String Theory

[linwood]

I know nothing about string theory.

The few concepts I am familair with are due only to their popping up in comparison to the Big Bang.

I`m reading this site first because well...it looks pretty straightforward.

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Think of a guitar string that has been tuned by stretching the string under tension across the guitar. Depending on how the string is plucked and how much tension is in the string, different musical notes will be created by the string. These musical notes could be said to be excitation modes of that guitar string under tension.

In a similar manner, in string theory, the elementary particles we observe in particle accelerators could be thought of as the "musical notes" or excitation modes of elementary strings.

In string theory, as in guitar playing, the string must be stretched under tension in order to become excited. However, the strings in string theory are floating in spacetime, they aren't tied down to a guitar. Nonetheless, they have tension. The string tension in string theory is denoted by the quantity 1/(2 p a'), where a' is pronounced "alpha prime"and is equal to the square of the string length scale. [/font]

http://superstringtheory.com/index.html

Anyone want to post anything about this theory please do so.

 

[Nick Soapdish]

I know nothing about string theory.

The few concepts I am familair with are due only to their popping up in comparison to the Big Bang.

I`m reading this site first because well...it looks pretty straightforward.

Anyone want to post anything about this theory please do so.

I am not very fond of String Theory. Most scientific advancements are driven by conceptual breakthroughs. String Theory on the other hand seems to have been developed by working out tons of complex mathematical problems and then throwing in the concepts at the end to fit the derivations. It seems to me they just started adding hypothetical dimensions to the Universe until they were able to compromise quantum and relativity. I see String Theory as a substantial mathematical exercise, but not a serious theory. It has been 5 or 6 years since I read much about it, so my memory of the details of the theory are not very clear.

I prefer the Loop Quantum Gravity theory, as far as Quantum Gravity theories go.

 

[linwood]

String Theory on the other hand seems to have been developed by working out tons of complex mathematical problems and then throwing in the concepts at the end to fit the derivations.

Uhh..yeah.

I`m 4 chapters into this "String Theory for Dummies" kind of site and well ..heh.
I`m going to put it off a little while longer and check out the Loop Quantum Gravity theory you`re speaking of.

I at least have a basis for understanding the concepts there but if anyone wants to use this thread for expounding on String Theory feel free and I`ll lurk it and stay quiet for a change.

 

[Pah]

I am not very fond of String Theory. Most scientific advancements are driven by conceptual breakthroughs. String Theory on the other hand seems to have been developed by working out tons of complex mathematical problems and then throwing in the concepts at the end to fit the derivations. It seems to me they just started adding hypothetical dimensions to the Universe until they were able to compromise quantum and relativity. I see String Theory as a substantial mathematical exercise, but not a serious theory. It has been 5 or 6 years since I read much about it, so my memory of the details of the theory are not very clear.

I prefer the Loop Quantum Gravity theory, as far as Quantum Gravity theories go.

Loop Quantum Gravity Carlo Rovelli, as of 1997 http://relativity.livingreviews.org/Articles/lrr-1998-1/node1.html

Long standing open problems within the theory (such as the lack of a scalar product, the incompleteness of the loop basis and the related difficulty of dealing with identities between states, or the difficulty of implementing the reality conditions in the quantum theory) have been solidly and satisfactorily solved. But while it is fairly well developed, loop quantum gravity is not yet a complete theory. Nor has its consistency with classical general relativity been firmly established yet. The sector of the theory which has not yet solidified is the dynamics, which exists in several variants presently under intense scrutiny. On the other hand, in my opinion the strength of the theory is its compelling capacity to describe quantum spacetime in a background independent nonperturbative manner, and its genuine attempt to synthesize the conceptual novelties introduced by quantum mechanics with the ones introduced by general relativity.

String theory is consistent with Quantum Theory and the Theory of Relativity.

