Upper bounds on the reheat temperature of the early universe, as they appear for example in classes of supergravity models, impose severe constraints on the thermal leptogenesis mechanism. To analyse these constraints, we extend the flavour-dependent treatment of leptogenesis to include reheating. We solve the flavour-dependent Boltzmann equations to obtain the leptogenesis efficiency as a function of the flavour dependent washout parameter 1, M_1_αand of m_N_1/T_(RH), the ratio of the mass of the lightest right-handed neutrino over the reheat temperature, and calculate the minimal values of the reheat temperature compatible with thermal leptogenesis in type I and type II seesaw scenarios.
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