Interesting, but the paper seems to have a nasty habit of simply redefining what "capacity" means in a quantum context, to basically, "Well, if we have two interacting channels, one changes the other to have non-zero capacity." And if I interpret it that way, it simply rewords the problem to be different from the original interpretation. Also, there's a significant amount (even for an arxiv paper) of speculation present (which is interesting!). From the paper: Nonetheless, each channel has the potential to \activate" the other, effectively cancel- ing the other's reason for having no capacity. We know of no analog of this effect in the classical theory. Per- haps each channel transfers some different, but comple- mentary kind of quantum information. If so, can these kinds of information be quantfied in an operationally meaningful way? Are there other pairs of zero-capacity channels displaying this effect? Are there triples? Does the private capacity also display superactivation? What new insights does this yield for computing the quantum capacity in general?
One "classical" analogy is that of orthogonally-crossed polarizers, which, upon insertion of another polarizer with principle axis somewhere between that of the originals, will allow light to shine through where none was before.
"Publishing" on arxiv isn't really what one normally thinks of as publishing. It's a way to get interesting results out into the scientific community, so that they can be vetted and proofread by others before they appear in print. Rather a nice thing, I think. It means that more people can get access to the results, earlier, and without paying for them.
Interestingly enough, if one captures all of the phase data (as by using not-quite-evanescent waves), the resolution isn't restricted by the classical far-field limit of 1/2 wavelength. Because they're doing holography, they should be capturing at least *some* of the phase info.
The arxiv paper (referenced elsewhere in these posts) mentions that the obtainable information drops rapidly at 75nm. Their phase-recovery algorithm, combined with the snr inherent in the system, conspire to do this. It's really not a function of the computer post-processing (which can't, after all, improve the image resolution). The caption on one of the figures in the linked article is simply a little misleading; however, the entire article is quite good. Science reporting ftw!
I'm a bit skeptical. Whatever information one can get is present in the original diffraction pattern. "Processing" *probably* means interpolation, or convolution with the known regular array. One can only keep the same information already present, or lose information in this way. They probably mean that the pattern was smoothed so as to look nicer to the eye (which is certainly valid), but I doubt they increased resolution in any way.
Could you expand a little on that statement? I have two interpretations:
* Noisy-channel capacity theorems state that if information is being sent at less than channel capacity, error correcting codes can, in principle, ensure no errors on the part of the receiver, even in the presence of noise (in which case outside observers should have no problems decoding any messages);
* However, if information is being sent at over channel capacity, errors can grow without bound. If some civilization was communicating near the channel capacity (which they're likely to do to maximize information flow), and we happened to listen in (thus our interstellar channel is different, and probably has lower -- perhaps much lower -- capacity), then we're likely to receive lots of errors.
Aw. And it appears that this has been posted from the not-mere-sluttiness dept. It appears that slashdot editors already stooped to the lowest from of humor in posting the headline, and I've just fallen into their redundancy trap. Tricky, tricky!
You simply keep taking the same exam over and over again until you get a grade your happy with. That's why kids from Catholic schools do so badly when they get to a University run by the Jesuits and yes I am a faculty member at a Jesuit University and yes the failure rate for students from Catholic schools is double that of public schools
No, no, no. Fill it with hairdressers, tired TV producers, insurance salesmen, personnel officers, security guards, management consultants, and telephone sanitizers.
I would have absolutely agreed a few years ago. Traditional fluorescents hurt my eyes after a while, and incandescents are slightly warmer, and yellower, like natural light. However, the new compact fluorescents are awfully good, and with certain ones I can't tell the difference between them and incandescent bulbs.
Moore himself (you're probably aware of this, but I'm sure many people are not, and I just learned a lot of this today) couched his observations in terms of cost. He was extremely prescient! A presentation by Moore himself has some plots showing several factors (lithography cost, shrinking sizes, etc.) vs. time. http://download.intel.com/research/silicon/Gordon_Moore_ISSCC_021003.pdf
If the radar gun was indeed a Doppler radar device, then that's as close to a measurement of instantaneous speed as one can define. It doesn't need two distance measurements at different times; it needs a frequency shift over several (I'm guessing 50 - 100 for any sort of resolution) cycles of the wave. Since the period of the radar is likely something on the order of 0.05 ns, a Doppler radar gun may make its velocity determination with measuring only 1 - 10 ns, with great accuracy. That's instantaneous enough for Gov't work.
Instantaneous speed is very important. No one cares if your average speed for an hour before an accident was 55 mph; they care if your instantaneous speed when you hit a pylon or another car was 120 mph.
True, and I know lots of Harley riders, most of whom are very nice. However, anyone who rides an unmuffled motorcycle and is proud of its noise is, by definition, at least an inconsiderate jerk.
Then your professor probably didn't focus on those aspects. You're right -- there is little field mechanics specified in M&T. But you have to realize that almost anything (certainly at the undergrad. level) involving Lagrangians or Hamiltonians implicitly involves field mechanics, since Laplacians are only definable on fields (the derivatives sample configurations close to the point in question in phase space).
