We have therefore satisfied our first two requirements: we have four formalisms for temporal quantization which are well-defined and manifestly symmetric between time and space.
We have also made some progress on satisfying the reasonably simple criteria: we have no need for factors of , Wick rotation, or the like. We get well-behaved path integrals, if we are careful to apply them to well behaved functions.
And we have reasonably simple expressions for the Schrödinger equation:
And kernel:
Interesting they show up as equal partners here; can start with either.
Connection to general relativity interesting as well.