The h Bar

1:12 AM

they defined bulk modulus in an earlier chapter, so probably it's better to focus on that first

amanuel2

This book is well known for doing absolute shit in explaining, but searched online and good! Thanks

5:47 AM

@JMac How is it useful?

I'm speculating what "asdffasdf" will be. I have no idea what "asdfasdf" is, and yet, I'm speculating.

And I'm even calling it useful and meaningful.

6:12 AM

@JohnRennie What do you think about our little debate here with JMac? Do you think that speculating what something will be, even though you don't know what that thing will be like, is useful or meaningful? If my view is wrong, I need to know, cuz it's driving me crazy.

I have spent many happy hours, often while drinking beer, speculating about things I don't know and I heartily endorse the activity :-)

@JohnRennie Oks :P

ah, the "shut up while you're not drunk" philosophy

3

@JohnRennie Would you call it meaningful or useful?

@Semiclassical I consider all those hours spend late at night in the bar speculating about BSM physics to be time well spent!

@NovaliumCompany "meaningful" - no. "Useful" - no. "Enjoyable" - hell yes!

6:20 AM

@JohnRennie Do you think the AI stories about what AI will do and will be like of Ray Kurzweil and other similar authors are of any use other than entertainment?

No, though don't knock entertainment.

What do you mean don't knock entertainment? I'm not saying entertainment is not useful.

I'm not trying to prove JMac wrong here, I'm trying to prove to myself that I am right, because it's a view that I strongly support and if it's not rational, I need to know.

6:57 AM

@JohnRennie what is your favorite BSM model

7:24 AM

@Slereah you don't want to listen to me ranting about my theory of life, the universe and everything, or at least not without lots of alcohol to numb the pain. Trust me on this :-)

7:35 AM

Well what's the gauge group you like, at least :p

7:47 AM

@Slereah consider the configuration space of a clock. The world line of the clock is a trajectory in this space parameterised by the proper time of the clock. So what selects this trajectory from all of the the possible trajectories? Well, the requirement that a clock be a clock selects it because a clock is by definition something that evolves with proper time in a specific way.

The point being that observers, i.e. we humans, are basically clocks as well so our trajectories through our configuration space are correlated with the clock. We have to observe the clock evolving along a certain trajectory because we couldn't observe any other trajectory.

I did warn you :-)

I did ask you about beyond the standard model physics, though :p

Not sure that qualifies

If you don't throw in like 5 Lie groups I don't think it qualifies as BSM stuff :p

Your average BSM model

To be honest I'm scared to look into BSM because I once had to work with some SU(3) theory by hand, and I shudder to think of working with SU(5)

:-)

Noooo

Anyhow, human observers observe a trajectory for the universe through its configuration space that correlates with their own just as they select a trajectory for the clock.

Oh no @JohnRennie was a crank all along

7:57 AM

The difference is that I'm not writing articles about it on my web site :)

In fact I only discuss it when drunk (I started drinking early today)

You can, but be sure to use the proper crank webdesign

Everything written in upper case and in bright colors on a white background

Einstein agreed with me before the Illuminati assassinated him to protect their secrets.

Einstein certainly shared a disdain for having his quantum theory contain actual quantum mechanics

QM emerges naturally from Rennie theory because there are a number of trajectories close enough to the clocks to approximate a regular tick, and the observed trajectory is given by ... pause for fanfare ... a PATH INTEGRAL!!!

Damn I'm good.

2

You know one thing I wonder is if anyone ever actually made an Einstein-style unified theory that had at least some aspects of QM

ie : discrete levels

I've never read anything to confirm or deny that it's possible or not

If you have a classical theory, is it impossible to have discrete levels?

Actually that might make a nice PSE post

I'll make it

8:13 AM

@Slereah :O Damn

@JohnRennie Rennie theory, cool. I want Novalium theory as well.

Q: Can classical theories exhibit quantum-like effects?

0

For quite a while in the first half of the 20th century, many physicists tried to concoct some manner of unified theory to explain all known phenomenon, a lot of them using geometric theories (ie teleparallelism, affine gravity, asymmetric metric theories, Kaluza-Klein, etc). While their main goa...

9:41 AM

First time I have seen Slereah doing something on main site :-)

I do many things on main site

if you read the GR tag I pop up

10:41 AM

Oho!

Secret

11:31 AM

philosophising how multiple omnipotents fight each other found many similarities between them and quantum states

every omnipotent action effectively measures the target so the outcome behaves like an eigenvalue until another action is inflicted

So, if A's action is turning B blue, then "B is blue" will be true despite nothing else can be said about B. B can then unblue themselves with their action

More interestingly, if A's action is to command themselves the following sequence "create a rock so heavy it cannot lift and then lift it", then A actually will not be able to lift the rock in order to satisfy the requirement for omnipotence to do anything successfully because the whole event becomes fact until it is finished

Secret

1:19 PM

actually screw that, someone have corrected my mistake

multiple omnipotents will just cancel out the slightest disagreement

A: Does a pulley rotate due to internal friction between the pulley and string?

