I don't remember seeing any of the other actors in anything else since.
Actually, Carrie Fisher was the therapist in Austin Powers 2 for the support group that Dr. Evil and his son go to. I enjoyed this very brief role at least as much as all the Princess Leia stuff and to some degree it has replaced her Star Wars appearance as my primary Carrie Fisher association.
They have all appeared in other stuff, but like you I remember mercifully little of it. Mark Hamill was in "A Boy and His Dog", another sci-fi flick. He was also in a Simpsons ep, "Mayored to the Mob" in 1998, where he pretends to have a broken ankle to make Homer carry him through an angry crowd. Some characters never change.:-)
Actually, according the link in the original post "molds eyeglasses", he has come up with a goggle-like device that you wear, and as you look around it observes how your eyeballs and lenses change, using feedback to determine the correct prescription... it's in the article about halfway down.
To me, this seems at least as interesting as being able to actually manufacture eyeglasses. I mean, that's great, but cheap and quick fabrication is... not really old news, but... people have been working on that kind of thing for a while, right? How much of his eyeglass fabricator represents significant new advances, versus putting known techniques to a new (and highly laudable!) use? Maybe I'm wrong there, I don't know. But this prescription sensor seems really amazing. Being able to monitor the shape of the lens and cornea as they flex around.... Am I wrong? That seems pretty amazing to me. But he didn't win any awards for that part of it, so maybe that's actually less significant?...
That would totally suck, except---irony alert---the GOTOs would actually be really, really sweet. Maybe that's how the teleporters on Star Trek really work?
Yeah, that web site looks pretty sketchy to me, not that I'm an expert. The photo you mentioned has a white area in the foreground---could be snow, could be hail---and a HUGE non-white area in the background. That is NOT a picture of a "small hail-free patch", surrounded by an area with hail. There is no hail or snow visible on the far side of the hail-free area. It does not seem possible from the picture on their website to verify that the white stuff is actually hail; it could be snow. The whole thing could be Photoshop.
Other pages on the site have:
* inconsistent information (every 5.5 seconds; every 6 seconds; every 5 seconds; the noise level is listed at various levels, too...) * dubious statements like "supersonic explosions do not affect animals" * incorrect spelling and punctuation * overuse of jargon and jargon-y words (such as "ascending thermionic explosions"). Looking at this web site, I got the feeling that they did not want me to understand how it works, they just want me to be impressed. * Worst of all: statistics! Why do they start the noise level measurements 50m away? Are you not supposed to go closer than 50m while it's operating? What if you install this on the roof of your car?
Of course, they don't have to explain their patented super-invention to me. But if they are going to deliberately withhold information, they could have been less patronizing about it! Overall, the site seems to have a very low level of professionalism. To whatever degree this reflects on the device itself, it reflects poorly.
Oooh, a challenge. Were we not actually interested in the ethics involved so much as the bragging rights (aka, karma)?... Please, let's stick to logic and reasoning here.
Now, to get back to the point, I don't understand what you mean and I would like it if you could explain a little. Either what he has done is based on previous work and he should cite it, or it is not based on any previous work. In that case, there's nothing to diverge from. I do agree with you that completely original work with no reference or comparison whatsoever to any prior literature does not need references. Are you saying that a substantial portion of ANKOS fits this description? Alternatively, have I misunderstood your post?
He claims no where in the book that I could find that others had not also covered much of this ground
It's not enough to be silent on the question of whether others have already covered the ground. A respectable writer has to devote serious effort to documenting previous writings on the subject. It's not even enough to say "this has been done"; you have to say by whom, when, in what journal...
Bibliographies serve an essential and fundamental purpose. They are not just there to make typesetting difficult!:-) So, if Wolfram "doesn't claim no-one has done it before", that's short of actually admitting others have done it (or related things) before, which in turn is still short of saying THESE people have done THESE things in THESE papers.
Serious scientific books and papers list everything that's even **related** (well, closely related) to the topic at hand. The burden is on the author, not the reader, to indicate how much of the material is new.
one of the few things stopping me from purchasing a phone is the fact that I do not want to pay for hundreds of features that I will never use. All I want is an address book and a way to make calls.
