The h Bar

Kyle Kanos

00:17

@DanielSank I concur with the generalization of Jamal's answer: questions devoid of physics shouldn't be here. Math questions & Engineering questions posted here are often fuzzy, if you will, because they're closely related to physics.

Why there is such a bias against engineering-type questions and not math-type questions, I cannot say. I have been trying to avoid pushing away good experimentally-oriented questions, but I'm just one guy (who happens to be all-pro at most reviews).

@JohnDuffield Have you considered the fact that many/most of your posts contain fringe/crackpot/incorrect notions in them and that's why you're getting downvotes?

DanielSank

01:07

Suppose I post the following:
"I was trying to measure the electron dipole moment this morning. In doing this, I found that I needed a more stable laser. To do this, I need an op-amp with less noise. How can I build a less noisy op-amp for measuring the electron dipole moment?"

Is that on-topic? How about this:
"I was trying to compute the cross section of <some particle physics process> this morning. In doing this, I found that I needed to do a path integral. To do this, I need to understand exponentiation of sums of non-commuting linear operators. How can I simplify this exponent of a sum of non-commuting linear operators to compute the scattering cross section?"

What's the real difference between these, and why are users of this site so inclined to close the first and not the second?

Kyle Kanos

> Why there is such a bias against engineering-type questions and not math-type questions, I cannot say. me an hour ago

I would say that (1) is fine and (2) might be too broad

Maybe, for (2).

It is possible, though, that Electrical Engineering might be able to answer question (1) better than physics users could, but this could be the whole chicken-egg thing with regards to experimentalists on site

alarge

@DanielSank Is it fair to reformulate your question as why do physics inspired engineering questions get closed but physics inspired math questions don't? Well I think the reason is that most physicists use math as a tool to do physics, but only a relative few (the experimentalists, whose numbers are not great on SE) use engineering as this tool.

FenderLesPaul

01:46

@0celo7 aw ok; hope you get home safe!

We can discuss chapter 12 another time

obe

02:17

Quantum trick

DanielSank

02:37

@KyleKanos Yes, I know you said that and I understand that you try to be fair in this issue.

Thanks!

@KyleKanos Yes, indeed. Of course, this requires the question asker to realize that what he/she actually cares about is less noisy op-amps and not actually anything really laser related. I would say the same thing about the math question askers.

Kyle Kanos

Ouch...I just stole the accept from someone with my so-so answer over on Science Fiction & Fantasy

DanielSank

The asker is often better off focusing the question on something very specific. In both cases all the lead up and context is irrelevant and the asker should just ask the important part of the respective specialized sites.

Kyle Kanos

Guy has 28 upvotes to my 5.

DanielSank

Of course, there are some cases where the asker doesn't know that a less noisy op-amp is the right direction, and might want to ask a more general question like "what can I do in <description of laser system> to make it more stable?"

Kyle Kanos

Probably true in a large portion of questions :/

FenderLesPaul

03:12

there's a fantasy stack exchange? whaaaat

Kyle Kanos

@FenderLesPaul I suppose you haven't looked at the sites listed at Stack Exchange

FenderLesPaul

03:51

@KyleKanos yeah I've basically never used any of them except PSE and Mathematica SE

Danu

05:21

@JohnDuffield That's just nonsense. Nothing here contradicts basic special relativity.

skill patrol

How can you even think about contradicting the most famous equation in the 20th century?

Danu

06:10

@JohnDuffield Just to correct your mistake: $E=\sqrt{m^2c^4+p^2c^2} $ so your argument doesn't even work ;)

John Duffield

06:50

@KyleKanos : many/most of my posts do not contain fringe/crackpot/incorrect notions. I'm a relativist, this post got the serial downvote treatment even though it says the same as Ben Crowell's in the duplicate: physics.stackexchange.com/questions/195218/…

@dmckee : yes, search on Duffield, you can find recent links to my answers by 0celo7, and comments like "Shit Duffield is on a roll today" along with "John Duffield is a crackpot" and "Why does that John Duffield fellow have like 2k rep when he's clearly insane?". Then take a look at the pattern of downvotes on my reputation. It's coordinated.

ACuriousMind

08:57

@DanielSank unless OP shows that standard tricks like BCH are not straightforward to apply, I 'D actually close that one as homework - like.

user54412

Ok, all 3 answers here and 1/2 deleted answers here think the Roche limit has something to do with head-on collisions between planets. Why does everyone seem so certain about this?