2:18 PM

Proving causality business involves proving a lot of tedious linear algebra

gosh dang

Johan Liebert

0

A frictionless pulley is a pulley that experiences no losses due to friction. So, it is referring to kinetic friction, since only kinetic friction causes energy losses (energy released as heat). It thus essentially means: no kinetic friction between the pulley and its axle or anything else like t...

Can there be static friction in the absence of kinetic friction?

My students are taking their group quiz today. I’m trying to decide to what extent their setup is sensible

They’re given a sealed box of copper which contains argon, along with the box’s properties and the initial temperature/pressure of the gas

They’re then told the box is heated for 6 minutes at 100 watts (so a known amount of heat enters the gas)

The question then asks them to 1) find the final temperature of the gas, and 2) find the (“very small”) change in the box’s volume

Thing is, to compute the first one, they’re supposed to equate the heat that flows into the system with the change in internal energy

Ie no work done by the gas, hence no change in volume

(Hmm, does it actually need that assumption? The work done by the gas is done on the box)

Secret

2:42 PM

box and whatever the atmosphere is squeezing the box

atmospheric pressure should have a role on how much work is done by the gas on the box

but it should be very small in comparison to the gas pressure inside

Also we assume all that heat is delivered into the gas, and not the copper

otherwise we actually need to subtract out that copper heat capacity

Prof wants them to include heating of copper

Yes that, what I think! does n, t the container effect temperature of gas?

They’re definitely assuming that the box and the gas remain in thermal equilibrium

Also, the box and the gas have comparable heat capacities in the stated problem

(If you take the box’s given mass of 100 g and it’s literature density of 9 g/cm^3, then the volume is a mere 11cm^3. But the box is supposed to a cube with 50 cm sides, which would require a thickness of 7.3 microns. So, not exactly realistic.)

3:05 PM

P=W/t=100.6.60=36000. Heat supplied.

If the work done is negligible!

Righr

(If you take the box to have 50 cm sides with thickness 1cm, the volume of material is approximately 15000 cm^3 and so the mass is 135 kg. So waaaay more)

One more thing.

Regarding the conductivity of box.

I mean we supplied or do work for 6 minute.

@JohnRennie This reminds me of the classic essay Simulation, Consciousness, Existence by roboticist Hans Moravec, written in 1998. Hans is a bit of a MWI evangelist, but don't let that hamper your enjoyment of that essay. ;) FWIW, Greg Egan explored similar ideas in his 1994 novel Permutation City.

Like I said, they assume the box and the gas are in thermal equilibrium

@PM2Ring whoaa, hi sir!

3:10 PM

Hi, @Yuvraj

@PM2Ring do you know about vernier caliper.

?

@YuvrajSingh... Yes. In my high school, we had a giant Vernier device, to make it easier for students to see what's going on.

But I haven't used one for a few decades...

@PM2Ring that, s the my weakest topic in physics. During my jee exam too I had struggled a lot in this.

Google is your friend, as far as that goes

Though that doesn’t help on an exam

@Semiclassical Thanks! But I have one genuine doubt.

@PM2Ring sir problem is when question says we 10 division on vernier scale coincides with 9 division on mains scale.

So least count for vernier scale is 9/10=0.9

But at the same time question says least count of main scale is 1mm.

That mean this 1mm divided into 10 division.

It depict the least count is 0.01

Both statement contradict.

3:18 PM

I just had a quick look at the Wikipedia article en.wikipedia.org/wiki/Vernier_scale It looks pretty good. When I was at school we drew Vernier scales on cardboard to help get the concept into our brains. :)

!

That, s my doubt sit!

@PM2Ring

@YuvrajSingh... This topic is tricky to discuss on chat, especially without diagrams. This animated diagram from Wiki is pretty good:

And I really can't explain it better than the text under that diagram. Maybe you should get together with a class mate or 2 and discuss it. Or plead with your teacher. :)

What’s going on in The h bar?

Hello, Hello is anybody in there?

You are only coming through in waves
Your lips move but I can't hear what you're saying

3:47 PM

Rock the h-bar

@PM2Ring It doesn’t have to be like this, all we have to make sure is that we KEEP TALKING

@PM2Ring Thanks for the diagram, but sir my question is more than theoretical. What I mean which one is the actual least count?

I got a serious problem (no joking this time) and I must discuss it, and I find you people to be faithful. I feel insecure...

Guru Vishnu

@YuvrajSingh...: In addition to the Wiki page PM 2Ring suggested, the following webpage is quite useful - miniphysics.com/how-to-read-a-vernier-caliper.html

I actually referred a YouTube video to understand this concept along with Screw gauge.

@YuvrajSingh... As Wiki says, "The difference between the value of one main scale division and the value of one Vernier scale division is known as least count of the Vernier. It is also known as Vernier constant." For the Vernier in the diagram I posted here the least count is 0.1

That page @GuruVishnu linked is good, and its diagrams are more precise than the animated one I posted here (which is a bit wobbly).

4:06 PM

If anyone get some free time then please discuss my issue with me

@Knight You're a teenager. It's perfectly normal at that age to oscillate between being over-confident and under-confident. You're still in the process of formulating an adult worldview and attitude. I have sympathy for your situation; OTOH, I don't know if this chat room is a great place for such discussions.

