The h Bar

Slereah

16:00

> $\hat 2$

It's an interesting paper because it doesn't seem crazy if you don't read it

It has a reasonable layout

Proper tex

Equations that look like correct equations

But then you start reading the words

And you know why it's on vixra

Either it's a crazy paper or it's some interuniversal Teichmuller theory where he just never wrote down what the hell he's talking about

0celo7

@Slereah wot

S^n is not a product space

Slereah

I'm leaning towards crazy paper

Secret

> If you spot anything that is dimensionally incorrect, it is garbage no matter how brillant it is (it is not brillant in this case)

(where's that quote of feymann when I need him...)

0celo7

16:15

@Slereah double helix alien DNA confirmed

Slereah

that's not alien DNA, that's just to channel the power of the cosmos

keelynet.com/unclass/hardy1.htm

it's this apparently

Apparently the proper geometric product is $$uv = u \lfloor v + u \wedge v$$

$\lfloor$ some inner product defined on multivectors, I suppose

I kinda want to see if you could define a spacetime on a Hilbert manifold sometime

Just to see if it even makes sense

0celo7

How would you define the signature of the metric?

Slereah

tough one

What's the smallest Hilbert space that isn't $\Bbb R^n$, is it just $L^2$

Secret

hmm... can a quantum version of spacetime be written as a superposition of classical metrics in GR...?

0celo7

@Slereah yes

(Assuming the underlying measure space is sigma finite)

Slereah

16:26

Is $L^2 \approx \Bbb R^{\Bbb N }$ in some sense

I do remember that it is also $\mathfrak l^2$

0celo7

L^2 is a separable Hilbert space and those are all isomorphic

Slereah

Which is just infinite series of complex numbers

Is there an infinite dimensional Hilbert manifold that is real

0celo7

What?

Slereah

That is a vector space on the field $\Bbb R$ instead of $\Bbb C$

Or is it still $L^2$

0celo7

L^2...

Slereah

16:28

Aight

I guess the only difference is the inner product

$f^2$ instead of $f^* f$

0celo7

Yes

Slereah

I was just wondering to get a good feeling why you can consider a Hilbert manifold a manifold

What's the proper definition of $\mathfrak l^2$ again, converging series of numbers?

I forget what $\mathfrak{l}^2$ is called

I think it was Heisenberg's original QM idea

Balarka Sen

@0celo7 Jiggling, my dude.

0celo7

@Slereah little ell two

@Slereah L^2 Norm in the counting measure

@BalarkaSen wot

Secret

reddit.com/r/askscience/comments/23qa23/…

hmm...

Balarka Sen

16:36

@0celo7 Call me Thurston and tickle my beard

Secret

o wait covariance

Anonymous

@Slereah Are $\mathfrak{l}^2$ and $\ell^2$ different ? (I don't know actually)

Slereah

One is german looking

Anonymous

I meant the meaning of those two :P

Anonymous

Not that they look different

Anonymous

16:41

$\ell^2$ is the space of square summable sequences

Secret

arxiv.org/pdf/1702.03011.pdf

that is not useful

bleh, I need to stop thinking about black holes for a while

Slereah

Can you build an atlas between it and $\BBb R^\Bbb N$

0celo7

Wot

What inner product are you putting on that thing

I have a hunch it’s literally ell^2

Slereah

Well why are Hilbert manifolds manifolds

Or are they not exactly manifolds

0celo7

Read Lang’s differential geometry book

He models everything on the Banach category

Most everything still works

Secret

16:56

[Random thought to be checked]

I wonder if the uncertainty principle applies well enough in spacetime metric such that you can spontaneously change its topology and back (e.g. having CTCs as part of the flucturation in the metric) as long it is within the bounds of uncertainty...

John Rennie

From Facebook. Not that I make a habit of reposting Facebook pictures here, but this one is so appropriate for me that I just had to share it.

Slereah

You belong on facebook, OLD MAN

ncatlab.org/nlab/show/convenient+manifold

This sound convenient

Secret

too little vegetables

John Rennie

You can never have too few vegetables

Slereah

There's a paper on QM in Hilbert manifolds

Curve those quantum states

Abcd

17:09

@JohnRennie I don't get what gravitational potential of a solid sphere "at internal point" means.

How can we displace sphere internally?

Because the definition is "gravitational potential at a point is equal to the work done per unit mass by an external agent in moving a particle slowly from reference point to the given point."

John Rennie

@Abcd take some point inside the sphere, and put a test mass at that point. Then measure the work per unit mass needed to move the test mass from that point to infinity. That's the gravitational potential at that point.

