  Baryon inhomogeneities can be generated very early in the universe. These
inhomogeneities then decay by particle diffusion in an expanding universe. We
study the decay of these baryon inhomogeneities in the early universe using the
diffusion equation in the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric. We
have studied the decay starting from the electroweak phase transition. We
calculate the interaction cross section of the quarks with the neutrinos, the
electrons and the muons and obtain the diffusion coefficients. The diffusion
coefficients are temperature dependent. We find that the expansion of the
universe causes the inhomogeneities to decay at a faster rate. We find that the
baryon 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 (greater than $10^5$
times the background density), they will have no effect on the quark hadron
phase transition. After the quark hadron phase transition, 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 upto the nucleosynthesis epoch
in an expanding universe.
