Good Pop Level String Article

[BenTheMan]

http://download.iop.org/pw/PWSep07strings.pdf

 

This is a pretty good article, and sumarizes the attitudes of the people in the field (at least that I know) pretty well.

[Martin]

http://download.iop.org/pw/PWSep07strings.pdf

 

This is a pretty good article, and sumarizes the attitudes of the people in the field (at least that I know) pretty well.

 

thanks for the link. I'd go farther and say it is not just "pretty good" It is an excellent article of its kind (whether you call it Pop or something else) with lots of historical facts, quotes from string personalities, and much much more.

 

I hadn't registered the history goes back 40 years. Offhand I would have said 30.

 

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UPDATE REPLY TO NEXT POST

(which is why you should include the 1998 Maldacena paper in your 5 year index!).

 

I DID of course include maldacena's 1998 paper in my citation count. It was one of the highly cited ones I averaged to get the 2002 figure. (because in 2002 it was recent, i.e. published in the past five years). I think you may be mistaken, but if I missed something I'd be glad to have it pointed out.

[BenTheMan]

Yeah---strings are still the best way to understand the strong force, in my opinion. At least, when I describe hadronization to people it's always the analogy that I use. I always thought that it was ironic that it took fourty years for people to go in a huge circle, and realize that string theory really COULD describe the strong force, via AdS/CFT (which is why you should include the 1998 Maldacena paper in your 5 year index!).

[Martin]

... AdS/CFT (which is why you should include the 1998 Maldacena paper in your 5 year index!).

1998 Maldacena was included in the 2002 tally from the git-go:-)

 

Article provides much informative detail but is not particularly balanced.

Readers who want some contrasting POV for balance could try

 

http://www.math.columbia.edu/~woit/wordpress/?p=593

[vincent]

The position and momentum probability distributions are Fourier transforms of each other (as are energy and time). The uncertainty principle falls straight out of that.

 

Right. It is a direct result of the basic principles of quantum mechanics that the narrower the probability distribution of one obervable is, the broader that of it’s conjugate will be.

 

However the time-energy inequality is not on the same footing as the position-momentum uncertainty principle since there is no Hermitian operator corresponding to time. Yes, time is a dynamical quantity in that it varies with time, but in a trivial self-referential way and is really just a parameter on which other quantities depend. The actual meaning of ΔE and Δt in the time-energy inequality are respectively the spread in the energy distribution and the amount of time it takes for the wavefunction to changed appreciably.

 

On a much deeper level…If you did not have uncertainty as a fundamental part of the measured system, then one could predict the outcome of each eventuality with 100% accuracy....

 

…therefore contradicting the tenets of quantum mechanics. Fine. But I would apply the term “on a much deeper level” instead to the relation between the uncertainty principle and the principle of complementarity.

 

When due to the basic principles of quantum mechanics the use of one classical concept excludes the use of another, they are said to be complementary. The principle of complementarity says that the experimental arrangements that measure complementary properties are mutually exclusive and are both needed to demonstrate all of the physics of quantum mechanical systems.

 

For example, consider wave-particle duality as applied to an electron which is the first form in which one usually encounters the concept of complementarity. Wave-particle duality is often erroneously described as meaning that the electron is simultaneously wave and particle. But this is impossible since particle and wavelike characteristics are strictly incompatible. What saves us is the uncertainty principle which says that there are no experiments one can perform in which the position of the electron, this being the particle aspect, and the momentum of the electron, this being the wave aspect, can be simultaneously measured to arbitrarly high precision.

 

Thus the deeper meaning of the uncertainty principle is that it is the condition that ensures the logical consistency of quantum mechanics.

 

Uncertainty and unitarity are coupled. I think...

 

A unitary quantum theory is one in which probability is conserved. Though they're pathological, one can imagine nonunitary theories in which the uncertainty principle formally still holds.

[iNow]

What saves us is the uncertainty principle which says that there are no experiments one can perform in which the position of the electron, this being the particle aspect, and the momentum of the electron, this being the wave aspect, can be simultaneously measured to arbitrarly high precision.

 

Thus the deeper meaning of the uncertainty principle is that it is the condition that ensures the logical consistency of quantum mechanics.

 

Thank you, Vincent. Your knowledge of the topic is admittedly beyond my own. However, I personally think there must still be a better explanation than that which has been offered, as this is a bit like saying the bible exists because religion would not have any central tenets without it. There is something inherent in the universe that makes the outcome of events non-absolute. The principle of uncertainty is a description of this.

 

 

The only thing that is absolute is change itself.

[vincent]

Thank you, Vincent. Your knowledge of the topic is admittedly beyond my own. However, I personally think there must still be a better explanation than that which has been offered, as this is a bit like saying the bible exists because religion would not have any central tenets without it. There is something inherent in the universe that makes the outcome of events non-absolute. The principle of uncertainty is a description of this.

 

 

The only thing that is absolute is change itself.

 

Hi iNow,

 

I obviously posted in the wrong thread. Sorry about that. I added my response to your above post at the end of my original post which I've copied to the correct thread http://www.scienceforums.net/forum/showthread.php?p=358312#post358312