People often say "speed of light in a vacuum" to further define a point of referrence.

I'm wondering, could one say that the ground state of the electromagnetic spectrum is "mass at absolute zero" to further define a point of reference?

 

also, does mass have weight at absolute zero?

does mass experience decay at absolute zero?

The questions are ill-formed. A spectrum does not have a ground state, a system does. Mass has weight in a gravitational field. Whether it undergoes decay depends on the specific nuclei involved.

And since you can't get to absolute zero...

A spectrum does not have a ground state, a system does.

Could someone explain the ground state of a free electron. I came across this comment:

Martin Veltmann "Facts and Mysteries in Elementary Particle Physics" pg. 249

 

Consider an electron at rest, i.e. with zero momentum; it is then in its lowest energy state. If it were to emit a photon of finite energy then an electron with even less energy would be left behind, which is not possible. The same then holds also for a freely moving electron, which one could imagine to be an electron at rest as seen by a moving observer.

Free electrons are discussed in solar flares, in cosmology "first light", and in statistical mechanics - but i have not read any discussion of what the ground state of a single free electron means.

 

Does your statement "... a system does" imply that a single free electron cannot have a ground state?

 

If a free electron can have a ground state, how do they experimentally determine such a value? How is the electron momentum handled?

Veltmann is proposing a thought experiment that demonstrates what I said: a free electron cannot spontaneously emit a photon. It does not matter if it's at rest with respect to the observer, because it is at rest in its own frame. That would violate conservation of energy in that frame, and physics has to work in all frames. In order to have an excited state, there must be an interaction with something else, i.e. a system.