Density inhomogeneities can be generated very early in the universe. They are one of the reasons for all the large-scale structures in the early universe. Density inhomogeneities play an important role in nucleosynthesis calculations and affect the phase transition dynamics. These inhomogeneities decay by particle diffusion in the early universe. We have studied the decay starting from the electroweak phase transition up to the starting of the nucleosynthesis era. We study the decay of these inhomogeneities in the early universe with and without considering the expansion of the universe. We calculate the interaction cross-section of the quarks with the neutrinos, the electrons, and the muons and obtain the diffusion coefficients. We find that the expansion of the universe causes the inhomogeneities to decay at a faster rate. We find that the inhomogeneities generated at the electroweak epoch have very low amplitudes at the time of the quark hadron phase transition. So unless inhomogeneities are generated with a very high amplitude, they will have no effect on the quark hadron phase transition. In the hadronic phase, we have considered the interaction of neutron, proton, electron, and muon. We include the interaction of the muons with the neutrons and the protons till 100 MeV. We also find that large density inhomogeneities generated during the quark hadron transition with sizes of the order of 1 km must have amplitudes greater than 10^5 times the background density to survive up to the nucleosynthesis epoch in an expanding universe.
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