178,083 research outputs found
Preface
No full textThis volume collects contributions from speakers at the INdAM Workshop “Birational Geometry and Moduli Spaces”, which was held in Rome on 11–15 June 2018. The workshop was devoted to the interplay between birational geometry and moduli spaces and the contributions of the volume reflect the same idea, focusing on both these areas and their interaction. In particular, the book includes both surveys and original papers on irreducible holomorphic symplectic manifolds, Severi varieties, degenerations of Calabi-Yau varieties, uniruled threefolds, toric Fano threefolds, mirror symmetry, canonical bundle formula, the Lefschetz principle, birational transformations, and deformations of diagrams of algebras. The intention is to disseminate the knowledge of advanced results and key techniques used to solve open problems. The book is intended for all advanced graduate students and researchers interested in the new research frontiers of birational geometry and moduli spaces
Deformation of Hilbert schemes of points on a surface
No full textLet S be a smooth projective surface over the complex numbers; let S-(r) be its r-fold symmetric product and S-[r]] the Hilbert scheme of O-dimensional subschemes of length r.
In case K-S is trivial, the deformation theory of S[PI has been studied by Beauville and Fujiki in order to construct examples of higher-dimensional symplectic manifolds. In that case S-[r] has deformations which are not Hilbert schemes of points on a surface.
We prove that under suitable hypotheses (e.g, if S is of general type) this cannot happen; every (small) deformation of S-(r) and S-[r] is induced naturally by a deformation of S (in particular, all deformations of S-(r) are locally trivial)
A Logical Verification Methodology for Service-Oriented Computing
No full textWe introduce a logical verification methodology for checking behavioural properties of service-oriented computing systems. Service properties are described by means of SocL, a branching-time temporal logic that we have specifically designed to express in an effective way distinctive aspects of services, such as, e.g., acceptance of a request, provision of a response, and correlation among service requests and responses. Our approach allows service properties to be expressed in such a way that
they can be independent of service domains and specifications. We show an instantiation of our general methodology that uses the formal language COWS to conveniently specify services and the expressly developed software tool CMC to assist the user in the task of verifying SocL formulae over service specifications. We demonstrate feasibility and effectiveness of our methodology by means of the specification and the analysis of a case study in the automotive domain
Smoothing semi-smooth stable Godeaux surfaces
No full textWe show that all the semi-smooth stable complex Godeaux surfaces, classified in
[M. Franciosi, R. Pardini and S. Rollenske, Ark. Mat. 56 (2018), no. 2, 299–317], are
smoothable and that the moduli stack is smooth of the expected dimension 8 at the
corresponding points
Stable maps and branch divisors
No full textWe construct a natural branch divisor for equidimensional projective morphisms where the domain has lci singularities and the target is nonsingular. The method involves generalizing a divisor construction of Mumford from sheaves to complexes. The construction is valid in flat families. The generalized branch divisor of a stable map to a nonsingular curve X yields a canonical morphism from the space of stable maps to a symmetric product of X. This branch morphism (together with virtual localization) is used to compute the Hurwitz numbers of covers of the projective line for all genera and degrees in terms of Hodge integrals
A Model Checking Approach for Verifying COWS Specifications
No full textWe introduce a logical verification framework for checking functional properties of service-oriented applications formally specified using the service specification language COWS. The properties are described by means of SocL, a logic specifically designed to capture peculiar aspects of services. Service behaviours are abstracted in terms of Doubly Labelled Transition Systems, which are used as the interpretation domain for SocL formulae. We also illustrate the SocL model checker at work on a bank service scenario specified in COWS
A Framework to Evaluate 5G Networks for Smart and Fail-Safe Communications in ERTMS/ETCS
No full textETCS is an European system for high speed trains control and protection within ERTMS, the European standard for rail traffic management system. ERTMS/ETCS implementations use GSM-R for communications. As GSM-R is becoming obsolete, the adoption of more advanced technologies is investigated for next generation trains. New communication systems for railway infrastructures are expected to overcome the limitations of GSM-R, providing enhanced performance and reliability, as well as safety and security functionality to meet the requirements of the future signalling systems, control and users’ applications. While 4G technologies (LTE and LTE-A) are currently tested in a few field trials, railway operators should consider that fifth generation (5G) mobile communications technologies will soon be available. One of the foundational aspects of the 5G architecture is control-plane programmability, achieved through the SDN paradigm. Being aware that in a railway scenario this opportunity can be exploited to dynamically reconfigure the network behavior to better match the communication flows produced by moving trains, we aim at defining a framework, integrating formal modeling and analysis tools and techniques into a network emulator, to evaluate the impact on ERTMS/ETCS safety and security deriving from the adoption of an SDN model in the communication infrastructure. In this paper we describe a first step towards this objective, by presenting a first proof-of-concept implementation of the framework and its use to reproduce a simple railway infrastructure. In our current implementation, Finite State Machines are used to model communication protocols between ERTMS/ETCS entities and to automatically produce code and Promela models. Generated code is directly used to control the network behavior while the Promela model allows to generate and verify a network configuration by model checking
On the Hilbert scheme of curves in higher-dimensional projective space
No full textIn this paper we prove that, for any n ≥ 3, there exist infinitely many r ∈ N and for each of them a smooth, connected curve Crin ℙrsuch that Crlies on exactly n irreducible components of the Hilbert scheme Hilb(ℙr). This is proven by reducing the problem to an analogous statement for the moduli of surfaces of general type
Deformations of semi-smooth varieties
No full textFor a singular variety X, an essential step to determine its smoothability and study its deformations is the understanding of the tangent sheaf and of the sheaf T-X(1) := epsilon(l)(xt) (Omega(X), O-X). A variety is semi-smooth if its singularities are etale locally the product of a double crossing point (uv = 0) or a pinch point (u(2) - v(2)w = 0) with affine space; equivalently, if it can be obtained by gluing a smooth variety along a smooth divisor via an involution with smooth quotient. Our main result is the explicit computation of the tangent sheaf and the sheaf T(X)1 for a semi-smooth variety X in terms of the gluing data
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