How Does RG Flow Change Dimensions in Ising Universality Classes?

[atyy]

In http://arxiv.org/abs/0912.3272 , figure 1.2 says that the 2D and 3D Ising universality classes are related by a renormalization flow. How can the RG flow change dimension? Is there anything I could read that does the calculation in more detail?

 

[DrDu]

In http://arxiv.org/abs/0912.3272 , figure 1.2 says that the 2D and 3D Ising universality classes are related by a renormalization flow. How can the RG flow change dimension? Is there anything I could read that does the calculation in more detail?

Maybe if the coupling between neighbouring sheets becomes irrelevant?