The h Bar

Obliv

00:46

jeez who wrote young sheldon

it's so cringe I can't bear to watch it :P sometimes shows up on my feed

maybe it is good outside of the short clips I see idk

Allie

01:37

@SirCumference dude i kept writing this all day today on accident

it was strange

for some reason h bar is just satisfying to write

bolbteppa

07:42

Physics is hard, string theory is hard

Ryder Rude

07:55

hi

Consciousness, a Quantum Physics Perspective

►

his approach to physics is extremely spiritual in nature. i had never seen a physicist like him

he is John Hagelin. he does superstring theory, unified field theory and consciousness research

bolbteppa

John Hagelin

John Samuel Hagelin (born June 9, 1954) is the leader of the Transcendental Meditation (TM) movement in the United States. He is president of Maharishi International University (MIU) in Fairfield, Iowa, and honorary chair of its board of trustees. The university was established in 1973 by the TM movement's founder, Maharishi Mahesh Yogi, to deliver a "consciousness-based education". Hagelin graduated with a Ph.D., in physics, in 1981, from Harvard University, and did several months of post-doctoral research at CERN, before moving to do further post-doctoral work at the SLAC. In 1984, he became...

Ryder Rude

yes.. that's him! His face and style reminds me of Von Neumann

he is extremely calm in any talk u see of him

bolbteppa

I like the fact that he is a proponent of meditation, string theory and David Lynch, however this consciousness unified field stuff looks like the worst kind of nonsense imaginable

If you abstract TM out from all the 'extra stuff', you apparently get something like this

The Relaxation Response

The Relaxation Response is a book written in 1975 by Herbert Benson, a Harvard physician, and Miriam Z. Klipper. The response described in the book is an autonomic reaction elicited by a mental device and a passive attitude that has been used for altered states of consciousness throughout various religious traditions and cultures. The scientific characterization of the relaxation response was initially prompted by research studies on Transcendental Meditation ("TM"), a yogic meditation technique, that was presented primarily to people in the Western world. == Origin == Benson writes in his book...

This unified field stuff looks like a dealbreaker it looks that bad, but maybe I'm being too hard

Ryder Rude

08:14

@bolbteppa oh

@bolbteppa is unified field.theory.not regarded as mainstream anymore

bolbteppa

> by all accounts a gifted scientist, well-known and respected by his colleagues", but that his effort to link the flipped SU(5) unified field theory to TM "infuriates his former collaborators"

> Anderson wrote that two-page advertisements containing rows of partial differential equations had been appearing in the U.S. media, purporting to show how TM affected distant events

Ryder Rude

his wiki says he got into both physics and spirituality during his school days, which explains his current views on physics

i think those initial days shaped him largely

@bolbteppa yes... mainstream physicists tend to reject these ideas.. but it's nice to have someone credible with different views

bolbteppa

You lose all credibility if you start doing things like this, it's a real shame he started going overboard saying this stuff

Ryder Rude

it's not much different from how many physicists r also religious. these views are only complementary to physics, these do not directly affect their physics research

Mr. Feynman

09:16

@SirCumference 💀

@Obliv why cringe? :(

ACuriousMind

09:28

@RyderRude People who are part of a cult-adjacent spiritual organization, are employed by a university belonging to that organization and have a history of clearly unscientific claims are not "credible". Stop pushing pseudoscience as "interesting".

2

Slereah

09:39

there's only one cult here and it is the worship of @ACuriousMind

Ryder Rude

@ACuriousMind the word "cult" carries a negative meaning around it. let's just call it organisation. by credible, i meant that he is credible in physics, as in, he has studied and researched physics.

@ACuriousMind but this experiment is clearly pseudoscientific. it just means that studying physics does not get one rid of all pseudoscientific views

i did not push this experiment as credible. i didnt know about it. i just meant his views on consciousness and quantum mechanics, which are unpopular but cannot be called pseudoscience

ACuriousMind

@RyderRude The negative connotation was fully intended, and I'm not the only one who would characterize this as a cult.

@RyderRude Connecting quantum mechanics and consciousness (or other spiritual stuff) is a classic characteristic of pseudoscience. I feel fully comfortable calling "the thesis that consciousness is a unified field that contains nature's programming code" (description of the video you linked) pseudoscience

Ryder Rude

@ACuriousMind i can understand this to some extent... after reading about that experiment

Silly Goose

what if i define consciousness as the unified field that contains nature's programming code; then, it's a tautology ;D

bolbteppa

This guy was in the What the... and The Secret, that's basically the epitome of the worst kind of quantum woo nonsense

Ryder Rude

09:52

@ACuriousMind i define pseudoscience as claims about scientific results without any evidence. Claims about the ontology are not pseudoscientific, or we would have to classify all of idealism as pseudoscientific when it's a valid philosophy

ACuriousMind

Note: I'm not saying there are no good scientific or philosophical discussions of consciousness in the context of quantum mechanics, just...most of them are nonsense