Assume the test mass can pass through the material of the sphere e.g. it passes through a tunnel

Abcd

Okay fine. I was thinking the other way round.

John Rennie

Cor, Eddie Clarke just died.

So that's the last of the original Motorhead lineup gone.

Man I'm getting old.

Slereah

Next, you!

Secret

arxiv.org/pdf/0704.3306.pdf

This need to go further so that spacetime metrics themselves become quantum states

dies

John Rennie

17:19

Eddie Clarke was only ten years older than me. Mind you he spent his life drinking, taking drugs and having sex with groupies, while I've wasted mine.

3

Anonymous

@JohnRennie Maybe you're joking, but in my opinion one of the greatest rewards one can get from life is a healthy old age...

Prathyush Poduval

@Blue I would rather have a balance of both

long life and fun seems better

Slereah

I want to do drugs and be immortal

2

Anonymous

Depends on whether you define taking drugs as fun

John Rennie

@Slereah should be OK as long as you stick to taking Sanatogen

Prathyush Poduval

17:22

@Blue is there any limit to the no of lines an IDLE shell console can print? (I'm running a long code and it stopped printing at 92000 lines)

@Blue well if you're immortal.....

Mr. Xcoder

smells star and flag abuse

2

John Rennie

I haven't seen any flags ... yet ... :-)

Prathyush Poduval

do you want to see? coz i can flag myself :P

John Rennie

Can you flag your own posts? Not that I recommend you attempt the experiment :-)

Mr. Xcoder

There has been a massive flag spam yesterday from The H Bar and from The Russian SO chat rooms, so better be cautious @>10kusers.

Prathyush Poduval

17:25

@JohnRennie i I tried it out

Anonymous

@PrathyushPoduval Maybe! IDLE has too many restrictions

Prathyush Poduval

@Mr.Xcoder too late.....

John Rennie

Hmm I don't see any flag notifications ...

Mr. Xcoder

Nor do I (...yet...)

Prathyush Poduval

5 mins ago, by Prathyush Poduval

long life and fun seems better

is what i flagged

John Rennie

17:27

@Mr.Xcoder what went on yesterday? I skimmed the chat log this morning but didn't see anything suspect.

Anonymous

You can flag your own post for moderators, only.

Mr. Xcoder

@JohnRennie Oh wait sorry two days ago (evening)

Probably self-flags go directly to mods (because who would flag himself as spam?)

Prathyush Poduval

oh damn

John Rennie

@Mr.Xcoder what went on two days ago?

Mr. Xcoder

@JohnRennie IIRC there was a flag spam

Anonymous

17:28

@Mr.Xcoder I'd vouch for self-spam flags

Anonymous

:P

Anonymous

Some people would surely use it on daily basis

John Rennie

@Mr.Xcoder you mean someone flagging posts for no good reason?

Mr. Xcoder

Yes, precisely

Prathyush Poduval

@Slereah hey,where can I learn to use conformal mapping to solve laplace equation?

John Rennie

17:30

@Mr.Xcoder I imagine the community mods will have had words with that person ...

Anonymous

@PrathyushPoduval Any complex analysis book would have that

Mr. Xcoder

But there were multiple persons, and not only in The H Bar

Prathyush Poduval

@Blue hmm okay

Mr. Xcoder

Anyway, gtg o/

Anonymous

@Mr.Xcoder \o

Cows

17:38

I have some quasi-personal / perspective type physics questions I want to ask and would appreciate some personal perspectives

1.) I only in the past couple of years began studying physics seriously. Seriously to think about things deeply

for example

Lie Groups, Lie algebras, exponential maps, non-relativistic and relativistic spinors

and particles

Essentially how taylor expansions are cool hehe

or also

topology, and topological invariants

So my personal question is the following

Do people really know what they are doing or studying when they first start studying physics

Is it even possible to study anything in Physics and know it well, the first time?

Even Quantum mechanics concepts, and spectral theory

I am only beginning to know what is going on

bolbteppa

@Cows no

Takes ages to make sense of anything

Lots of people don't even think non-relativistic spinors exist for example, that they come only as an approximation to the Dirac equation solution or something

Cows

wow

bolbteppa

Quick search on physicsforums and you'll see comments like that

Cows

Yeah these things are honestly quite deep

John Rennie

I think when you learn something new it takes a while before you see how what you've learned fits in with everything else. You only really understand when you have that bigger picture.

So you go through life convinced you don't really understand anything :-)

Which is odd given how many of the non-scientists I meet go through life convinced they do understand everything ...