DanielSank

@ACuriousMind You say that, but I have an enormous list of questions like this which aren't closed. in fact, they're answered well. This means that someone (or a lot of someones) doesn't think these should be closed.

0celo7

09:17

@ChrisWhite Why the heck are you up?!

user54412

Jul 6 '13 at 18:29, by Chris White

@CrazyBuddy Also, as a ~~grad student~~ slave, I don't sleep. Sleep is for the weak, and the unpublished.

0celo7

I'm unpublished too

user54412

I was actually trying to sleep, but I kept ending up debugging code in bed and I figured it was more efficient to do that on a computer.

0celo7

brb shower, train, breakfast, morning news

I'll brb in 2.5 hours

Well fuck I woke up an hour early

::shrugs, starts Skyrim::

started up on the first try!

Yashas Samaga

09:54

Hi!

Can someone help me with this? What is the difference b/w Approach velocity and relative velocity?

user54412

@YashasSamaga Without more context I'd say nothing. Maybe one is the negative of the other in someone's mind, but that's not an interesting difference.

0celo7

This mod made a second Blackreach.

I have no carrying capacity!

Yashas Samaga

10:14

@Chris My homework problem :V

skull patrol

10:26

@YashasSamaga what do you mean by "approach" velocity?

Also, all speed is relative :-)

gonenc

Carroll on falling into a schwarzschild black hole:

> We would never see the observer cross the schwarzschild radius, we would just see them move more and more slowly (and become redder and redder, as if embarrassed to have done something as stupid as diving into a black hole)

0celo7

10:54

You could fall into a black hole and not even notice it

They're sneaky little bastards

gonenc

@0celo7 well you'd die

and the tidal force you'd certainly notice

0celo7

11:04

@gonenc not if it's big enough

gonenc

@0celo7 having crossed the event horizon there is no way you are not gonna feel tidal forces as the curvature $\to \infty$

yuggib

11:25

just a random rant: why on earth it seems that nowadays (theoretical) physicists know better homology and algebra than operator theory (in particular the spectral theorem), and the analysis of PDEs??

ACuriousMind

11:39

@yuggib I guess because you can "wing" operator theory by pretending it is linear algebra (and we are taught to do so even in the theoretical courses), but there's no such possibility for homology, is there?

(not saying this is a good state of affairs, but it is a fact that the subtleties of operator theory are ignored in most QM courses)

yuggib

@ACuriousMind probably the second part is true...the first, however, may lead to clamorous mistakes

ACuriousMind

I'm not denying that

yuggib

@ACuriousMind probably the same people think that QFT is just pretty diagrams and combinatorics; and completely understood...

ACuriousMind

@yuggib yes, there definitely is a high correlation between thinking all QM is just linear algebra and all QFT is just calculation of Feynman diagrams

0celo7

@ACuriousMind RS talk go well?

ACuriousMind

11:50

@0celo7 wasn't yet

This frigging seminar takes place from 6pm to 8pm

yuggib

@ACuriousMind T__T

0celo7

I'll ask again at 8-6+ε PM

gonenc

@0celo7 don't forget to use the wrong time zone! :D

0celo7

-6

What else would that be!?

@gonenc I guarantee you could be inside of a huge fucking black hole and not notice it.

gonenc

@0celo7 how come

0celo7

11:53

The curvature goes to infinity, but that might be over several AU

It's well known that nothing special happens inside of the horizon

The tidal forces could well be stronger outside of a large star cluster

gonenc

@0celo7 I know however a black hole with radius more than several AU is pretty damn unlikely

@0celo7 still inside the horizon I won't be able to communicate with my body outside

0celo7

How large is the largest black hole we (think we) know of?

gonenc

that may give it away

0celo7

There's a PSE post about being half inside of the horizon

No clue what the conclusion was

gonenc

@0celo7 what does it mean to be half inside?

either you are in or out?

0celo7

11:58

Like you stick a pole inside and try to yank it out

8

Q: Thought Experiment - Poking a stick across a Black Hole's Event Horizon

The classical explanation of a black hole says that if you get to close, you reach a point - the event horizon radius - from which you cannot escape even travelling at the speed of light. Then they normally talk about spaghetti. But here's a thought experiment. What if I have a BH with event hor...

gonenc

@0celo7 that is an interesting thing...

