Are there any physisists on the forum?

[twentysix by twentyfive]

if abiding by the string theory, all matter is made of tiny strings which create weight etc then nothing can go beyond the speed of light becuase forces exist upon the strings wouldnt be able to exist, same theory that if you went below K, -273 or around there thne there is no energy at all for the quarks and strings inside them that the particle simply cannot exist

Err I don't think so. At Absolute Zero (-273 ish Celcius) matter exists in it's ground state. Ground states have energy but the energy is not available. That would certainly apply to quarks. The Vacuum energy that exists in empty space is a similar concept which comes in through Quantum Field Theory. String theory I don't know about so much. Are you saying that all obseved paricles and quantum fields arise from quantum excitations of Strings? Indeed this is about what I do understand. If so I would expect that the Strings themselves to have non zero energies in their ground states (absolute zero). Else everything just vanishes............. Or maybe that's the idea?

 

[Davidc]

Echo (arXic isn't proper peer review ho ho ho how many times have I heard that one) echo.

It's just holography again, getting rid of the parameters problem mentioned earlier...

Don't know - I've seen it mentioned but little more. Sooner or later someone will solve the conundrum of what gives rise to gravity. Whenever that happens I'm sure the starting hypothesis will receive more than its fair share of analysis and attention.

If its on arxiv give it time and if its any good it'll get polished and published.

It's the sort of thing that I've always found casually interesting but not inspiring so I can wait.

 

[661-Pete]

Pete - were these the 2 you were thinking of - or is there another I've forgotten

The phase velocity was certainly one of them, yes, thanks for explaining it better than I could (I was thinking of de Broglie wave functions, but more or less the same thing).

The other one, entangled states - well it was at the back of my mind but couldn't remember: now it rings a bell (pun intended? ). Never got as far as 2nd quantization or QED, does that sort it out?

Another example - a bit frivolous and not very scientific, but it illustrates a point.

Imagine a hugely powerful laser, strong enough, when shining from Earth, to cast a spot of light on the Moon. Put this laser on a turntable and rotate it so as to complete one rev per second, allowing the spot of light to sweep across the moon once every revolution.
Then that spot of light is moving across the moon at a lot more than light speed (about 8c).
But that's OK because the places on the Moon 'visited' by the spot have no causal connection with each other, and no matter, energy or information is conveyed from point to point on the Moon. So it doesn't violate Relativity.

The point is: light speed is certainly a limit, but only for certain types of motion.

 

[twentysix by twentyfive]

The phase velocity was certainly one of them, yes, thanks for explaining it better than I could (I was thinking of de Broglie wave functions, but more or less the same thing).

The other one, entangled states - well it was at the back of my mind but couldn't remember: now it rings a bell (pun intended? ). Never got as far as 2nd quantization or QED, does that sort it out?

Another example - a bit frivolous and not very scientific, but it illustrates a point.

Imagine a hugely powerful laser, strong enough, when shining from Earth, to cast a spot of light on the Moon. Put this laser on a turntable and rotate it so as to complete one rev per second, allowing the spot of light to sweep across the moon once every revolution.
Then that spot of light is moving across the moon at a lot more than light speed (about 8c).
But that's OK because the places on the Moon 'visited' by the spot have no causal connection with each other, and no matter, energy or information is conveyed from point to point on the Moon. So it doesn't violate Relativity.
The point is: light speed is certainly a limit, but only for certain types of motion.

Ah yes indeed. But that it is a phase velocity too - just another way of looking at it. And De Broglie is again phase velocity.

No I don't think that QED does sort it out. It is one of THE puzzles at the moment I think and solving this may (big may there) sort other puzzles about the nature of reality too. It's a clue

I'm getting on a bit now. The one thing I will miss when I eventually shuffle off (if one can actually miss anything in that state) is all this fascinating stuff and the solution to the puzzle. Of course this assume that there is a solution and things aren't just layer upon layer of onion skins. We are about 2 or 3 layers in now...

New theory of the Universe announced - "It's an infinte set of shells like the layers of an onion" - says 26x25

 

[marinyork]

Ah yes indeed. But that it is a phase velocity too - just another way of looking at it. And De Broglie is again phase velocity.

No I don't think that QED does sort it out. It is one of THE puzzles at the moment I think and solving this may (big may there) sort other puzzles about the nature of reality too. It's a clue

QED certainly doesn't sort it out. Anyway what I was told by someone involved in quantum information in the 80s and 90s was that people got bored of 50 years of arguments and went off to do other slightly different things and this is getting there rather like the story the other week about using a quantum computer to calculate the hydrogen molecule spectrum to 20 bits of accuracy.

Btw I don't know what you were saying earlier but I would point out that the Maldacena conjecture is not controversial.

 

[twentysix by twentyfive]

Btw I don't know what you were saying earlier but I would point out that the Maldacena conjecture is not controversial.

Lost me there I'm afraid. I Googled and Wikipedia plunged me straight into the deep end . I'd need to do a bit of reading to get to some level of understanding on that. Have you any references? I have heard some of the terms (such as AdS Space) used but I need to do a bit of homework.

