We studied the critical state stability in a large cubic sample of a single crystalline La(1.85)Sr(0.15)CuO(4) for different sample orientations with respect to the external magnetic field as well as the dynamics of the flux jumps. It is shown that t
hermomagnetic avalanches develop in dynamic conditions characterized by significantly lower magnetic diffusivity than the thermal one. In this case, critical state stability depends strongly on cooling conditions. We compared predictions of the isothermal model and of the model for the weakly cooled sample with experimental results. In both models, the field of the first flux jump decreases with an increase of sweep rate of the external magnetic field. We also investigated the influence of external magnetic field on the dynamics of the following stages of the thermomagnetic avalanche. It is shown that the dynamics of the flux jumps is correlated with the magnetic diffusivity proportional to the flux flow resistivity.
A generalized Euler sequence over a complete normal variety X is the unique extension of the trivial bundle V otimes O_X by the sheaf of differentials Omega_X, given by the inclusion of a linear space V in Ext^1(O_X,Omega_X). For Lambda, a lattice of
Cartier divisors, let R_Lambda denote the corresponding sheaf associated to V spanned by the first Chern classes of divisors in Lambda. We prove that any projective, smooth variety on which the bundle R_Lambda splits into a direct sum of line bundles is toric. We describe the bundle R_Lambda in terms of the sheaf of differentials on the characteristic space of the Cox ring, provided it is finitely generated. Moreover, we relate the finiteness of the module of sections of R_Lambda and of the Cox ring of Lambda.
