Elementary particles in the early Universe

The high-temperature limit of Standard Model generated by the contractions of gauge groups is discussed. Contraction parameters of gauge group $SU(2)$ of Electroweak Model and gauge group $SU(3)$ of Quantum Chromodynamics are taken identical and tending to zero when temperature increase. Properties of the elementary particles change drastically at the infinite temperature limit: all particles lose masses, all quarks are monochromatic. Electroweak interactions become long-range and are mediated by the neutral currents. Particles of different kind do not interact. It looks like some stratification with only one sort of particles in each stratum. The Standard Model passes in this limit through several stages, which are distinguished by the powers of contraction parameter. For any stage the intermediate models are constructed and the exact expressions for the respective Lagrangians are presented. The developed approach describes the evolution of Standard Model in the early Universe from the Big Bang up to the end of several nanoseconds.