The $phi^4_3$ Hamiltonian
The $phi^4_3$ model is a simple interacting three-dimensional quantum field model that has been very well studied. Nikolay Barashkov and I recently established the Markov property for this model, leading to the most natural (disclaimer: in my opinion) construction of the finite volume Hamiltonian. The infinite volume Hamiltonian in this model, and others, is at a less satis- fying state of affairs. I plan to explain some aspects of the construction and then segway to an experimental discussion about infinite volumes.