If that's all you want, you'd better buy a phone, sooner rather than later.
Someone else mentioned Motorola 120e; I have a Motorola 120i, which is pretty much the same, and I agree with the earlier poster. It is a good phone which should fit your needs without too much extra fluff.
Humans do have some protection against UV. Tanning. Melanin. It's not perfect and complete protection, but I'd say it qualifies as a protection strategy...
The attacker must: Be on your local network Already have control of your DHCP server
I thought the attacker only has to have a fake, evil DHCP server which responds faster than the true good DHCP server...? Of course this is hard to do, and controlling the supposed-to-be good DHCP server would work more reliably, but I don't think that's exactly required.
zach
What a snoozer of an article
on
Real Security?
·
· Score: 3, Interesting
Bleh. Are his articles all like this? He has some anecdotes about bad security, with a "D'oh!" in between practically every paragraph---though that slows down after he gets tired of it, a page or two in. Then there's a story about a program called "Tresor" and some guy who had a weird problem with bundles acting like folders instead of application files. The assertion is made point-blank that this is an Apple bug, not a Tresor bug.
OK. Has this been reported or observed anywhere else? I've never heard of it, or seen it myself, though I've only been using OSX for a little under a year. If anyone can point me to a reference, I'd appreciate it. The article doesn't give any refs. I don't understand how he's so sure it's an Apple bug, unless it's so well-known that, gosh, everyone knows it's an Apple bug without even needing a link to, like, a Knowledge Base article or anything... but if it were that well-known, I hope I would know about it. So I have my doubts about this. If anyone knows one way or the other, I'd like to hear about it.
But really that's not the main point of the article, right? It's just one security flaw in a fairly specific situation. So the article, as far as I can tell, is a few anecdotes and a bunch of "D'oh!"s. Oh yeah, plus some insults and derision for all the programmers and the university professors who taught them. Thanks a lot, Tog.
His thesis---that security needs to be designed to actually make things secure, not theoretically securable---is, well, it's OK I guess. For one thing, he doesn't really argue for it---just provides anecdotes. That's not a coherent logical argument. Worse, it barely even ties in with the anecdotes anyway. So the hospital requires TOO MANY passwords. That does **not** make it theoretically securable, OK? (I can require 200 passwords, but it's not theoretically securable if the computer and fax machine are in the hallway.) He's right that security systems have to aim for real security, but he's wrong in saying that the problem is that people aim for "theoretical securability". Am I wrong here? Is there ANY theory of anything under which these systems are considered theoretically securable?
The only common thread I can think of, apart from inadequate security in general, is that the people who designed the security had an incomplete approach to security; they secured one part of the system (e.g., getting in with a password) way too much, and other parts (e.g., physical security of the fax machine) not enough. Or, they were unnecessarily protective, at the cost of user convenience (as in the VW radio example).
If I'm criticizing the article, maybe I should try to be constructive about it, right? I guess the anecdotes really point towards the two different themes in the previous paragraph: security model should be "complete", and there should be some kind of a balance between security and usability.
I may be wrong about my interpretation of his article. If there's a better way to read this article as it's written, please tell me. I suspect not, but hey. Or just call me a monkey, that's cool too.:-)
Well, to wrap it up, he has a good point, basically, but no argument for it. Just a few isolated anecdotes, not all of which I believe. This is not high-quality writing. Sorry, Tog. I've read of few of your user-interface-design columns, and I liked them a little better. This one just didn't do it for me, I guess.
The whole story smacks of dubiousness (OW!). They quote this one guy, Crandall, about 15 times. They reference his blog. The publisher of some ipod web thingy has heard of it... from the same guy. There's an unnamed Pixar spokeswoman who's never heard of it... but she's too busy to look into it? What the heck?
Wired reporter: I need one source that doesn't flow directly from this Crandall joker. I think I'll phone up Pixar.
"We listened for about 30 seconds," Crandall said. "No words were exchanged. We nodded and walked off."
OK, so some people say thanks and others don't. Fine.
But here's the clincher: He listens to indigenous music from northern Europe all the time, and has never heard trance. Yeah, right! Indigenous music from northern Europe?!:-) Nothing against the sub-sub-genre of indigenous music from northern Europe, ok, but I doubt he's really into it... all the time... and has been for the last ten years.
