Assuming there are multiple dimensions -- If the universe stops expanding and starts contracting, would this event affect one dimension, select dimensions, or all of them?

The expansion of the universe takes place for all space dimensions (presumably three), so the contraction would affect the same.

Assuming there are multiple dimensions -- If the universe stops expanding and starts contracting, would this event affect one dimension, select dimensions, or all of them?

 

We have three spatial dimensions and one temporal dimension. This isn't an assumption, it's what we observe.

 

Are you perhaps referring to multiple universes, rather than dimensions?

 

We have three spatial dimensions and one temporal dimension. This isn't an assumption, it's what we observe.

 

Are you perhaps referring to multiple universes, rather than dimensions?

I think the OP might be referring to the extra dimensions posited in Kaluza-Klein theory or String theory. Interesting question. I would expect if they were expanding or contracting (assuming they exist) the laws of physics would be changing over time, unless they were all somehow geared to orchestrate or compensate each other in some manner.