BTW - does anyone inderstand Hawking Radiation? My concern is that the Black Hole seems to radiate the ordinary matter (from the vacuum pair production fluctuations) whilst the anti matter apparently is sucked in and "evaporates" the black hole. Why the assymmetry? Or have I got it completely A over T?

 

[Yellow Fang]

This curiosity does not defy Relativity Theory as no information is carried by the phase of a wave.

Is this true? I seem to remember reading in an OU Digital Communications module that information was often encoded in the phases of the carrier waves.

 

[Yellow Fang]

If any of you geeks are genuinely interested in this stuff, I've got the course materials for the O.U. course "Space, Time, and Cosmology."

Without a doubt the most unrewarding experience I've ever had the misfortune to have to endure - I hated every minute of it - but it does cover mechanics, transformations, Special & General relativity, and Cosmology.

After this course I still don't know anything about relativity or cosmology, but now I don't care that I don't know.

It would cost abot£15 to post the lot if anyone wants it.

Well, at least you have something to chat about to Myleen Klass if you ever get the opportunity. I seem to remember reading that she studied the same course.

 

[twentysix by twentyfive]

Is this true? I seem to remember reading in an OU Digital Communications module that information was often encoded in the phases of the carrier waves.

Indeed it is. Information carried by the wave is encoded over many many cycles of the wave. Then the crest breaking thing isn't the appropriate speed - it is the wave speed itself. Indeed the energy content of the wave which contains the information travels at wave speed.

 

[Tollers]

Is that tiny, amount of extra velocity important? Could they not simply fire a beam of particles across one accelerated beam at 90 degrees?

But as the particles are travelling in opposite directions on a collision course their relative speed is 2x speed of light. If one beam was fired at 90%. the impact would only have half of the energy.

 

[marinyork]

Lost me there I'm afraid. I Googled and Wikipedia plunged me straight into the deep end . I'd need to do a bit of reading to get to some level of understanding on that. Have you any references? I have heard some of the terms (such as AdS Space) used but I need to do a bit of homework.

BTW - does anyone inderstand Hawking Radiation? My concern is that the Black Hole seems to radiate the ordinary matter (from the vacuum pair production fluctuations) whilst the anti matter apparently is sucked in and "evaporates" the black hole. Why the assymmetry? Or have I got it completely A over T?

AdS is not complicated, just ignore all the metrics and that bobbins if you haven't done much Riemmanian Geometry. It is just saying that it is some geometry with a particular solution of the field equations of GR and you add in some cosmological constant. So anyway you just get a product space of that and something else that works for and let's choose a five dimensional sphere and you get one of the famous original five string theories. There is a correspondance between this and some sort of field theory. Really very loosely all it is saying in a way is that string theory is at some level the same as a quantum field theory (in a specific case which we'll ignore).

As people have asked I might have a look and see what Penrose has to say on the matter (I forget) if people want to get hold of something in the library.

Sorry I don't understand your point about black holes, I thought it was believed that they do give out anti matter too, but you'd have to ask an astrophysicist to make absolutely sure on that one.

 

[twentysix by twentyfive]

AdS is not complicated, just ignore all the metrics and that bobbins if you haven't done much Riemmanian Geometry. It is just saying that it is some geometry with a particular solution of the field equations of GR and you add in some cosmological constant. So anyway you just get a product space of that and something else that works for and let's choose a five dimensional sphere and you get one of the famous original five string theories. There is a correspondance between this and some sort of field theory. Really very loosely all it is saying in a way is that string theory is at some level the same as a quantum field theory (in a specific case which we'll ignore).

As people have asked I might have a look and see what Penrose has to say on the matter (I forget) if people want to get hold of something in the library.

Sorry I don't understand your point about black holes, I thought it was believed that they do give out anti matter too, but you'd have to ask an astrophysicist to make absolutely sure on that one.

Thanks Marinyork. I sort of understand what's going on now. Effectively String theory and QFT have a correspondence. That is good news for ST otherwise it would be a dead duck.

I didn't mean to imply that no ordinary matter was sucked in to, or no anti matter emmitted from, the black hole - only that on average it amounts to the black hole evaporating. I suppose I'm assuming that the black hole is ordinary matter as it was presumably formed from collapsed stars and the like.

 

[Yellow Fang]

If any of you geeks are genuinely interested in this stuff, I've got the course materials for the O.U. course "Space, Time, and Cosmology."

Without a doubt the most unrewarding experience I've ever had the misfortune to have to endure - I hated every minute of it - but it does cover mechanics, transformations, Special & General relativity, and Cosmology.

After this course I still don't know anything about relativity or cosmology, but now I don't care that I don't know.

It would cost abot£15 to post the lot if anyone wants it.

Can I have second dibs after Night Train?

 

[marinyork]

Can I have second dibs after Night Train?

You got the pdfs, michael, just out of curiosity?

Many people like Schutz - gravity from the ground up. It's a physicist's version of GR if you er get my drift .

 

[twentysix by twentyfive]

Many people like Schutz - gravity from the ground up. It's a physicist's version of GR if you er get my drift .

Are you a mathematician then MY?

As a physicist I know I'm not a mathematician

I think that was your drift