3

Cows

17:48

lol, yeah if only they knew . . .

ooolb

hello!

Anonymous

@JohnRennie :P reminds me of my daily encounters

John Rennie

@Blue tell me about it :-)

Anonymous

@JohnRennie It would take days to tell all of them. XD For example, we have a nanny (who looks after my little brother) who stays with us. She keeps telling me her theories about global warming and earthquakes occurring because of quarrel between gods and demons (I'm not joking!). And when I try to explain, she tells me that science has blinded me from the well-established laws of nature

Anonymous

I don't blame her. But that represents the general awareness level

CooperCape

18:26

lmao it is god quarrels.

That was a chapter in my physics AS

Semiclassical

19:11

plz stop hurting me bibtex

staaahp

@Blue discovering that kind of ignorance is a bit like coming across an old bit of WW2 ordnance which never went off

which is to say, don't touch it and stay out of the blast radius :P

Abcd

Is it possible that dark matter is supernatural?

Semiclassical

Insofar as 'dark matter' is a term of physics and not of theology, no.

You could come up with some supernatural concept and call it dark matter, but it won't be what a physicist means by the term.

If you mean "is it possible that dark matter has no possible scientific explanation", well...it's not impossible from a philosophical point of view, but I wouldn't bet on it.

Abcd

We can't see dark matter, just like we cant see the supernatural.

Semiclassical

We also can't see individual air molecules by eye. That doesn't make them supernatural.

The only difference between dark matter and regular matter for a physicist is that our ability to interact with the former is apparently far weaker than the latter.

Plus...we do 'see' dark matter, insofar as the reason we postulate its existence is based on other empirical facts.

Abcd

I feel that physics for next generation students is going to be really hard.

Semiclassical

19:25

eh, depends on what part of physics you're talking abouto

particle physics, quite possibly.

condensed matter, though, is probably going to stay healthy.

Abcd

what about school students?

will newtonian mechanics be removed from books?

Semiclassical

again, depends on what you mean

hahaha no

Abcd

But newton's law of gravitation is wrong...

Semiclassical

Depends on what you mean by 'wrong.' It is not the final theory of gravity, no.

On the other hand, it is still a very good approximation of many astronomical systems.

Abcd

it should be renamed then, "theory of gravitation"

Semiclassical

19:28

Depends what we're talking about. "Newtonian mechanics" is not just "oh hey gravity has F=Gm1m2/r^2"

CooperCape

Everything you learn in school is an approximation/.

Semiclassical

@CooperCape That's approximately true :P

CooperCape

Every year begins with "wot u heard last year is wrong"

it's just a bit of a meme

Semiclassical

( e^(i pi)+1=0 is not an approximate statement, for instance. but by and large yes)

when I say "newtonian mechanics" I mean Newton's three laws of motion

F=ma and all that

Abcd

even they aren't perfect...

CooperCape

19:30

Those are useful tho

Don't nasa use those

for some things

Semiclassical

And regardless of what quantum mechanics or relativity theory have to say, Newton's laws are still exceptionally important

The car you drive, by and large, doesn't give a damn about the uncertainty principle or how spacetime is warped by matter.

Abcd

lol, yes.

Semiclassical

What matters are how the car responds to and exerts forces

CooperCape

ewww mechanics

I ain't into that

Semiclassical

So the idea that Newtonian mechanics is somehow obsolete is just not correct. It may not present an active field of study in the same way as particle physics etc, but it is still a huge part of physics as education.

Abcd

19:33

I see.

Semiclassical

And you're not likely to understand how quantum mechanics or general relativity work without a solid handle on Newtonian mechanics.

Now, if you ask how physics as a research discipline is going to change...there, I'm not sure.

There are certain subjects within physics which are sufficiently grounded in experimental and technological needs that I don't see them going away. (Hence my statement about cond-mat theory.)

On the other hand, particle physics seems to be in a tough spot insofar as LHC confirmed the Higgs boson but hasn't yet suggested new physics.

It could certainly be the case that we've run into a wall there which we won't easily be able to overcome.

CooperCape

It makes me feel really sad when I read a book written pre LHC and it's like LHC may prove this or that and you read it like 'well....'

Semiclassical

yeah

the tricky thing is that one can always say "well, maybe if we push the energy up a bit more then we'll see new physics"

CooperCape

What comes after a TeV...

Semiclassical

philosophically, anyways. the trouble is getting someone to pay for that :P

CooperCape

19:38

An EeV?

Semiclassical

@CooperCape Bankruptcy :P

CooperCape

Shame...

