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Yu-jong Tzeng

Publications and source records attributed to Yu-jong Tzeng.

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Enumeration of singular varieties with tangency conditions

We construct the algebraic cobordism theory of bundles and divisors on smooth varieties. It has a simple basis (over Q) from projective spaces and its rank is equal to the number of Chern invariants. As an application we study the number of singular subvarieties satisfying given tangent conditions with a fixed smooth divisor, where the subvariety is the zero locus of a section of a vector bundle. We prove that the generating series gives a homomorphism from the algebraic cobordism group to the power series ring. This implies that the number of singular subvarieties with tangency conditions is governed by universal polynomials of Chern numbers, when the vector bundle is sufficiently ample. This result combines and generalizes the Caporaso-Harris and Vakil's recursive formulae, Gottsche's conjecture, De Jonquiere's Formula and relative node polynomials from tropical geometry. In the revised version, we allow the tangency conditions to be at assigned and unassigned points and prove the existence of universal polynomials and a formula for generating series. This completes the most general case of such enumeration of singular varieties for any dimension. We also correct the proof in Section 5, 6 when the divisor D is not irreducible, and Theorem 2.2. Typos are corrected.

math.AG

Universal polynomials for singular curves on surfaces

Let S be a complex smooth projective surface and L be a line bundle on S. For any given collection of isolated topological or analytic singularity types, we show the number of curves in the linear system |L| with prescribed singularities is a universal polynomial of Chern numbers of L and S, assuming L is sufficiently ample. Moreover, we define a generating series whose coefficients are these universal polynomials and discuss its properties. This work is a generalization of Gottsche's conjecture to curves with higher singularities.

math.AG

Algebraic cobordism of filtered vector bundles on varieties: Notes on a work of Lee and Pandharipande

The construction of double point cobordism groups of vector bundles on varieties in the work [Lee-P] (arXiv:1002.1500 [math.AG]) of Yuan-Pin Lee and Rahul Pandharipande gives immediately double point cobordism groups of filtered vector bundles on varieties. We note also that among the four basic operations -- direct sum, tensor product, dual, and Hom -- on vector bundles on varieties, only taking dual is compatible with double point cobordisms of vector bundles on varieties in general, by a demonstration on an example of vector bundles on Calabi-Yau 3-folds. A question on refined and/or higher algebraic cobordisms of vector bundles on varieties is posed in the end.

math.AG

A Proof of the Göttsche-Yau-Zaslow Formula

Let S be a complex smooth projective surface and L be a line bundle on S. Göttsche conjectured that for every integer r, the number of r-nodal curves in |L| is a universal polynomial of four topological numbers when L is sufficiently ample. We prove Göttsche's conjecture using the algebraic cobordism group of line bundles on surfaces and degeneration of Hilbert schemes of points. In addition, we prove the the Göttsche-Yau-Zaslow Formula which expresses the generating function of the numbers of nodal curves in terms of quasi-modular forms and two unknown series.

math.AG