It sounds like you're mad you didn't take a fluid mechanics course or that electrodynamics didn't cover gravitational fields. Maybe you were too advanced for the course. How did your contemporaries feel about the level covered?
Haha. Marion and Thornton is an *excellent* advanced-undergraduate text for classical mechanics. For that level of student, you really can't go wrong with it.
Goldstein is (of course) much more advanced, but reasonably good. If the poster wants a very mathy introduction to mechanics at the graduate level, he should try V.I. Arnold's "Mathematical Methods of Classical Mechanics".
One book I'd suggest he stays away from (though he won't be able to, probably), is Arfken for mathematical methods. Instead, try to find a copy of Morse and Feschbach (super expensive if you get a new copy of both volumes). The rigor might make a dyed-in-the-wool mathematician weep, but it's all there.
In the US we don't seem to have much interest in our technological past.
Perhaps, but compared to the museums I saw in China a few years ago, the entire US is a veritable Smithsonian. For example, I was quite excited to visit the Xi'an Terra Cotta Warriors museum. It was laid out relatively well, but there were almost *no* explanations of anything you could see, in either Chinese or English. People would wander around, looking very quickly, but it was almost impossible to learn anything there. *Why* was a gold bowl of interest? It was beautiful, but did it belong to an Emperor? A general? A courtesan? The scale model (actual artifact) of a carriage was neat, but did it use interesting gearing? Was it used to transfer warriors to the battlefield? Where was it found? Was it supposed to look just like the full-scale ones, or were parts missing, or was it just an elaborate toy for someone? It was the same for the Forbidden City and Summer Palace in Beijing, and the Great Wall was kind of a joke.
There are all these fabulous technological and historical artifacts in that country, but very little interest (it seemed) in teaching anyone what any of it meant, or where things came from. I think that's starting to change (a lot of the history is incorporated into everyday life, after all) for the better, at least.
Slashdot Mirror
http://arxiv.org/PS_cache/arxiv/pdf/0807/0807.4935v1.pdf
Interesting, but the paper seems to have a nasty habit of simply redefining what "capacity" means in a quantum context, to basically, "Well, if we have two interacting channels, one changes the other to have non-zero capacity." And if I interpret it that way, it simply rewords the problem to be different from the original interpretation. Also, there's a significant amount (even for an arxiv paper) of speculation present (which is interesting!). From the paper: Nonetheless, each channel has
the potential to \activate" the other, effectively cancel-
ing the other's reason for having no capacity. We know
of no analog of this effect in the classical theory. Per-
haps each channel transfers some different, but comple-
mentary kind of quantum information. If so, can these
kinds of information be quantfied in an operationally
meaningful way? Are there other pairs of zero-capacity
channels displaying this effect? Are there triples? Does
the private capacity also display superactivation? What
new insights does this yield for computing the quantum
capacity in general?
One "classical" analogy is that of orthogonally-crossed polarizers, which, upon insertion of another polarizer with principle axis somewhere between that of the originals, will allow light to shine through where none was before.
"Publishing" on arxiv isn't really what one normally thinks of as publishing. It's a way to get interesting results out into the scientific community, so that they can be vetted and proofread by others before they appear in print. Rather a nice thing, I think. It means that more people can get access to the results, earlier, and without paying for them.
Interestingly enough, if one captures all of the phase data (as by using not-quite-evanescent waves), the resolution isn't restricted by the classical far-field limit of 1/2 wavelength. Because they're doing holography, they should be capturing at least *some* of the phase info.
The arxiv paper (referenced elsewhere in these posts) mentions that the obtainable information drops rapidly at 75nm. Their phase-recovery algorithm, combined with the snr inherent in the system, conspire to do this. It's really not a function of the computer post-processing (which can't, after all, improve the image resolution). The caption on one of the figures in the linked article is simply a little misleading; however, the entire article is quite good. Science reporting ftw!
http://arxiv.org/PS_cache/arxiv/pdf/0801/0801.4969v3.pdf
I'm a bit skeptical. Whatever information one can get is present in the original diffraction pattern. "Processing" *probably* means interpolation, or convolution with the known regular array. One can only keep the same information already present, or lose information in this way. They probably mean that the pattern was smoothed so as to look nicer to the eye (which is certainly valid), but I doubt they increased resolution in any way.
Barney and Miss Beazley?
Trying to be smart and funny, are we?
It's spelt "pronunciation". No o.
Both correct and FAIL at the same time! You win at least half an Intarweb.
Could you expand a little on that statement? I have two interpretations:
* Noisy-channel capacity theorems state that if information is being sent at less than channel capacity, error correcting codes can, in principle, ensure no errors on the part of the receiver, even in the presence of noise (in which case outside observers should have no problems decoding any messages);
* However, if information is being sent at over channel capacity, errors can grow without bound. If some civilization was communicating near the channel capacity (which they're likely to do to maximize information flow), and we happened to listen in (thus our interstellar channel is different, and probably has lower -- perhaps much lower -- capacity), then we're likely to receive lots of errors.
Is the latter point what you mean?
