the multiverse ?

[1123581321]

Hi, i was wondering if the multiverse (in theory) still exists if we don't consider m-theory and quantum theory..

[ajb]

Hi, i was wondering if the multiverse (in theory) still exists if we don't consider m-theory and quantum theory..

 

What is meant by exist here?

 

Are you suggesting that there should be a notion of classical many worlds?

 

In the context of something akin to the string landscape we do have analogues from more "conventional physics". For example, consider general relativity. Based on quite general arguments we know that a universe that is simply connected, homogeneous and isotropic must be described by the FRW cosmologies. Note that we have three distinct solutions here. They correspond to the classification of three dimensional spaces of constant curvature. (Lets forget all about the cosmological constant for now.)

 

So, we can talk about the "cosmological general relativity landscape". It consists of three points, each describing a different universe. Only one of these is ours, it appears to be the one corresponding to a flat universe. Big question "why this solution?"

 

 

The string landscape is a similar problem, however there are much more than just three choices!

[1123581321]

ajb, what exactly do you mean by simply connected ?

[ajb]

Technical assumption from topology.

 

So, first it must be path-connected, so every two points can be joined by a path. Intuitively this means the space is "in one piece".

 

Secondly, every path can be continuously deformed into any other path that has the same initial and final points. Intuitively this means the space "has no holes".