Semiclassical

I think Peta

CooperCape

Ahh right yeah.

bolbteppa

define 'solid handle on newtonian mechanics' :p

Semiclassical

19:39

lol

"Whatever the physics profs who are writing the written exams say it is." :P

bolbteppa

You only know a field when you teach it (excuse not to know things)

Semiclassical

yeah

my feeling about my latex right now:

encrypted-tbn0.gstatic.com/…

CooperCape

Actually a solid handle on newtonian mechanics is not what I need for my maths a level cause the systems broken

I can get an A* in maths with 36% in mechanics.

Or if I really nail the rest 16%...

Semiclassical

tbf there's parts of newtonian mechanics which really just showed up in coursework for me

CooperCape

I can honestly say I'm awful at it ;)

Semiclassical

19:44

e.g. non-inertial reference frame stuff

but I'm someone who mostly does quantum

if you're doing GR, I suspect understanding non-inertial newtonian mechanics helps a lot

CooperCape

Oh gosh. Thank god we deal with still stuff.

At least that makes energy conservation easier for us.

Couldn't cope if the observer was moving.

Semiclassical

better version:

CooperCape

I remember spending ages with latex screwing me over for a school writeup I did.

I should imagine yours is 1. A lot more important and 2. A lot harder ;)

Semiclassical

latex by itself isn't toooo bad, usually

latex plus figures is a bit annoying

CooperCape

I was being a foolish youth.

Semiclassical

19:46

latex plus bibtex problems is suffering

CooperCape

Keep it to one tex thx

idek what bibtex is

Semiclassical

bibliography stuff

CooperCape

ahhh right of course

(well not exactly of course, but it makes sense)

0celo7

20:27

@Semiclassical indeed

Hence, don’t use bibles

Put in the bibliography by hand

Semiclassical

i'm trying to avoid that, since this is for a thesis and I need to make sure the formatting is right

skullpatrol

How many pages is your thesis?

Semiclassical

dunno yet

skullpatrol

(If you don't mind me asking :)

Semiclassical

it'll be a bunch of papers stapled together, as my advisor puts it

and each of those papers had different formatting, so it's a bit tricky to gauge how much that'll take altogether

So I dunno :P

skullpatrol

20:36

ok

bolbteppa

20:54

If I ever ask why anything works with a computer I end up at the plug socket + quantum field theory and then never get anywhere, get lost trying to figure out why a computer even wants to add :(

ACuriousMind

21:19

@EmilioPisanty Yes, you're late, that one's a classic ;)

theDoctor

does newton's law of gravity work under water?

ACuriousMind

I can now report SAP mixes excellent cocktails at their conferences :)

theDoctor

perhaps the force is the same towards the center of earth, but the water forms a resistance so that it's acceleration is smaller...

now I know the truth: intertial mass is slightly greater than gravitational mass.

intertial

ACuriousMind

@Slereah Hey, sorry, I think that was just my phone - I wasn't really in here all day

theDoctor

the difference is perhaps 10^(-20)g -- that's called pulling a wild hair out of my ass.

(10^-20)g

ACuriousMind

21:24

@theDoctor Please either substantiate your claims with mainstream physics or leave this room.

theDoctor

oh bejuses, is this a bar or what?

what are YOUR credentials?

ACuriousMind

My credentials are that I'm a moderator and room owner that will remove you from this room if you continue to troll.

theDoctor

can trolls ask valid scientific questions?

ACuriousMind

You may think of me as a bouncer.

theDoctor

or are you overmoderation?

overmoderating

nevermind, I retract this line of thought from this room.

ACuriousMind

21:30

@JohnRennie It is a persistent pattern: The people I've learned the most from are the ones insisting they're not qualified to teach anyone anything.

2

Semiclassical

i.e. the reverse of the usual Dunning-Kruger effect

ACuriousMind

@Semiclassical It's called the impostor effect, and it's very real.

Semiclassical

right

Slereah

Me I just don't learn anything

Learning is for nerds

2

ACuriousMind

@Slereah Nerds are cool though

Slereah

21:34

To question the orthodoxy you have to know what the orthodoxy is

theDoctor

I've had 400 years of it, bro.

Slereah

You don't seem that old

ACuriousMind

@Slereah So much yes.

theDoctor

the heliocentric model isn't sufficient to account for all observations

Slereah

The heliocentric model actually works.