Ryder Rude

that is understandable..

there is this tendency among some physicists to make fun of all idealism philosophies as pseudoscientic, which is i think is a bad use of the term "pseudoscience". As long as one is conservative about the experimental predictions", it's not pseudoscience

bolbteppa

Linking SU(5) field theories to meditation is not just pseudoscience its lunacy

Ryder Rude

e.g. wondering about QM and consciousness theories is not pseudoscience... saying that mind can influence the moon is pseudoscience

@bolbteppa it depends on if one makes predictions without any basis

simply making falsifiable a mathematical framework, and philosophies about ontology, are not pseudoscience

ACuriousMind

@RyderRude I don't know what "some physicists" (that for all I know you just invented) using the term 'pseudoscience' unjustly for some other philosophies has do to with you posting this nonsense here

You can't defend posting obvious nonsense by saying that sometimes someone else might call something else nonsense too soon

Ryder Rude

10:07

im sorry.... i should be more careful about what i post

Slereah

@bolbteppa which gauge group would it be tho

Sanjana

@ACuriousMind What would you recommend for a good scientific discussion of consciousness in the context of QM?

Slereah

@Sanjana what qualifies as good in this context

Sanjana

whatever ACM thinks to be "good" is good :)

Slereah

There isn't really any good reason to think consciousness should be connected to QM anymore than economics or bees

Ryder Rude

10:14

that is wrong... many physicists past and present have linked qm to consciousness. if they were randomly linking things, many would have linked qm to bees too

to disagree with it is one thing. to say it has no basis is wrong

Slereah

People have linked consciousness to many things

That is just a popular topic to which to apply things

Ryder Rude

random linkages are not comparable with modern trained physicists doing the linking

Slereah

Name 5

ACuriousMind

@Sanjana Nothing

bolbteppa

@ACuriousMind You opened the Pandora's box :p

Ryder Rude

10:16

@Slereah Penrose, Chalmers is a philosopher, Heisenberg, Schrodinger, Bohm

ACuriousMind

I was just making clear that I don't think there's something inherently wrong with "consciousness" and "quantum mechanics" appearing in the same text - but every instance I do know of is wrong at best and intentionally deceptive at worst

Sanjana

@Slereah I once heard NdGT say that it is not good practice to try to explain two not so well understood things in terms of other. (I guess when he says QM is not well understood he just means that it QM is done in terms or probabilities and hence never even meant to be well "understood")

Slereah

Heisenberg, that nazi

Ryder Rude

replace him with Von Neumann

Slereah

Von Neumann wanted to do a nuclear holocaust

Obviously insane

Ryder Rude

10:17

just Penrose should be sufficient then

Slereah

Penrose is getting old

We all know he has lost it

Ryder Rude

he's been into it since he was young though. he didnt make it up in his 80s

Sanjana

@ACuriousMind sad

Ryder Rude

Bohm was also into it at a younger age

ACuriousMind

@RyderRude when did von Neumann write anything on consciousness?

Ryder Rude

10:19

Von Neumann–Wigner interpretation

The von Neumann–Wigner interpretation, also described as "consciousness causes collapse", is an interpretation of quantum mechanics in which consciousness is postulated to be necessary for the completion of the process of quantum measurement. == Background: observation in quantum mechanics == In the orthodox Copenhagen interpretation, quantum mechanics predicts only the probabilities for different observed experimental outcomes. What constitutes an observer or an observation is not directly specified by the theory, and the behavior of a system under measurement and observation is complet...

add Wigner @Slereah

ACuriousMind

@RyderRude I know the Wiki article; had you read it you would know that von Neumann didn't really say anything except point out that you can put the point of collapse anywhere between the measurement device and the observer

If you know of any place where von Neumann wrote anything about consciousness specifically, please list that source

Ryder Rude

yeah..it seems like Wigner added the crucial points. thanks.. i overlooked it

Von Neumann may have said it but the wiki doesnt quote him

ACuriousMind

If not, do you really think skimming Wikipedia articles then making rather big claims about some physicists writing about QM and consciousness is the right way to do this?

Ryder Rude

sorry... i didnt read about Von Neumann properly

ACuriousMind

why do you act as if you are somehow knowledgeable around the discussion of QM and consciousness when your sources are misreading Wikipedia articles? I mean, it's fine to be interested in the topic, but grandiosely stating that e.g. von Neumann is someone who's written good things on the topic when you haven't even read those things is just pointless

just a waste of everyone's time, really

@Sanjana Why is that sad? Why does consciousness have to have something to do with quantum mechanics? Because both seem like magic? :P

Slereah

10:29

The fact that all observation depends ultimately on a conscious observer is also true in classical mechanics :p

Ryder Rude

"because both of them seem like magic?" is a popular but incorrect take on the topic

Slereah

That's why idealism is a thing

Can't see the thing-in-itself and all that

ACuriousMind

@Slereah sure but there's it's intuitive™ ;)

