@HDE226868 Depends, DavidZ usually prepared agendas and we had some constructive meta discussions, but he's busy lately and I don't see any real issues we should discuss, so... ::shrug::
Hey guys, was just reading a paper on orbital decay due to gravitational radiation and I came across a formula that the author derives for the luminosity in the gravitational waves. How can gravitational waves have luminosity?
In other words, a change in energy of the source over time. The orbital decay of a system (if it's a binary) or the change in spin (in the case of a lone object) comes from that luminosity. Gravitational waves carry away energy corresponding to this energy loss.
Well the author derives that the luminosity in the gravitational waves is derived as a function of third order time derivative of the quadruple moment tensor
@V.H.Belvadi Right. Those other journals originally existed because we didn't have the internet and publishers were required to produce the reading material itself.
Then, after arXiv, those journals became needed for only one purpose: curating the literature.
@AccidentalFourierTransform It is the reason for the slight headache I'm still having from drinking far too much of it yesterday, so yeah, you might say I like it ;)
This has several benefits over the present system:
1. The overlay journals can feature works after they've been published. This means, for example, that a work which initially looks uninteresting, but turns out to be important, can be featured on a "good" overlay journal rather than sitting in obscurity forever.
True, about overlay journals. But they should be bound to only go by pre-print servers and not, as some do now, also link to subscription-based journals.
@HDE 226868 . $L=\sigma AT^{4}$ and the L of gravitational waves of a particular binary that I have calculated is 1.2026e-81W. I can find the total elliptical area covered by the binary in its elliptic orbit and hence find the temp. T turns out to be of the order of -24kelvin. What could be the significance of this temp?
At the end of the day, the reason for journals to have existed is itself somewhat archaic. Pre-print servers are the way to go, but, like anything open access, they can get crowded fast, so overlay journals as a curating system will wrap things up nicely.
@AccidentalFourierTransform I'm not really the person to ask. To me QFT and black magic are largely indistinguishable except that QFT involves fewer orgies.
@NaveenBalaji I can't see that it makes any sense to assign a temperature to the production of gravitational waves because it's not a statistical process.
@AccidentalFourierTransform sYM also won't necessarily be about path integrals, you could investigate their BPS spectra or something. I don't know how exactly people do that currently but I heard a talk yesterday about it that didn't contain any path integrals ;)
@ACuriousMind am I expected to have a strong prior knowledge about the topic I choose? or am I expected to know the fundamentals and master them as I go on?
@ACuriousMind That sounds awfully advanced for a masters. Would students normally have gained enough proficiency to work on supersymmetric field theories for a masters?
@JohnRennie Some have ellipticity due to "mountains", from small deformities arising from a magnetic field or accretion. The strain from the nearest is a couple of orders of magnitude below LIGO's sensitivity at the right frequencies, though.
@JohnRennie Students here focusing on QFT/string theory would know about supersymmetric field theories, yes.
@AccidentalFourierTransform I find it strange that you're expected to come up with a topic - here, you choose a supervisor and the two of you then work it out together what exactly the topic will be (although you having a rough idea of course helps)
@ACuriousMind wow. I didn't do the specialist physics course at Cambridge, but I'm fairly sure they didn't do more than very basic QFT (if any) as undergrads.
any debroglie-bohm fans or anti copenhagenists around? naysayers? just ran into this amazing site/ ref, whaddya think? substantial electron-cloud like replication via emergent behavior in oildrop experiments http://dotwave.org/quantumlike-statistics-of-deterministic-waveparticle-interactions-in-a-circular-cavity/ / Gilet, Phys Rev E
@JohnRennie Not exactly as an extra (you have some freedom in choosing courses, but you must choose some, and QFT is an option for that), but it's not required if that's what you mean
@DanielSank youve heard churchill on democracy right? "its the worst possible system except for all the rest..." there is some greater awareness/ investigations of the limitations of peer review, mainly due to psychological tendencies/ cognitive biases etc
@TerryBollinger there is some very exciting new work originating in ~2011 due to Coudier that is being built on heavily, also by Bush (just cited, dotwave.org ). "they dont work" is increasingly out-of-date (to put it politely) & growingly reminiscent of the century-old assertion eg that "photons dont work"
@DHMO thanks I'll look that up. When I say it doesn't work, I mostly mean that I'm not aware of a way to explain entanglement using pilot wave theory. Val was trying to prove just that point when he made his and equality.
