Flux lattice melting and the onset of H-c2 fluctuations

The flux lattice melting temperature in YBa2Cu3O7-delta has been shown to b e very close to that of the onset of fluctuations around H-c2(T). Here, we present a theoretical argument in support of the idea that this occurs beca use the increased strength of the fluctuations as a function of magnetic fi eld pushes away the first order flux lattice melting transition. The argume nt is based on hydrodynamic considerations (the Hansen-Verlet freezing crit erion). It is not specific to high-temperature superconductors and can be g eneralized to other systems. (C) 2000 Elsevier Science B.V. All rights rese rved.