Ryder Rude

im just saying that it's ok if u call the viewpoint wrong. but saying "both of them seem like magic" is not properly replying to why people linked qm and consciousness in the first place

u can call something wrong, but the reason must be proper

people linked qm and consciousness because, like Von Neumann said, the collapse line has to be drawn somewhere between the device and the observer

if u dont want to reject the Schrodinger equation, u draw it at the observer

Slereah

It started with Eddington who was also insane

Ryder Rude

10:33

and then depending on the philosophy, u either get many worlds or a consciousness based interpretation

naturallyInconsistent

There seems to be a requirement for someone to have proper reasons to call something wrong, but the bar is somewhat lowered when it comes to bringing indefensible pseudoscientific woo into the conversation, and of claiming that such is credible.

ACuriousMind

10:47

@Slereah nah, it's a natural part of the physicist lifecycle :P

Sanjana

10:57

@ACuriousMind When you out of all people said "I'm not saying there are no good scientific or philosophical discussions of consciousness in the context of quantum mechanics" I started expecting something very mathematical, or atleast a text which defines what consciousness even is...

Slereah

Consciousness is hard to define

But that is a question best left to neuroscientists

ACuriousMind

you might call it a hard problem, even!

Slereah

In the 19th century many dimensional geometry was the cool new thing and people were wondering if the soul was some 4th dimensional part of us

Ryder Rude

Chalmers has made "Integrated Information Theory" to mathematically identify consciousness, but "consciousness" is an undefined primitive in his theory

Slereah

It is always the latest thing

ACuriousMind

11:01

@Sanjana there isn't even consensus that consciousness exists at all as a meaningful term

Ryder Rude

it's okay to have undefined primitives. "we cant even define subjective experience " is a popular incorrect argument against idealism

Sanjana

If the internet didn't make me conscious of consciousness,I wouldn't be thinking of it :)

Ryder Rude

youtu.be/hUW7n_h7MvQ?si=ZoFQFbPNlWuVCv8r in this video, Witten compares consciousness to the undefined symbols at the beginning of a math book

other incorrect arguments include "people believe in Santa Claus, doesnt mean he's real". these arguments fall apart when u think about them for a minute

Silly Goose

@RyderRude i think one can read ACM's comment with an emphasis on meaningful rather than existing

oh maybe i misread what your comment was responding to

Ryder Rude

@SillyGoose sorry i wasnt disagreeing with anything ACM said. i see the order of the messages makes it look that way

Silly Goose

11:14

is there discussion of a measurement problem in classical mechanics :P

Ryder Rude

ACM only says "consciousness may not be meaningful", which is different from saying "consciousness cant be defined, therefore it's meaningless". the latter is the popular incorrect argument i addressed

no one in the chat made the incorrect argument, but it's one of the most important ones in the discussion of consciousness

@SillyGoose no, because classical mechanics is compatible with hidden variables, hence there is no point of collapse

the hidden variable formulations of QM was made somewhat to get rid of collapse

but there r the "easy" measurement problems in classical mechanics ofc :P. I mean things about limitations of measurement accuracy

Silly Goose

also i could think that one of the characteristics of a classical state is actually not intuitive at all. i am talking of the characteristic that a classical state remains unperturbed upon measurement or upon interaction with an ambient environment

what does one need to give up to believe in hidden variable theory of quantum mechanics?

Ryder Rude

yes..that should be related to the "easy" measurement problems ;)

naturallyInconsistent

There actually is an extremely famous classical measurement problem.

Ryder Rude

@SillyGoose at least one of : locality and non conspiracy

Gerard T'hooft is working on classical theories that r both non local and have superdeterminism

@SillyGoose see this physics.stackexchange.com/questions/32203/… . t'hooft made stackexchange into a discussion forum ;)

ACuriousMind

11:26

@SillyGoose I mean, this is clearly not true in the way you stated it: Plenty of classical measurement techniques change the thing being measured (e.g. if you measure mass in a mass spectrometer, you're changing a lot of about the position and momentum of the particle)

Ryder Rude

t'hooft doesnt participate anymore, maybe because he got warnings for these wierd posts

new research stuff is not allowed on the site

Silly Goose

@ACuriousMind hm well do you know what the characteristic i mean to say is

ACuriousMind

The point is not that a classical state remains unperturbed during a real measurement, but that it is theoretically possible to assign unique values for all observables to a classical state - hence "measuring" those observables in an ideal sense

Silly Goose

well my actual question is if foundations of classical mechanics is a field and has problems as "bad" as foundations of quantum mechanics

ACuriousMind

this should be obvious and intuitive to you since classically a state is given by values of $x$ and $p$ and all observables are just functions of $x$ and $p$

Ryder Rude

11:29

yes. classical mechanics's states have well defined values fundamentally

ACuriousMind

@SillyGoose not really, because there isn't a lot of problems to resolve - the main problem of classical mechanics is that, unfortunately, it turned out not to describe the reality we live in :P