0celo7

I think that's it

gonenc

> Funnily enough, you will never get to find out what happens when you try to pull it back, because you won't live to see the stick pass through the event horizon.

^nice argument

again

4 mins ago, by gonenc

either you are in or out?

however even a nicer question would be, what an observer inside the horizon would see

cause clearly then the pole passes the horizon

0celo7

Also, when does the pole get cut off

Is it like sticking it into a grinder

Or is it more like a saw

gonenc

@0celo7 yeah surely the pole has to break at some point cause it has to go towards singularity

but what if the gravitational pull is not enough to break the pole

0celo7

12:08

But every point on the pole has to go it

gonenc

@0celo7 nah if I'm holding the pole in my hand outside the horizon not every point of the pole has to go to the singularity

think as if I'm trying to poke the black hole

0celo7

Every point that passes the horizon has to go in

I'm thinking as you stick it in further, the black hole will shave off the tip of the pole

gonenc

@0celo7 yes that is true but I'm holding the other end of the pole, so it has to break ie cut off at some point

@0celo7 how does it shave my pole? around the event horizon it is almost like flat space

0celo7

I'm not sure, but the since the light comes are slightly tipped inside of the horizon, I don't thing standing still is a possibility

So the pole has to go somewhere

gonenc

@0celo7 we are missing something

the information that I'm holding the pole fixed doesn't travel faster than the speed of light

that means the info that I'm holding it won't reach the end of the pole until it is too late??

0celo7

12:14

We're probably asking the wrong question. If we are hovering above the black hole, it's true we will never actually be able to pole it.

I meant to say poke it, but pole works too.

gonenc

@0celo7 yeah but say alice is falling into the black hole with the pole whereas bob tries to poke the black hole

bob won't be able to poke it from his view but what about alice?

0celo7

So Alice is inside

gonenc

@0celo7 yup

0celo7

And she's looking out for the pole

gonenc

@0celo7 yup

0celo7

12:16

Will she just see a mess of particle from an annihilated pole? How the hell does anything cross the horizon intact then?

Well fuck

gonenc

@0celo7 why would she see an annihilated pole?

0celo7

Ah, I don't think you can lower the pole in a controlled fashion

Nvm the annihilation

So you let it fall on a geodesic and grab it when it's half way through

Only that's not possible because it can never cross the horizon...

gonenc

@0celo7 from the perspective of bob but not of alice

0celo7

Yes but Bob is the one who needs to yank it

gonenc

@0celo7 bob can yank it after a time $t$ whether or not he sees the pole passing the horizon

this is so f*cked up

0celo7

12:22

Does the pull get redshifted then?

gonenc

@0celo7 do you mean the info that I pull get redshifted?

0celo7

This is why we don't study extended objects and black holes

gonenc

@0celo7 maybe we should

rigid objects in GR would be a nice lecture to attend

0celo7

There's a whole book on the subject IIRC

gonenc

rigid body in general relativity google search didn't return much results

0celo7

12:25

Not that title

gonenc

@0celo7 well rigid body isn't even properly defined in SR

0celo7

12:59

@ACuriousMind You got rekt by John Duffield last night

I've never understood what the whole Trump hair thing is about...

ACuriousMind

@0celo7 <insert generic joke about your female parent here>

0celo7

What is wrong with his hair?

@ACuriousMind I'm an orphan

ACuriousMind

@0celo7 <insert batman reference here>

0celo7

Also why is everyone praising McCain...by all accounts he ended up in that camp because he was a daredevil and flew too low.

...and he would have never been a pilot if not for his father the admiral.

skill patrol

np

0celo7

13:09

I can't type today.

ACuriousMind

:22936788 test

Heh, the mobile chat app allows to ping deleted posts.

Bug or feature?

skill patrol

buggy feature

or featured bug?

:-)

0celo7

Lol

skill patrol

@ACuriousMind but I didn't get a ping?

ACuriousMind

@skillpatrol hmm...well useless feature or harmless bug, then

skill patrol

13:19

Are You Pondering What I'm Pondering

►

ACuriousMind

No, I don't think so :P

Jimself

narf

ACuriousMind

13:40

...narf?

skill patrol

narf. Pinky's favorite random word in the show Pinky and the Brain. Pinky: NARF! ahha what am i doing here, brain? naaaarf.

Jimself

^ that

ACuriousMind

Narf.

