The h Bar

12:58 AM

hello @DanielSank

how have you been?

2:48 AM

Anyone interested in cosmic DNA, 80 light-years long? physics.stackexchange.com/questions/482727/… 1 more vote needed

Emilio Pisanty

3:48 AM

@PM2Ring happy to oblige

Emilio Pisanty

4:12 AM

@Semiclassical the wavefunction is obviously real

psi-epistemicists are plain bonkers

(and in that I'm including myself in my psi-epistemicists phases)

(which cover some 35% of the time, I reckon)

4:26 AM

Thanks, @EmilioPisanty You might like to throw a dupe vote at this, or offer a better target. Or maybe even an answer. :D

11 hours ago, by PM 2Ring

I just voted to close this optics question as a dupe: https://physics.stackexchange.com/questions/482724/why-does-a-prism-refract-light-into-a-rainbow The existing answers are not good. :(

John Rennie

4:49 AM

@PM2Ring closed!

Excellent. Thanks, John.

5:58 AM

@RyanUnger no, haven't played any of the series, really

6:21 AM

@ACuriousMind Although I may sound silly, I'm giving you a note, just remember this: November 3 - President Trump Got Re-Elected

@ACuriousMind Just tag me, my prediction back, if you remember, in November 3

7:12 AM

morning

Novalium Company

8:24 AM

@Slereah MoRnInG

Q: How radioactive might the Moon's surface water be? Could it be unsafe to drink?

8:57 AM

I wonder if it's possible to buy lenses with specific refractive index functions

Like a lens with a specific $n(x,y,z)$

uhoh

2

NASA Chief Scientist Jim Greene asks: Can we go (to the Moon) and drink the water? The source of the water in this case would be ice deposits to be found in permanently shaded areas on the Moon. Is there any speculation on how radioactive water on the Moon might be? There are cosmic rays a...

I'm not sure if I should have asked this here or there, one would probably need a neutron and proton flux to do it properly, though there may be literature on this somewhere already

9:18 AM

Wooooooooooooooow!

@Slereah Good Afternoon sir

@Secret Hello bro :) What's up?

such a lens will probably be very hard to manufacture unless n(x,y,z) is smooth

Nothing really, just doing some 3D avatar modelling

Ok

uhoh

@Slereah there are GRIN and GRADIUM lenses with standard index profiles, and some custom profiles would certainly be obtainable with $$money

Wow

are you going to change your avatar? @Secret

9:21 AM

@skullpatrol hello :)

That's a secret

hi pal :)

What are you reading these days?

@skullpatrol Have you heard the sad story of time traveller? He was badly struck in 2019 :(

Wondering because in the ultrastatic limit, geodesics of spacetimes can be approximated as lenses

Wooooooooow, wonderful

@AbhasKumarSinha why is that "sad"?

9:26 AM

@skullpatrol According to the agreement with the government he was supposed to keep the time machine and other devices secret, which he didn't. So, they are not letting him go back

@skullpatrol Interestingly he made some predictions which became true and now he says that Donald Trump will be back as a president (I don't believe it)

Why time travel when you can just overwrite entire sections of the worldlines

Time travel is sooooo yesterday

That guy telling us about future of India youtu.be/eOrO0WEo_Gc

He also showed a video of 2100 , I laughed very badly, you can't hold laughter after watching that video

Each time traveler, from the gazbillion of possible futures. Little did they knew that by 3 November 2020, there will only be two timelines left

9:32 AM

Yes

@secret you also know Chinese?

Woow, very skillful

@Secret @skullpatrol Suppose you to be in their place, if you are struck in past which you don't know because you voilated rules of government, so what's the best thing you'll do then?

Do stuff that triggers the grandfather paradox

@Secret Yes Yes, that's my kind...

so that as the universe tries to reset, you are booted back to the last stable state of the universe (i.e. booted back into the future where you came from)

(of course, one need to store stuff outside of time before doing that)

@Secret So what if there are multiple universes?

