Do theories of quantum gravity require that space-time is a lattice?

james.goetz

Do theories of quantum gravity require that space-time is a lattice instead of a continuum?

I guess this question has been addressed elsewhere, but I would appreciate hearing different points of view. Please dummy down the responses so a philosopher can understand it.

Mark M

James, quantum gravity strongly implies a discrete spacetime. First, look at black hole thermodynamics. Specifically, a region has what is called a Bekenstein bound - a limit to the amount of information a region can contain, a maximum density. Trying to exceed this density will simply result in the growth of the event horizon around this region. Next, look at LQG, which is based purely around a dicrete spacetime, no question there. Finally, M-theroy also implies a discrete spacetime - without getting into detail, it breaks strings down into discrete 'string bits'. I see no possible way that spacetime couldn't be discrete on the planck scale.

Naty1

See IS SPACETIME QUANTIZED here:
http://www.knowledgerush.com/kr/encyclopedia/Spacetime/

A different perspective:
http://arxiv.org/abs/1010.4354

“The equivalence of continuous and discrete information, which is of key importance in information theory, is established by Shannon sampling theory: of any bandlimited signal it suffices to record discrete samples to be able to perfectly reconstruct it everywhere, if the samples are taken at a rate of at least twice the bandlimit. It is known that physical fields on generic curved spaces obey a sampling theorem if they possess an ultraviolet cutoff.”

Interesting discussions in these forums:

Good discussions here:
http://physicsforums.com/showthread.php?t=391989

http://www.physicsforums.com/showthr...71#post3558771

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james.goetz	Do theories of quantum gravity require that space-time is a lattice? Tweet Do theories of quantum gravity require that space-time is a lattice instead of a continuum? I guess this question has been addressed elsewhere, but I would appreciate hearing different points of view. Please dummy down the responses so a philosopher can understand it.