This monkey Crandall desperately wants attention. He desperately wants people to let him listen to their iPods. So he decides to start a trend. So he calls up Wired and plants a story, and the reporter doesn't think to question the fact that noone else has heard of this...
(Tinfoil hat time: And maybe he's traveling to Cambridge soon, so he nudges them a bit, saying he's heard it's starting there, too, so they'll be ready when he gets there!?)
OK, I'm done ranting now.
zach
Re:Impact for Panther/Jaguar users?
on
Darwin, Fink Updates
·
· Score: 3, Interesting
I'm no expert, but it seems to me that Darwin is kind of like the thing running "under" Jaguar or Panther.
Roughly, Darwin is the underlying part of the operating system; the rest of Jaguar/Panther is mostly user interface stuff. This is what Apple charges money for---Darwin they give away, and the user interface part is $129 (per year:-) ).
So you wouldn't install Darwin if you already have Jag or Panther. Only if you have another computer that you want to set up with a free OS (and you don't mind installing user interface stuff like X windows), or maybe if you want to set up a "dual boot" thing on a single computer. I could imagine this latter setup being useful for testing, or for servers (normally don't need GUI, but every now and then reboot into GUI?).
Presumably every update that's made to Darwin is also released for Jaguar/Panther via Software Update. At least, I hope so. (Insert here standard comment about Apple being taken seriously in Enterprise.)
OK, good point, why have a bundle at all? For one thing, bundles are much easier to deal with than general manifolds---we don't even understand 3-manifolds, let alone 10-manifolds (eg, Poincare conj.). For another thing, if MathWorld says it's a product, and I'm curious about generalizing it, I think it's reasonable to make a small step to fiber bundles, before leaping all the way up to general manifolds. But as you say, the question generalizes up more.
I hope you don't mind if I pick a nit or two in your post:
a product of manifolds is just a product of manifolds. not a bundle.
But isn't it a trivial bundle, in two different ways, as you point out with reference to the example of a cylinder?
Anyway, most bundles are not trivial, and non-trivial bundles can't be simply "turned sideways" like a product can. I could be wrong, but it seems to me that in the topological category, and maybe in the smooth category as well, "most" bundles have a "unique" bundle structure map (in the sense that any two of them differ by a unique automorphism of the bundle space). On the other hand, spacetimes live in the category of smooth spaces with a tensor field which satisfies some conditions, etc... and in that category, maybe bundle structures are not unique?
So I was going to disagree with you about non-existence of canonical bundle structures, but actually you're probably right!:-)
Anyway, I don't mean to argue about fiber bundles per se... Sorry... Thanks for the discussion, it's helped me think through my question a little more carefully than I had originally, and even given me a few new questions to think about!
If you don't mind, I'd like to ask you a somewhat stupid question. Would quantum computers be able to do anything with things like elliptic curve cryptography? There are various crypto schemes coming from algebraic geometry---hyperelliptic curves and so on. I'm not an expert, but it's my understanding that they don't rely on difficulty of factoring integers.
Yes, of course you're right about the tensor and signature. That was silly of me. Thanks. I think the issue is partly physics terminology vs. math terminology: for me, a form is actually symmetric... I should have been more careful.
I have to point out, however, that a 6-dimensional fiber bundle on a 4-dimensional space IS a 10-dimensional manifold! Locally it looks like a product, but globally it can fail to be a product. Still, even if it's not a product, it is always a manifold. A product is a specific example of a fiber bundle---a trivial example, in the technical sense of "trivial"... So why can't space-time be a nontrivial bundle?
Example: a cylinder in R^3 is a bundle of lines over a circle. It's trivial---a cylinder is the product of a line and a circle. A Moebius band is **also** a bundle of lines over a circle: to see this, draw a circle down the center of the band, and that's the base space; then all the "perpendicular" lines going edge to edge on the band are the fibers. The Moebius band is non-trivial. This takes some proof, but it's true.
I am *not* BS'ing this. I know whereof I speak. Many books on topology, such as Munkres, have good explanations of trivial vs. non-trivial bundles.