Then just use what you can do in the past

Governments can confisticate the time machine, but not the gadgets you brought with you

and if I were a time traveler, I will probably have a time map ready, along with many other time manipulation accessories

9:39 AM

@Secret You came here empty handed, then what?

@Secret You don't have any extra devices

I'll go to bear Grylls to make a show on what to do if you're lost in dimensions and how to get back to original time

Or, I'll start teaching people Kung fu there and earn money and live in peace, without time machine, life would be simple and peaceful

That's the best thing...

Secret's Top Secret

XD

Do we have time machine labs? Or projects? Or journals? Or something like that... I'll read that tho for now

Bye

9:57 AM

Who needs time travel when one possesses a DWO device

10:10 AM

sciencedirect.com/science/article/pii/S0262407919309029

Good luck trying to expand these microuniverses enough so we can visit them

Ajay Mishra

hi @Secret

hi

Ajay Mishra

are you one of the bots?

not a bot but can you tell

10:38 AM

thanks

np

for the defense

pal

:-)

11:31 AM

@JohnRennie How did Einstein knew that gravity is a pseudo force, without any experiment, just basic postulates of SR?

12:00 PM

if we knew how geniuses know what they know; we would have a lot more of them @AbhasKumarSinha

@skullpatrol hiiiii

hello

@skullpatrol Do you know real analysis?

ncatlab.org/nlab/show/Polyakov+action

Polyakov is indeed the energy functional

@Slereah Good afternoon sir....

@Slereah Sir, do you know Real Analysis?

12:22 PM

Not as much as I'd like

but you can try asking a question

also don't call me sir

@Slereah How do you understand complex Epsilon Delta definitions? It's been 30 times since I've read that and still it makes no sense to me. The problem is whole definition is written in single sentence, so after reading a bit later part, I forget the notations and variable names. I can't digest this much. What should I do now?

Got a link to what you're talking about?

I'm beginning to get sick of this guy and his stream of misinformation. physics.stackexchange.com/questions/482788/…

2

@Slereah what?

XD

Loong

12:45 PM

@PM2Ring Hm, I cannot check the content because I get already derailed by his terrible typography.

1:13 PM

@Loong I agree that the lack of a space after a comma is annoying, although he does sometimes remember the space. He's not a big fan of paragraphs, either. But what annoys me more is that he ignores evidence that his claims are wrong.

2

FWIW, I'm kind of getting used to missing spaces after punctuation marks. It appears to be fairly popular with various ESL people (especially those whose mother tongue doesn't use an alphabetic writing system), and I try to make allowances for that. I'm not so tolerant of such flaws when they come from someone who appears to be a native speaker of English.

JMac

2:02 PM

@PM2Ring Yeah, trying to say that "no, it propagates much faster than the speed of sound" without any reason seems pretty weird. I pointed out that his logic kinda fails anyways. He's saying it should move at c, but that's the speed of light through a vacuum, and a nail (using the example there); obviously isn't a vacuum, so he didn't even give the right speed by his own logic

2:22 PM

@JMac Thanks. I'm doubtful that we can get him to change his mind, but at least future readers will see our objections.

Kyle Kanos

Unless his posts get Roomba'd

user280247

Hi

JMac

I'm fine with it being heavily downvoted with upvoted comments disputing it; that's about as good a sign as we can show without just "censoring" everything that is wrong

2:45 PM

Yeah, if we just censor & delete all the misinformation, someone else will just come along and repeat it anyway.

It's a shame that it's a bit impractical to demonstrate that the hammer pulse travels at the speed of sound. It'd make a pretty boring Mythbuster's episode. :)

I used to know a guy who worked in railroad maintenance. Try telling those guys that long chunks of steel are perfectly rigid and they'd just laugh at you.