2

gonenc

@0celo7 what did I miss? I've read the chat history and didn't found anything...

0celo7

it's there

gonenc

13:43

@0celo7 is it the relativity stuff?

0celo7

yes

ACM doesn't know special relativity

ACuriousMind

... I need to convince someone to change their name to ACM just to make this chat room more confusing.

gonenc

@ACuriousMind or you can pick a shorter username so that we can refer to you more easily ;) :D

0celo7

BJ

ACBJ

Kyle Kanos

@JohnDuffield A proton being an antiparticle is definitively incorrect. Schwarzschild singularity at $r=r_s$ is indeed a coordinate artefact, despite your saying otherwise. Speed of light in vacuo is widely accepted to be constant, despite your insistence otherwise (multiple posts here). I can go on too, if you really want, that was just skimming through 3-4 negatively voted answers in your profile.

0celo7

13:47

A Curious ~~Blow Job~~ Bjorn Juliger

Kyle Kanos

Most of the posts I've seen from you are of this type: GR is wrong, SR is wrong, GR coordinate system is wrong

gonenc

@0celo7 I don't quite understand how the discussion got started though. the guy just referred to dmckee??

@0celo7 ACuriousBJ

would be the best user name :D @ACuriousMind

ACuriousMind

@0celo7 you are not the first to make that joke by a long shot :P

@gonenc Pfft... If you peasants want to refer to me, type my glorious name in full ;)

Kyle Kanos

Okay Bjoern

0celo7

@BJ The proof that black holes can't asexually reproduce is very elegant.

gonenc

13:50

@ACuriousMind I don't quite sure how I should pronounce Björn though, even though I know German pretty well :D

@0celo7 wat?

0celo7

"pretty well"

gonenc

:P :D

0celo7

@ACuriousMind Although the proof falls in the category "this would be a lot less nice if we didn't have such convenient definitions"

ACuriousMind

@KyleKanos my nickname. Also, not sure if you belong to the peasants, Dr. Kanos.

0celo7

@ACuriousMind He doesn't even have his PhD yet...

ACuriousMind

13:52

@gonenc just as it is written - it's just the one syllable

0celo7

@ACuriousMind No it's Byo-errn

Roll the r

gonenc

@ACuriousMind I'm not sure about the BJ part

ACuriousMind

@gonenc that's what she said

3

0celo7

lol

gonenc

@ACuriousMind like seriously :D

0celo7

13:55

Seriously, what the fuck is wrong with Trump's hair!?

For as long as I can remember, people have been making fun of it!

ACuriousMind

Well, dunno how to explain it - to me, it's really just a 'b' sound followed by a 'j'

@0celo7 those are great until you have to unpack the definitions in an application :D

gonenc

@ACuriousMind If it is like plain b followed by j I don't have any problem, I thought it would sound somewhat different since it is widely used in swedish

Kyle Kanos

So it's not the two syllable bah-jeyrn?

gonenc

@KyleKanos I guess this is the correct pronunciation

ACuriousMind

It's bjœʁn, for those capable of IPA

Kyle Kanos

13:59

I don't like India Pale Ales, too bitter

Jimself

^ speaking of which, the Toronto Festival of Beer is on Friday. I'm so excited

Kyle Kanos

Shame I can't make it

Jimself

It is a shame. Beer fest is a big thing

Kyle Kanos

I can believe it

ACuriousMind

@Jimself Canada sounds more inviting every day.

gonenc

14:03

@ACuriousMind 👍

Jimself

Some beers are only brewed specifically for this festival and can't be bought elsewhere. Flying Monkeys once made a nice orange creamsicle beer. It was uncanny

gonenc

@0celo7 ^maybe because of this

ACuriousMind

@Jimself how many people usually attend it?

Jimself

@gonenc I still can't get over the fact that he is orange

skill patrol

that's not orange; it's a florida sunburn

Jimself

14:07

@ACuriousMind Good question. I don't know the estimates, over the full festival, there's quite a lot of people. Last time I was there, there were easily a few thousand people on the grounds

It usually runs for three days

ACuriousMind

@skillpatrol how is a Florida sunburn different from any other sunburn?

Jimself

@ACuriousMind magnets

3

skill patrol

^that

:-)

ACuriousMind

@Jimself thank you for your kind explanation :)

Jimself

I do what I can :-)

skill patrol

14:13

where would the bermuda triangle be without you :P

0celo7

@gonenc I don't see the issue.

