the event is relayed to our senses?

I think the issue here is the following:

Suppose we have a timelike separated event A followed by B. Then in some inertial frames travelling at superluminal velocities, it will look like B preceeds A.

But when we observe it, we only see events A and events B. In practice, how will we know whether e.g. event B is travelling back in time vs it is actually travelling forward, but move in a manner as if it is travelling back in time?

The Dark Side

ROFL

0

Q: On the Definition of the Tits Building of a semisimple Lie group and face posets

Let $G$ be a semisimple Lie group. The set $\mathcal{P}$ of all proper parabolic subgroups of $G$ with reversed inclusion relation forms a poset $$ (\mathcal{P}, \supseteq). $$ It follows from the structure theory of parabolic subgroups that there can be constructed a simplicial complex $\Delta(G...

lie-groups simplicial-complex bruhat-tits-theory

Secret

arxiv.org/pdf/1511.02538.pdf

Slereah

@0celo7 Is the norm on Minkowski space for analysis just the Euclidian norm

Pretty sure it is since it defines the topology

Secret

14:31

Newcomb's paradox

In philosophy and mathematics, Newcomb's paradox, also referred to as Newcomb's problem, is a thought experiment involving a game between two players, one of whom purports to be able to predict the future. Whether the problem actually is a paradox is disputed. Newcomb's paradox was created by William Newcomb of the University of California's Lawrence Livermore Laboratory. However, it was first analyzed and was published in a philosophy paper spread to the philosophical community by Robert Nozick in 1969, and appeared in Martin Gardner's Scientific American column in 1974. Today it is a much debated...

I don't think there's a paradox. If a predictor is imperfect, then there are two different ways to think about what maximise means

if the predictor is 99.9999999999% perfect, then go with the strategy that picks box B, otherwise, it is always safe to pick A+B

In other news, I wonder if any time travel scenario that cannot be realised by CTCs must all be self inconsistent in some manner

Put it simply, does there exists an isomorphism between the class of all self inconsistent time travel schemes and the grandfather paradox?

0celo7

@Slereah Yes, but as you should know, all norms on a finite dimensional vector space are equivalent.

They all induce the topology and are roughly proportional.

Slereah

What about the norm $d(x,y) = \delta_{xy}$

0celo7

How is that a norm?

Slereah

The norm is $|x| = 1$

0celo7

That's not a norm...

Slereah

14:42

true

Emilio Pisanty

sigh

0celo7

15:38

@Slereah also don't you mean $1-\delta_{xy}$...

Hritik Narayan

@EmilioPisanty Yes, that triggered an odd mixture of laughter and sighing from me

0celo7

15:53

@JohnRennie How do I grind garlic more finely?

John Rennie

@HritikNarayan The Rindler horizon is simpler than you think. Have a read through this. In fact I think understanding the Rindler horizon is a good way to understand horizons in GR.

@0celo7 I'm not sure I'd grind it too finely as I think the taste suffers. If you really want a smooth paste I guess just keep crushing it or maybe use a pestle and mortar.

0celo7

That sounds expensive

I'm looking for things an impoverished college student can do

Did you get my message about the garlic sauce?

John Rennie

Yes. Glad it worked out :-)

0celo7

Probably a 1,000 calorie sauce plus whatever from the pasta and chicken

I also had a vinegar-based bean salad which complemented the sauce very well

John Rennie

Details, details :-)
Chicken is a low calorie meat. Pasta is quite low calorie too.

I guess it's not good for the waistline to eat cream sauces with every meal, but then you'd get pretty sick of cream sauces if you did :-)

Slereah

15:59

@0celo7 stop buying books

Giskard42

Anyone know what the alternative to pashen's law is at higher vacuum?

0celo7

@Slereah I have not bought a book in a week

@JohnRennie details?

@JohnRennie It's pretty damn good. I had some unexpected problems, like the cheese not melting correctly. I had to scrape some of it off the bottom of the saucepan, but who doesn't like a little burnt cheese :)

John Rennie

From memory raw chicken is about 100 calories per 100 grams. Dry pasta is about 350 calories per 100g.

Balarka Sen

@0celo7 Stop using internet

John Rennie

So unless you eat a massive amount, chicken and pasta is going to be a low calorie meal.

Giskard42

16:08

"I'm afraid that in this regime there are no simple analytical solutions..." Dang it! I've gone outside the environment!

0celo7

Giskard42

@0celo7 That looks really good. Now I have a sudden urge to cook pasta.

0celo7

Chicken got a little overdone, I underestimated the size of the chicken breast

Had to cut it in pieces to cook the centers

Giskard42

Upon enhancing the image, it appears there is no Parmesan cheese. How could you?