Since you allow the base space to be a general 4-manifold M, you might as well allow non-trivial bundles. Locally they will be trivial; locally M is just R^4 (with a tensor field, etc.).
Yes, I had the hanging problem. I did something like this:
1. Turn SSL off in prefs (unfortunately, at this point your password, and a bunch of Mail traffic, goes out in cleartext, so this procedure is kind of not so good:-( )
*** Maybe quit Mail in here and start again? I forget:-p
2. Turn it back on
3. Open Activity window. My copy of Mail was going bananas trying open, close, open, close, and open various connections. Cancel everything.
4. "Get new mail". Now you can click in the box without hanging.
If you click-and-drag, you get the text of the cert. So use option, to get the actual certificate file.
I managed to get the certificate into Keychain, no problem. Unfortunately Mail still doesn't like it. In my case, it's not a self-signed certificate---I think the issue might be an unknown certificate authority (Comodo Systems). Always worked before.
The error message now is "The certificate for the server is not valid." Clicking Continue makes everything work OK, and in tcpflow the traffice **looks** like it's encrypted. Anyone have any ideas about this? Is it in fact the CA and how can I get the computer to accept it? Thanks.
Panther works just dandy on my laptop, not that I'm a power user or anything.
BUT, I just noticed one of my iPod cables is fraying! (The cable with the "wired remote" is fraying just above the plaug that goes into the iPod.) WTF!!!
As far as utilities and programs not working---well, (1) that's not much of a surprise, there, now is it? and (2) there are many, many, many, many more of them now than there were when 10.1 morphed into Jaguar. So I'd suspect that the vast majority of things that don't work are not things for Apple to worry about, and they'll just get fixed when the developers get around to it; and maybe some things *are* because of Apple bugs, but not most.
For example, someone said uControl doesn't work. Well, gosh. I sincerely hope it gets fixed soon, but is it Apple's "fault" that they changed and updated all the APIs and stuff?
Anyway, there are enough *real* bugs to go around... programs that stopped working is just a distraction.
Plus my ipod cable. Grrrrrr. Let's see if this Scotch tape can hold it together?...
I'm stupid. I meant to say also the following. What if we specify an ample line bundle L on the C-Y 3-fold X; this is a polarization of X? Ample in algebraic geometry is the same as positive in several complex variables.
Among other things, this gives a *volume* of X, a positive real number, which is the same kind of volume that we're used to thinking of---like a cube with sides all equal to 1 has volume 1, etc. The Griffiths and Harris book would explain this better than I can.
The volume is something like $L^3/sqrt{2\pi}$, or something like that. Since it's physics, there are some kind of units. If this volume is small enough (i.e. measured in small enough units), it might suggest a reason why we can't move "along" the six dimensions corresponding to the C-Y 3-fold bundle: something small like an electron already fills up the tiny volume.
The above-linked page has a rough definition of the kind of space a 10-dimensional string theory might live on. I don't know why they take a product $M \times V$ --- why not allow a more general bundle of C-Y 3-folds?
The imaginary version of string theory which exists only in my mind has the universe as a bundle of Calabi-Yau 3-folds over $M$ (a real 4-manifold with a Minkowski metric, or something like that... anyway, a $(3,1)$ form --- that's a Minkowski metric, right???). That's 10 dimensions. The 11- or other-dimensional kinds of string theory, I have no idea.
Being an algebraic geometer (in training), I think of a C-Y 3-fold as a smooth projective complex 3-dimensional variety, or manifold, with trivial canonical bundle.
Well, that's the space. Then all kinds of crap happens *in* the space, with strings and stuff, and that's a whole nother story...
Slashdot Mirror
I'm sure there is a country out their who's population speaks ...whatever it is people from Mordor speak!
That country would be... Mordor.
zach
I don't remember seeing any of the other actors in anything else since.
:-)
Actually, Carrie Fisher was the therapist in Austin Powers 2 for the support group that Dr. Evil and his son go to. I enjoyed this very brief role at least as much as all the Princess Leia stuff and to some degree it has replaced her Star Wars appearance as my primary Carrie Fisher association.
