I could also have taken Hebrew, but I had no time since I also wanted to take all the science classes. In retrospect, I could've done without chemistry (the teacher taught us nothing).
@infinitesimal Yes (as is the normal path for people who study at a university). It was a "humanistic gymnasium", which means it has a focus on ancient languages and the accompanying history.
@ACuriousMind you said you didn't VTC, that you have time . . . but you did VTC. The question is clear: Q. comm. scheme transfers quantum states without transmitting physical particles. . . . * if physical particles did not carry information between sender and receiver, what did?* . . . scientists may be able to transmit info. over vast distances without the need of a physical medium . . . (Could there be) a fundamental reality of info. that informs matter as to what states it can be in?
@infinitesimal Haha, yeah, I don't think there is more to say in general
@Sofia When I said I did not VTC I hadn't. I didn't want to cast the first vote but see whether others thought about the question as I do. The upvotes on my comments and the fact that two close votes were quickly cast without me showed me that I'm not alone in my attitude, and then I also VTC'd.
@Danu Of course the designation of today as pi day (and of course, pi-moment an hour ago in my time zone) depends on the goofy month-day-year way that we write dates in some parts of the world. Which didn't stop me from saying "Hurrah!".
@ACuriousMind I don't attack you - that has to be top clear. But I'd like to tell you that the user saw that there isn't need of particles, info. travels without particles, and the question is, are there particles at all?
@ACuriousMind And I believe you in what you say. Now, I am a system analyst, I had to do with customers that don't know to express clearly what they want.
@Sofia It is not our aim here to sort out what the people who ask questions here "really want". They ask a question, we answer it. They ask an unclear question, we ask them to clarify and don't answer it.
@ACuriousMind you didn't have such chances until now (I think). This is why, when I see a nebulous question, I get into it according to my professional skills. You say we ask them to clarify and don't answer it. We ask them, or we VTC?
@infinitesimal behind what seems a stupid question, there may be a great question.
@Gowtham Well, 5 VTC put a question "on hold", but "on hold" and "closed" are the same thing. The "on hold" wording is merely intended to stress that questions can (and will) be reopened if the reason for the close votes is addressed.
@ACuriousMind The O.P. browsed all sort of material. Now, this is the problem, and it pops up all the time: if no need for particles, then why particles, why states, etc. As to the article it's title is so misleading that even I thought that we have here some FTL proposal. Well, there is no FTL, is just seems to be a very economical processing of a single photon passed between the two parties.
@ACuriousMind well, I'll try to contact the user, and proposed reformulation, if he/she didn't get offended and didn't turn the back on us.
@ACuriousMind as to GR, there I have no idea.
@ACuriousMind by the way, the article made so much noise because its economical way of passing info. It's smth. connected to Vaidman-Elithur + Zeno effect. It's a blessed thing that such articles are brought to our attention.
@Sofia You seem to still have a strange impression of what this site is supposed to be. We are not here to discuss interesting new articles, assess new theories, or debate the "correct" interpretation of physics. (Well, we can do those things in chat, but it's not the purpose of the site)
@KyleKanos , @ACuriousMind We cannot accuse the O.P. of ignorance. It's because of the ignorance that they ask us. As to what you say that are not here to discuss interesting new articles, do you know someone who has A Curious Mind?
@infinitesimal I know that you are a fine and lovely person, I don't feel offended.
@Sofia Closing a question is not "accusing" the OP of anything, it is just saying the question isn't clear in physical terms, in this case. It is also not the purpose of this site to help individual users to learn express themselves in an intellegible manner.
also OP pretty much answers the question himself, doesnt he ? "So General Relativity would be describing matter at large scales and QM would consist of a non physical wave function of information that describes what states matter can be in. "
@KyleKanos I don't deal with gravitation, but I heard of Q. gravitation - the user also may have heard - well, that part of the question I didn't delve my nose into. But about the QM part, it deserves an answer. I suppose you saw what I wrote to the Curious Mind, it's the way the things are presented in articles, no need of particles so it's really misleading.
