This Week's Finds in Mathematical Physics (Week 232) - Greg Egan

A forum discussion :-

"Would it be correct to assume that the ordinary tangent vector p still
transforms in the usual way? In other words, suppose I'm living in a
2+1 dimensional universe, and there's a point particle with rest mass m
and hence energy-momentum vector in its rest frame of p=m e_0. If I
cross its world line with a certain relative velocity, there's an
element g of SO(2,1) which tells me how to map the particle's tangent
space to my own. Would I measure the particle's energy-momentum to be
p'=gp? (e.g. if I used the particle to do work in my own rest frame)
Would there still be no upper bound on the total energy, i.e. by making
our relative velocity close enough to c, I could measure the particle's
kinetic energy to be as high as I wished?"


5 out of 5

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