vacuum energy questions

[BJC]

my understanding is that vacuum energy is the particle ground state energy

 

1) why is this field a constant, static field?

 

2) how is the "absolute" energy density derived?

 

3) Why is this field considered as negative energy (negative pressure) in cosmology? I assume this has to do with the convention of the direction of force being from potential energy (PE) and vacuum energy cannot decrease.

 

4) Other than by assumption, how is vacuum energy related to dark energy?

 

5) Rather than cause a "real" expansion of space why not creation / annihilation of virtual gravitons and subsequent virtual space?

 

 

Not sure where to put this - not even sure if the questions make sense. It just seems to me that vacuum energy is being touted as a ubiquitous "snake oil cure"