@KyleKanos Yeah, I must say I like that way of writing dates, too. It also organizes folders and files that are named with their dates correctly if you sort them alphabetically, as usual.
@ACuriousMind My pictures folder is sorted that way: ~/Pictures/YYYY/MM/DD. It drove me batty that my first camera phone saved it MMDDYYYY format while my 2nd camera phone does it the proper YYYMMDD format
@ACuriousMind Ah you!!! The kindness in bone and flesh!!! It is also not the purpose of this site to help individual users to learn express themselves in an intelligible manner. Maybe it's opposite, some effort from us to understand what they ask? We are intellectual people, physicists. By the way, were you a teacher, or not yet? When you are, you'll see.
@KyleKanos @KyleKanos I think the question has to be split.
General relativity, also known as the general theory of relativity, is the geometric theory of gravitation published by Albert Einstein in 1915[1] and the current description of gravitation in modern physics.
Quantum mechanics (QM; also known as quantum physics, or quantum theory) is a fundamental branch of physics which deals with physical phenomena at nanoscopic scales, where the action is on the order of the Planck constant.
@Sofia What? How? The guy's question is about the incompatibilities of GR & QM, how on earth do you propose of splitting the fundamental aspect of the question!? That makes no sense
@infinitesimal Hmm, maybe the phrase "very basic" was incorrect (they do seem to require knowing something about physics). But it does indeed state what the theories describe
@Sofia You are interpreting the question in your own, particular way. The question, quite clearly, is about combining GR and QM, not about whether there are particles or not. Me being kind or a teacher or any other thing has nothing to do with that.
@ACuriousMind One (very minor) advantage of year-month-day, is that if you use the filenames as meta-data then alphabetical sorting is also chronological sorting.
@infinitesimal About date? No, they don't anywhere I've been and been able to understand the language (not saying much). You can sort of defend the month-day-year thing on that basis.
When we're talking about dates the planning horizon is most often a few weeks long. Meaning that month changes are common enough to need disambiguation, but year changes are not.
But for long term purposes, you need to disambiguate both and the question is how to order the information.
@StanShunpike the first one, you will probably have trouble if you don't read them in order, again see the amazon reviews and online discussions of these books, these videos mediacore.ictp.it/categories/classical-mechanics follow the book pretty closely , also yes about the random variable.
Well volume 4 begins using things from the middle of volume 2 and volume 3 and goes on like that the whole way, I don't understand your eagerness to jump into the heavy stuff when you have to develop the basics like, I mean angular momentum, spin, the atom, interacting electromagnetism, will take forever tbh
You are guaranteeing yourself not to learn anything, you'll just have to memorize, I mean if you want the quick shortcut route just watch Susskind's lectures online
Well, define jump ahead. For Classical E&M I am reading Jackson and Griffiths. For QM I am reading Ballentine and Griffiths. It looks like I'm going to add Landau volumes 1 and 2. For spinors, I'm reading Cartan's introduction. For Hilbert spaces, I'm reading Kolmogorov and Fomin. Does that qualify as jumping ahead? I am reading Quantum Field Theory for the Gifted Amateur, which is like QFT for dummies.
"It's a lot of amazing and mathematically accurate work that is going to lead to many followups but one may still have the feeling that the real "paradigm shifts" are mostly taking place elsewhere. So while Witten writes fundamental papers in the early stage - that are later followed by lots of other researchers – I would still say that there has almost always been a "paradigm shift" done by someone else before Witten wrote his important paper." Fighting words?
@bolbteppa So, does my course of study makes sense? If not, how would you approach it? I mean, I am learning a lot, so I'm pleased but if there's a better way to go about it I'm open to it.
@Sofia quixote the question is indeed a mixed up mishmash but maybe something to salvage; try more open minds elsewhere; why dont you just bite the bullet & take the red pill? =D
@StanShunpike I think bolbteppa is saying you should do the "usual" progression: Classical mechanics -> Electromagnetism & SR -> Quantum mechanics & Statistical physics -> QFT & GR instead of jumping into QFT without having a proper grasp of Hamiltonian mechanics and QM.
