Ara es mostren els items 27-46 de 48

    • New slope inequalities for families of complete intersections 

      Barja Yáñez, Miguel Ángel; Stoppino, Lidia (2024-01-01)
      Article
      Accés obert
      We prove f-positivity of Ox (1) for arbitrary dimensional fibrations over curves f:X¿B whose general fibre is a complete intersection. In the special case where the family is a global complete intersection, we prove numerical ...
    • Numerical Bounds of Canonical Varieties 

      Barja Yáñez, Miguel Ángel (1998)
      Article
      Accés obert
      We study surfaces and threefolds whose canonical maps are birational (canonical surfaces and threefolds). In the case of canonical surfaces we prove that the known inequlity for its invariants is not sharp if the surface ...
    • On a conjecture of Fujita 

      Barja Yáñez, Miguel Ángel (2000)
      Article
      Accés obert
    • On the bicanonical map of irregular varieties 

      Barja Yáñez, Miguel Ángel; Lahoz Vilalta, Martí; Naranjo del Val, Joan Carles; Pareschi, Giusseppe (2010-02)
      Report de recerca
      Accés obert
      From the point of view of uniform bounds for the birationality of pluricanonical maps, irregular varieties of general type and maximal Albanese dimension behave similarly to curves. In fact Chen-Hacon showed that, at least ...
    • On the slope of bielliptic fibrations 

      Barja Yáñez, Miguel Ángel (1997)
      Article
      Accés obert
      Let $\pi :S\longrightarrow B$ be a bielliptic fibration. We prove $S$ is, up to base change, a rational double cover of an elliptic fibration and that $\pi $ is isotrivial provided it is smooth. Finally, we prove that the ...
    • On the slope of fibred surfaces 

      Barja Yáñez, Miguel Ángel; Zucconi, Franco (2000)
      Article
      Accés obert
      We give an asymptotically sharp lower bound for the slope $\lambda (f)$ of a fibration $f:S\longrightarrow B$, where $S$ is a surface and $B$ is a curve, if there exists an involution on the general fibre $F$ of $f$. ...
    • On the slope of fibred surfaces 

      Barja Yáñez, Miguel Ángel; Zucconi, Franco (1998)
      Article
      Accés obert
    • On the slope of fibred threefolds 

      Barja Yáñez, Miguel Ángel (1998)
      Article
      Accés obert
      We study from a geographical point of wiew fibrations of threefolds over smooth curves $f: T \longrightarrow B$ such that the general fibre is of general type. We prove the non-negativity of certain relative invariants under ...
    • On the topological index of irregular surfaces 

      Barja Yáñez, Miguel Ángel; Naranjo, J. C.; Pirola, Gian Pietro (2005)
      Article
      Accés obert
      We study the topological index of some irregular surfaces that we call generalized Lagrangian. We show that under certain hypotheses on the base locus of the Lagrangian system the topological index is non-negative. For ...
    • Positivity properties of relative complete intersections 

      Barja Yáñez, Miguel Ángel; Stoppino, Lidia (2014-10)
      Report de recerca
      Accés obert
      We give conditions for f-positivity of relative complete intersections in projective bundles. We also derive an instability result for the fibres.
    • Slope inequalities for fibrations of non-maximal Albanese dimension 

      Barja Yáñez, Miguel Ángel (2021-06-15)
      Article
      Accés obert
      We study and obtain Slope inequalities for fibred irregular varieties of non-maximal Albanese dimension. We give a comparison theorem between Clifford–Severi and Slope inequalities for this type of fibrations. We also ...
    • Slope inequalities for higher dimensional irregular fibrations 

      Barja Yáñez, Miguel Ángel (2022-07-28)
      Article
      Accés restringit per política de l'editorial
      We prove the equivalence between Clifford-Severi inequalities for good classes of varieties of maximal Albanese dimension and Slope Inequalities for such varieties fibred over curves. This provides a big set of new Slope ...
    • Stability and singularities of relative hypersurfaces 

      Barja Yáñez, Miguel Ángel; Stoppino, Lidia (2014-07-30)
      Report de recerca
      Accés obert
      We study relative hypersurfaces, and prove an instability condition for the fibres. This is the starting point for an investigation of the geometry of effective divisors on relative projective bundles.
    • Surfaces on the Severi line 

      Barja Yáñez, Miguel Ángel; Pardini, Rita; Stoppino, Lidia (2016-05-01)
      Article
      Accés obert
      Let S be a minimal complex surface of general type and of maximal Albanese dimension; by the Severi inequality one has K-S(2) >= 4 chi(O-S). We prove that the equality K-S(2) = 4 chi(O-S) holds if and only if q(S) := ...
    • The eventual paracanonical map of a variety of maximal Albanese dimension 

      Barja Yáñez, Miguel Ángel; Pardini, Rita; Stoppino, Lidia (2019)
      Article
      Accés obert
      Let Xbe a smooth complex projective variety such that the Albanese map of Xis generically ¿nite onto its image. Here we study the so-called eventual m-paracanonical map of X, whose existence is implied by the results of ...
    • The representation problem of pairs of symmetric second order tensors in the context of solid mechanics 

      Barja Yáñez, Miguel Ángel; Carol, Ignacio; Planas Vilanova, Francesc d'Assís; Rizzi, Egidio (2003)
      Report de recerca
      Accés restringit per decisió de l'autor
    • The structure and slope of bielliptic fibrations 

      Barja Yáñez, Miguel Ángel (1997)
      Article
      Accés obert
    • TOPOLOGIA 

      Barja Yáñez, Miguel Ángel (Universitat Politècnica de Catalunya, 2014-06-03)
      Examen
      Accés restringit a la comunitat UPC
    • TOPOLOGIA (Examen 2n quadrim) 

      Barja Yáñez, Miguel Ángel (Universitat Politècnica de Catalunya, 2005-04-05)
      Examen
      Accés restringit a la comunitat UPC
    • Topologia. Apunts 

      Barja Yáñez, Miguel Ángel; Pascual Gainza, Pere; Roig Martí, Agustín; Carreras, Judit; Amorós Torrent, Jaume (Universitat Politècnica de Catalunya, 1998)
      Apunts
      Accés obert