Temperature variation of the pseudogap in underdoped cuprates

We consider thermal evolution of the spectral function A(Omega,T) in underdoped cuprates at T>T-c. We find that in the strong-coupling Limit, the fermionic Green's function near (0,pi) behaves as G(-1)(Omega)proportional to root Omega 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(Omega) and a broad maximum at larger frequencies. We find that classical fluctuations predominantly add a frequency independent term to G(-1)(Omega). This term destroys the leading edge gap at T=T*(k) which has a maximum value of about 200 K near (0,pi).