arXiv subjects

Fabrizio Catanese

Publications and source records attributed to Fabrizio Catanese.

At least 109 records · Page 6Linked to original sources

arXiv2007

Differentiable and deformation type of algebraic surfaces, real and symplectic structures

Lecture 1: Projective and Kähler Manifolds, the Enriques classification, construction techniques. Lecture 2: Surfaces of general type and their Canonical models. Deformation equivalence and singularities. Lecture 3: Deformation and diffeomorphism, canonical symplectic structure for surfaces of general type. Lecture 4: Irrational pencils, orbifold fundamental groups, and surfaces isogenous to a product. Lecture 5: Lefschetz pencils, braid and mapping class groups, and diffeomorphism of ABC-surfaces. Epilogue: Deformation, diffeomorphism and symplectomorphism type of surfaces of general type.

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arXiv2006

Double Kodaira fibrations

The existence of a Kodaira fibration, i.e., of a fibration of a compact complex surface $S$ onto a complex curve $B$ which is a differentiable but not a holomorphic bundle, forces the geographical slope $ ν(S) = c_1^2 (S) / c_2 (S)$ to lie in the interval $(2,3)$. But up to now all the known examples had slope $ ν(S) \leq 2 + 1/3$. In this paper we consider a special class of surfaces admitting two such Kodaira fibrations, and we can construct many new examples, showing in particular that there are such fibrations attaining the slope $ ν(S) = 2 + 2/3$. We are able to explicitly describe the moduli space of such class of surfaces, and we show the existence of Kodaira fibrations which yield rigid surfaces. We observe an interesting connection between the problem of the slope of Kodaira fibrations and a 'packing' problem for automorphisms of algebraic curves of genus $\geq 2$.

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arXiv2006

Fibrations of low genus, I

In the present paper we consider fibrations $f: S \ra B$ of an algebraic surface onto a curve $B$, with general fibre a curve of genus $g$. Our main results are: 1) A structure theorem for such fibrations in the case $g=2$ 2) A structure theorem for such fibrations in the case $g=3$ and general fibre nonhyperelliptic 3) A theorem giving a complete description of the moduli space of minimal surfaces of general type with $ K^2_S = 3, p_g = q=1$, showing in particular that it has four unirational connected components 4) some other applications of the two structure theorems.

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arXiv2006

The classification of surfaces with p_g = q = 0 isogenous to a product of curves

We classify all the surfaces with p_g = q = 0 which admit an unramified covering which is isomorphic to a product of curves. Beyond the trivial case \PP^1 x \PP^1 we find 17 families which we explicitly describe. We reduce the problem to a combinatorial description of certain generating systems for finite groups which we solve using also MAGMA's library of groups of small order.

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arXiv2006

A volume maximizing canonical surface in 3-space

Answering a question posed by Enriques, we construct a minimal smooth algebraic surface $S$ of general type over the complex numbers with $K^2 = 45$ and $p_g = 4$, and with birational canonical map. Our surface is a regular (q=0) ball quotient which is an etale quotient of a Hirzebruch covering of the plane. The canonical system $|K_S|$ has a fixed part and the degree of the canonical image is 19.

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arXiv2006

Chebycheff and Belyi polynomials, dessins d'enfants, Beauville surfaces and group theory

We start discussing the group of automorphisms of the field of complex numbers, and describe, in the special case of polynomials with only two critical values, Grothendieck's program of 'Dessins d' enfants', aiming at giving representations of the absolute Galois group. We describe Chebycheff and Belyi polynomials, and other explicit examples. As an illustration, we briefly treat difference and Schur polynomials. Then we concentrate on a higher dimensional analogue of the triangle curves, namely, Beauville surfaces and varieties isogenous to a product. We describe their moduli spaces, and show how the study of these varieties leads to new interesting questions in the theory of finite (simple) groups.

