Understanding Causal Set Theory and Its Implications for the Universe

[causalset]

Anyone heard of causal set theory before? Basically, it is a concept that our universe should be viewed solely as set of discrete events and the causal relations between them. I wrote a thesis where I described the Lagrangians of quantum fields. Please let me know what you think: arXiv:0905.2263

 

[atyy]

Is this related to Sorkin's work?

 

[causalset]

Yes, Sorkin founded it

 

[cesiumfrog]

What counts as an "event" (when you are describing quantum fields)?

 

[causalset]

Every point of space time is referred to as event. The only reason there are finitely many "events" is that I assume that there are only finitely many points in space time; they just are spaced so densely that they look continuous to us.

By the way, when I say "spaced so densely", it is not a well defined term since there is nothing "between" these points (after all, spacetime=points). So, according to causal set theory, spacetime, by its nature, is discrete, and its discrete elements are called events.

 

[atyy]

How is a continuum derived from discrete elements?

I've heard Xiao-Gang Wen say something similar, like the fundamental elements are spins or qbits with nothing between them. But I think when he talks about the low energy limit, that assumes some sort of fixed smooth background to define low energy.

 

[cesiumfrog]

Thinking of the Milne spacetime, it seems like it would be difficult for the density of a discrete spacetime not to produce a preferred frame?

(I'm not really disagreeing with the discrete approaches, just wondering if you could explain it a little more?)