On the sectional irregularity of congruences.
The irregularity of ruled surfaces in three dimensional projective space.
Let S be a ruled surface in P3 with no multiple generators. Let d and q be nonnegative integers. In this paper we determine which pairs (d,q) correspond to the degree and irregularity of a ruled surface, by considering these surfaces as curves in a smooth quadric hypersurface in P5.
Vector fields from locally invertible polynomial maps in ℂⁿ
Let (F₁,..., Fₙ): ℂⁿ → ℂⁿ be a locally invertible polynomial map. We consider the canonical pull-back vector fields under this map, denoted by ∂/∂F₁,...,∂/∂Fₙ. Our main result is the following: if n-1 of the vector fields have complete holomorphic flows along the typical fibers of the submersion , then the inverse map exists. Several equivalent versions of this main hypothesis are given.
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