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arXiv2006

Surface classification and local and global fundamental groups, I

Given a smooth complex surface S, and a compact connected global normal crossings divisor $D = \cup_i D_i$, we consider the local fundamental group, i.e., the fundamental group Gamma of T-D, where T is a good tubular neighbourhood of D. One has a surjection of Gamma onto the fundamental group of D, and the kernel $\sK$ is normally generated by geometric loops $\ga_i$ around the curve $D_i$. Among the main results, which are strong generalizations of a well known theorem of Mumford, is the nontriviality of $\ga_i$ in the local fundamental group, provided all the curves $D_i$ of genus zero have selfintersection <= -2. (in particular this holds if the canonical divisor is nef on D), and under the technical assumption that the dual graph of D is a tree.

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arXiv2006

Complex surfaces of general type: some recent progress

Chapters : Old and new inequalities; Surfaces with $χ=1$ and the bicanonical map; Surfaces with $p_g=4$; Surfaces isogeneous to a product, Beauville surfaces and the absolute Galois group;Lefschetz pencils and braid monodromies;DEF, DIFF and other equivalence relations.

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arXiv2006

Real structures on torus bundles and their deformations

We describe the family of real structures $σ$ on principal holomorphic torus bundles $X$ over tori, and prove its connectedness when the complex dimension is at most three. From this and previous results of the authors follows that the differentiable type (more precisely, the orbifold fundamental group) determines the deformation type of the pair $(X, σ)$ provided we have complex dimension at most three, fibre dimension one, and a certain 'reality' condition on the fundamental group is satisfied.

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arXiv2005

Even sets of nodes on sextic surfaces

We determine the possible even sets of nodes on sextic surfaces in $\Pn 3$, showing in particular that their cardinalities are exactly the numbers in the set $\{24, 32, 40, 56 \}$. We also show that all the possible cases admit an explicit description. The methods that we use are an interplay of coding theory and projective geometry on one hand, of homological and computer algebra on the other. We give a detailed geometric construction for the new case of an even set of 56 nodes, but the ultimate verification of existence relies on computer calculations. The construction gives a maximal family, unirational and of dimension 27, of nodal sextics with an even set of 56 nodes. According to a general theorem of Casnati and Catanese each such nodal surface $F$ is given as the determinant of a symmetric map for an appropriate vector bundle $\E$ depending on $F$. The first difficulty here is to show the existence of such vector bundles. This leads us to the investigation of a hitherto unknown moduli space of rank 6 vector bundles which we show to be birational to a moduli space of plane representations of cubic surfaces in $\PP^3$. The resulting picture shows a very rich and interesting geometry. The main difficulty is to show the existence of "good" maps $ϕ$, and the interesting phenomenon which shows up is the following: the "moduli space" of such pairs $(\E, ϕ)$ is reducible, indeed for a general choice of $\E$ the determinant of $ ϕ$ is the double of a cubic surface $G$.

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arXiv2005

Q.E.D. for algebraic varieties

We introduce a new equivalence relation, denoted by $A.Q.E.D.$ (= Algebraic-Quasi-Étale- Deformation) for complete algebraic varieties with canonical singularities: it is generated by birational equivalence, by flat algebraic deformations, and by quasi-étale morphisms, i.e., morphisms which are unramified in codimension $1$. $\C$-Q.E.D is the similar relation for compact complex manifolds and spaces. By a recent theorem of Siu dimension and Kodaira dimension are invariants for $A.Q.E.D.$. The question whether conversely two algebraic varieties of the same dimension and with the same Kodaira dimension are Q.E.D. -equivalent has a positive answer for curves and using Enriques' classification we show that the answer to the $\C$-Q.E.D. question is positive for special algebraic surfaces (Kodaira dimension at most $1$) and for compact complex surfaces with Kodaira dimension $0, 1$ and even first Betti number. The appendix by Sönke Rollenske shows that the same does not hold if we allow odd first Betti number( Kodaira surfaces form a single class). The answer to the A.Q.E.D. question is yes for special complex algebraic surfaces, while the appendix due to Fritz Grunewald shows that the answer is no for surfaces of general type. Because the (rigid) Kuga-Shavel type surfaces of general type obtained as quotients of the bidisk via discrete groups constructed from quaternion algebras belong to countably many distinct Q.E.D. equivalence classes.