3:01 PM

@Slereah I chickened out and didn’t get the books

I’ll never know physics

3:17 PM

Is it because book has BOO in it

String theory may please ur analysis bone because it's a lot of boring boundary condition business

An old question about closed spacetimes just got bumped. physics.stackexchange.com/a/482934/123208 He doesn't exactly sound like a crank, but the preamble on his vixra page is a bit grandiose.

If he's just talking about a toy universe with positive curvature, that's fine. OTOH, maybe he's claiming that the real universe is positively curved, and that he's miraculously solved a whole bunch of problems...

4:06 PM

@Slereah I’m gonna try not buying books until I’ve got the time to read them

Therefore preventing having a massive backlog of books I’ll never read

@Slereah Go for the eyes!

sorry, wrong boo

@RyanUnger given what you've got yourself into, I would spend my time making those insane $l^p$ inequalities become childsplay, I don't believe a human being can have intuition for such ugliness :p

4:37 PM

@bolbteppa what

user280247

do you think this paragraph is correct:

user280247

A gas expanding against a piston, in an adiabatic process, can do work even though there is no
change in its kinetic or potential energy ; the work is done at the expense of the
internal energy of the gas.

user280247

It can be shown that DU=W (where DU is difference in internal energy) in simple adiabatic processes, but doesn't kinetic energy of the gas changes?

JMac

@santimirandarp The wording seems a bit weird to me, but I can understand what they are saying. If you're considering the state of the gas as an internal energy, then you wouldn't also consider it kinetic energy. I assume by "kinetic energy" they are talking about the net kinetic energy of the piston-gas system, where the movement of the gas isn't thought of as a "kinetic energy"; but instead is a stored internal energy of the gas

user280247

4:57 PM

UHmmm...

user280247

so it's not about the gas

5:39 PM

@RyanUnger from page 9 on here look at the use of inequalities on pde's, you should really master this stuff to prep for what's ahead of you, more generally the first 4 chapters of the book it's based on

6:36 PM

> psi-epistemicists are plain bonkers

↑ lol! copenhagen interpretation is the epitome of psi-epistemicism...! and its originators were [x] and [y]...

7:53 PM

okay, i've found a rather major problem in the results of my simulator code, but i can't find the root. i occasionally get probabilities that don't sum to 1 for all the basis states, which is obviously really wrong. since it usually happens after some measurement of a single qubit occurs, i'm guessing it has to do with how i'm handling renormalization.

what i'm doing is taking $1/\sqrt{\text{norm}}$ and then multiplying that by the state.

i'm finding the norm by taking the inner product of the state with itself and then taking the square root of that.

is that all correct?

Sounds about right. Is the sum you get slightly off from 1 or wildly wrong?

wildly wrong... around .86

it's probably not floating point arithmetic screwing with me.

Then you likely just have an ordinary bug somewhere :;)

yup =/

ah well, at least i'm getting closer

thanks for your help

8:09 PM

@heather See if you can reduce it to a MCVE. Then bring it to the Python room. Andras may be able to help. He's not into quantum computing, but he is a quantum physicist, so he should be able to see if you've made any mistakes turning your maths into Python.

@PM2Ring sounds good...i might pop by later once i've looked through the code more =)

Have you considered unit testing bits of your code to ensure the individual parts do what they're supposed to do?

Stuff like "this function normalises a vector" should be straightforward to test

yeah, i don't do it formally, but i run smaller simulations that involve just the specific function i'm testing to see if it works out.

i have to head out for now; thank you for your help!

user280247

8:30 PM

guys, I'm struggling with something simple

user280247

maybe someone wants to help

user280247

for adiabatic processes DU=-W_{tot}

user280247

It seems very similar to normal calculations in classical mechanics

user280247

But there is a difference isn't it? The system can change its temperature...or is this reasoning wrong?

Jake Rose

@santimirandarp try and use latex if you can

adiabatix does $not$ mean isothermal

user280247

8:33 PM

but latex isn't enabled in the chat @JakeRose

Jake Rose

It is...