The point of modern physics is that there's no prefered reference frame

Hence the heliocentric model is just as valid

theDoctor

21:36

oh but there is a preferred reference frame: the observer

Slereah

Of course they didn't know that back then but most people don't seem to understand the actual problem of the heliocentric model :p

theDoctor

figure this, genius: the lens

do you think the lens can be explained by physics alone?

ACuriousMind

I, a genius, figure the lens.

Slereah

Well, geocentric, not heliocentric

theDoctor

okay, let's rationate.

Slereah

21:37

The lens has been figured out a little while back

theDoctor

no ithasn't

explain why there is a preferred axis in observing through a lens

when the lens itself is symmetrical?

Slereah

Anywhere between Ancient Greece or the 19th century, depending on what you think count

The lense has a rotational symmetry, hence there is indeed a preferred axis

theDoctor

he's a testable experiment (kind of like the double-slit): construct a room that is tilted at a 30degree angle.

@Slereah: if it had COMPLETE rotational symmetry, then nothing could be focused, except light without an image.

like a magnifying glass focuses the sun.

Slereah

wot

theDoctor

light would be perhaps converge, yet it would not JUST UNDER converge to show an image.l

IN ONE AXIIS.

this is why Galileo was EXCOMMUNICATED.

Slereah

21:40

I think you'd better diagram what you're trying to say

It's not very clear

theDoctor

you can image, if light is entering the lens ,and there is NO preferential treatment (like a slit, of an snake's eye, for example) on any axis, it would simply focus into more light at the convergence point.

but there is SOME OTHER FACTOR that makes it focus into an image.

Slereah

I'm not sure what you mean, but

ACuriousMind

@Slereah I forget, do you have a day job?

Slereah

You do know that you need two lenses to make a telescope, right?

@ACuriousMind That I do

theDoctor

LIGHT vs. IMAGE

grok that

ACuriousMind

21:43

@Slereah Whatcha doing there?

theDoctor

yes

Slereah

@ACuriousMind not much

Coding websites when necessary

ACuriousMind

@Slereah :(

Slereah

Hopefully not for much longer

Might be getting a machine learning job soon

ACuriousMind

Nice

Slereah

21:44

Well I still think it's boring but not a lot of GR jobs out there :p

ACuriousMind

Y'know, I always thought commercial stuff would be boring but...it's surprisingly interesting to be part of something that many other people will actually use

Slereah

I say let them all burn!

I mean learning machine learning was alright, but most jobs are just inputting data

theDoctor

in other words: does a lens focus LIGHT or INFORMATION?

can it really preserve directional data?

ACuriousMind

@Slereah okay, that sucks

Slereah

Would be nice to code machine learning stuff but these days most people just use existing software

theDoctor

21:47

how does the light know that it is entering a lens and must conform to it's curvature by the time it exits?

Slereah

Like the new google thing

TensorFlow or whatever

theDoctor

this goes right to the heart of the double-slit experiment.

Slereah

I should try to recode a neural network

Last time I tried it was pretty slow but I know how to program GPUs now

Should go better

ACuriousMind

@Slereah But...why?

Slereah

Why not

ACuriousMind

21:49

You can trust many people better versed in the matter than you have done that

theDoctor

anyway... something to think about.... have a nice day!

Slereah

I can also trust other people to play video games better than me

ACuriousMind

The excitiing thing about NN is not to implement them, but to come up with applications for them

Slereah

I can do that too!

Also keep in mind that coding something yourself for a specific application can be more efficient than using a general purpose algorithm

ACuriousMind

@Slereah It won't be something you can sell though

Slereah

21:51

If I could sell anything I work on in my sparetime I'd be rich!

ACuriousMind

Sure, crafting code for one specific application can be more efficient than anything else

Slereah

also part of the benefit is showing it to potential employers

ACuriousMind

But in the end, the age of the cloud is about developing things that can be used by everyone, everywhere

Slereah

Look at me, I know what I'm doing

To hell with the cloud I say

I've got my own server

ACuriousMind

Businesses don't want to purchase specific on-premise solutions anymore, they want infinitely scalable and adaptable technology that works in any cloud, always.

Slereah

21:53

Yes, but it would show employers I know what I'm doing :p

ACuriousMind

@Slereah I got a job without any coding projects to show for. :P

Slereah

The economy is pretty dire these days!

You gotta stand out

Even with like three degrees it's tough

ACuriousMind

@Slereah I got my job even though my master's degree isn't even finalized. You just need to convince them that you can do the work you're applying for.

Slereah

I try my best!

0celo7

Sam probably starts talking about wormholes and non-Hausdorff manifolds and gets shooed out by security

@ACuriousMind what happened to you

Transcript for