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Ai-Ko Liu

Publications and source records attributed to Ai-Ko Liu.

10 recordsLinked to original sources
arXiv2004

A Note About Universality Theorem as an Enumerative Riemann-Roch Theorem

The paper is a short supplement of the longer paper "The Algebraic Proof of the Universality Theorem", preprint math.AG/0402045. In this short note, we outline the geometric meaning of Universality theorem (conjecture by Gottsche) as a non-linear extension of surface Riemann-Roch Theorem, inspired by the string theory argument of Yau-Zaslow to probe non-linear information from linear systems of algebraic surfaces. The universality theorem is an existence result which reflects the topological nature of the Riemann-Roch problem. We also outline the crucial role that Yau-Zaslow formula has played in our theory. At the end, we list a few open problems related to the algebraic solution of the problem.

math.AG↗
arXiv2004

The Residual Intersection Formula of Type II Exceptional Curves

The paper is a part of our program to build up a theory of couting immersed nodal curve on algebraic surfaces, as an enumerative Riemann-Roch theory (outlined in math.AG/0405113). In this paper, we discuss the excess intersection theory of the so-called type two exceptional curves, which plays the analogous role as the "index of speciality" (h^2) in the classical surface Riemann-Roch formula. We show that the algebraic family Seiberg-Witten theory of type I exceptional curves can be generalized to the theory of type II exceptional curves when the family moduli spaces are not regular of the expected dimension.

math.AG↗
arXiv2004

Cosmic String, Harvey-Moore Conjecture and Family Seiberg-Witten Theory

In this paper, we study the enumeration of virtual numbers of immersed nodal curves along certain Calabi-Yau K3 fibrations. By using the concept of cosmic strings, we verify the modularity conjeture of the generating function of immersed nodal curves from String theory (Harvey-Moore). Based on the theory defining virtual numbers of nodal curves on algebraic surface (applying to a pencil of lattice polarized K3), a mathematical definition of virtual numbers of immersed rational curves (so-called Gopakumar-Vafa numbers) for Calabi-Yau K3 fibrations is given and it is shown to match up with string theory prediction.

math.AG↗
arXiv2004

The Algebraic Proof of the Universality Theorem

In the long paper "Family Blowup formula, Admissible Graphs and the Enumeration of Singular Curves (I)" (appearing in JDG), the author solved the enumeration problem of nodal (or general singular) curve counting on algebraic surfaces by using techniques from differential topology/symplectic geometry (including family Seiberg-Witten theory) and some ideas derived from Taubes' "SW=Gr". In the current paper, we offer an algebraic proof of the "universality theorem", showing that the counting of nodal curves for 5$δ$-1 very ample complete linear systems are controled by universal polynomials of the characteristic classes. The theorem (implicitly) was the backbone of the earlier long paper(cited above). In the current paper, we derive the result by using intersection theory and the concept of localized contributions of top Chern classes, and therefore relaxing the dependence on the symplectic techniques.

math.AG↗
arXiv2003

Family Switching Formula and the $-n$ Exceptional Rational Curves

In this paper, we derive the family switching formula of -n two-sphere fiber bundle embedded in a smooth four-manifold fiber bundle. In the smooth category, it is a partial generalization of Fintushel-Stern's argument for four-manifolds. We also derive an algebraic analogue of the family switching formula, allowing the P^1 fibration to carry singular fibers. At the end, we apply the idea of switching to compare the canonical algebraic Kuranishi models of different classes on the so-called "universal family".

math.DG↗
arXiv2003

The Family Blowup Formula of the Family Seiberg-Witten Invariants

In the paper we formulate and derive the family blowup formula of family Seiberg-Witten invariants. The formula has been used in the enumerative application of counting singular curves on algebraic surfaces. We first give a topological derivation of the formula by using family index theorem. Then we define the algebraic (family) Seiberg-Witten invariants for algebraic surfaces and then give an algebraic derivation of the family blowup formula for the algebraic family Seiberg-Witten invariants.

math.DG↗
arXiv2001

Family Seiberg-Witten invariants and wall crossing formulas

In this paper we set up the family Seiberg-Witten theory. It can be applied to the counting of nodal pseudo-holomorphic curves in a symplectic 4-manifold (especially a Kahler surface). A new feature in this theory is that the chamber structure plays a more prominent role. We derive some wall crossing formulas measuring how the family Seiberg-Witten invariants change from one chamber to another.

math.GT↗