The gravitational equations (General Relativity) allow waves of all
frequencies, just like the E.M. equations. However, gravitational waves
have not yet been directly detected. There is evidence from slowing
rotations of some dense stars that they do indeed exist just as they
ought to according to the theory.
Bosons certainly can and do interact. By an odd coincidence, I was
just lecturing on that today. The low temperature properties of He4
(good boson atoms) crudely resemble predictions for non-interacting
particles, but show very interesting distinct features that can only
come from interactions. There are countless other examples, but I
couldn't resist recycling today's lecture.
Actually, all interactions we know about are mediated by bosons.
Photons are bosons (they have spin 1) and are exchanged in
electromagnetic interactions. The strong nuclear force works by
exchanging gluons, which also have spin 1. Protons and neutrons are
held together also by the strong force but it is more convenient to
think of the particle they exchange as pions, which are collections of
quarks, antiquarks, and gluons. Pions have spin zero, and are therefore
also bosons. The weak force is exchanged by W and Z particles which are
also bosons. Bosons interact with fermions by these interactions.
Bosons can also interact with each other. The rate at which photons
interact with each other is very very small for low-energy photons.
Gluons on the other hand interact with each other quite strongly, as do
(published on 10/22/2007)