2

@PM2Ring Sir I don’t why but I get this feeling “I’m working less than others on my target therefore I will not achieve what I aim to achieve”. You probably would say that the best thing to do is to work more but it’s not like that I work sufficiently but then also some lunatic in my head says “other people of your age studies 10-12 hours and you work only for max 6 hours.

Although formally (or officially, I don’t which word is better) I work for 6 hours but in reality I work much more than that, I think that’s what I do. But then also I get this feeling of insecurity

4:34 PM

@Knight I suggest that studying 12 hours a day is excessive. There's only so much new information that you can absorb in a day. Trying to overdo it, and not having a healthy balance of activities can lead to burn-out.

Also, many competent people fear that they aren't as good as others may perceive:

Impostor syndrome

Impostor syndrome (also known as impostor phenomenon, impostorism, fraud syndrome or the impostor experience) is a psychological pattern in which one doubts one's accomplishments and has a persistent internalized fear of being exposed as a "fraud". Despite external evidence of their competence, those experiencing this phenomenon remain convinced that they are frauds, and do not deserve all they have achieved. Individuals with impostorism incorrectly attribute their success to luck, or interpret it as a result of deceiving others into thinking they are more intelligent than they perceive themselves...

dsm

Alright, dumb question. How do I embed an SE post into this chat?

Q: Arriving at the $\big(\pi_\ell,P_\ell(\mathbb{C}^2)\big)$ representation of $\mathfrak{su}(2)$

@Knight OTOH, you certainly could do more work on improving your English grammar. I think your physics & mathematics skills are good, but you do need to improve your language & communication skills.

@dsm Just post the URL with no other text.

dsm

Oh, that direct? Nice, thanks!

0

I think I'm really close, but confused on applying the multivariable chain rule and untangling the result. The $(\Pi_\ell,P_\ell(\mathbb{C}^2))$ representation of $SU(2)$ induced from the fundamental representation $(\Pi,\mathbb{C}^2)$ is given by $$(\Pi_\ell(A)\hspace{.5mm}p)(v)\equiv p(\Pi(A^{...

mathematical-physics quantum-spin group-theory representation-theory lie-algebra

@Slereah if you're in the mood for more representation theory

4:57 PM

@PM2Ring Sir I'm working on my grammar.

@PM2Ring Thank you sir for searching this on internet but I'm sorry I think I haven't got that syndrome.

5:10 PM

@Knight You may not have that syndrome, but I think perhaps your insecurity is similar to that syndrome.

5:26 PM

The dirty secret of “imposter syndrome”, I think, is that modern careers tend to demand that you pretend like you know what you’re doing

5:45 PM

@PM2Ring Yes I think it was similar.

Aaron Stevens

6:52 PM

@PM2Ring I definitely suffer from impostor syndrome

enumaris

7:03 PM

impostor!

Aaron Stevens

@enumaris That is probably the worst thing you can do to someone with impostor syndrome :)

enumaris

D:

8:03 PM

"If I have seen further than others, it is because I am surrounded by dwarfs."
- Murray Gell-Mann

3

9:59 PM

@Slereah What is the meta-theory of theories here in which you can classify a given theory as 'classical'? :P

@ACuriousMind I guess a theory described by an action functional

But quantum mechanics is described by an action functional! (in the path integral formalism)

Well then it's not an action, is it!

You're supposed to extremize the action, not make it a measure :p

So far the topological soliton answer is probably the closest to what I had in mind

@Slereah So, what exactly is the question - if you have an action, that's an action of some continuous-valued variables or fields, otherwise the standard calculus of variation doesn't work.

I guess the best example would be the standard one of the era

Can you make a bound system that has a discrete energy spectrum?

10:07 PM

What does "energy spectrum" mean in a classical theory?

Are there configurations of the system of different energies, with no configurations of the energies in between

Although more importantly I guess, can you transition from one to the other

The topological solitons have discrete energies, but they're also invariants of the system I think?

So I'm not sure it helps

I guess it helps a little but I think it may indeed be impossible

Because something something smoothness path connected whatevet

@Slereah ...and the solitons are not the only allowed states of the system! There's plenty of non-solitonic waves even in a water tank where you can produce a solitonic one

Sure but there's non-bound states in QM :p

So that is fine

I don't think you can really have a solitonic version of the hydrogen atom, though

I don't even know what that means, really

Hm

10:14 PM

@Slereah Since your configuration space is smooth (you're varying the action, after all), and energy is a function of your configuration variable, I do not see how this could happen without energy being non-continuous on configuration space. A theory with a non-continuous energy functional certainly is not a "classical theory of least action".

Yeah that is what I suspect

But then why did it take so long for people to accept that it wouldn't work???

What did they have in mind

Although I suppose that the experimental results may not necessarily need actual discrete energies

Maybe only some energies are stable configurations???

I dunno

I guess there is the case of discrete energies for compact spatial dimensions

Although not super helpful

@Slereah People today still occasionally will refuse to accept quantum mechanics, it doesn't surprise me that much :P