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Deformations of hypersurfaces with a one-dimensional singular locus. (English) Zbl 0733.32026

Let f: (\({\mathbb{C}}^{n+1},0)\to ({\mathbb{C}},0)\) be a germ of an analytic function with isolated singularity. Then there exists a Morsification \(f_ s: {\mathbb{C}}^{n+1}\to {\mathbb{C}}\), which has only \(A_ 1\)- singularities. The author generalizes this fact to the case in which the singular locus \(\Sigma\) of \(f^{-1}(0)\) is a curve. Under this new circumstance, one needs to add \(A_{\infty}\) and \(D_{\infty}\) singularities to the list of the allowable singularities of \(f_ s\). Here \(A_{\infty}\) and \(D_{\infty}\) are respectively defined by \(y^ 2_ 1+...+y^ 2_ n=0\) and \(y_ 0y^ 2_ 1+...+y^ 2_ n=0\) for some local coordinates \((y_ 0,y_ 1,...,y_ o)\). The main theorem states that if \(\Sigma\), defined by the ideal I, is smoothable and if \(f\in I^ 2\), then f has a Morsification. The upper bound for the number of \(D_{\infty}\) singularities is also investigated.
Reviewer: E.Horikawa (Tokyo)

MSC:

32S25 Complex surface and hypersurface singularities
32G10 Deformations of submanifolds and subspaces
58E05 Abstract critical point theory (Morse theory, Lyusternik-Shnirel’man theory, etc.) in infinite-dimensional spaces
32S30 Deformations of complex singularities; vanishing cycles
32A38 Algebras of holomorphic functions of several complex variables
Full Text: DOI

References:

[1] Artin, M., Deformations of singularities, (Tata Institute Lectures, 54 (1976), Springer: Springer Berlin) · Zbl 0142.18602
[2] Buchsbaum, D. A.; Rim, D. S., A generalized koszul complex II, Trans. Amer. Math. Soc., 111, 197-224 (1964) · Zbl 0131.27802
[3] Burch, L., On ideals of finite homological dimension in local rings, Proc. Cambridge Philos. Soc., 64, 949-952 (1968) · Zbl 0172.32301
[4] de Concini, C.; Strickland, E., On the variety of complexes, Adv. in Math., 41, 57-77 (1981) · Zbl 0471.14026
[5] Eagon, J. A.; Northcott, D. G., Ideals defined by matrices and a certain complex associated with them, (Proc. Royal Soc. London, 69 (1962)), 188-204, A2 · Zbl 0106.25603
[6] Ferrand, D., Suite regulière et intersection complète, C.R. Acad. Sci. Paris, 264, 427-428 (1967) · Zbl 0154.03801
[7] Goryunov, V. V., Bifurcation diagrams of some simple and quasi homogeneous singularities, Functional Anal. Appl., 17, 23-27 (1983) · Zbl 0558.58021
[8] Gromoll, D.; Meyer, W., On differentiable functions with isolated critical points, Topology, 8, 361-369 (1969) · Zbl 0212.28903
[9] Herzog, J., Deformationen von Cohen-Macaulay Algebren, J. Reine Angew. Math., 318, 83-105 (1980) · Zbl 0425.13005
[10] Huneke, C., The koszul homology of an ideal, Adv. in Math., 56, 295-318 (1985) · Zbl 0585.13006
[11] de Jong, T., Some classes of line singularities, Math. Z., 198, 493-517 (1988) · Zbl 0628.32028
[12] de Jong, T., The virtual number of \(D_∞\) points, Topology, 29, 175-184 (1990) · Zbl 0752.32010
[13] Józefiak, T., Ideals generated by minors of a symmetric matrix, Comment. Math. Helv., 53, 595-607 (1978) · Zbl 0398.13009
[14] Lê, D. T., Calcul du nombre de cycle évanouissants d’une hypersurface complexe, Ann. Inst. Fourier, 23, 4, 261-270 (1973) · Zbl 0293.32013
[15] Looijenga, E. J.N., Isolated Singular Points on Complete Intersections, (Lecture Note Series, 77 (1984), Cambridge University Press: Cambridge University Press Cambridge) · Zbl 0552.14002
[16] Matsumura, H., Commutative Algebra, (Math. Lecture Note Series, 56 (1970), Benjamin: Benjamin New York) · Zbl 0211.06501
[17] Narasimhan, R., Lecture Notes in Mathematics, 25 (1966), Springer: Springer Berlin · Zbl 0168.06003
[18] Palamadov, V. P., Deformations of complex spaces, Russian Math. Surveys, 31, 3, 129-197 (1976) · Zbl 0347.32009
[19] Pellikaan, R., Hypersurface singularities and Jacobi modules, (Thesis (1985), Rijksuniversiteit Utrecht) · Zbl 0589.32017
[20] Pellikaan, R., Finite determinacy of functions with non-isolated singularities, Proc. London Math. Soc., 57, 1-26 (1988)
[21] Pellikaan, R., Projective resolutions of the quotient of two ideals, Indag. Math., 50, 65-84 (1988) · Zbl 0657.13014
[22] Schaps, M., Deformations of Cohen-Macaulay schemes of codimension 2 and non-singular deformations of curves, Amer. J. Math., 99, 669-684 (1977) · Zbl 0358.14006
[23] Schlessinger, M., Rigidity of quotient singularities, Invent. Math., 14, 17-26 (1971) · Zbl 0232.14005
[24] Serre, J.-P., Algèbre locale, multiplicités, (Lecture Notes in Mathematics, 11 (1975), Springer: Springer Berlin) · Zbl 0091.03701
[25] Siersma, D., Isolated line singularities, Proc. Sympos. Pure Math., 40, 485-496 (1981), part 2 · Zbl 0514.32007
[26] Siersma, D., Singularities with critical locus a 1-dimensional complete intersection and transversal \(A_1\), Topol. Appl., 27, 51-73 (1987) · Zbl 0635.32006
[27] Simis, A.; Vasconcelos, W., The syzygies of the conormal module, Amer. J. Math., 103, 203-224 (1980) · Zbl 0467.13009
[28] Storch, U., Zur Längenberechnung von Moduln, Arch. Math., 24, 39-43 (1973) · Zbl 0257.13013
[29] Teissier, B., The hunting of invariants in the geometry of discriminants, (Holm, P., Real and Complex Singularities (1977), Sijthoff and Noordhoff: Sijthoff and Noordhoff Alden a.d. Rijn), 565-677, Oslo 1976 · Zbl 0388.32010
[30] Vasconcelos, W., Ideals generated by \(R\)-sequences, J. Algebra, 6, 309-316 (1967) · Zbl 0147.29301
[31] Huneke, C.; Ulrich, B., Residual intersections, J. Reine Angew. Math., 390, 1-20 (1988) · Zbl 0732.13004
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