They have all appeared in other stuff, but like you I remember mercifully little of it. Mark Hamill was in "A Boy and His Dog", another sci-fi flick. He was also in a Simpsons ep, "Mayored to the Mob" in 1998, where he pretends to have a broken ankle to make Homer carry him through an angry crowd. Some characters never change.
zach
Actually, according the link in the original post "molds eyeglasses", he has come up with a goggle-like device that you wear, and as you look around it observes how your eyeballs and lenses change, using feedback to determine the correct prescription... it's in the article about halfway down.
... not really old news, but ... people have been working on that kind of thing for a while, right? How much of his eyeglass fabricator represents significant new advances, versus putting known techniques to a new (and highly laudable!) use? Maybe I'm wrong there, I don't know. But this prescription sensor seems really amazing. Being able to monitor the shape of the lens and cornea as they flex around.... Am I wrong? That seems pretty amazing to me. But he didn't win any awards for that part of it, so maybe that's actually less significant?...
To me, this seems at least as interesting as being able to actually manufacture eyeglasses. I mean, that's great, but cheap and quick fabrication is
zach
That would totally suck, except---irony alert---the GOTOs would actually be really, really sweet. Maybe that's how the teleporters on Star Trek really work?
zach
Yeah, that web site looks pretty sketchy to me, not that I'm an expert. The photo you mentioned has a white area in the foreground---could be snow, could be hail---and a HUGE non-white area in the background. That is NOT a picture of a "small hail-free patch", surrounded by an area with hail. There is no hail or snow visible on the far side of the hail-free area. It does not seem possible from the picture on their website to verify that the white stuff is actually hail; it could be snow. The whole thing could be Photoshop.
Other pages on the site have:
* inconsistent information (every 5.5 seconds; every 6 seconds; every 5 seconds; the noise level is listed at various levels, too...)
* dubious statements like "supersonic explosions do not affect animals"
* incorrect spelling and punctuation
* overuse of jargon and jargon-y words (such as "ascending thermionic explosions"). Looking at this web site, I got the feeling that they did not want me to understand how it works, they just want me to be impressed.
* Worst of all: statistics! Why do they start the noise level measurements 50m away? Are you not supposed to go closer than 50m while it's operating? What if you install this on the roof of your car?
Of course, they don't have to explain their patented super-invention to me. But if they are going to deliberately withhold information, they could have been less patronizing about it! Overall, the site seems to have a very low level of professionalism. To whatever degree this reflects on the device itself, it reflects poorly.
zach
Oooh, a challenge. Were we not actually interested in the ethics involved so much as the bragging rights (aka, karma)?... Please, let's stick to logic and reasoning here.
Now, to get back to the point, I don't understand what you mean and I would like it if you could explain a little. Either what he has done is based on previous work and he should cite it, or it is not based on any previous work. In that case, there's nothing to diverge from. I do agree with you that completely original work with no reference or comparison whatsoever to any prior literature does not need references. Are you saying that a substantial portion of ANKOS fits this description? Alternatively, have I misunderstood your post?
Zach
He claims no where in the book that I could find that others had not also covered much of this ground
:-) So, if Wolfram "doesn't claim no-one has done it before", that's short of actually admitting others have done it (or related things) before, which in turn is still short of saying THESE people have done THESE things in THESE papers.
It's not enough to be silent on the question of whether others have already covered the ground. A respectable writer has to devote serious effort to documenting previous writings on the subject. It's not even enough to say "this has been done"; you have to say by whom, when, in what journal...
Bibliographies serve an essential and fundamental purpose. They are not just there to make typesetting difficult!
Serious scientific books and papers list everything that's even **related** (well, closely related) to the topic at hand. The burden is on the author, not the reader, to indicate how much of the material is new.
zach
one of the few things stopping me from purchasing a phone is the fact that I do not want to pay for hundreds of features that I will never use. All I want is an address book and a way to make calls.
If that's all you want, you'd better buy a phone, sooner rather than later.
Someone else mentioned Motorola 120e; I have a Motorola 120i, which is pretty much the same, and I agree with the earlier poster. It is a good phone which should fit your needs without too much extra fluff.
zach
*ding*ding*ding* you get the joke, congratulations!
