Preprints de Matemàtiques - Mathematics Preprint Series

URI permanent per a aquesta col·leccióhttps://diposit.ub.edu/handle/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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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.
Panoràmica del sistema decimal posicional des dels orígens indis a l'Arismètica de Santclimen
(Universitat de Barcelona, 1997) Pla i Carrera, Josep
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.
On cardinal sequences of scattered spaces
(Universitat de Barcelona, 1997) Martínez Alonso, Juan Carlos
Large deviations for stochastic Volterra equations in the plane
(Universitat de Barcelona, 1997) Rovira Escofet, Carles; Sanz-Solé, Marta
Development of the density: a Wiener-chaos approach
(Universitat de Barcelona, 1997) Márquez, David (Márquez Carreras); Sanz-Solé, Marta
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.
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.
Construction of 2̂m S_n- fields containing a C_(2̂m ) - field
(Universitat de Barcelona, 1997) Crespo Vicente, Teresa
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
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.
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.
Stochastic evolution equations with random generators
(Universitat de Barcelona, 1996) León, Jorge A.; Nualart, David, 1951-
We prove the existence of a unique mild solution for a stochastic evolution equation on a Hilbert space driven by a cylindrical Wiener process. The generator of the corresponding evolution system is supposed to be random and adapted to the filtration generated by the Wiener process. The proof is based on a maximal inequality for the Skorohod integral deduced from the Itô’s formula for this anticipating stochastic integral.
Convergence within nonisotropic regions of harmonic functions in B^n
(Universitat de Barcelona, 1996) Cascante, Ma. Carme (Maria Carme); Ortega Aramburu, Joaquín M.
We study the boundedness in Lp(n) of the projections onto spaces of functions with spectrum contained in horizontal strips. We obtain some results concerning convergence along nonisotropic regions of harmonic extensions of functions in Lp(n) with spectrum included in these horizontal strips.
Estimation of densities and applications
(Universitat de Barcelona, 1996) Caballero, M. E. (María Emilia); Fernández, Begoña; Nualart, David, 1951-
In this paper we show some estimates for the density of a random variable on the Wiener space that satisfies a nondegeneracy condition using the stochastic calculus of variations. The case of a diffusion process is considered, and an application to the solution of a stochastic partial differential equation is discussed.
On the Cohen-Macaulayness of diagonal subalgebras of the Rees algebra
(Universitat de Barcelona, 1996) Lavila Vidal, Olga
We consider the blowing up of ℙ k/n−1 along a closed subscheme defined by a homogeneous idealI ∪A=k[X 1, …,X n ] generated by forms of degree ≤d, and its projective embeddings by the linear systems corresponding to (I e) c , forc≥de+1. The homogeneous coordinate rings of these embeddings arek[(I e) c ]. One wants to study the Cohen-Macaulay property of these rings. We will prove that if the Rees algebraR A (I) is Cohen-Macaulay, thenk[(I e) c ] are Cohen-Macaulay forc>>e>0, thus proving a conjecture stated by A. Conca, J. Herzog, N.V. Trung and G. Valla.
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.
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...
A strong completeness theorem for the gentzen systems associated with finite algebras
(Universitat de Barcelona, 1996) Gil, Àngel J.; Rebagliato, Jordi; Verdú, B. (Buenaventura)
In this paper we study consequence relations on the set of many sided sequents over a propositional language. We deal with the consequence relations axiomatized by the sequent calculi defined in [2] and associated with arbitrary finite algebras. These consequence relations are examples of what we call Gentzen systems. We define a semantics for these systems and prove a Strong Completeness Theorem, which is an extension of the Completeness Theorem for provable sequents stated in [2]. For the special case of the finite linear MV-algebras, the Strong Completeness Theorem was proved in [10], as a consequence of McNaughton's Theorem. The main tool to prove this result for arbitrary algebras is the deduction-detachment theorem for Gentzen systems.
A maximal inequality for the Skorohod integral
(Universitat de Barcelona, 1996) Alòs, Elisa; Nualart, David, 1951-

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