I mean I guess you get stuff like Norton's dome and discussions of causation

Ryder Rude

classical point particle mechanics also has infinite potentials.... but these problems r all mathematical technicalities

nothing fundamental like the qm measurement problem

Silly Goose

@ACuriousMind in real life, I can see assigning a definite (or at least approximate) $x, p$ to something like a baseball. if i take a video of it in a fixed frame, then i can set a coordinate system and etc. but this intuitive assignment and ability to find a definite $x, p$ seems limited to phenomena that a human can see.

also can i really not conjure up some exotic classical observable not dependent on $x, p$ :P some internal d.o.f. or something

or perhaps i should say find a classical system with internal d.o.f

ACuriousMind

@SillyGoose I don't know what you mean here - classical mechanics, by its very definition, says that states are given by tuples $(x,p)$ and that observables are functions $f(x,p)$

you seem to confuse the concept of "classical mechanics" with "the real world" :P

(also the $x,p$ are generalized coordinates so your "internal d.o.f." objection is substanceless)

Silly Goose

well i guess it is difficult to speak of because i am trying to question a reliance on intuition and its relation to the established theory of classical mechanics

ACuriousMind

11:36

I don't know what that means

Silly Goose

@naturallyInconsistent what is it?

Ryder Rude

humans evolved in a classical non relativistic world, therefore they intuit that physics @SillyGoose

Silly Goose

@RyderRude well im questioning that people would even "intuit" classical physics

Ryder Rude

oh

Silly Goose

or perhaps making the claim that it is possibly a lie to say that classical mechanics is "intuitive" but i think such a claim would be hard to argue for without defining a reasonable definition of inuitive

ACuriousMind

11:39

you're obsessing too much about the vague notion of "intuition"

May 3, 2021 at 16:28, by ACuriousMind

imo, "intuition" is just a word for "I have seen this so often I don't need to think about it anymore" like 90% of the time

Ryder Rude

it is a lie, as people used to believe that things would come to a stop without an external force

Silly Goose

the point being to inquire about the nature of the difficulties encountered in developing a theory like classical mechanics versus in developing a theory like quantum mechanics

Ryder Rude

so people did not really intuit the basics of classical mechanics

Silly Goose

right so i feel then it would be inappropriate to call any physics intuitive. it is perhaps a poor pedagogical euphemism for the phrase "get used to it"

ACuriousMind

@SillyGoose I agree - when I say "it should be intuitive to you" I mean "you should be familiar with" most of the time

naturallyInconsistent

11:41

@SillyGoose Imagine you have a fluid. If you want to determine the positions and velocities of every mesoscopic packet, microscopic enough that we arent losing too much information, yet macroscopic enough that things like density and so on are well-defined, then you have to put a lot of detectors in your fluid. But the information they give you is only sufficient to predict for a short time, until the missing bits blow up to wash all your predictions into uncertainty. Now, the important part is

Ryder Rude

people sort of "intuited" the classical concept of position

and velocity

but we needed Descartes to get to co ordinatea

so the formulation of classical mechanics was not at all obvious

naturallyInconsistent

that if you take the limit of zero distance between detectors, i.e. your entire fluid is now just all detectors, you will still only be able to predict for a short time into the future. This is the original butterfly effect.

Silly Goose

i should try to erase "intuitive" from my vocabulary :P

Ryder Rude

note that people intuited what position is, but formulating it using real numbers took centuries

even animals intuit position and velocity. it is a crucial part of survival

millenia ago, we first had mathematicians identifying lines and areas with numbers

naturallyInconsistent

@SillyGoose Remember the whole "How would the motion of the Sun appear to humans if the Earth were the one to rotate?"---The same goes for quantum measurements -> classical measurements.

Slereah

11:46

@ACuriousMind there's tons of discussion of classical foundations

It's not a very pressing issue, but that never stopped people

Ryder Rude

then people figured out that there were irrational lengths. then after centuries, they invented more numbers so lines r completely isomorphic to numbers

Silly Goose

@naturallyInconsistent is there a name for this system?

Slereah

Position is very much not intuited

People debated for centuries whether or not a point made sense

naturallyInconsistent

@SillyGoose Our weather?

Slereah

Euclidian space is not as intuitive as you might think :p

Silly Goose

11:48

@naturallyInconsistent xD

Ryder Rude

that has to do with the technical details. but the vague concept of position is very much intuited among animals @Slereah

Slereah

Well the vague concept is pretty far from classical mechanics

ACuriousMind

@naturallyInconsistent I think we're looking for "chaos theory" if the aim is to get a buzzword to learn more about systems like that :P

naturallyInconsistent

Chaos theory is often introduced from the standpoint of wanting to describe the weather

@ACuriousMind hey, just give meow meow a bit of time to type that out...