I don't think I would be able to generate new physics ideas. I would make a good physics teacher, but I don't think I wanna be just a teacher. I think I have a better chance at generating new economics ideas because psychology and the way people think comes intuitively to me.
@ACuriousMind something somewhat lost on you & many here (se & even wider in scientific fields), science is not a static entity but evolves/ advances thru, roughly, (new) interpretations
@vzn Well, as you might have guessed, I don't think it has to be that way. I don't think it is that way, I don't see what the major achievements of physics and/or other sciences have to do with interpretations. Ontology is irrelevant for predictive power and technological progress.
@ACuriousMind in early stages of new theories it is difficult to separate the two. anyway there are a lot of cutting edge new observations in the QM area & personally think something is "afoot" so to speak.
@StanShunpike well you've got QED in your QFT book so if you can hack it by all means go ahead, and you could use Susskind's videos theoreticalminimum.com to get the core ideas, I cannot bear the headache of studying things and coming up against concepts that require reading half a book to understand one equation anymore, but if you can handle it and read those books to get the core ideas go right ahead!
guess my pt is something like the following: "scientists" who always say "there is nothing new in these results/ papers/ etc" will eventually be wrong & ultimately, unscientific
@vzn You are free to think so :) I think it's a lot of hype about results that are interesting and achievements in and of themselves, but nothing that "shatters our foundations".
@StanShunpike yeah so there are a ton of ways to do it, you can do it the classical thermodynamics way (in Young/Freedman University Physics) or you can do it the thermo-stat_phys way as in Huang's 'intro to stat phys' (or the Berkeley physics series book) or you can do it the stat_phys-thermo way as in Landau (and kind of Pathria)
@vzn There's a quote from Schopenhauer: (translated) "Every truth runs through three stages: First it is distorted and ridiculed. Then it is vehemently fought against. Finally, it is accepted as self-evident"
@bolbteppa what do you mean different ways? there are different ways to study thermo? Like are these different backgrounds? Like is one more grounded in one discipline than another?
@vzn We don't have to choose a focus more specific than "theoretical physics" (that may be part of the problem), but my specialty is probably QFT, in particular gauge theories/non-perturbative approaches
@vzn Yeah, the problem is that not having the answer doesn't necessarily mean the question is interesting ;)
"When I am posting this message, it's the the birthday of Albert Einstein, also known as the π day. More precisely, as you may check, this blog post was written on 3/14/15 at 9:26:53.589793238... am"
Alright, question guys: so I'm making a list of basic properties that can be described using quantum state vectors. So far I have the following: position, momentum, angular momentum, spin, energy levels. Is that it?
@ACuriousMind Honey, I see a list of deleted answers of mine. Part of them are no more in the site. How to delete them permanently, i.e. from the list of deleted answers?
Can I clear Deleted Questions & Answers by me?
No, you can't.
Once they are older than 90 days they will no longer appear in that list.
As a side note - we don't "permanently delete" things. Deleted items are not rendered for users except for the author, moderators and high reputation us...
After 90 days, the list is cleared it seems
But that does not mean the items are permanently deleted
@KyleKanos Thank you. In the list of deleted answers there are old things that, if I try to get in, I see that they don't exist in the site. So, they are of no use to me anymore. So, you say, whatever is older than 3 months will be discarded from the list? If so, it's good.
A.k.a. the 2015 Questions to Answer Refactoring Konversion (QuARK)
A.k.a. the great cheese move of 2015.
TL:DR; we are looking to change the navigation of the question lists on the site. We are not looking to remove any functionality or break any existing link. This is not final. We’re taking...
@ACuriousMind So two things I want to verify: (1) the time evolution operator tells us the a wave function $\psi(t)$ given an initial wave function $\psi(0)$ and (2) this is a consequence of the time dependent SE and the basic properties of the exponential function. Correct?
@ACuriousMind Oh, I didn't realize the action could only be with a Lagrangian. I'm not surprised I'm confused about that though. I still don't get QMechanic's definition of the Hamiltonian version of the action.
