Temperature variation of the pseudogap in underdoped cuprates

We consider thermal evolution of the spectral function A(Ω,T) in underdoped cuprates at T>Tc. We find that in the strong-coupling limit, the fermionic Green's function near (0,π) behaves as G^-1(Ω)∝√Ω in the whole frequency range relevant to photoemission experiments. The analysis of the pairing problem with this form of G yields a leading edge gap in A(Ω) and a broad maximum at larger frequencies. We find that classical fluctuations predominantly add a frequency independent term to G^-1(Ω). This term destroys the leading edge gap at T=T*(k) which has a maximum value of about 200 K near (0,π).