Ryder Rude

yes. that's what i was saying too. the tools for the precise formulation of classical mech took centuries

ACuriousMind

11:49

@naturallyInconsistent jinx :)

Ryder Rude

and even then, not everyone intuited Galilean mechanics even vaguely, as people are known to have gotten it wrong

naturallyInconsistent

Sigh, some people will never intuit social norms.

ACuriousMind

@Slereah what, you mean Euclidean space and time are not inner and outer a priori forms of intuition? :O

Ryder Rude

@Slereah what did u mean here? were Euclid's postulates controversial

ACuriousMind

Kant would like a word

Ryder Rude

11:51

people debated parallel posulate for long

naturallyInconsistent

Kant can't have a word. Einstein threw a curveball blocking his path.

though, of course, Kant left too many words

Slereah

@RyderRude very

Silly Goose

what is an alternative to taking (some notion of) spacetime as a priori knowledge

Ryder Rude

@Slereah oh

ACuriousMind

@naturallyInconsistent nah, imagine how long his sentences would have been today where he wouldn't be limited by the space on the actual paper ;P

naturallyInconsistent

11:53

@SillyGoose bolbteppa will be very annoyed if you started going into causal dynamical triangulation

Ryder Rude

now that i think about it, euclid's postulates can be said to be over committed ontologically, as they say lines can be extended forever

Mr. Feynman

Would Kant use LaTeX or Word though?

naturallyInconsistent

@ACuriousMind I would have elected to channel the paper to Fermat instead.

ACuriousMind

@SillyGoose making it a posteriori knowledge instead? :P

Ryder Rude

this, and the existence of points, migjt have been a source of debates

as people back then thought of euclidean space in the physical sense

Silly Goose

11:54

i cannot conceive of what it would mean for (some notion of) spacetime to be obtained a posteriori-ially

Slereah

They had all kinds of objections

ACuriousMind

like, we have our senses, we build a model of our sensory expressions in our head and discover it's useful to label the position of stuff with numbers, bam, spacetime!

naturallyInconsistent

@SillyGoose well, you can sit on it...

ACuriousMind

y'know, classic Humean stuff, tabula rasa-style

naturallyInconsistent

@ACuriousMind ouchie

Ryder Rude

11:55

@Slereah oh

Slereah

If you wish to learn more you can read the pyrrhonists or the epicurians on the topic

They were pretty anti-geometry

Ryder Rude

i will check it out..

Slereah

I'm told that the sophists were also quite against it, but no writings survive alas

Silly Goose

but in what does an a posteriori spacetimer think they exist in before their a posteriori knowledge was obtained

Ryder Rude

were there gang wars between them :P

weird that people back then subscribed to schools

Silly Goose

11:57

well it's not a problem to not know what one is i suppose

or is in

ACuriousMind

@SillyGoose your mistake there is assuming any notion of objective existence :P

Slereah

They certainly wrote pretty mean things

ACuriousMind

Hume is not called a radical skeptic for nothing :P

Ryder Rude

oh :P

Silly Goose

i'd like to see a definition of knowledge to an a posteriorist :P

ACuriousMind

11:57

that's not the term, but: go read Hume

Ryder Rude

i dont see physicists today having a school surname

maybe philosophers do

Silly Goose

well i sympathize with hume's sun business...but it is not very useful in day-to-day life as deemed by society

Relativisticcucumber

Slereah

Physicists originally was a school surname

ACuriousMind

Hume was apocryphally more or less the trigger for Kant to develop the whole line of a priori/a posteriori distinction because he disagreed so much with Hume grounding everything in the senses

Ryder Rude

11:58

lol

Slereah

It was the philosopher who dealt with natural philosophy

Mostly guys of the platonic school

Ryder Rude

people today dont have badass titles... "astrophysicist" , "particle physicist" , etc

Slereah

Hume mostly just infuriated all 18th century philosophers into doing the modern philosophy

ACuriousMind

@SillyGoose if you care about usefulness to day-to-day life what are you doing in a physics chat?

Relativisticcucumber

did bolbteps leave the chat bc they were annoyed 0.o

money in the bank!

Silly Goose

12:01

well i don't care about usefulness in day-to-day life that much :P i care about eventually being able to work on something interesting to me

but i personally think people in general operate on a day-to-day level and also a more abstract level and switch between the two depending on the occasion

naturallyInconsistent

@Relativisticcucumber defo winning at mah job

Silly Goose

@Relativisticcucumber all the times i said bundle

naturallyInconsistent

@SillyGoose cuddle bundle!!!

Silly Goose

should i read a treatise of human nature :P

how is this book cited 30,000 times 0.o

ACuriousMind

Let's perhaps not have celebrating annoying other users on the starboard, alright?

