Luon

According to quantum mechanics energy in physical systems cannot be exchanged in arbitrarily small portions, but is quantised. A single elementary particle is an example for such a quantum. In a many body system energy cannot only be carried by individual elementary particles, but also by their collective movement. The elementary quanta of these collective excitations or "plasma waves" often behave as if they were actual particles themselves and are usually referred to as quasiparticles. Well-known examples of this behaviour are phonons or plasmons. A luon is a hypothetical quasiparticle that can be interpreted as collective excitation of scalar fields in a hot plasma. Since numerous scalar fields appear in many extensions of the Standard Model of particle physics, luons could play a role in the early universe at very high temperatures. However, it is difficult to confirm their existence in nature. The only elementary scalar field the existence of which is supported by experimental data is the Higgs field. The creation of a plasma of Higgs bosons in the laboratory would require temperatures of more than $10^{15}$ Kelvin because of their large mass of 125 GeV. This problem is even more severe for the even heavier hypothetical scalar fields in theories of particle physics beyond the Standard Model.