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Preprints de Matemàtiques - Mathematics Preprint Series

URI permanent per a aquesta col·leccióhttps://hdl.handle.net/2445/151238

La sèrie Preprints de Matemàtiques, Mathematics Preprint Series, és una col·lecció de publicacions realitzades pel Personal Docent i Investigador de la Facultat de Matemàtiques i de l'Institut de Matemàtiques de la Universitat de Barcelona (IMUB), en col·laboració amb investigadors convidats per l'IMUB.

La col·lecció, impulsada pel professor Eduard Casas Alvero, abasta de l'any 1986 fins el 2009 i correspon a la versió d'articles científics sense revisió entre parells, alguns dels quals van ser publicats en una revista acadèmica i científica.

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Mostrant 1 - 20 de 107
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    Acute thrombosis induced by drug-coated balloons dilation in neoatherosclerosis plaque, successfully treated with a MicroNet-covered stent: A Case Report and Literature Review
    (Universitat de Barcelona, 2024) Stefanini, Matteo; Maresca, Luciano; Ginanni Corradini, Luca; Balocco, Simone; Rigla, Juan; Simonetti, Giovanni
    Background The operator's ability in performing carotid stenting (CAS) has improved clinical outcomes. However, more than 3% of patients need to be treated again after CAS. Most of the cases requiring further intervention are affected by hyperplasia. The recommended procedure is the DEBalloon. On the other hand, the literature reports a small number of carotid neoatherosclerosis cases and is recommended to be treated using elective Micronet-covered stent. Discriminating between the two types of in-stent-restenosis ISR (hyperplasia or neoatherosclerosis) is critical for a positive outcome. Case summary We describe a case in which a patient treated with carotid stenting 8 years before, was diagnosed with ISR. Due to the development of neurological symptoms and progressive increases in Peak Systolic Velocity (PSV) eight years following carotid stenting, a DEBalloon was used in a carotid in-stent-restenosis (ISR) standard procedure. About ten minutes after the procedure, the patient developed hemiplegia consistent with the treated carotid territory. The implantation of a MicroNet-covered stent excluded the thrombus and reverted symptoms with a normal MR control at 24 h. Conclusion This case illustrates that when in-stent stenosis evolves years after the stent implantation, neoatherosclerosis should be assessed, and a MicroNet-covered stent should be considered.
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    Product logic and the deduction theorem
    (Universitat de Barcelona, 1997) Adillón, Román; Verdú, B. (Buenaventura)
    In this paper we prove the following negative result: Product Logic [9] does not have the Deduction Theorem, that is, there is no binary defined connective in the language of Product Logic such that the Deduction Theorem is satisfied with respect to it. We prove this theorem mainly by using algebraic methods: we prove that Product Logic is algebraizable, that the variety of Product Algebras is its equivalent quasivariety semantics and that this variety has no equationally definable principal congruences.
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    On cardinal sequences of scattered spaces
    (Universitat de Barcelona, 1997) Martínez Alonso, Juan Carlos
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    Large deviations for stochastic Volterra equations in the plane
    (Universitat de Barcelona, 1997) Rovira Escofet, Carles; Sanz-Solé, Marta
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    Locally finite quasivarieties of MV-algebras
    (Universitat de Barcelona, 1997) Gispert Brasó, Joan; Torrens Torrell, Antoni
    In this paper we show that every locally finite quasivariety of MV-algebras is finitely generated and finitely based. To see this result we study critical MV-algebras. We also give axiomatizations of some of these quasivarieties.
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    Development of the density: a Wiener-chaos approach
    (Universitat de Barcelona, 1997) Márquez, David (Márquez Carreras); Sanz-Solé, Marta
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    Analytical invariants of conformal transformations : a dynamical system approach
    (Universitat de Barcelona, 1997) Gelfreich, Vasily G.
    The paper is devoted to the problem of analytical classification of conformal maps of the form f: z z+z2+ ... in a neighborhood of the degenerate fixed point z=0. It is shown that the analytical invariants, constructed in the works of Voronin and Ecalle, may be considered as a measure of splitting for stable and unstable (semi-)invariant foliations associated with the fixed point. This splitting is exponentially small with respect to the distance to the fixed point.
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    Construction of 2̂m S_n- fields containing a C_(2̂m ) - field
    (Universitat de Barcelona, 1997) Crespo Vicente, Teresa
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    On the Cohen-Macaulay property of the fiber cone of ideals with reduction number at most one
    (Universitat de Barcelona, 1997) Cortadellas Benítez, Teresa; Zarzuela, Santiago
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    Higuer bott Chern forms and Beilinson's regulator
    (Universitat de Barcelona, 1996) Burgos Gil, José I.; Wang, Steve
    In this paper, we prove a Gauss-Bonnet theorem for the higher algebraic K-theory of smooth complex algebraic varieties. To each exact n-cube of hermitian vector bundles, we associate a higher Bott-Chen form, generalizing the Bott-Chern forms associated to exact sequences. These forms allow us to define characteristic classes from K-theory to absolute Hodge cohomology. Then we prove that these characteristic classes agree with Beilinson's regulator map.
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    A characterization of monotone and regular divergences
    (Universitat de Barcelona, 1996) Corcuera Valverde, José Manuel; Giummolè, F
    In this paper we characterize the local structure of monotone and regular divergences, which include f-divergences as a particular case, by giving their Taylor expansion up to fourth order. We extend a previous result obtained by Čencov, using the invariant properties of Amari's α-connections.
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    Global efficency
    (Universitat de Barcelona, 1996) Corcuera Valverde, José Manuel; Oller i Sala, Josep Maria
