wdlang said:why?
i can see the link between spin value and the statistics in quantum mechanics
fermi said:Well, actually there are spinless fermions of sorts. It just depends on what you define to be a "real" particle is. I am of course talking about Faddeev-Popov Ghosts in quantized non-Abelian Gauge theories. These particles are spinless fermions (in other words spin = 0, but they anti-commute.) However they do not possesses positive definite norm, which makes them less "real" if you like. More to the point, however, they depend on the choice of gauge. Interestingly, infinite renormalization constants depend on these spinless fermions, but finite gauge invariant quantities do not: they simply cancel out. This amazing fact is far from obvious by any argument that I have heard of. It takes a lot of hard formalism to prove it. So you decide for yourself if Faddeev-Popov Ghosts are real spinless fermions. Most physicists will not elevate them to the status of being "real" particles however.
If you are worried about the standard phrase "let us study spinless fermions" that you can find in many books on QM and condensed matter, then my answer would be no, there is no contradiction in imposing anticommutation relations on spinless fermions. Very often in non-interacting problems the spin degree of freedom is irrelevant, so you can forget it altogether and then, in the end, multiply your end result by a factor of two. In this case you just have too identical "flavors" of fermions that do not talk to each other. For example, most textbook solutions for the famous Tomonaga-Luttinger model (fermions in one spatial dimension) are done for spinless fermions, since then bosonization leads to a simple solution in terms of charge waves.wdlang said:the problem i am concerned with is, possibly there is no contradiction if we take a spinless or spin integer particle and impose fermionic commutation relations on it
Fermions are particles that follow the Fermi-Dirac statistics, which states that no two identical fermions can occupy the same quantum state. This means that fermions need to have an intrinsic property that distinguishes them from each other, and this property is known as spin. Spin is a quantum mechanical property that indicates the intrinsic angular momentum of a particle. Thus, fermions are always associated with spin in nature because it is a fundamental property that allows them to obey the Fermi-Dirac statistics.
As of now, there are no known particles in nature that are spinless fermions. All known fermions, such as electrons, protons, and neutrons, have spin. The search for spinless fermions is ongoing in the field of particle physics, as it could potentially lead to a better understanding of the fundamental forces and particles in the universe.
No, fermions cannot exist without spin. As mentioned before, spin is a fundamental property of fermions, and it is necessary for them to have an intrinsic property that distinguishes them from each other. Without spin, fermions would not be able to obey the Fermi-Dirac statistics and would not function as we currently understand them.
No, it is not possible for a fermion to lose its spin. Spin is an intrinsic property of a particle and cannot be changed or removed. However, it is possible for a fermion to change its spin state, which is known as spin flipping. This can occur when a fermion interacts with another particle or when it is subjected to a strong magnetic field.
As of now, there is no evidence that spinless fermions exist in nature, so they cannot be created in a laboratory setting. However, scientists are actively researching and exploring the possibility of creating spinless fermions through experiments and simulations. If successful, it could open up new possibilities in the field of particle physics and our understanding of the universe.