@santimirandarp There are scripts & bookmarklets that can be used to enable MathJax here. I use a bookmarklet on my Android phone. It's not perfect, but it works.

user280247

8:52 PM

:) thanks...@PM2Ring

user280247

it seems strange to me that this systems are 'half way' between thermodynamics and classical mechanics, is there something special about those systems?

Emilio Pisanty

9:21 PM

@ACuriousMind you were thinking of Boo from Monsters Inc? You sick, sick man

??? No, I was thinking of a giant miniature space hamster!

@ACuriousMind I got a perk that lets me eat rotten food

Sounds like it will cut down on medical expenses

oh, you meant in the game

@ACuriousMind Yeah. The "realism" is cut down by abusing the currency system and perks

You can get unlimited money pretty easily

Not using a glitch

@ACuriousMind wait really? i thought you were talking about Boo Radley or something

from To Kill A Mockingbird

9:37 PM

have you seen the movie To Kill A Mockingbird Bird?

yeah

the black and white one you mean, right?

yup

i highly recommend checking out 12 Angry Men

huh...never heard of it before, but sounds really interesting

i'll keep that in mind

hey @HDE226868 how's life treating you

HDE 226868

@heather It's good! I just moved into my summer program on Sunday, and we had an intro to it today. I'm at Columbia doing an REU; I'm with a group doing gamma-ray astronomy. I'll meet the professor tomorrow. Living in the city is . . . weird. But I'm sure I'll adjust.

How are things with you?

@HDE226868 pretty good! almost done with sophomore year - this week, then finals week (most of which will be pretty easy) and then i'm home free

we'll be visiting my grandparents over the summer too, which is great

HDE 226868

9:50 PM

Glad to hear it.

Are you doing any thinking about colleges yet?

a bit. i was pretty sure where i was going to go and then we moved, so now i have very little idea.

@heather hi, where do you live now then? ps re your simulator, another option is comparing it to other systems, esp on small problems that exercise the different parts...

iowa to southern california

i feel like i've mentioned it in here before

maybe not...

southern cal, cool... probably some big city? did 1 of your parents switch jobs?

yep and yep

9:57 PM

you're a golden state fan now?

i don't really follow sportsball

← also has very strong urge to do some homegrown physics experiments for very many yrs, dabbled in it...

sometimes a little baseball

but there i'm primarily in favor of the Minnesota Twins

that would be @Semiclassical's team also

yeah

though investing much faith in Minnesota sports teams seems...unwise

10:02 PM

← esports fan :)

are you still in Rome?

i'm in london now until Friday

← re psi epistemic vs ontic, yikes, slippery/ subtle stuff, was just brushing up & then found to my surprise they are both for LHVs only, and copenhagen ("psi-complete") is excluded by defn. have to think about this much more. physics.stackexchange.com/questions/290522/… arxiv.org/abs/0706.2661

yeah, that distinction doesn't seem to work very clearly for Bohmian mechanics either

@Semiclassical hmmm, more twists? thought bohmian mechanics is fully ontic, thought that was a large part of its rationale...? having hard time getting grasp on this... :|

10:11 PM

yeah, c.f. this bit from the BM entry on the Stanford Encyclopedia of Philosophy:

looking again, Harrigan + Spekkens footnote is now confusing me some more... sigh

"Dürr, Goldstein, & Zanghì (1997) and Goldstein & Teufel (2001) ... suggest that from a deeper perspective than afforded by standard Bohmian mechanics or quantum theory, the wave function should be regarded as nomological, as an object for conveniently expressing the law of motion somewhat analogous to the Hamiltonian in classical mechanics, and that a time-dependent Schrödinger-type equation, from this deeper (cosmological) perspective, is merely phenomenological."

> Note that while Bohr argued for the completeness of the quantum state, he did so within the context of an instrumentalist rather than a realist approach and consequently his view is not the one that we are interested in examining here. Despite this, the realist ψ-complete view we have in mind does approximate well the views of many researchers today who identify themselves as proponents of the Copenhagen interpretation.