Aw. And it appears that this has been posted from the not-mere-sluttiness dept. It appears that slashdot editors already stooped to the lowest from of humor in posting the headline, and I've just fallen into their redundancy trap. Tricky, tricky!
S3 is a total slut.
You simply keep taking the same exam over and over again until you get a grade your happy with. That's why kids from Catholic schools do so badly when they get to a University run by the Jesuits and yes I am a faculty member at a Jesuit University and yes the failure rate for students from Catholic schools is double that of public schools
Please tell us that you teach writing. Please.
I'm taking it as a very clever form of satire: confusing New Jersey as a state versus a city; confusing Canada with England.
I mean, it's pretty obvious that it's a Canadian article because it's in English and Canada is the only state in the Union that speaks English.
I'm taking that as very clever satire. It's pretty obvious you confused a country with something that can speak!
No, no, no. Fill it with hairdressers, tired TV producers, insurance salesmen, personnel officers, security guards, management consultants, and telephone sanitizers.
I would have absolutely agreed a few years ago. Traditional fluorescents hurt my eyes after a while, and incandescents are slightly warmer, and yellower, like natural light. However, the new compact fluorescents are awfully good, and with certain ones I can't tell the difference between them and incandescent bulbs.
Moore himself (you're probably aware of this, but I'm sure many people are not, and I just learned a lot of this today) couched his observations in terms of cost. He was extremely prescient! A presentation by Moore himself has some plots showing several factors (lithography cost, shrinking sizes, etc.) vs. time. http://download.intel.com/research/silicon/Gordon_Moore_ISSCC_021003.pdf
Roughly parabolic on a log-log scale.
http://www.intel.com/technology/mooreslaw/pix/originalgraph.gif
If the radar gun was indeed a Doppler radar device, then that's as close to a measurement of instantaneous speed as one can define. It doesn't need two distance measurements at different times; it needs a frequency shift over several (I'm guessing 50 - 100 for any sort of resolution) cycles of the wave. Since the period of the radar is likely something on the order of 0.05 ns, a Doppler radar gun may make its velocity determination with measuring only 1 - 10 ns, with great accuracy. That's instantaneous enough for Gov't work.
Instantaneous speed is very important. No one cares if your average speed for an hour before an accident was 55 mph; they care if your instantaneous speed when you hit a pylon or another car was 120 mph.
True, and I know lots of Harley riders, most of whom are very nice. However, anyone who rides an unmuffled motorcycle and is proud of its noise is, by definition, at least an inconsiderate jerk.
Fine. One of the reasons there's nobody there is because of all of the assholes on their Harleys :)
Then your professor probably didn't focus on those aspects. You're right -- there is little field mechanics specified in M&T. But you have to realize that almost anything (certainly at the undergrad. level) involving Lagrangians or Hamiltonians implicitly involves field mechanics, since Laplacians are only definable on fields (the derivatives sample configurations close to the point in question in phase space).
It sounds like you're mad you didn't take a fluid mechanics course or that electrodynamics didn't cover gravitational fields. Maybe you were too advanced for the course. How did your contemporaries feel about the level covered?
Haha. Marion and Thornton is an *excellent* advanced-undergraduate text for classical mechanics. For that level of student, you really can't go wrong with it.
Goldstein is (of course) much more advanced, but reasonably good. If the poster wants a very mathy introduction to mechanics at the graduate level, he should try V.I. Arnold's "Mathematical Methods of Classical Mechanics".
One book I'd suggest he stays away from (though he won't be able to, probably), is Arfken for mathematical methods. Instead, try to find a copy of Morse and Feschbach (super expensive if you get a new copy of both volumes). The rigor might make a dyed-in-the-wool mathematician weep, but it's all there.
Yeah! And I always liked Tupper's self-referential formula: http://mathworld.wolfram.com/TuppersSelf-ReferentialFormula.html
Just translate everything to brainfuck, and send that sourcecode. Problem solved.
(Some people claim that this brilliant---nay, genius---solution will just make things harder for you, but you can never tell until you try, right?)
In the US we don't seem to have much interest in our technological past.
Perhaps, but compared to the museums I saw in China a few years ago, the entire US is a veritable Smithsonian. For example, I was quite excited to visit the Xi'an Terra Cotta Warriors museum. It was laid out relatively well, but there were almost *no* explanations of anything you could see, in either Chinese or English. People would wander around, looking very quickly, but it was almost impossible to learn anything there. *Why* was a gold bowl of interest? It was beautiful, but did it belong to an Emperor? A general? A courtesan? The scale model (actual artifact) of a carriage was neat, but did it use interesting gearing? Was it used to transfer warriors to the battlefield? Where was it found? Was it supposed to look just like the full-scale ones, or were parts missing, or was it just an elaborate toy for someone? It was the same for the Forbidden City and Summer Palace in Beijing, and the Great Wall was kind of a joke.
There are all these fabulous technological and historical artifacts in that country, but very little interest (it seemed) in teaching anyone what any of it meant, or where things came from. I think that's starting to change (a lot of the history is incorporated into everyday life, after all) for the better, at least.