- #1

marcus

Science Advisor

Gold Member

Dearly Missed

- 24,738

- 787

there is a basic physics reason why emergent geometry is hot, probably several basic reasons. Let us know why you think it is. Here's my take.

We see an explosion of meetings now about emergent geometry.

The most immediate cause that triggered this is that Loll's group got deSitter spacetime to EMERGE as a feynmann path integral of random geometries

where they didn't put in any 4D manifold by hand. the deSitter arises from MICROSCOPIC PLANCKSCALE DEGREES OF FREEDOM that assemble themselves in chaotic fractally fashion at small scale but somehow manage to achieve a recognizable 4D geometry at larger scale.

The idea of emergent geometry (and matter) is that space time is an

**illusion**and likewise particle fields are an illusion. There are more fundamental degrees of freedom which are busy interacting evolving at small scale according to their own dynamics, their own laws.

The game (Loll's game and the game of all these people coming to the workshop) is to find a way to MODEL these little atoms of pure existence, and their dynamics, so that you can put a bunch in the computer and have them swarm together like ants or bees so that a collective emerges that looks like space time and matter.

A word that some people use is "epiphenomenon" and an analogy is solidstate or condensed matter. There is the basic fundamental phenomenon and there is the "epi" stuff that arises from it---the larger scale processes that the microscopic stuff supports. Soundwaves are an "epi" supported by a host of bumping air molecules.

The thrust of this emergent geometry research is to go down to a deeper level.

There is a great variety of ideas, different mental pictures. Most of them won't appeal to everybody. Many of them don't appeal to me and i suspect most will turn out to be wrong.

But that's how it is supposed to work.

It is an active field and it is snowballing. That means a free-for-all bar-room brawl of ideas. So here comes this MIT conference to point this out. The actual title is Emergent Gravity but gravity is the geometry of spacetime so that is just a synonym. And matter interacts with geometry so it must arise from the same microscopic descriptors and be included too.

I will get the list of participants----many of them we have already discussed their work here at PF over the past 3 or 4 years. And I will get some links to a few papers mainly as a refresher----to remind us of the different approaches they take to emergent spacetime and matter.