[as an aside - I looked in Google for "parallel worlds" and was given, amongst other things "Parrallel Worlds by Michio Kaku in which he continues his writing about M-Theory, Superstring Theory, and the parrallel universise that can occur within those theories" on a reading list - MY LIST in http://www.religiousforums.com/forum/showthread.php?t=8375 end aside]

From the Doubleday Book review

As astronomers wade through the avalanche of data from the WMAP satellite, a new cosmological picture is emerging. So far, the leading theory about the birth of the universe is the “inflationary universe theory,” a major refinement on the big bang theory. In this theory, our universe may be but one in a multiverse, floating like a bubble in an infinite sea of bubble universes, with new universes being created all the time. A parallel universe may well hover a mere millimeter from our own.

The very idea of parallel universes and the string theory that can explain their existence was once viewed with suspicion by scientists, seen as the province of mystics, charlatans, and cranks. But today, physicists overwhelmingly support string-theory, and its latest iteration, M-theory, as it is this one theory that, if proven correct, would reconcile the four forces of the universe simply and elegantly, and answer the question “What happened before the big bang?”

I should mention that this work depends on mutliple dimensions and, quite frankly, I'm not up to the challange of telling what's what about them

M-Theory, the current irteration of the "grand theory of everything", says that branes are composed of strings in "sheet" configuration and that collisions of branes produce universes in multiple dimensions

I really wish I could do more but the book I have makes it difficult for me to remember the data because of it's newness. I do not have the education to easily go from relativity to quantum mechanics and cosmology. I will see if I can scan and edit some material but no promisies

 

[Nick Soapdish]

Loop Quantum Gravity Carlo Rovelli, as of 1997 http://relativity.livingreviews.org/Articles/lrr-1998-1/node1.htmlString theory is consistent with Quantum Theory and the Theory of Relativity.

[as an aside - I looked in Google for "parallel worlds" and was given, amongst other things "Parrallel Worlds by Michio Kaku in which he continues his writing about M-Theory, Superstring Theory, and the parrallel universise that can occur within those theories" on a reading list - MY LIST in http://www.religiousforums.com/forum/showthread.php?t=8375 end aside]

From the Doubleday Book review


I should mention that this work depends on mutliple dimensions and, quite frankly, I'm not up to the challange of telling what's what about them

M-Theory, the current irteration of the "grand theory of everything", says that branes are composed of strings in "sheet" configuration and that collisions of branes produce universes in multiple dimensions

I really wish I could do more but the book I have makes it difficult for me to remember the data because of it's newness. I do not have the education to easily go from relativity to quantum mechanics and cosmology. I will see if I can scan and edit some material but no promisies

Actually I read about half of Kaku's book 5 or 6 years ago. It is my primary exposure to the theory.

The reason I prefer Loop Quantum Gravity is because of its conceptual foundations. The ideas behind strings and banes do not seem nearly as elegant. Even though string theory has dozens of pages of mathematical derivations behind it, history seems to favor the more elegant theory.

 

[Pah]

The first evidence for string theory?

* 18 December 2004
* From New Scientist Print Edition. Subscribe and get 4 free issues.
* Marcus Chown

The theory is our best hope of understanding how the universe works at its most fundamental level. It suggests that the basic constituents of matter are impossibly narrow threads of concentrated energy. The various different ways these superstrings can vibrate correspond to different fundamental particles, such as the up-quark and the muon-neutrino

One of the strangest features of string theory is that it requires many more dimensions than we can see: the only way the vibration modes of the superstrings can be sufficiently diverse to create all particles is if the superstrings vibrate in a space-time of 10 dimensions. Of course, we appear to live in a universe with only four dimensions - three of space and one of time - so string theorists have postulated that the extra dimensions are "rolled up" much smaller than the dimensions of an atom. However, until now no one had seen evidence to support string theory, and many scientists dismiss its ideas as untestable conjectures. But are they about to be proved wrong?

