A "Fermi ball" is a concept that arises in quantum mechanics and particle physics, specifically in the context of describing the distribution of particles in momentum space. The term is often used in discussions related to Fermi-Dirac statistics, which govern the behavior of fermions — particles such as electrons. In a Fermi gas, the distribution of particles at absolute zero temperature can be depicted as a ball in momentum space, where the radius of the ball corresponds to the Fermi momentum.
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