The idea that the wave function is a real thing is cray haha, I can't believe people debate this stuff when wave functions nearly lose all meaning in qft

are they saying Bohrs position was "ψ-complete"? and if so how can a "ψ-complete" pov be realist in any way? and how is realism at all compatible with copenhagen? thought they were diametrical opposites... this feels all mixed up to me :(

10:15 PM

@bolbteppa I think the defense to that objection would be that you can still work with the so-called "functional Schrodinger equation" for bosonic QFT (not sure about fermionic)

but regardless it's hard to argue that the wavefunction as a construct has been very productive in QFT

Schrödinger functional

In mathematical physics, some approaches to quantum field theory are more popular than others. For historical reasons, the Schrödinger representation is less favoured than Fock space methods. In the early days of quantum field theory, maintaining symmetries such as Lorentz invariance, displaying them manifestly, and proving renormalisation were of paramount importance. The Schrödinger representation is not manifestly Lorentz invariant and its renormalisability was only shown as recently as the 1980s by Kurt Symanzik (1981). Within the Schrödinger representation, the Schrödinger wavefunctional...

It gives quantum field operators, not like wave functions

"functional schrodinger equation", not "schrodinger functional"

Like it's not your garden variety wave function you plug into $H = T + V$ and solve to get stationary states, wave functions etc

c.f. page 17 here for details : arxiv.org/pdf/0707.3685.pdf

Yeah, same formalism, the Hatfield reference in the wiki sets it up for qft really nicely

Have to compute fun things like compute $\det \sqrt{-\nabla^2 + m^2}$ going down this path :p

10:21 PM

regardless, the status of Bohm vis a vis QFT is not something I find particularly pleasant

I posted some quotes from that Nik paper the other day about this - seems like the big issue is, how can particles have well-defined paths if relativity allows particles to be created and destroyed

ya

Not sure what that is even an issue really, from $p^2 = m^2$ couldn't you just say they become energy and energy-momentum is overall conserved so it's all fine

i'm not versed in it, so I dunno

Yeah, I would love to know what the real issue is

You can even set up Yang-Mills in the Schrodinger functional formalism, let alone fermions etc

10:28 PM

← now suspects there is a consistent/ classical hybrid psi ontic + epistemic system... o_O

That last paper setting up the functional stuff, wonder why that doesn't work

P20: "The pilot-wave models are further formulated with respect to a preferred frame of reference. In the context of a relativistic quantum field theory this will imply pilot-wave models that are not Lorentz invariant. Nevertheless, in quantum equilibrium these pilot-wave models will reproduce the standard quantum theoretical predictions.

Therefore the empirical predictions of the pilot-wave models will be Lorentz invariant, at least when the quantum theoretical predictions are Lorentz invariant [16,17, 70, 71]. There are some attempts to formulate Lorentz covariant pilot-wave models.An overview of these is given by Tumulka [38]. See however also Valentini [72] for an argument that the fundamental symmetry of pilot-wave theories is Aristotelian rather than Lorentzian."

yeeeah...

In QFT they first got results non-covariantly that were experimental, this was enough for the subject to be valid

It's entirely possible, in my opinion, that BM is ultimately only a suitable interpretation for one specific part of QM---namely, non-relativistic wave mechanics---and that outside of that realm it just isn't a productive approach.

Honestly, that couldn't be true, there's no way this can't be extended to qft without being total garbage

I'd bet it can be extended to qft because it steals the basic formalism

enumaris

10:37 PM

any bash expert here? need help with a quick command lol

Like you're simply talking about the enlarging of a symmetry group and it's consequences, Galilean is a subgroup of Poincare, and QFT shows it can be done

I suspect the distinction to be made is "can be done" and "can be done without it being a colossal pain in the ass"

The fact strings can unify GR and QM is enough to show it can be done, even if it doesn't apply to our world it's still possible in some sense, which has been more than enough to validate studying strings for the past 40+ years