Undergrad Light-Like Separation: Is It Possible?

[novice_hack]

Is it possible for all the events in a field to be light-like separated from each other? What would such a field be like?

 

[vanhees71]

What do you mean by "events in a field"?

Events in relativity are points of the space-time manifold. A field is a function of events, $f(x)$ (where $f$ can be all kinds of quantities, scalars, vectors, tensors, or various kinds of spinors or also operators of all these kinds when it comes to QFT, and $x$ are coordinates, $(x^0,x^1,x^2,x^3)$).

 

[novice_hack]

Ok. I suppose I meant: can all the spacetime intervals between events be light-like?

 

[jbriggs444]

Ok. I suppose I meant: can all the spacetime intervals between events be light-like?

The set of events comprising a light-like geodesic would have that property.

However, if you included any additional event not on that trajectory then it seems clear that such an event would have space-like separation from some events on the trajectory and a time-like separation from others.

Note that you must be talking about flat space-time since the "spacetime interval" between events is ambiguous otherwise.

 

[Dale]

Ok. I suppose I meant: can all the spacetime intervals between events be light-like?

The spacetime interval is defined along a path. It requires more than just specifying a pair of events. It requires specifying the path from one to the other. So the question really is not well formed.