Axions: Axions are hypothetical particles that were introduced to solve the strong CP problem in quantum chromodynamics (QCD). They are very light and have extremely weak interactions with ordinary matter. Axions could potentially make up a significant portion of dark matter.
Sterile Neutrinos: Sterile neutrinos are hypothetical particles that do not participate in weak interactions. They are similar to ordinary neutrinos but have much larger masses. Sterile neutrinos could contribute to dark matter if they are sufficiently massive and abundant.
Primordial Black Holes: Primordial black holes are small black holes that could have formed in the early universe. If they are sufficiently small, they can avoid detection and could account for a portion of dark matter.
Fuzzy Dark Matter: Fuzzy dark matter refers to a class of models in which dark matter is composed of compact objects with masses ranging from 10^-22 to 10^12 solar masses. These objects can be black holes, neutron stars, or other dense structures.
Bosonic Dark Matter: Bosonic dark matter refers to particles that have integer spins, such as scalar bosons or vector bosons. These particles can have different masses and interaction properties, and they could potentially contribute to dark matter.
Self-Interacting Dark Matter (SIDM): SIDM is a type of dark matter that can interact with itself through non-gravitational forces. This interaction can lead to self-scattering and other effects that could have observational consequences.
The search for dark matter particles continues to be an active area of research, and new experiments and observations are constantly probing for evidence of these mysterious entities.