Humans do have some protection against UV. Tanning. Melanin. It's not perfect and complete protection, but I'd say it qualifies as a protection strategy...
The attacker must:
Be on your local network
Already have control of your DHCP server
I thought the attacker only has to have a fake, evil DHCP server which responds faster than the true good DHCP server...? Of course this is hard to do, and controlling the supposed-to-be good DHCP server would work more reliably, but I don't think that's exactly required.
zach
Bleh. Are his articles all like this? He has some anecdotes about bad security, with a "D'oh!" in between practically every paragraph---though that slows down after he gets tired of it, a page or two in. Then there's a story about a program called "Tresor" and some guy who had a weird problem with bundles acting like folders instead of application files. The assertion is made point-blank that this is an Apple bug, not a Tresor bug.
:-)
OK. Has this been reported or observed anywhere else? I've never heard of it, or seen it myself, though I've only been using OSX for a little under a year. If anyone can point me to a reference, I'd appreciate it. The article doesn't give any refs. I don't understand how he's so sure it's an Apple bug, unless it's so well-known that, gosh, everyone knows it's an Apple bug without even needing a link to, like, a Knowledge Base article or anything... but if it were that well-known, I hope I would know about it. So I have my doubts about this. If anyone knows one way or the other, I'd like to hear about it.
But really that's not the main point of the article, right? It's just one security flaw in a fairly specific situation. So the article, as far as I can tell, is a few anecdotes and a bunch of "D'oh!"s. Oh yeah, plus some insults and derision for all the programmers and the university professors who taught them. Thanks a lot, Tog.
His thesis---that security needs to be designed to actually make things secure, not theoretically securable---is, well, it's OK I guess. For one thing, he doesn't really argue for it---just provides anecdotes. That's not a coherent logical argument. Worse, it barely even ties in with the anecdotes anyway. So the hospital requires TOO MANY passwords. That does **not** make it theoretically securable, OK? (I can require 200 passwords, but it's not theoretically securable if the computer and fax machine are in the hallway.) He's right that security systems have to aim for real security, but he's wrong in saying that the problem is that people aim for "theoretical securability". Am I wrong here? Is there ANY theory of anything under which these systems are considered theoretically securable?
The only common thread I can think of, apart from inadequate security in general, is that the people who designed the security had an incomplete approach to security; they secured one part of the system (e.g., getting in with a password) way too much, and other parts (e.g., physical security of the fax machine) not enough. Or, they were unnecessarily protective, at the cost of user convenience (as in the VW radio example).
If I'm criticizing the article, maybe I should try to be constructive about it, right? I guess the anecdotes really point towards the two different themes in the previous paragraph: security model should be "complete", and there should be some kind of a balance between security and usability.
I may be wrong about my interpretation of his article. If there's a better way to read this article as it's written, please tell me. I suspect not, but hey. Or just call me a monkey, that's cool too.
Well, to wrap it up, he has a good point, basically, but no argument for it. Just a few isolated anecdotes, not all of which I believe. This is not high-quality writing. Sorry, Tog. I've read of few of your user-interface-design columns, and I liked them a little better. This one just didn't do it for me, I guess.
zach
A lot of people would kill just to have the books written already...
The whole story smacks of dubiousness (OW!). They quote this one guy, Crandall, about 15 times. They reference his blog. The publisher of some ipod web thingy has heard of it... from the same guy. There's an unnamed Pixar spokeswoman who's never heard of it... but she's too busy to look into it? What the heck?
p od_greeting.html)
:-) Nothing against the sub-sub-genre of indigenous music from northern Europe, ok, but I doubt he's really into it... all the time... and has been for the last ten years.
Wired reporter: I need one source that doesn't flow directly from this Crandall joker. I think I'll phone up Pixar.
*ring* *ring*
Pixar: Hello?
Wired reporter: Hello! Ipod jacking, blah, blah, blah...
Pixar: Uh... look... I'm really busy with... umm, the Finding Nemo DVD release! Yeah!
*click*
--
OK, why on earth should I believe even one word from this story?