@DHMO The "collapse" only happens when you do not model the measurement apparatus itself quantumly. Otherwise you get to explain the measurement results with "decoherence" and "einselection", at least in principle. The Schrödinger equation is as deterministic as the evolution equations of Bohmian mechanics.
The difference between standard QM and Bohmian mechanics is not determinism, but realism. QM is non-realist (the "value" of an observable does not always uniquely exist prior to measurement) but local, Bohmian mechanics is realist but non-local.
@DanielSank Another thing that would make the question I posed about the frequency modulation quantum is that when your modulation has some width it will actually start to dephase the system, will it not?
@DHMO Well, first of all "collapse" is a feature that is present in the Copenhagen interpretation, but not in all interpretations. That the result of a measurement is an eigenstate of the observable measured is only called "collapse" when it is modeled as an instantaneous and unexplained phenomenon
And when you measure the position of an electron, you force it into a highly localized state, in which then its momentum/velocity is very uncertain and doesn't have a definite value (this is one manifestion of the uncertainty principle)
@ACuriousMind new versions of debroglie-bohm pilot waves are not exactly "nonlocal" or rather its subtle... hard to explain but the pilot wave does not violate light-cone causality, and yet has both local/ nonlocal properties... some of this can be seen/ explained in the new view of the 2-slit experiment...
@vzn Of course it doesn't violate causality - it reproduces QM results! Violating causality and being non-local are two different things, and one has to be very careful what one means by "causality" in the quantum context.
@ACuriousMind anyway "locality" is a concept that came out of Bell analysis & think it is being redefined as we speak... what oil drop experiments seem to show is that (quite initially surprisingly) even (some) classical systems seem to exhibit nonlocality in the bell sense. ... it seems to relate to emergent properties...
@vzn I recall in a public seminar one professor who worked in quantum computers have recently sent to publication a finding that the quantum state is a real thing. Thus in a sense, the wavefunction is a real entity and not just a math construct.
Stef simmons: the indistinguishability of non orthogonal quantum states cannot be ascribed entirely to a lack of knowledge of what precise state of reality is produced upon preparing a certian quanutm state
google search however cannot locate any paper, possibly it has not gone online yet
@Secret yes have heard/ collected refs to some of that new/ recent work, some of it is experimentally based (much like bell experiments), need to dig up specifics...
@Secret it makes no sense to prove that a mathematical object is a "real thing". How could you prove that a Cauchy sequence is a real thing? how could you prove that a partial derivative is a real thing?
@AccidentalFourierTransform By "the wavefunction is real" people usually refer to the weak measurement of the wavefunction, e.g. arxiv.org/abs/1112.3575
@ACuriousMind so far nobody is saying weak measurement pushes std QM so far as to imply its incomplete, but lately seems to me we're right on the verge of it...
which is precisely why I'm sceptical of the claims that whatever they measured is actually the "wavefunction" because standard QM also has phase freedom, i.e. for any quantum state the real and imaginary part of the "wavefunction" is not actually defined.
@ACuriousMind right. but whats fascinating is that defining it in some way may not actually contradict QM and may actually lead to predictions that std QM cannot make.
@ACuriousMind "trouble" is a loaded word. its subjective. it depends how married to convention one is. (many would have said, in his time einstein or maybe even planck was a huge "troublemaker" eh?)
@vzn What do you want to define? What predictions are you talking about? (I read that Bush article you gave me last time I asked that. It makes exactly zero claims that QM needs to be amended and it makes exactly zero non-standard predictions)
@ACuriousMind dont have all the answers, actually have very few. last few yrs have tingling spider sense that something big is playing out and wont fully shake out for years (much like "last time" ~1century ago). think youve identified "phase freedom"/ weak measurement etc as maybe a bridge between the old and the new theory in the way photons/ wavefn/ shroedinger eqn were a century ago. it takes years to try to push discrepancies between the theories and in the interregnum seem indistinguishable.
