Matter as excitations of spacetime lattice?

  • #26
tom.stoer
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Think about the surface of a lake. It looks like a smooth manifold. If you look closer, you will find water molecules or even H and O atomes. So it seems as if the surface consists of H and O atoms. But in principle the very concept of "manifold", "surface", "water waves" has disappeared. There are only atoms.

It's the same with the spin network in LQG. There is not space between the "lattice points" - just as there is no water between the atoms. The water "is" the atoms - or the other way round "the atoms are the water".
 
  • #27
marcus
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Think about the surface of a lake. It looks like a smooth manifold. If you look closer, you will find water molecules or even H and O atomes. So it seems as if the surface consists of H and O atoms. But in principle the very concept of "manifold", "surface", "water waves" has disappeared. There are only atoms.

It's the same with the spin network in LQG. There is not space between the "lattice points" - just as there is no water between the atoms. The water "is" the atoms - or the other way round "the atoms are the water".
Classic. I like how these 7 words have some resonance: "There is no water between the atoms."
There should be a short introductory QG book written in such clear style.
 
  • #28
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It's the same with the spin network in LQG. There is not space between the "lattice points" - just as there is no water between the atoms. The water "is" the atoms - or the other way round "the atoms are the water".
Okay, so the interactions that allow things like waves are modeled by adjacent "lattice points" bumping up against each other in some well defined but chaotic manner? Or is there some rules built into any particular LQG model to account for the interactions of adjacent lattice points.
 
  • #29
tom.stoer
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The dynamics of LQG is well-defined. It's based on so-called spin networks. Every link (edge) in the network carries something like a spin; of course nothing really "spins", but it's similar in the mathematical language used. At every vertex, where different links (spins) meet, they are "intertwined". The spin network therefore carries additional information in its vertices and edges. There are well-defined rules how these spins interact; there are rules how additional vertices and links can be created. Each vertex represents an "atom of space" - a minimal volume. Each link represents a minimal surface.

On this level the mathematical structure is rather clear. One big question is how matter could emerge from these structures w/o additional input. Another question is how the well-known spacetimewe observe (the "water") emerges from these structures.

There is some progress especially regarding the second problem, but the whole picture is not complete - it's work in progress.
 

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