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Thermal dark matter abundance under non-standard macroscopic conditions in the early universe

The standard theoretical estimation of the thermal dark matter abundance may be significantly altered if properties of dark matter particles in the early universe and at the present cosmological epoch differ. This may happen if, e.g., a cosmological phase existed in the early universe during which dark matter particles were temporarily unstable and their abundance was reduced through their decays. We argue that a large class of microscopic theories which are rejected due to the dark matter overproduction, may actually be viable theories if certain macroscopic conditions were satisfied in the early universe. We explicitly demonstrate our mechanism within the minimal supersymmetric standard model with the bino-like lightest supersymmetric particle being a phenomenologically viable dark matter candidate under the condition that the early universe carried a global R-charge which induced the instability phase.