Thom polynomials and Schur functions: the singularities I_{2,2}(-)

We give the Thom polynomials for the singularities $I_{2,2}$ associated with maps $({\bf C}^{\bullet},0) \to ({\bf C}^{\bullet+k},0)$ with parameter $k\ge 0$. Our computations combine the characterization of Thom polynomials via the ``method of restriction equations'' of Rimanyi et al. with the techniques of Schur functions.Comment: 21 pages; Ann. Inst. Fourier vol.57; this is expanded Sect.4 of math.AG/0509234; new added results: Theorem 11 (based on P-ideals of singularities) and explicit expressions for the coefficients of the Thom polynomials of I_22(-) (Propositions 17, 18, 19); references update

Symmetric polynomials and divided differences in formulas of intersection theory

The goal of the paper is two-fold. At first, we attempt to give a survey of some recent applications of symmetric polynomials and divided differences to intersection theory. We discuss: polynomials universally supported on degeneracy loci; some explicit formulas for the Chern and Segre classes of Schur bundles with applications to enumerative geometry; flag degeneracy loci; fundamental classes, diagonals and Gysin maps; intersection rings of G/P and formulas for isotropic degeneracy loci; numerically positive polynomials for ample vector bundles. Apart of surveyed results, the paper contains also some new results as well as some new proofs of earlier ones: how to compute the fundamental class of a subvariety from the class of the diagonal of the ambient space; how to compute the class of the relative diagonal using Gysin maps; a new formula for pushing forward Schur's Q- polynomials in Grassmannian bundles; a new formula for the total Chern class of a Schur bundle; another proof of Schubert's and Giambelli's enumeration of complete quadrics; an operator proof of the Jacobi-Trudi formula; a Schur complex proof of the Giambelli-Thom-Porteous formula.Comment: 58 pages; to appear in the volume "Parameter Spaces", Banach Center Publications vol 36 (1996) AMSTE

Positivity of Thom polynomials II: the Lagrange singularities

We show that Thom polynomials of Lagrangian singularities have nonnegative coefficients in the basis consisting of Q-functions. The main tool in the proof is nonnegativity of cone classes for globally generated bundles.Comment: 16 pages, reduced introduction but new chapter about Legendrian singularities. The title is change. Correction in the formula for A_7 and a sign correction in formula (29

Positivity of Schur function expansions of Thom polynomials

Combining the Kazarian approach to Thom polynomials via classifying spaces of singularities with the Fulton-Lazarsfeld theory of numerical positivity for ample vector bundles, we show that the coefficients of various Schur function expansions of the Thom polynomials of stable and unstable singularities are nonnegative.Comment: 12 pages, various modification of the expositio