Jimself

@skillpatrol France

skill patrol

:D

gonenc

@0celo7 it looks funny there is no issue :D

0celo7

lol

Jimself

14:13

the French Triangle just doesn't have the same ring

ACuriousMind

@Jimself I believe that's usually called a menage a trois

skill patrol

what is it in german?

Jimself

@ACuriousMind explains what happened to Amelia Earhart.

ACuriousMind

@skillpatrol the Bermuda triangle?

skill patrol

@ACuriousMind a menage a trois

ACuriousMind

14:17

Uh... Dreiecksbeziehung, I think

skill patrol

Ménage à trois

A ménage à trois (French for "household of three") is a domestic arrangement in which three people having romantic and/or sexual relations with each other occupy the same household. It is a form of polyamory. == Historical instances == History has a number of examples of ménages à trois relationships. Sir William Hamilton (British ambassador to Naples), his wife Emma Hamilton, and her lover, the naval hero Admiral Horatio Lord Nelson, were in a ménage à trois from 1799 until Nelson's death in 1805. The German intellectual Dorothea von Rodde-Schlözer, her husband Mattheus Rodde and the Fre...

. Erwin Schrödinger, his wife Annemarie Bertel and his mistress Hilde March had a ménage à trois :O

no wonder he chose a cat

gonenc

@skillpatrol the rule of three...

0celo7

14:36

@ACuriousMind never heard of that

Not that I'm the authority

But that word is not in the average German-American middle schooler's dictionary

gonenc

@0celo7 it is "Dreieck" = triangle + "s" (for joining two words) + "Beziehung" = relationship

0celo7

@gonenc I know how German works

Just because you can make a compound word doesn't mean people use it

gonenc

@0celo7 What I'm trying to say is that you really shouldn't expect it to be in an ordinary dictionary.

@0celo7 though Duden has chosen Dreiecksverhältnis over Dreiecksbeziehung in the dictionary of german lanugage

funnily Ménage-à-trois is also in the dictionary :D

0celo7

@ACuriousMind Exactly. To define a black hole a la differential topology, one creates an unphysical spacetime and embeds the physical spacetime in it. Then one defines null infinity and defines the black hole region as the region not in the causal future of null infinity. Then one assumes spacetime is strongly asymptotically predictable and defines a region in the unphysical spacetime containing the non black hole region in the physical spacetime so that this region is globally hyperbolic. (cont.)

@ACuriousMind By a theorem, this new region contains Cauchy surfaces. What we perceive as a "black hole" is the intersection of one of these Cauchy surfaces and the black hole region in the physical spacetime.

Wald mentions that this is all nonsense if all one is given is some initial data and is told to solve the Einstein equations for it.

*causal past of null infinity

Not 100% correct, but you get the gist

Given all this, it takes but a few lines to show black holes cannot asexually reproduce :D

Jimself

@0celo7 So they have to use eHarmony too?

skill patrol

14:53

they use eDisharmony :P

0celo7

@Jimself lol

Kyle Kanos

Can anyone tell me how "trouble with my computer" prevents one from doing an interview?

0celo7

@KyleKanos If my computer is on the fritz, I have to fix it that instant before it gets worse

Jimself

@KyleKanos It exploded and now the house is on fire

0celo7

And while everything I did to it is fresh in my memory

Kyle Kanos

14:57

@0celo7 But what if you work with a Tech company so you've got a building full of computers?

0celo7

@KyleKanos yeah, fire

@Jimself the hard drive went all beyblade on the cat

Kyle Kanos

@Jimself I'd expect not a word for a day or two from someone who went through an explosion & subsequent fire.

0celo7

@KyleKanos are you trying to get out of an interview?

Jimself

@KyleKanos Well if they have to miss the interview, it's just common courtesy to let you know. What are they going to do? Let you worry?

Kyle Kanos

@0celo7 No. I had one scheduled for 10 am and they messaged me at 10:45 saying that they were having computer issues

0celo7

14:59

@KyleKanos I see

Jimself

@KyleKanos They finally got the fire under control and felt it was calm enough to be able to message you

0celo7

^^

seems reasonable

Jimself

you should send a fruit basket or something. They probably lost more than a computer in the fire

0celo7

@Jimself Can quantum effects allow a black hole to bifurcate?

