Fundamental theorems for timelike surfaces in the Minkowski 4-space (Q6610142)

This paper deals with time like surfaces free of minimal points in the Minkowski space \( \mathbf{R}^{4}_{1} \). At first the authors introduce pseudoorthonormal frame field and propose the corresponding derivative formulas and integrability conditions. This way they obtain system of 6 functions satisfying 4 PDE (natural conditions). In Theorem 3.2 Frobenius theorem enables them to verify that these 6 functions determine the time like surface up to a motion in \(\mathbf{R}^{4}_{1} \). The results obtained in the paper are not interesting and up to date at all.