The discussion centers on the requirement for fields acquiring vacuum expectation values (v.e.v.) to maintain the same quantum numbers as the vacuum, particularly in the context of the Standard Model. It asserts that symmetries such as local Lorentz invariance and neutrality must be preserved when introducing these fields. The conversation highlights that while scalar mesons, like pions, are compatible with these symmetries, vector mesons pose a challenge as their existence could imply a violation of Lorentz invariance due to potential symmetry-breaking. This leads to the conclusion that only scalar mesons should exist under these constraints.
PREREQUISITESThis discussion is beneficial for theoretical physicists, particle physicists, and students studying quantum field theory, particularly those interested in the implications of symmetries and vacuum states in the Standard Model.
javierR said:That's why condensations of neutral scalars and neutral, Lorentz-scalar groupings of fermions are allowed in the Standard Model.