> The crisis consists precisely in the fact that the old is dying and the new cannot be born; in this interregnum a great variety of morbid symptoms appear. en.wikiquote.org/wiki/Antonio_Gramsci
@ACuriousMind agreed its about evidence. the evidence is accumulating & being actively collected by inspired/ hardworking/ openminded/ even visionary individuals/ researchers as we speak. the trial/ judge/ jury/ executioner are not yet assembled. or maybe they are. o_O
I'm concerned at Meta posts such as this one. That's where a poster claims that an answer to a physics question is "evidently wrong within standard peer reviewed physics" when it isn't. Indeed the answer concerned (mine) refers to the Einstein digital papers to support its case:
"An atom absorb...
do you think you could ask him to let you finish the homework once you get the concept in class, so you can spend more time reading harder things at home
like after the first day he explained simple algebraic proofs, I understood that, did the homework, and a week or two later when he started segment proofs I took a crack at the homework and figured it out on my own
@Skyler, I'm already doing the homework in class, I do it as I listen =P
yeah, the thing is, it's like an accelerated track math thing; there's classes taking algebra I right now, classes taking geometry right now, and classes taking algebra II right now (plus a kid taking trig and prob/stats)
so he is teaching advanced kids
i have some friends i sit with who pick it up quickly too
@heather during homework time if both of you are done it might be a good idea to share a bit of what you've learned with friends and see if anybody is interested in learning with you some of it
teaching something to someone is hard, but makes you really learn it
and the number one way to do higher level physics homework is with exactly 1 other partner
@Skyler, we both work together on calc sometimes, but my friend isn't quite as interested in doing that as just chatting, so. plus they prefer biology =P
the other interesting thing, though, is sometimes my science teacher asks what I'm working on, because he saw me with a couple of science books as well as the math books, so we got in a conversation about quantum computing.
@Skyler I find some biology interesting sometimes but no more than most other sciences, I wouldn't describe myself as ever having been "fascinated" by it.
@heather I remember having to draw bark patterns in a biology exam in highschool after we spent a morning between 6 and 8am in a stupid wood somewhere and were supposed to learn that
hence, I was never that partial to biology :D but there's really nice things, simulation of predator-prey-food-networks for example, lot's of biopolymer physics, bio-informatics ...
@Skyler, oh, the teacher asked me to explain some of it, so I started, and then he asked me to come in when I arrived on the bus thursday and we could continue the conversation
You can replace `below` with `above` depending on whether you want the label above or below the arrow. You could also use `left` and `right` if you have a vertical arrow. And the `pos=0.5` can be adjusted to any number between 0 and 1 if you want the label to be closer to one end than the other. Note the use of `--` rather than `to`. You might also be able to do this with `to`, but the interaction between `to` and `pos=...` is iffy.
@Skyler I believe you - I was tempted to do my Bachelor&Master at the biology department myself
user246160
@Sanya Even learning pattern of leaves is extremely interesting (much more than it sounds) once you get into it. No wonder that some people dedicate their whole lives studying plant patterns :) But yeah it is boring only if you have to mug it up for exams !
hi guys! i have to solve this equation. actually the professor needs us to find the Λ and i dont know if my steps are right. can someone help me please? im not a physic student , im a mathematician so this kind of staff are too high leveled for me. thanks :)
@heather actually I was a student, the AP bio teacher (who I never had a class with before that) approached me while I was sitting in the library and said they wanted to start something with a USC professor that was similar to my summer research project
@heather well, remember that just because a question is a homework problem doesn't make it off topic. There is such a thing as a good way to ask homework questions. (But this particular case is definitely close-worthy.)
@Skyler, sure, I'll be around until 5:00 definitely, maybe until 5:45 or 6:00, not sure
user246160
@Sanya I agree. The problem is not with the subject. What makes biology boring for some people is the rote learning methods at lower levels. But once you start learning it practically it gets extremely interesting. I once spent my whole summer holidays collecting butterflies and noting their patterns. And I got to learn a lot about insects from that. :) And patterns do have a lot of advantages/disadvantages if you want to know in depth.
@DavidZ, so, I noticed Khan Academy added grammar lessons to their site, I don't know, but maybe would it make sense to add that link somewhere where it explains english is the language to be used here?
@Doraemonドラえもん in the end, I do believe that what makes people choose subjects is the typical teaching style and the typical way of working in them, not so much the content - which is a bit sad because e.g. biology is really fascinating too.
So question for everyone: I kind of need some money for college (let me rephrase, a lot of money). What are some good scholarships to go after, especially for 8th/9th grade?
I'm concerned at Meta posts such as this one. That's where a poster claims that an answer to a physics question is "evidently wrong within standard peer reviewed physics" when it isn't. Indeed the answer concerned (mine) refers to the Einstein digital papers to support its case:
"An atom absorb...
hi guys! i have to solve this equation. actually the professor needs us to find the Λ and i dont know if my steps are right. can someone help me please? im not a physic student , im a mathematician so this kind of staff are too high leveled for me. thanks :)