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arXiv2005

The 3-cuspidal quartic and braid monodromy of degree 4 coverings

We study the discriminant of a degree 4 extension given by a deformed bidouble cover, i.e., by equations z^2= u + a w, w^2= v + bz. We first show that the discriminant surface is a quartic which is cuspidal on a twisted cubic, i.e.,is the discriminant of the general equation of degree 3. We then take a(u,v), b(u,v) and get a 3-cuspidal affine quartic curve whose braid monodromy we compute. This calculation of the local braid monodromy is a step towards the determination of global braid monodromies, e.g. for the (a,b,c) surfaces previously considered by the authors. In the revision we fill a gap (noticed by the referee) in the proof of the classical theorem that any quartic surface which has the twisted cubic as cuspidal curve is its tangential developable, and we changed a base point in order to make a picture correct.

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arXiv2005

The Noether inequality for smooth minimal 3-folds

Let X be a smooth projective minimal 3-fold of general type. We prove the sharp inequality K^3_X >= (2 /3)(2p_g(X) - 5), an analogue of the classical Noether inequality for algebraic surfaces of general type

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arXiv2005

Diffeomorphism of simply connected algebraic surfaces

In this paper we show that even in the case of simply connected minimal algebraic surfaces of general type, deformation and differentiable equivalence do not coincide. Exhibiting several simple families of surfaces which are not deformation equivalent, and proving their diffeomorphism, we give a counterexample to a weaker form of the speculation DEF = DIFF of R. Friedman and J. Morgan, i.e., in the case where (by M. Freedman's theorem) the topological type is completely determined by the numerical invariants of the surface. We hope that the methods of proof may turn out to be quite useful to show diffeomorphism and indeed symplectic equivalence for many important classes of algebraic surfaces and symplectic 4-manifolds.

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arXiv2005

Trecce, Mapping class group, fibrazioni di Lefschetz ed applicazioni al diffeomorfismo di superficie algebriche

Purpose of the Conference article, intended for a wider audience, is to introduce concepts and techniques used by Bronislaw Wajnryb and the author in order to show the diffeomorphism of certain elementary algebraic surfaces, called ABC surfaces, which are not deformation equivalent. In the first part are recalled the concepts of connected sum, surgeries, Poincare' group, Braids, Riemann surfaces and Dehn's Mapping class group. Then the topics become more advanced, including Lefschetz fibrations, ABC surfaces, symplectic fibrations and braid monodromy.

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arXiv2005

Deformation in the large of some complex manifolds, II

The compact complex manifolds considered in this article are principal torus bundles over a torus. We consider the Kodaira Spencer map of the complete Appell Humbert family (introduced by the first author in Part I) and are able to show that we obtain in this way a connected component of the space of complex structures each time that the base dimension is two, the fibre dimension is one, and a suitable topological condition is verified.

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arXiv2004

Beauville surfaces without real structures, I

Inspired by a construction by Arnaud Beauville of a surface of general type with $K^2 = 8, p_g =0$, the second author defined the Beauville surfaces as the surfaces which are rigid, i.e., they have no nontrivial deformation, and admit un unramified covering which is isomorphic to a product of curves of genus at least 2. In this case the moduli space of surfaces homeomorphic to the given surface consists either of a unique real point, or of a pair of complex conjugate points corresponding to complex conjugate surfaces. It may also happen that a Beauville surface is biholomorphic to its complex conjugate surface, neverless it fails to admit a real structure. First aim of this note is to provide series of concrete examples of the second situation, respectively of the third. Second aim is to introduce a wider audience, especially group theorists, to the problem of classification of such surfaces, especially with regard to the problem of existence of real structures on them.

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arXiv2004

The Maximum Likelihood Degree

Maximum likelihood estimation in statistics leads to the problem of maximizing a product of powers of polynomials. We study the algebraic degree of the critical equations of this optimization problem. This degree is related to the number of bounded regions in the corresponding arrangement of hypersurfaces, and to the Euler characteristic of the complexified complement. Under suitable hypotheses, the maximum likelihood degree equals the top Chern class of a sheaf of logarithmic differential forms. Exact formulae in terms of degrees and Newton polytopes are given for polynomials with generic coefficients.

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