A Castelnuovo bound for smooth surfaces.
A categorical quotient in the category of dense constructible subsets
A. A'Campo-Neuen and J. Hausen gave an example of an algebraic torus action on an open subset of the affine four space that admits no quotient in the category of algebraic varieties. We show that this example admits a quotient in the category of dense constructible subsets and thereby answer a question of A. Białynicki-Birula.
A character approach to Looijenga's invariant theory for generalized root systems
A character on the quasi-symmetric functions coming from multiple zeta values.
A characterization of
A characterization of ample vector bundles on a curve.
A Characterization of Balanced Rational Normal Surface Scrolls in Terms of Their Osculating Spaces II.
A Characterization of Complex Homogeneous Cones.
A Characterization of Five-Dimensional Jacobian Varieties.
A characterization of hyperelliptic Jacobians.
A characterization of integral elliptic automorphic forms
A characterization of non-hyperelliptic Jacobi varieties.
A characterization of p-bases of rings of constants
We obtain two equivalent conditions for m polynomials in n variables to form a p-basis of a ring of constants of some polynomial K-derivation, where K is a unique factorization domain of characteristic p > 0. One of these conditions involves Jacobians while the other some properties of factors. In the case m = n this extends the known theorem of Nousiainen, and we obtain a new formulation of the Jacobian conjecture in positive characteristic.
A characterization of proper regular mappings
Let X, Y be complex affine varieties and f:X → Y a regular mapping. We prove that if dim X ≥ 2 and f is closed in the Zariski topology then f is proper in the classical topology.
A characterization of quasi-homogeneous Gorenstein surface singularities
A characterization of the complex affine line.
A characterziation of IPn by vector bundles.
A chracterization of A-discriminantal hypersurfaces in terms of the logarithmic Gauss map.
A class of counterexamples to the Cancellation Problem for arbitrary rings
We present a class of counterexamples to the Cancellation Problem over arbitrary commutative rings, using non-free stably free modules and locally nilpotent derivations.
A class of diophantine equations connected with certain elliptic curves over