The guy's blog, says that they thank each other:
We then stand and listen to each other's music for a minute or so, unjack, thank the other person and move on... (from: http://tingilinde.typepad.com/starstuff/2003/09/i
The Wired article says they don't speak at all:
"We listened for about 30 seconds," Crandall said. "No words were exchanged. We nodded and walked off."
OK, so some people say thanks and others don't. Fine.
But here's the clincher: He listens to indigenous music from northern Europe all the time, and has never heard trance. Yeah, right! Indigenous music from northern Europe?!
This monkey Crandall desperately wants attention. He desperately wants people to let him listen to their iPods. So he decides to start a trend. So he calls up Wired and plants a story, and the reporter doesn't think to question the fact that noone else has heard of this...
(Tinfoil hat time: And maybe he's traveling to Cambridge soon, so he nudges them a bit, saying he's heard it's starting there, too, so they'll be ready when he gets there!?)
OK, I'm done ranting now.
zach
I'm no expert, but it seems to me that Darwin is kind of like the thing running "under" Jaguar or Panther.
:-) ).
Roughly, Darwin is the underlying part of the operating system; the rest of Jaguar/Panther is mostly user interface stuff. This is what Apple charges money for---Darwin they give away, and the user interface part is $129 (per year
So you wouldn't install Darwin if you already have Jag or Panther. Only if you have another computer that you want to set up with a free OS (and you don't mind installing user interface stuff like X windows), or maybe if you want to set up a "dual boot" thing on a single computer. I could imagine this latter setup being useful for testing, or for servers (normally don't need GUI, but every now and then reboot into GUI?).
Presumably every update that's made to Darwin is also released for Jaguar/Panther via Software Update. At least, I hope so. (Insert here standard comment about Apple being taken seriously in Enterprise.)
zach
OK, good point, why have a bundle at all? For one thing, bundles are much easier to deal with than general manifolds---we don't even understand 3-manifolds, let alone 10-manifolds (eg, Poincare conj.). For another thing, if MathWorld says it's a product, and I'm curious about generalizing it, I think it's reasonable to make a small step to fiber bundles, before leaping all the way up to general manifolds. But as you say, the question generalizes up more.
:-)
I hope you don't mind if I pick a nit or two in your post:
a product of manifolds is just a product of manifolds. not a bundle.
But isn't it a trivial bundle, in two different ways, as you point out with reference to the example of a cylinder?
Anyway, most bundles are not trivial, and non-trivial bundles can't be simply "turned sideways" like a product can. I could be wrong, but it seems to me that in the topological category, and maybe in the smooth category as well, "most" bundles have a "unique" bundle structure map (in the sense that any two of them differ by a unique automorphism of the bundle space). On the other hand, spacetimes live in the category of smooth spaces with a tensor field which satisfies some conditions, etc... and in that category, maybe bundle structures are not unique?
So I was going to disagree with you about non-existence of canonical bundle structures, but actually you're probably right!
Anyway, I don't mean to argue about fiber bundles per se... Sorry... Thanks for the discussion, it's helped me think through my question a little more carefully than I had originally, and even given me a few new questions to think about!
If you don't mind, I'd like to ask you a somewhat stupid question. Would quantum computers be able to do anything with things like elliptic curve cryptography? There are various crypto schemes coming from algebraic geometry---hyperelliptic curves and so on. I'm not an expert, but it's my understanding that they don't rely on difficulty of factoring integers.
Thanks,
zach
I don't think QC affects elliptic curve cryptography.
Yes, of course you're right about the tensor and signature. That was silly of me. Thanks. I think the issue is partly physics terminology vs. math terminology: for me, a form is actually symmetric... I should have been more careful.
I have to point out, however, that a 6-dimensional fiber bundle on a 4-dimensional space IS a 10-dimensional manifold! Locally it looks like a product, but globally it can fail to be a product. Still, even if it's not a product, it is always a manifold. A product is a specific example of a fiber bundle---a trivial example, in the technical sense of "trivial"... So why can't space-time be a nontrivial bundle?
Example: a cylinder in R^3 is a bundle of lines over a circle. It's trivial---a cylinder is the product of a line and a circle. A Moebius band is **also** a bundle of lines over a circle: to see this, draw a circle down the center of the band, and that's the base space; then all the "perpendicular" lines going edge to edge on the band are the fibers. The Moebius band is non-trivial. This takes some proof, but it's true.