Jimself

@0celo7 I don't know

I'm not much of a black hole guy

Kyle Kanos

15:00

Plausible. Yet the news does not show any major fires in several months.

0celo7

Like the second law of black hole thermo is violated by Hawking radiation, so it's not crazy to think that theorem (no bifurcation) can be violated as well, right?

Jimself

If it happened today, it might not have made news yet

@0celo7 like I said, not much of a black hole guy

0celo7

0

Q: lensing formula experimental data

The gravitational lensing formula is given by equation $a=4M/r$. Is there any experimental data for this equation. I am trying to plot a curve for this equation and the real experimental data and check for the accuracy. I would really appreciate a table of data for the angle of deflection at each...

general-relativity experimental-physics gravitational-lensing

@KyleKanos Dupe.

Kyle Kanos

So it seems tom & Rick are in a close war? One wants A closed as a dupe of B and the other wants B closed as a dupe of A

Jimself

link?

Kyle Kanos

15:05

1

Q: Why friction is zero when wheel slip is zero?

From most graph, when the tire doesn't slip, then the friction is zero, for example see the below image Why there is no friction when there is no slip? As the car stand still on slope, there is no slip but still there is friction holding the car against gravity

everyday-life friction

4

Q: Does a tire need to slip to generate force?

Recently, I have been doing some research on racing and tire modelling. While I was doing this, I encountered many curves like those shown below. While I understand the need of slip angles to generate lateral forces (those perpendicular to the direction of motion), the need to have slip in the...

kinematics rotational-dynamics friction rotation rotational-kinematics

I think the bottom one is the better question & answer of the two

0celo7

@Jimself I'm considering asking a PSE question about bifurcation, so I need to get my facts straight. Does Hawking radiation actually violate the second law (dA>0)?

In my mind it does, but I haven't studied quantum black holes yet.

Kyle Kanos

0

Q: Gravitational lensing experimental data

Is there any experimental data for the gravitational lensing equation $$ \alpha=\frac{4M}{b} $$ where $b$ is the distance of closest approach, $M$ is the mass of the object. I tried Google but didn't find anything.

general-relativity gravitational-lensing

Sadly, we can't close as a dupe

Jimself

@0celo7 I really don't know. But given that the mainstream view of Hawking radiation goes back and forth so much, I'm waiting until everything settles down to get more into it

0celo7

@KyleKanos Why?

Kyle Kanos

No answers

0celo7

15:08

whaaat

@ACuriousMind Do you know if Hawking radiation violates the second law of black holes?

I'm counting on you having paid attention in that seminar

Kyle Kanos

I've commented as much though

0celo7

Wiki says the second law is violated

Jimself

^ I usually trust wiki in things like this

What does PSE say about it? If nothing, consider fashioning a question for which the answer might be a bit more in-depth than "Wiki says this"

0celo7

I'm not going to ask about the second law

Jimself

and write your own answer, of course. That way it's here for anyone needing it

0celo7

15:12

I have 3 books that discuss that part, I just haven't gotten to it

I'm wondering if theorem 12.2.1 (black holes need eHarmony) in Wald can be circumvented somehow

Unrelated: can black holes scatter?

Actually that's misleading. The black hole number can never increase, even if there are multiple black holes.

Unless completely new ones are formed.

i.e. black holes can't reproduce ever, period

Jimself

@0celo7 That explains why they live in dark places away from the light and bring down everyone else around them

0celo7

@Jimself well that's the classical theorem

Perhaps the fancy quantum black holes are more social and prolific.

Paul Rieckhoff, president of Iraq and Afghanistan Veterans of America, wrote a column in the New York Daily News Monday titled "Trump's vile comments on McCain an insult to all veterans."

"Trump's asinine comments about Sen. John McCain's service are an insult to everyone who has ever worn the uniform -- and to all Americans," writes Rieckhoff.

cnn.com/2015/07/21/politics/…

My dad, a Vietnam vet, said he finally respects Trump because he put McCain down.

cnn.com/2015/07/21/politics/…

:'D the master at work

FenderLesPaul

15:33

Mornin

skill patrol

hi pal

FenderLesPaul

How goes it?

0celo7

Good morning

skill patrol

not too bad, you?

0celo7

@FenderLesPaul Have you done exercise 8.8.a in Wald?

FenderLesPaul

15:35

@0celo7 yes black holes can scatter

0celo7

I hand waved it when I read that section

@FenderLesPaul can "no black hole bifurcation" be avoided quantumly?

