I came across this statement in the book "Quantum Field theory and the Standard Model".
"A particle can be defined as a set of states that mix only among themselves under Poincare transformations."
What does this statement mean?
Asked
Active
Viewed 119 times
1
-
1Possible duplicates: https://physics.stackexchange.com/q/21801/2451 , https://physics.stackexchange.com/q/73593/2451 , https://physics.stackexchange.com/q/224812/2451 , https://physics.stackexchange.com/q/277986/2451 and links therein. – Qmechanic Nov 06 '17 at 18:53
-
5Possible duplicate of Why do we say that irreducible representation of Poincare group represents the one-particle state? – Wrichik Basu Nov 06 '17 at 19:05
-
1Also a set of particles satisfies the suggested "definition". A crucial ingredient is missed: from a given state one can reconstruct all states using the action of Poincare' group. In other words the representation is irreducible. – Valter Moretti Nov 06 '17 at 19:39