Ryder Rude

12:07

wiki says Hume introduced the problem of induction

i guess other people had to have known it before him but Hume populaised it

Silly Goose

"I believe it will not be very necessary to employ many words in explaining this distinction" XD

Ryder Rude

is Hume readable in terms of vocabulary?

philosophical writings tend to over complicate things

Slereah

Hume isn't too tough to read

Silly Goose

here is a sample to judge

Slereah

He is no Kant

Ryder Rude

12:10

@Slereah i will read then. thanks

@SillyGoose lemme see

Silly Goose

there is a link to his "a treatise on human nature": files.ethz.ch/isn/125487/5010_Hume_Treatise_Human_Nature.pdf

is an entangled state a simple or complex perception :P

Slereah

Do you perceive entangled states

Ryder Rude

@SillyGoose after a long time, i found a philosophical text enlightening

naturallyInconsistent

pity the darkness

Silly Goose

@Slereah well hume does not define perception :P

Sanjana

12:15

Ryder Rude

ive always wondered if thought was a qualia

Silly Goose

so i guess im not sure. but if an apple is an example of somethign that can be perceived i would assume an entangled state also is

Ryder Rude

hume seems to say it forms a spectrum with other qualia

Sanjana

What is the boundary condition corresponding to outgoing waves and why is it equivalent to that particular pole prescription?

Ryder Rude

some philosophers would say only thoughts exist and feelings dont exist, and thoughts are pure information. but even thoughts are a feeling

Silly Goose

12:16

well maybe hume defined perception elsewhere explicitly or implicitly, but i have not seen an explicit definition in this work preceding the first mention of "perception" and i am uncertain if it has been defined implicitly in this work

Ryder Rude

@SillyGoose it has the look of a modern text

Hume might be my favorite philosopher already

Silly Goose

after doing some mathematics and physics philosophy seems a bit more approachable

ACuriousMind

@SillyGoose "perception" here is used in its dictionary meaning (1b here) of "any mental image" - it's just anything we "see in our mind"

Silly Goose

hm well i am intrigued to see how hume relates ideas to knowledge...if he does

Ryder Rude

@SillyGoose what philosophy texts did u like reading

Silly Goose

12:25

i haven't really read many. i liked some sections of aristotle's nicomachian ethics and some sections of aristotle's poetics.

but i think i liked such works because they were somewhat understandable and also helped give me a notion of what "western thought" comes from and looks like in relation to other types of thinking

so not really for the philosophical content per se

naturallyInconsistent

@Sanjana that is googleable. It is a rather important condition and comes from us imposing causality

Sanjana

@naturallyInconsistent I have done this in case of wave equation and KG equation where the condition indeed comes from causality. Here I am dealing with Helmholtz equation instead...

Silly Goose

i feel like philosophy texts are the ultimate instance of "the exercise of left to the reader" :P but in this case the exercises have no solutions

2

naturallyInconsistent

@Sanjana Helmholtz equation also comes from trying to solve the wave equation. It is the same conditions, even if we start applying them to further and further applications that dont map onto waves any more

Ryder Rude

yeah. philosophy is annoying for that reason

i sometimes feel all the philosophy ive made is all baloney

it's because there's no depth..

maybe it's just how i understand philosophy or maybe philosophy is like that

Sanjana

12:33

@naturallyInconsistent Yes, I got this from wave equation itself by fourier transforming in time only, but still I don't understand why the pole prescription is like that... I mean, I do think there should be some PSE answer on this which clarifies this, but I can't find it

When you are free, can you please send me a reference or something? I think it is a pretty well discussed issue

naturallyInconsistent

@Sanjana do you remember it from QFT or from wave equation or KG equation? The argument is exactly the same. The integral is not-well-defined, but we swap it for a well-defined contour integral as a shorthand to remember what well-defined integral we are actually trying to do

Sanjana

@naturallyInconsistent Yes I remember why we had to do this, but I am asking why does this particular prescription correspond to the physical problem of outgoing waves... E.g. I know the arguments for pushing the pole to the LHP for the retarded GF for wave eqn/KG eqn. Similarly, I wanna know why we are putting one pole in the UHP and one in the LHP in this case

That is one way of defining the integral out of others, why does that way correspond to outgoing waves...

Tong's notes says what Jackson says "it's obvious"

Silly Goose

hume pulled out the bijection $\varphi: \text{SimpPerc} \to \text{CompPerc}$

naturallyInconsistent

@Sanjana oh dayum. They arent helpful. It has to do with whether you are even allowed to close the contour in the UHP or LHP when you consider the input variables, and then you will pick up the contributions. A brief check then tells you if your choice is causal, anti-causal, retarded, advanced, etc.

Sanjana

@naturallyInconsistent Yes...I know that too. I know that we should close the contour in such a way that the semicircular part gets damped and then if we include both the poles then we get retarded (for LHP), advanced (for UHP) and Feynman/anti-Feynman if we take one of the poles.