FenderLesPaul

I haven't done that one; let me take a look at it now

and I'm afraid I don't know the answer to the bifurcation question

0celo7

My hand wave proof is pretty much that in a globally hyperbolic spacetime there are no topological obstructions (holes, lines removed, etc.) that would prevent J(C) from being closed

I.e. it is known that I(C) is open by definition, so since there are no obstructions we simply set J(C)=cl(I(C))

FenderLesPaul

oh shoot; actually I'll take a look at 8.8a in just a bit, I forgot I had to read a paper for group meeting at 2pm

0celo7

But then I don't use the fact that $C\subset\Sigma$ or $C$ is closed

@FenderLesPaul that's fine

John Duffield

15:56

@Kyle Kanos : the proton IS more like the positron than the electron, the GR field interpetation says the Schwarzschild singularity is NOT a coordinate artefact, and you should check that speed of light with Don Koks at Baez. What you shouldn't do is and downvote me when I refer to Einstein and the evidence and tell you something you don't know.

0celo7

::chuckles::

Kyle Kanos

sigh a "likeness" is not an equivalence and is definitively contrary to the standard model that says the proton is a particle and antiproton the anti-particle.

And I can find all sorts of people (published and unpublished) who believe in the variable speed of light. That does not at all mean they are right

And what you shouldn't do is tell people how to vote on answers. Many of your downvoted answers are contrary to known & accepted physics. If you don't want the downvotes, don't post crap

4

Or at least start showing effort rather than resorting to [insert famous guy here] says so because it's really a logical fallacy to do so

5

0celo7

yay my loan got accepted

FenderLesPaul

@0celo7 congrats broski!

0celo7

@FenderLesPaul Did you have to do the "entrance counseling" too?

FenderLesPaul

16:14

@0celo7 I don't recall such a thing

what does it entail?

0celo7

a bunch of reading and questions about how you plan to pay back the loan, sign here for your soul, etc.

I didn't read any of it, I just used common sense and got a 100

I wonder what happens if you get something wrong

FenderLesPaul

Nope I didn't have to do that

0celo7

eh, whatever

FenderLesPaul

At least you got your monies

Kyle Kanos

16:32

So I answered this question because I vaguely recalled the source from a prior question (linked in the previous link here). Then I remembered that this guy emailed me this morning asking for help & am hoping that doesn't start a trend :/

0celo7

16:47

@ChrisWhite you ever do exercise 8.8.a in Wald?

user54412

And what exactly is 8.8?

Jimself

@KyleKanos Guess who was one of the users I was thinking of when I described fringe physicists in my recent meta post.

0celo7

Let $\Sigma$ be a cauchy surface and $C\subset \Sigma$ be closed. Show that $J^+(C)$ is closed. (Assume spacetime is globally hyperbolic.)

Jimself

And why I said they are arguably the most annoying type

^ messages will self destruct in 2 minutes

^ that was low

0celo7

:(

Kyle Kanos

16:50

@Jimself Undoubtedly so

Jimself

hmmm.... 2 minutes seems to be the time when you can't delete any more

user54412

@0celo7 ~1/20 AU (a few billion solar masses)

user54412

@Jimself Quick: Start new site, be a mod, get network-wide chat superpowers.

2

user54412

@0celo7 Sounds pretty familiar. Also probably pretty straightforward ;)

Jimself

@ChrisWhite Okay! Be back in 5 minutes

0celo7

16:55

@ChrisWhite My sarcasm meter is broken

Kyle Kanos

@Jimself Flag Danu or HDE?

0celo7

@ChrisWhite please pick one: 1. You think I should do it myself. 2. You don't know how to do it. 3. You're too lazy. 4. You're a troll.

user54412

@0celo7 You just haven't done nearly as much analysis or point-set topology as I had done by the time I started GR.

Jimself

@KyleKanos Thought about it, but there's not much point. Calling someone annoying or the basis for what I wrote isn't itself bad. The description is fair and calls these users valuable members if a bit grating. I'm sure they think the same of us and I stand by my opinions

user54412

@0celo7 1, 3, maybe 2 if I'm unlucky. Definitely 4.

0celo7

16:58

@ChrisWhite Yes, so I need a hint

Jimself

we also all know who I'm talking about when I mentioned the technically proficient troll

Kyle Kanos

12262 came to mind

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