The answer lies with the big bang that kicked our universe into existence. String theory suggests that our universe may be a three-dimensional island or "brane" moving through 10-dimensional space, and that the big bang might have been caused by a collision between two such branes (New Scientist, 16 March 2002, p 26). This kind of collision would release a tremendous amount of energy, which would create a plethora of different kinds of stringy object. One type is the fundamental superstrings. Another is strange objects called Dirichlet or "D" branes that exist within each brane and as connections between branes, but intersect with only one dimension of our universe. As a result, they look to us like one-dimensional superstrings.

But these are not necessarily the tiny strings we associate with fundamental particles: they can be of all sizes right up to astronomical dimensions. "Contrary to what we used to think, fundamental strings need not be ultra-tiny," says Tom Kibble of Imperial College London. And the bigger strings can be big enough to leave a visible mark on our universe. That's because a string distorts the space around it in a unique way. We are used to objects with mass or energy distorting the space around them, rather like a person's weight distorting the flat surface of a trampoline. This distortion of space is the origin of every object's gravitational attraction. However, a string is somewhat different from a normal object. All its energy is held on a one-dimensional line, not spread through space, and this concentrated energy distorts the space around it into a conical shape, with the string as its axis.

Actually I read about half of Kaku's book 5 or 6 years ago. It is my primary exposure to the theory.

The reason I prefer Loop Quantum Gravity is because of its conceptual foundations. The ideas behind strings and banes do not seem nearly as elegant. Even though string theory has dozens of pages of mathematical derivations behind it, history seems to favor the more elegant theory.

Parallel Worlds is Kaku's latest publication - 2005. He has three earlier books.

I thought elegant, in this case, meant the theory was free of anomalities. I understand that gravity under quantum theory produces divergences. From page 195 of Parallel Worlds "Physicists had spent decades trying to patch up a quantum theory of of gravity, only to find it hopelessly riddled with new divergences and anomilies. Gradually, they realized the solution was to abandon the Band-Aid approach and adopt an entirely new theory."

Kaku does not give a history of quantum gravitational theory so Loop Quantum Gravity (LQG) is not specifically addressed. Continuing " ... In 1984, the tide against string theory suddenly turned"

Can you give us more about LQG and show how it addresses the union of quantum theory with relativity theory. I ask honestly - I just don't know if it does as much as string theory.

 

[michel]

I personally feel that I get on better with the 'string' theory; I also have an impish suspicion that scientists love to over complicate theories in order to maintain their high level of 'sage-ism'.
The string theory relies much on a frequency based existance, which makes sense, and allows us to explain various wuld be anomalies in nature.

 

[Nick Soapdish]

Parallel Worlds is Kaku's latest publication - 2005. He has three earlier books.

The book I read was Hyperspace.

I thought elegant, in this case, meant the theory was free of anomalities. I understand that gravity under quantum theory produces divergences. From page 195 of Parallel Worlds "Physicists had spent decades trying to patch up a quantum theory of of gravity, only to find it hopelessly riddled with new divergences and anomilies. Gradually, they realized the solution was to abandon the Band-Aid approach and adopt an entirely new theory."

The lack of anamalities is of course very important in any scientific theory, but I view elegance more as the intrinsic simplicity, beauty (stick with me here), or symmetry in the theory.

Kaku does not give a history of quantum gravitational theory so Loop Quantum Gravity (LQG) is not specifically addressed. Continuing " ... In 1984, the tide against string theory suddenly turned"

Can you give us more about LQG and show how it addresses the union of quantum theory with relativity theory. I ask honestly - I just don't know if it does as much as string theory.

The conceptual foundations in LQG have to do creating a new geometry for representing space-time. This new geometry treats the dimensions of space and time as discrete rather than continuous. This means if you get to a short enough distance in space, you cannot continue to divide that space; it becomes indivisible. This mirrors what we already know about the dimension of mass/energy within quantum physics, where we have a quanta of energy that cannot be further divided.

I do not claim to be anything close to an expert, but here is a link that goes into more detail: http://en.wikipedia.org/wiki/Quantum_loop_theory

 

[oracle]

The thing about science is, is that they study the components, say for instance seperate pieces of the puzzle. So we have things like electromagnetism, strong force, weak force, general relativity, quantum mechanics,etc. But, these are just pieces of the puzzle. M-theory is the endeavor to put these pieces together, so we have an overall picture of our universe. So far we have 5 string theories. Anyways, it's about putting the pieces of the puzzle together.

