#### marcus

Science Advisor

Gold Member

Dearly Missed

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I just had a hopeful thought, actually it was last night on the couch but it was already bedtime.

this is about this thread

https://www.physicsforums.com/showthread.php?t=81626

which so far has these results:

---who forecasts what, on the question of---

Spin Network: No, 2D is the max. Sum will blow up in higher dimension

Arivero: Yes for 3D but not 4D.

Meteor, selfAdjoint, Chronos, and I: Yes they will extend their result to 4D spacetime path integral.

---that's all so far---

It is really great that, at least in 2D spacetime, Loll Westra managed to include brief microscopic topological variation in their path integral. But there is so much MORE possible topo variation in 3D and 4D that I cannot see how they could include it in those higherdimension cases without the sum blowing up.

BUT WAIT! Their recent paper "Reconstructing the Universe"

http://arxiv.org/hep-th/0505154 [Broken]

provided some evidence that our 4D spacetime, at very microscopic scale, MAY ACT LIKE IT IS 2D !!!

so the topo variation in 4D, as long as you keep it brief and microscopic and causally harmless, as they do in their recent 2D paper, may actually be

controllable down at that tiny scale.

because at that tiny scale the universe is acting like a 2D spacetime

this is about this thread

https://www.physicsforums.com/showthread.php?t=81626

which so far has these results:

---who forecasts what, on the question of---

**Will Loll etc be able to extend sum over topologies to dim > 2?**Spin Network: No, 2D is the max. Sum will blow up in higher dimension

Arivero: Yes for 3D but not 4D.

Meteor, selfAdjoint, Chronos, and I: Yes they will extend their result to 4D spacetime path integral.

---that's all so far---

It is really great that, at least in 2D spacetime, Loll Westra managed to include brief microscopic topological variation in their path integral. But there is so much MORE possible topo variation in 3D and 4D that I cannot see how they could include it in those higherdimension cases without the sum blowing up.

BUT WAIT! Their recent paper "Reconstructing the Universe"

http://arxiv.org/hep-th/0505154 [Broken]

provided some evidence that our 4D spacetime, at very microscopic scale, MAY ACT LIKE IT IS 2D !!!

so the topo variation in 4D, as long as you keep it brief and microscopic and causally harmless, as they do in their recent 2D paper, may actually be

controllable down at that tiny scale.

because at that tiny scale the universe is acting like a 2D spacetime

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