Very interesting question

[Curious6]

This is a question I came about while thinking about the nature of matter and energy. According to string theory, the very fundamental building blocks of matter and energy are tiny vibrating strings. I was thinking to myself then: why are these the fundamental building blocks of the Universe, why is it not some other thing? Is there are any equation that would naturally predict strings to be the only possible option for building blocks? Also, would the TOE have something to say about strings being the only possible option for the building blocks of matter and energy? I'm sorry if this question sounds confusing, but I was just wondering about this!

 

[selfAdjoint]

The reason strings became so interesting is that point particles have inevitable problems with self energy infinities as the space (with its interacting quantum vacuum) shrinks to zero around them, but strings are automatically free of that problem. Also one of the earliest discoveries from strings was that they predict a spin-2 particle with all the properties of a graviton. This was enough to get string physics off the ground, and since then it has been a mine of theoretical "sweetness" that keeps physicists motivated, although no new checkable results have turned up.

If a real TOE ever turns up, one of its characteristics should be that it accounts for its predictions as necessary. That is just my predjudice, and it means I distinguish the term TOE from the term unification of forces.

 

[Mike2]

The reason strings became so interesting is that point particles have inevitable problems with self energy infinities as the space (with its interacting quantum vacuum) shrinks to zero around them, but strings are automatically free of that problem. Also one of the earliest discoveries from strings was that they predict a spin-2 particle with all the properties of a graviton. This was enough to get string physics off the ground, and since then it has been a mine of theoretical "sweetness" that keeps physicists motivated, although no new checkable results have turned up.

Don't the higher dimensional objects (branes) of M-theory also give a spin-2 graviton?

 

[alexsok]

Mike2
I'm not sure how to answer your question... the basic picture though is that higher dimensional objects (D-Branes, 5-Branes, etc) are situated in a putative higher dimensional space, known around the physics community as "the bulk" and the standard model particles and fields are confined to these membranes. The graviton, as one of the basic prediction of String theory is the only particle (at least relying upon the current depictin) that is allowed to propagate in the bulk and supposedly, is the sole reason why gravity is felt so weakly in our universe.

 

[Mike2]

Mike2
I'm not sure how to answer your question... the basic picture though is that higher dimensional objects (D-Branes, 5-Branes, etc) are situated in a putative higher dimensional space, known around the physics community as "the bulk" and the standard model particles and fields are confined to these membranes. The graviton, as one of the basic prediction of String theory is the only particle (at least relying upon the current depictin) that is allowed to propagate in the bulk and supposedly, is the sole reason why gravity is felt so weakly in our universe.

For example, could we not have a closed surface that vibrates in latitudonally, like many string stacked one a-top the other? Since every cross section is vibrating like a string, cannot one of those vibrational modes also be a graviton?

Or now that a surface has one more dimension to vibrate in, cannot a surface just as easily "incorporate" a graviton as a string? For surely, you can pick out a line (string) on a surface.

 

[sol2]

Mike2
The graviton, as one of the basic prediction of String theory is the only particle (at least relying upon the current depictin) that is allowed to propagate in the bulk and supposedly, is the sole reason why gravity is felt so weakly in our universe.

We are also then talking about something that can be felt strongly? This is the unification principal that speak to all dimensions? I think sometimes we forget how we got there, and how the consistancy of this action is defined?

We understand gravitation waves are not impeded like em waves are.

Learning to understand Webber bars and then the graduation to Ligo makes this a very interesting revelation in terms of Kip Thornes window on the universe?