In the snapshot I sent, they are taking the Feynman and anti-Feynman cases, my question again is what does these have to do with an outgoing spherical wave's b.c.s

naturallyInconsistent

12:47

@Sanjana The closing of the contour is fixed by the input variable. Whether you nudge the poles which way, is the thing that defines the very integral itself, and that also determines if it is Feynman, anti-Feynman, etc

Sanjana

@naturallyInconsistent Hmm that's what I said. Now, my question is... what is the relation of that particular pole prescription with the outgoing spherical wave b.c.s

naturallyInconsistent

@Sanjana errm, those are related? You can check that too. Isn't there some asymptotic form for you to check whether the waves are outgoing or not?

gtg

Sanjana

Ok.

But I still don't get how does that pole prescription correspond to outgoing waves only

ACuriousMind

13:19

@Sanjana DanielSank has an excellent answer on the relation between pole prescriptions and damping of oscillations ("waves") here - note that one way to close the contour there corresponds to $t>0$ ("outgoing") and the other to $t<0$ ("incoming")

Sanjana

@ACuriousMind But there's no $t$ in Helmholtz eqn.

Thanks for the ref. though

ACuriousMind

@Sanjana ...why does it matter?

$x\ll 0$ as "incoming" and $x\gg 0$ as "outgoing" makes the same kind of sense to me

Sanjana

@ACuriousMind What is $x$ here? In that integral we have only $r$ which is always greater than zero

And I still don't get why is there a $-i \epsilon$ in the denominator like that. I mean it could be that $(k \pm i \varepsilon)^2$, but it isn't...and that seemingly is decided by the fact that we are looking at "outgoing waves".

Jackson guesses the correct G.F. avoiding contour integrals and pole prescriptions (from knowledge of G.F. of Poisson's equation). The snapshot is from Haber's handout on radial green's function expansion.

bolbteppa

13:44

@Relativisticcucumber Definitely not annoyed, you'd be poor!

Sanjana

(With reference to my 2nd last text, instead of $k$ it should be $q$ above)

Sir Cumference

Had a weird dream where I was trying to figure out whether it's $2+2=4$ or $2 \times 2 =4$

3

Slereah

it's neither

Sir Cumference

well at some point i figured maybe it's 2 to the power of 2 equals 4

lucabtz

14:47

@ACuriousMind you mentioned before you didnt like the academic world and thats why you parted from academia. did you do a PhD? I am currently having similar thoughts and im not sure whether or not to pursue a phd

ACuriousMind

@lucabtz no, I didn't do a PhD (but many of my now-colleagues did and plenty of them don't regret it)

lucabtz

@ACuriousMind what do you work in?

ACuriousMind

software engineering, specifically linters and other quality tools for programming languages

lucabtz

@ACuriousMind your collegues have PhD in physics or information technology though?

ACuriousMind

plenty of my colleagues are math or physics PhDs - there's a running gag that SAP stands for Sammelstelle Arbeitsloser Physiker, which is German for "collection point for unemployed physicists"

some are trained computer scientists or IT people, but they're not even the majority

lucabtz

14:56

@ACuriousMind oh i see

Slereah

@ACuriousMind Quite common

ACuriousMind

yeah, it's not specific to this employer, software development is full of STEM people who didn't stay in academia

lucabtz

@ACuriousMind yeah im aware

bolbteppa

Think of it not as the end/highest-stage of your education, but instead as the very beginning/training-wheel stage of an academic career, and that you're asking someone to personally spend years preparing you like a Medieval apprentice to do that focusing on new stuff (not studying out of books), you also just need to be sure the opportunity cost is not too great if it all ends up not working out, which statistically is a real possibility

(In reality people treat it as the end stage of their education and figure out during that that they'd prefer to go to the SAP and sometimes that's valued but often its not)

lucabtz

@bolbteppa yeah i dont really know. i have been on a break for a month. gonna go to journal club this thursday and hopefully i will be back into the ideas of wanting to pursue PhD as i was before

i dont really see it as an end though, of course it is more of a start if i stay in academia

ACuriousMind

15:18

It's really a very personal decision - I know people who enjoyed their PhD immensely even if they already knew they wouldn't stay in academia afterwards, I know people who were miserable during their PhDs and still stayed in academia, etc.

Mr. Feynman

15:49

I'll quit my PhD before starting it

The only part of Physics I'm interested in is filled with people fighting over interpretations and it takes a god-tier mastery to do anything relevant :'(

Slereah

what part would that be

QM people don't argue that much over interpretation

imbAF

If one were to draw comparison between Fock states for photons and eigenstates of the quantum harmonic oscillator, one could see similarities between the eigenvalues of the corresponding eigenstates. In the QHO an energy eigenvalue is of the form $E_n=\hbar\omega_n(n+\frac 1 2)$. If we were to keep $\oemga_n$ fixed but increases n, that would translate physically into oscillations of same frequency but larger amplitude. Now for a system of photons, if the system would be in a fock state, the

corresponding energy would be again $E_n=\hbar\omega_n(n+\frac 1 2)$. But is it correct to say that here one cannot keep $\omega_n$ fixed and increase n, because that would represent a different state, since the nr. of particles, photons in this case, is fixed for a fock state. Would this be a difference between QHO eigenstates and eigenstates of the number operator ?