I am *not* BS'ing this. I know whereof I speak. Many books on topology, such as Munkres, have good explanations of trivial vs. non-trivial bundles.
Since you allow the base space to be a general 4-manifold M, you might as well allow non-trivial bundles. Locally they will be trivial; locally M is just R^4 (with a tensor field, etc.).
zach
though, or **because**? Yeesh.
Yes, I had the hanging problem. I did something like this:
:-( )
:-p
1. Turn SSL off in prefs (unfortunately, at this point your password, and a bunch of Mail traffic, goes out in cleartext, so this procedure is kind of not so good
*** Maybe quit Mail in here and start again? I forget
2. Turn it back on
3. Open Activity window. My copy of Mail was going bananas trying open, close, open, close, and open various connections. Cancel everything.
4. "Get new mail". Now you can click in the box without hanging.
If you click-and-drag, you get the text of the cert. So use option, to get the actual certificate file.
I managed to get the certificate into Keychain, no problem. Unfortunately Mail still doesn't like it. In my case, it's not a self-signed certificate---I think the issue might be an unknown certificate authority (Comodo Systems). Always worked before.
The error message now is "The certificate for the server is not valid." Clicking Continue makes everything work OK, and in tcpflow the traffice **looks** like it's encrypted. Anyone have any ideas about this? Is it in fact the CA and how can I get the computer to accept it? Thanks.
zach
Panther works just dandy on my laptop, not that I'm a power user or anything.
BUT, I just noticed one of my iPod cables is fraying! (The cable with the "wired remote" is fraying just above the plaug that goes into the iPod.) WTF!!!
As far as utilities and programs not working---well, (1) that's not much of a surprise, there, now is it? and (2) there are many, many, many, many more of them now than there were when 10.1 morphed into Jaguar. So I'd suspect that the vast majority of things that don't work are not things for Apple to worry about, and they'll just get fixed when the developers get around to it; and maybe some things *are* because of Apple bugs, but not most.
For example, someone said uControl doesn't work. Well, gosh. I sincerely hope it gets fixed soon, but is it Apple's "fault" that they changed and updated all the APIs and stuff?
Anyway, there are enough *real* bugs to go around... programs that stopped working is just a distraction.
Plus my ipod cable. Grrrrrr. Let's see if this Scotch tape can hold it together?...
zach
This time McNealy has gone way too far... He really has to go.
I'm stupid. I meant to say also the following. What if we specify an ample line bundle L on the C-Y 3-fold X; this is a polarization of X? Ample in algebraic geometry is the same as positive in several complex variables.
Among other things, this gives a *volume* of X, a positive real number, which is the same kind of volume that we're used to thinking of---like a cube with sides all equal to 1 has volume 1, etc. The Griffiths and Harris book would explain this better than I can.
The volume is something like $L^3/sqrt{2\pi}$, or something like that. Since it's physics, there are some kind of units. If this volume is small enough (i.e. measured in small enough units), it might suggest a reason why we can't move "along" the six dimensions corresponding to the C-Y 3-fold bundle: something small like an electron already fills up the tiny volume.
Ah, whatever. I'm just talking out my butt.
http://mathworld.wolfram.com/Calabi-YauSpace.html
The above-linked page has a rough definition of the kind of space a 10-dimensional string theory might live on. I don't know why they take a product $M \times V$ --- why not allow a more general bundle of C-Y 3-folds?
The imaginary version of string theory which exists only in my mind has the universe as a bundle of Calabi-Yau 3-folds over $M$ (a real 4-manifold with a Minkowski metric, or something like that... anyway, a $(3,1)$ form --- that's a Minkowski metric, right???). That's 10 dimensions. The 11- or other-dimensional kinds of string theory, I have no idea.
Being an algebraic geometer (in training), I think of a C-Y 3-fold as a smooth projective complex 3-dimensional variety, or manifold, with trivial canonical bundle.
Well, that's the space. Then all kinds of crap happens *in* the space, with strings and stuff, and that's a whole nother story...