99,201 research outputs found

    Special scrolls whose base curve has general moduli

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    In this paper we study the Hilbert scheme of smooth, linearly normal, special scrolls under suitable assumptions on degree, genus and speciality.Comment: Latex2e, shorter versio

    Seminatural bundles of rank two, degree one and c2=10c_2=10 on a quintic surface

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    In this paper we continue our study of the moduli space of stable bundles of rank two and degree 1 on a very general quintic surface. The goal in this paper is to understand the irreducible components of the moduli space in the first case in the "good" range, which is c2=10c_2=10. We show that there is a single irreducible component of bundles which have seminatural cohomology, and conjecture that this is the only component for all stable bundles

    Elliptic curve configurations on Fano surfaces

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    The elliptic curves on a surface of general type constitute an obstruction for the cotangent sheaf to be ample. In this paper, we give the classification of the configurations of the elliptic curves on the Fano surface of a smooth cubic threefold. That means that we give the number of such curves, their intersections and a plane model. This classification is linked to the classification of the automorphism groups of theses surfaces.Comment: 17 pages, accepted and shortened version, the rest will appear in "Fano surfaces with 12 or 30 elliptic curves

    Chiral SUSY Theories with a Suppressed SUSY Charge

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    The well-known Chiral and Gauge SUSY Actions realize the SUSY charge in terms of transformations among the Fields. These transformations are included in the Master Equation by coupling them to Sources. Here we show that there are new local SUSY Actions where the Chiral SUSY transformations are realized in terms of transformations among both Fields and Sources. These Actions can be easily obtained from the Chiral case by a very simple and local `Exchange Transformation', which carries along all the interactions without difficulty. For these new SUSY Actions, the SUSY charge does not exist in the relevant sector, because Sources do not satisfy Equations of Motion. Nevertheless, the `Exchange Transformation' ensures that the new Master Equation is true for the new Action. As a consequence, the Master Equation also is true for the new 1PI Generating Functional. This implies that a `Suppressed SUSY Charge' version of SUSY is still present. SUSY certainly becomes more obscure and less constrained in this case. But it is still very restrictive. The new theories can be obtained from the old theories by using a special technique, but it is not true that they are a sort of `broken version of supersymmetry'. They are simply a new type of theory that is governed by Supersymmetry, but without the use of Supercharges (except perhaps in some sectors). In particular the number of physical Bosonic and Fermionic degrees of Freedom are not equal for these new (sub)-Actions, although there is still Boson/Fermion mass degeneracy in a (sub)-Action, so long as there is still a Boson present. Notably, there is even a SUSY (sub)-Action where the physical Scalars are not present, so that the (sub)-Action contains physical Fermions only. In this theory the degeneracy of Bosonic and Fermionic masses is obviously not present.Comment: 21 pages This version has a better explanation of how and why these new representations of SUSY can and do exist, without contradicting the known results in SUSY theor

    A uniform definition of stochastic process calculi

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    We introduce a unifying framework to provide the semantics of process algebras, including their quantitative variants useful for modeling quantitative aspects of behaviors. The unifying framework is then used to describe some of the most representative stochastic process algebras. This provides a general and clear support for an understanding of their similarities and differences. The framework is based on State to Function Labeled Transition Systems, FuTSs for short, that are state-transition structures where each transition is a triple of the form (s; Ī±;P). The first andthe second components are the source state, s, and the label, Ī±, of the transition, while the third component is the continuation function, P, associating a value of a suitable type to each state s0. For example, in the case of stochastic process algebras the value of the continuation function on s0 represents the rate of the negative exponential distribution characterizing the duration/delay of the action performed to reach state s0 from s. We first provide the semantics of a simple formalism used to describe Continuous-Time Markov Chains, then we model a number of process algebras that permit parallel composition of models according to the two main interaction paradigms (multiparty and one-to-one synchronization). Finally, we deal with formalisms where actions and rates are kept separate and address the issues related to the coexistence of stochastic, probabilistic, and non-deterministic behaviors. For each formalism, we establish the formal correspondence between the FuTSs semantics and its original semantics
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