New reduction in the Jacobian conjecture.
Non-uniruledness and the cancellation problem
Using the notion of uniruledness we indicate a class of algebraic varieties which have a stronger version of the cancellation property. Moreover, we give an affirmative solution to the stable equivalence problem for non-uniruled hypersurfaces.
Non-uniruledness and the cancellation problem (II)
We study the following cancellation problem over an algebraically closed field of characteristic zero. Let X, Y be affine varieties such that for some m. Assume that X is non-uniruled at infinity. Does it follow that X ≅ Y? We prove a result implying the affirmative answer in case X is either unirational or an algebraic line bundle. However, the general answer is negative and we give as a counterexample some affine surfaces.
Non-zero constant Jacobian polynomial maps of
We study the behavior at infinity of non-zero constant Jacobian polynomial maps f = (P,Q) in ℂ² by analyzing the influence of the Jacobian condition on the structure of Newton-Puiseux expansions of branches at infinity of level sets of the components. One of the results obtained states that the Jacobian conjecture in ℂ² is true if the Jacobian condition ensures that the restriction of Q to the curve P = 0 has only one pole.
Note on the Jacobian condition and the non-proper value set
We show that the non-proper value set of a polynomial map (P,Q): ℂ² → ℂ² satisfying the Jacobian condition detD(P,Q) ≡ const ≠ 0, if non-empty, must be a plane curve with one point at infinity.
Number of singular points of an annulus in
Using BMY inequality and a Milnor number bound we prove that any algebraic annulus in with no self-intersections can have at most three cuspidal singularities.