 

[oracle]

[/color]
The conceptual foundations in LQG have to do creating a new geometry for representing space-time. This new geometry treats the dimensions of space and time as discrete rather than continuous. This means if you get to a short enough distance in space, you cannot continue to divide that space; it becomes indivisible. This mirrors what we already know about the dimension of mass/energy within quantum physics, where we have a quanta of energy that cannot be further divided.

In other words a singularity.

 

[linwood]

Ok from my wandering s I`ve been checking out M-theory.
It`s pretty interesting but difficult for me to believe in it`s original form (But you already guessed that )

Witten has an idea that might make those 11 dimensions unnecessary for M-Theory.
Which would make it far more acceptable for me.
Unfortunately as far as I can tell he has not really elaborated much ion this idea yet.
Anyone have any soruces on it?

Oh..here`s a cool little article that might help the layman get a better grasp of the concept of string theory.

http://education.guardian.co.uk/print/0,3858,5106816-108233,00.html

 

[Pah]

I personally feel that I get on better with the 'string' theory; I also have an impish suspicion that scientists love to over complicate theories in order to maintain their high level of 'sage-ism'.
The string theory relies much on a frequency based existance, which makes sense, and allows us to explain various wuld be anomalies in nature.

String theory is a simplification of the atomic structure. In the theory, all subatomic particles become strings, the elemental unit, with varying frequency. The particles associated with the force (gravitron, gluon, photon, weak gage bonsons which are respecively gravity, the strong force, electromagnetic force, and the weak force) become strings. All electrons and quarks become strings

Replacing the point-particle material with strings eleminates incompatibility between quatum mechanics and general relativity. The unification theory and the standard model of cosmology are replaced by string theory. There is no longer a separate set of physics for the micro and the macro of the material world.

 

[Pah]

Ok from my wandering s I`ve been checking out M-theory.
It`s pretty interesting but difficult for me to believe in it`s original form (But you already guessed that )

Witten has an idea that might make those 11 dimensions unnecessary for M-Theory.
Which would make it far more acceptable for me.
Unfortunately as far as I can tell he has not really elaborated much ion this idea yet.
Anyone have any soruces on it?

Oh..here`s a cool little article that might help the layman get a better grasp of the concept of string theory.

http://education.guardian.co.uk/print/0,3858,5106816-108233,00.html

Dimensions may be envised with this example of magnification. A hose is stretched beween two houses and has an ant traversing it. From a distance the hose looks like a one dimensional line. Closer observation lets the "line" become a two dimensional hose - the ant is visible, going accross the hose, dissappearing at times. In a higher degree of maginification the ant is found to be circling the hose. It is still considered two dimensional because the ant's position is defined by the lenght traveled and the degree of cirumlution. At the "closer observation" the 2nd dimension was difficult to see because it was "curled up" along the 1st dimension and was only seen with higher magnification.

Now imagine a stack of graph papers - the lowest paper reresenting 2 dimensions. The next highest paper represnts a higher magnification of one cell on the lower sheet. The third sheet represents a point on the second sheet and so forth. Now throw in the the loops the ant made along one of the lines on the first sheet as a coiled second sheet and contine that concept for all the sheets. It is only with the highest magnification can we see this structure. How small does this get? It approaches the Plank Length - a millionth of a billionth of a billionth of a billionth of a centimeter (10 to the minus 33 power of a centimenter)

 

[linwood]

Thank you Pah, that makes more sense.

I will always have a problem with the absolute terminology of science.

It gets on my nerves.

 

[Pah]

A review of my source, The Elegent Universe by Brian Greene
http://recharger.go.nease.net/Sci/Universe.htm

Information about dimensions and links to other "string" sites (I haven't been there yet)
http://people.cs.uchicago.edu/~mbw/astro18200/dimensions.html