Oh, no, ignore, above there is a discussion of cheese. Carry on.

0celo7

@Giskard42 It's melted in the sauce

Hritik Narayan

16:36

@JohnRennie It all made sense when I looked at the form of the metric. It's beautiful. So the same horizon in three dimensions would be like an infinitely large wall?

John Rennie

@HritikNarayan yes

But note that this is a coordinate singularity, just like a black hole event horizon. Spacetime is not singular there because, well, it's flat :-)

0celo7

@JohnRennie u can have a singularity without curvature blowup

John Rennie

You can?

Balarka Sen

What is a singularity? Where all the geodesics coming at it stops?

0celo7

@BalarkaSen That's the question

What does @JohnRennie mean by a singularity

If he means an s.p. or p.p. curvature singularity, then of course you need a blowup

Balarka Sen

16:47

If that's what it is then noncompleteness is the thing; there exists noncomplete flat manifolds like punctured plane

0celo7

but you could have a hole in it

@BalarkaSen incompleteness in the Lorentzian case is much, much subtler than in Riemannian geometry.

Balarka Sen

Ah OK

0celo7

There are three classes of geodesics, and you can have one class be incomplete without the others

John Rennie

I meant a curvature singularity. I'm unconvinced that manifolds with holes in have much relevance to the description of our universe.

Balarka Sen

@0celo7 Weird.

0celo7

16:51

And there are general results for when a spacetime is incomplete

generally speaking, an expanding cosmology must be past incomplete

(big bang)

Balarka Sen

i see

John Rennie

@0celo7: did you make any decision about the gaming PC?

Secret

17:19

0celo, you made me so hungry

0celo7

17:37

@JohnRennie Bernardo and I talked this morning and are ironing out details.

I'll talk to my dad about getting a monitor for me to free up some of my funds

He won't get a PC but I think I can convince him I need a monitor for educational purposes :)

I really would hate to spend more than $1500 total

@Secret :)

John Rennie

17:55

@0celo7 I looked into whether you could use second hand Dell, but the PSU in them isn't big enough. Dell's gaming range are the XPS desktops, and a second hand XPS 8700 with a respectable i7 is around $300, which leaves lots of money for the GPU.

But you would also need to upgrade the PSU and that makes them less of a bargain.

0celo7

@JohnRennie Let me finalize with Bernardo and then you can take another look

John Rennie

@0celo7 This would be the sort of thing you'd get on ebay. Maybe see what Bernardo thinks.

bolbteppa

18:18

This is why Cambridge is the best damtp.cam.ac.uk/user/examples/D18S.pdf

Emilio Pisanty

18:34

0

Q: newtons first law

f suppose there is a very very heavy object on a frictionless surface and if a force of very small magnitude is applied to object will the object move!!!? bcz what i believe is when i apply a force to a object it means transfer of energy and since in a very heavy object mass is more so when ene...

newtonian-mechanics

any takers?

0celo7

@JohnRennie @BernardoMeurer take a look

user129412

19:06

More of a sanity check than anything else; say I have an effective 1D problem (x and y are translationally invariant) with from z = 0 to z = t some dielectric layer of permittivity epsilon = epsilon1, and on top of that there is a semiconductor with epsilon = epsilon2. If I now apply a potential V1 at the bottom of the dielectric (at z = 0), I should be able to find the potential at z = t quite easily right?

Hritik Narayan

@EmilioPisanty how does one not lose it after they've run out of close votes for a day :'D

ACuriousMind

@HritikNarayan I used to run out of close votes regularly, it's annoying :P

dmckee

19:31

@rob I suspect this fell off you radar—buried in more pressing stuff. I'm still interested if the offer is still good, and if getting the finished product from your colleague is a problem I'd be grateful even for the data.

0celo7

@ACuriousMind you here?

Hritik Narayan

-1

Q: Question on Electrostatics

Please answer with correct options(more than one are correct) Also explain. Thanks

electrostatics

Just doesn't end

@ACuriousMind Yeah certainly is!

Sid

WOw.. that was mod-hammered.

0celo7

:(

dmckee

@HritikNarayan There are, of course, many more people out there that want someone to help them with their homework than you have close votes, but a fast and muss-free close is the least abusive thing we can do to discourage them.

@Sid It came to my attention with @HritikNarayan's first message here and it is a pretty cut-n-dry case.

Sid

19:38

Agreed. It is just that I am not a huge fan of mod-hammering questions..

that was a clear violation of policy, though.

No second thoughts about that.

Hritik Narayan

@dmckee True, that.

DanielSank

20:38

Hi, everybody.

heather

hello

DanielSank

Yo, Heather.

Transcript for