Mr. Feynman

@Slereah not "interpretations" literally. I mean things that are still far from any experimental verification and people are basically ready to kill each other for that

naturallyInconsistent

16:09

@Mr.Feynman what part is this?

lucabtz

@ACuriousMind yeah i guess

naturallyInconsistent

@imbAF you misunderstand the situation in photons. What we are really doing is akin to first doing normal mode decomposition in classical physics. Find the waves, the fixed $\omega$ and $\vec k$ that describes each particular type of possible collective motions, AND THEN quantising them. So, in your photons case, you have already fixed $\omega$, and then working out the quantised amplitudes you are allowed.

Note that in particular, $\omega$ is a continuous quantity, whereas the energy is quantised in units of $\hslash\omega$, i.e. $E=n\hslash\omega$

This means that energy is quantised on a continuous quantity. It is simultaneously quantised and continuous.

imbAF

I don't understand, how is that possible? And most importantly of all, doesn't it depend on the situation? If you are in a cavity, you would have discrete values, no?

But still I don't understand what you mean

naturallyInconsistent

In a cavity, yes, then $\omega$ is only allowed discrete values, but the energy is still quantised in terms of them. Then energy is no longer continuous

imbAF

And, would my analogy to the QHO be accurate?

naturallyInconsistent

16:16

Somewhat, but again, the $\omega$ are technically supposed to be fixed as you increase $n$ for that specific $\omega$

imbAF

but can you do that? Because in my class we said that the fock states, assuming the system (what is the system??), is in such a state

have definite photon numbers

or particle numbers

so, if you were to increase the index n, then you'd go to a new fock state

which I believe, is characterized by a new $\omega_n$

unless it is not, and you can have different fock states of same omega, meaning the difference between fock states is in the nr. of particles and not the frequency

naturallyInconsistent

We have somewhat no choice but to have to start with quantised quantities that are idealised to not be interacting with themselves. i.e. photons that are not interacting with other photons

@imbAF this alternative is the one that is correct.

imbAF

I see

@naturallyInconsistent regarding this

naturallyInconsistent

Between stat therm and the move from QHO to phonons and photons, the professor is supposed to emphasise to you multiple times that we are doing a swap in interpretation, from "one QHO, excited to higher energy levels" to "one mattress of many coupled springs, now re-decomposed into coupled modes, and the $n$ is now recast as number of photons in that wave mode, rather than energy level of the same QHO"

imbAF

are you using mode and state interchangeably ?

To me mode is something classical, I mean we mostly dealt with modes of the light wave in classical optics

Then in quantum optics, we are talking about the state

But I believe that is not correct right? The state must contain info. about the moe

mode*

@naturallyInconsistent in TE modes, the magnetic field might have components alongside the direction of propagation of the light wave?

naturallyInconsistent

16:27

No, I am not. In fact, it is quite delicate and worth talking about. In a Fock state, you have to specify how many photons are in each mode. So, something like $\left|n_1=2,n_2=3,\text{else zero}\right>$

Where I am talking about mode as in normal modes from classical mechanics.

imbAF

but the thing is, what should I understand with mode

you have gaussian mode,

naturallyInconsistent

@imbAF yes.

imbAF

Hermite-Gaussian mode , Laguerre gausian mode, TE,TEM, etc

these are all modes

I am currently doing a threat for this issue of mine

naturallyInconsistent

@imbAF any set you like, that is sufficient to span the part of the Hilbert space that you are caring about.

imbAF

"that is sufficient to span the part of the Hilbert space that you are caring about." what you mean by this ?

naturallyInconsistent

16:34

Well, if you have a quantum system, the states in it live in a Hilbert space. If your choice of set of normal modes to consider is sufficient to form a basis for the entire Hilbert space, with no overlap, then that is the best. Typically, though, we only care about a subset of the entire Hilbert space, e.g. just the spin-half part. Then we discard, say, the position dependence and just focus upon the spin-half part. As for the many modes, I worry that your "basis" is overcomplete

If it is overcomplete, you can reduce down to a basis, but it is typically easier to work with a "basis" that spans, but has overlapping parts that you find some way to work around.

Mr. Feynman

@naturallyInconsistent I mean, basically all of HEP that's beyond the SM

naturallyInconsistent

@Mr.Feynman oh, the sexy part. no wonder

imbAF

@naturallyInconsistent "normal modes to consider is sufficient to form a basis" aren't we using quantum states to form a basis?

naturallyInconsistent

@imbAF Well, remember, you have to be much more precise with what you mean by state now. If you already have Fock states defined, then you are not using them to form a basis. Instead, you tend to be using the non-interacting, independent, one-particle states as a basis to expand your Fock states. Those are what you might think as the good old quantum states.

Whereas, to avoid having to talk about this mouthful, and to connect better with what it is we practically do, I talk about classical normal modes as being the stand-in for those one-particle states.

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