There's something called the Feynman-Kac formula though, which says that $\mathrm{e}^{\mathrm{i}\int_{t_0}^{t_1} H(t)\mathrm{d}t} = \int_{q(t_0)}^{q(t_1)} \mathrm{e}^{\mathrm{i}S[q,\dot{q}]}\mathcal{D}q$, I think, where the integral on the RHS is the path integral.
@StanShunpike There's also not "the" action. You can also have something called the "abbreviated action", which is $\int p \mathrm{d}q$, and obeys Maupertuis' principle.
And you can have the "total Hamiltonian action" or the "extended Hamiltonian action" and several other things, it really depends on context
@StanShunpike I've written essays on this chat about how the Hamiltonian is just a Legendre transform of a Lagrangian, the action can be written in Lagrangian form or in Hamiltonian form
@bolbteppa QMechanic writes $L_H (q,\dot{q},p,t)$ and I actually didn't get until just now that when we Legendre transform the Hamiltonian, L becomes a function of p
@StanShunpike that is physically motivated in Landau book 1 (last chapter) and mathematically motivated in Gel'fand in 3 different ways so you have 4 similar ways to think about it waiting for you ;)
@StanShunpike It's...not that right. You usually go to a QFT picture to describe the quantization of the EM field, but if you just have a photon, you can do QM and say it has a wavefunction. The problem is that QM can't really deal with absorption/emission, so there's not much you can do with it.
Does anyone here like scotch? I'm not really fond of the smoky flavor. And the particular one I am drinking right (Glenfiddich 12) now has a bit of a fruity aftertaste.
@DanielSank Oh, that. Well, a bit strong, probably, but you need to use ad-hoc stuff like Fermi's golden rule, which is not really well motivated from QM
I can easily write down a Hammy which couples say an atom to a big collection of harmonic oscillators. No QFT needed there, and I still recover emission.
@dmckee Heheheh, I just never heard that applied to a rant. I like it.
@StanShunpike You're demanding blanket statement from me I won't give ;) If you are doing non-relativistic QM, everything is a quantum state that is equivalently described by a wavefunction, and every quantum state obeys the SE.
@ACuriousMind I mean, to me thinking of a discrete set of modes as a "QFT on a lattice" is the proverbial "going around your elbow to get to your @$$" :-)
@0celo7 yeah it's complex, my friend gave me half a years-old bottle of his since it made him (literally) sick and I loved it, this one will be the first I've had in years! :D
Are the only quantum objects elementary particles, atoms, etc? Like when I read about qubits, they talk about a super position sometimes between Heads and Tails. But the only true known quantum mechanical objects involve the usual microscopic pieces of matter right?
I am sitting in front of a superconducting qubit setup right now. I have seen it violate Bell's inequality.
Quantum mechanics applies to everything. The reason you don't normally see superpositions of big stuff is that they interact with so much random garbage (i.e. air molecules flying around) that the superpositions decohere on time scales so incredibly short that you can't see them.
What really makes something quantum mechanical is whether or not you have access to all of the information in the system. If a superposed state touches a lot of air molecules, some of the information is transferred to those air molecules (this is "entanglement"). Once this happens, in order to see quantum interference effects you'd have to get all of those air molecules to participate in your experiment.
However, when we take even very large things (like superconducting circuits) and isolate them from all the other stuff in their physical environment (i.e. by putting them in a vacuum chamber near 0 Kelvin) we see all the usual quantumy things happen!
So...since everything is physical, all of it involves quantum mechanics, but most of that information cant be accessed expecially when it comes to large systems
The entire business of experimental quantum computing is trying to make a big system where all the quantum information is contained and doesn't leak out into the environment.
@0celo7 what is the next number in this sequence: 1, 1, 2, 3, 5, 8, 13, 21, (...) [answer: it's pi because screw you that's why! My sequence, MY rules!]
@DanielSank why did Roger Penrose try to claim quantum gravity is a factor in neural computation? The more I learn, the more crazy that seems to even suggest
Can I clear Deleted Questions & Answers by me?
No, you can't.
Once they are older than 90 days they will no longer appear in that list.
As a side note - we don't "permanently delete" things. Deleted items are not rendered for users except for the author, moderators and high reputation us...
