A recent article at “HuffPost Science” titled “Unparticle in Earth’s Mantle? Physicists Peer Inside Planet in Effort to Confirm New Particle” brought my attention to the subject of “unparticle.”
The concept of “unparticle” was proposed by Harvard physicist Howard Giorgi in 2007. His first 2 papers on this subject are:
In the first paper on unparticles Giorgi wrote:
“And while my motivation is primarily just theoretical curiosity, the scheme I discuss could very well be a component of the physics above the TeV scale that will show up at the LHC. To my mind, this would be a much more striking discovery than the more talked about possibilities of SUSY or extra dimensions. SUSY is more new particles. From our 4-dimensional point of view until we see black holes or otherwise manipulate gravity, finite extra dimensions are just a metaphor. Again what we see is just more new particles. We would be overjoyed and fascinated to see these new particles and eventually patterns might emerge that show the beautiful theoretical structures they portend. But I will argue that unparticle stuff with nontrivial scaling would astonish us immediately.”
When particle physicists say “mass” they mean the “rest-mass” which is different from the relativistic mass. The effective mass of a particle increases when it is moving at speeds close to the speed of light. That effective mass is called relativistic mass.
The term “rest-mass” is a misnomer because particles are never at rest. Particles are always moving. Particles have intrinsic properties such as electric charge and spin. Intrinsic properties are constant, they don’t change. Intrinsic properties are independent of motion. The rest-mass is an intrinsic property and therefore a constant.
Particles with non-zero rest-mass are not scalable because rest-mass is not scalable. We can accelerate an electron and make it more energetic but we cannot change its rest-mass because rest-mass is intrinsic. The rest-mass is constant.
Giorgi’s theorized unparticles can have variable rest-mass. No such particles have been observed yet but I believe Howard Giorgi made a great contribution to physics by removing one of the mental blocks.
Unparticles would exhibit scale-invariance. The term “scale-invariance” has to be used carefully. I hate the fact that the term “scale-invariance” is also used in the context of self-similarity (fractals). That is a gross misuse of the term because self-similarity is a feature of nonlinearity while the “scale-invariance” is a feature of linearity. The term “scale-invariance” should only be used to mean linearity. You can get a better feeling for the linearity/nonlinearity dichotomy in “Nonlinearity and Scale”.
Unparticle is a speculative subject, and I have a speculative mind. I have no academic job to lose so I can be bold by saying that unparticles would be linear creatures. If unparticles are mediating a new type of force then that force would be a very long range force as a result of the linear nature of the unparticle.
You can even think of these linear creatures (unparticles) as ‘time-less’ because the “time-effect” is a manifestation of a fundamental nonlinearity.
If they exist, unparticles would be very interesting. It will be very difficult to detect them because they would interact very weekly with normal matter. Unparticles would be similar to neutrinos in that way.
I can imagine that unparticles would oscillate between individuality and collectivity. This kind of oscillation would be different than the particle/wave duality. When a particle is confined to a small volume of space it behaves like a wave. This is known as quantum behavior. The oscillations of the unparticle between individuality and collectivity would constitute a different kind of behavior.