    In this paper the global behaviour of an estimator is studied in framework of Intrinsic Analysis, (7). Two indices of performance of an estimator in a bounded region are analyzed: the average of the intrinsic risk (the loss function is the squared Rao distance) and the maximum risk. The Riemannian volume, provided by the Fisher metric on the manifold associated with the parametric model, allows us to take an average of the intrinsic risk. Cramér-Rao type integral inequalities for the integrated mean squared Rao distance of estimators are derived using variational methods, extending the work of éencov, [3]. Additionally, lower bounds for the maximum risk are also derived, by using integral expressions.
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    Hilbert polynomials over artinian local rings
    (Universitat de Barcelona, 1996) Blancafort, Cristina; Nollet, Scott, 1962-
    This paper characterizes Hilbert functions and Hilbert polynomials of standard algebras over an Artinian ring R0.
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    On the depth of the fiber cone of filtrations
    (Universitat de Barcelona, 1996) Cortadellas Benítez, Teresa; Zarzuela, Santiago
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    Stochastic Volterra equations in the plane: smoothness of the law
    (Universitat de Barcelona, 1997) Rovira Escofet, Carles; Sanz-Solé, Marta
    We give sufficient conditions ensuring the smoothness of the density for the law of the solution of Volterra equations in the plane. One of the motivations for the study of such class of equations is provided by non-linear hyperbolic stochastic partial differential equations appearing in the construction of some path-valued processes on manifolds. The proof is based on Malliavin Calculus.
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    On the contributions of Helena Rasiowa to mathematical logic
    (Universitat de Barcelona, 1996) Font, Josep M.
    Let me begin with sorne personal reminiscences. For me, writing a paper on the contributions of HELENA RASIOWA (1917-1994) to Mathematical Logic might be the result of several unexpected coincidences1 . My relationship with RASIOWA is academic rather than personal. Her book An algebraic approach to non-classical logics [41] is one the main sources that might be found guilty of my professional dedication to research in Algebraic Logic, if sorne
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    Intrinsic analysis of the statistical estimation
    (Universitat de Barcelona, 1996) Oller i Sala, Josep Maria; Corcuera Valverde, José Manuel
    The parametric statistical models with suitable regularity conditions have a natural Riemannian manifold structure, given by the information metric. Since the parameters are merely labels for the probability measures, an inferential statement should be formulated through intrinsic objects, invariant under reparametrizations. In this context the estimators will be random objects valued on the manifold corresponding to the statistical model. In spite of these considerations, classical measures of an estimator's performance, like the bias and the mean square error, are clearly dependent on the statistical model parametrizations. In this paper the authors work with extended notions of mean value and moments of random objects which take values on a Hausdorff and connected manifold, equipped with an affine connection. In particular, the Riemannian manifold case is considered. This extension is applied to the bias and the mean square error study in statistical point estimation theory. Under this approach an intrinsic version of the Cramer-Rao lower bound is obtained: a lower bound, which depends on the intrinsic bias and the curvature of the statistical model, for the mean square of the Rao distance, the invariant measure analogous to the mean square error. Further, the behavior of the mean square of the Rao distance of an estimator when conditioning with respect to a sufficient statistic is considered, obtaining intrinsic versions of the Rao-Blackwell and Lehmann-Scheffe theorems. Asymptotic properties complete the study.
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    An extension of Itô's formula for anticipating processes
    (Universitat de Barcelona, 1996) Alòs, Elisa; Nualart, David, 1951-
    In this paper we introduce a class of square integrable processes, denoted by LF, defined in the canonical probability space of the Brownian motion, which contains both the adapted processes and the processes in the Sobolev space L2,2. The processes in the class LF satisfy that for any time t, they are twice weakly differentiable in the sense of the stochastic calculus of variations in points (r, s) such that r ∨ s ≥ t. On the other hand, processes belonging to the class LF are Skorohod integrable, and the indefinite Skorohod integral has properties similar to those of the Ito integral. In particular we prove a change-of-variable formula that extends the classical Itô formula. Those results are generalization of similar properties proved by Nualart and Pardoux(7) for processes in L2,2.
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    Fundamentos de demostración automática de teoremas
    (Universitat de Barcelona, 1996) Martínez Alonso, Juan Carlos
    La Demostración Automática de Teoremas es actualmente un área de interés dentro de la Inteligencia Artificial. El problema general que se plantea en la Demostración Automática de Teoremas es el de encontrar métodos mecánicos para demostrar teoremas que se puedan llevar a la práctica. Los primeros avances importantes en este campo son debidos a Herbrand, que en el año 1930 presentó un primer método de demostración automática. De este método presentado por Herbrand se deduce que, bajo ciertas condiciones, es posible construir un programa de tal forma que si le suministramos como entrada una condición formal convenientemente codificada, el programa nos da una demostración de esa condición, en el caso en que dicha condición sea cierta. Las condiciones formales para las que se puede utilizar este método de demostración automática son enunciados que se pueden describir mediante fórmulas de un lenguaje de predicados sin el símbolo de identidad.. Sin embargo, se vio más adelante que dicho método resultaba ineficiente a la hora de llevarlo a la práctica. En el año 1965, Robinson introdujo el método de Resolución, que es un refinamiento del método desarrollad.o anteriormente por Herbrand. Sin embargo, el método de Resolución resultó ser mucho más eficiente que los métodos de demostración automática que se habían desarrollado hasta entonces. Actualmente, es un método básico de demostración automática que se utiliza en problemas de Inteligencia Artificial...