Now showing items 30-49 of 50

    • On a relative Fourier-Mukai transform on genus one fibrations 

      Burban, Igor; Kreussler, Bernd (Springer, 2006)
      We study relative Fourier-Mukai transforms on genus one fibrations with section, allowing explicitly the total space of the fibration to be singular and non-projective. Grothendieck duality is used to prove a ...
    • On moduli stacks of G-bundles over a curve (Pre-published version) 

      Hoffmann, Norbert (Springer, 2010)
      Let C be a smooth projective curve over an algebraically closed eld k of arbitrary characteristic. Given a linear algebraic group G over k, let MG be the moduli stack of principal G-bundles on C. We determine the set of ...
    • On semistable vector bundles over curves (Pre-published version) 

      Hoffmann, Norbert; Biswas, Indranil; Hein, Georg (Elsevier, 2008)
      Let X be a geometrically irreducible smooth projective curve de ned over a eld k, and let E be a vector bundle on X. Then E is semistable if and only if there is a vector bundle F on X such that Hi(X; F E) = 0 for i = 0; ...
    • The Picard group of a coarse moduli space of vector bundles in positive characteristic (Pre-published version) 

      Hoffmann, Norbert (Versita, co-published with Springer Verlag., 2012)
      Let C be a smooth projective curve over an algebraically closed field of arbitrary characteristic. Let Mss r,L denote the projective coarse moduli scheme of semistable rank r vector bundles over C with fixed determinant ...
    • Poincaré families and automorphisms of principal bundles on a curve (Pre-published version) 

      Hoffmann, Norbert; Biswas, Indranil (Elsevier, 2009)
      Let C be a smooth projective curve, and let G be a reductive algebraic group. We give a necessary condition, in terms of automorphism groups of principal G-bundles on C, for the existence of Poincaré families parameterized ...
    • Poincaré families of G-bundles on a curve (Pre-published version) 

      Hoffmann, Norbert; Biswas, Indranil (Springer Verlag, 2012)
      Let G be a reductive group over an algebraically closed field k. Consider the moduli space of stable principal G-bundles on a smooth projective curve C over k. We give necessary and sufficient conditions for the existence of ...
    • Rationality and Poincaré families for vector bundles with extra structure on a curve (Pre-published version) 

      Hoffmann, Norbert (Oxford University Press, 2007)
      Iterated Grassmannian bundles over moduli stacks of vector bundles on a curve are shown to be birational to an affine space times a moduli stack of degree 0 vector bundles, following the method of King and Schofield. ...
    • Response surface designs using the generalized variance inflation factors 

      O'Driscoll, Diarmuid; Ramirez, Donald E. (Cogent OA, 2015)
      We study response surface designs using the generalized variance inflation factors for subsets as an extension of the variance inflation factors.
    • Revisiting some design criteria 

      O'Driscoll, Diarmuid; Ramirez, Donald E. (Athens Institute for Education and Research, 2015)
      We address the problem that the A (trace) design criterion is not scale invariant and often is in disagreement with the D (determinant) design criterion. We consider the canonical moment matrix CM and use the trace of its ...
    • Solving cubic equations in two variables 

      Kreussler, Bernd (Irish Mathematical Society, 2007)
      After recalling a geometric construction of all Pythagorean triples of integers, the same idea is applied to find rational solutions of cubic equations in two variables. This leads to the definition of the Mordell-Weil ...
    • Some moduli stacks of symplectic bundles on a curve are rational (Pre-published version) 

      Biswas, Indranil; Hoffmann, Norbert (Elsevier, 2008)
      Let C be a smooth projective curve of genus g ≥ 2 over a field k. Given a line bundle L on C, let Sympl2n,L be the moduli stack of vector bundles E of rank 2n on C endowed with a nowhere degenerate symplectic form b : E ⊗ ...
    • Stability of Arakelov bundles and tensor products without global sections 

      Hoffmann, Norbert (Documenta Mathematica, 2003)
      This paper deals with Arakelov vector bundles over an arithmetic curve, i.e. over the set of places of a number field. The main result is that for each semistable bundle E, there is a bundle F such that E⊗F has at least ...
    • The stability space of the derived category of holomorphic triples and further investigations 

      Rüffer, Arne (2021-04-14)
      In this thesis we give a complete description of the Bridgeland stability space for the bounded derived category of holomorphic triples over a smooth projective curve of genus one as a connected, four dimensional complex ...
    • SU(5) heterotic standard model bundles (Pre-published version) 

      Hoffmann, Norbert; Andreas, Björn (Springer Verlag, 2012)
      We construct a class of stable SU(5) bundles on an elliptically fibered Calabi-Yau threefold with two sections, a variant of the ordinary Weierstrass fibration, which admits a free involution. The bundles are invariant under ...
    • Symbol functions for symmetric frameworks (Pre-published) 

      Kitson, Derek; Kastis, Eleftherios; McCarthy, John E (Elsevier, 2021-05-15)
      We prove a variant of the well-known result that intertwiners for the bilateral shift on ℓ2(Z) are unitarily equivalent to multiplication operators on L2(T). This enables us to unify and extend fundamental aspects of ...
    • Symmetric frameworks in normed spaces 

      Kitson, Derek; Nixon, Anthony; Schulze, Bernd (Elsevier, 2020-12-15)
      We develop a combinatorial rigidity theory for symmetric bar-joint frameworks in a general finite dimensional normed space. In the case of rotational symmetry, matroidal Maxwell-type sparsity counts are identified for a ...
    • Symmetric powers of trace forms on symbol algebras 

      Flatley, Ronan (Université D'Artois, 2013)
    • Torelli theorem for the Deligne-Hitchin moduli space (Pre-published version) 

      Biswas, Indranil; Gómez, Tomás L.; Hoffmann, Norbert; Logares, Marina (Springer Verlag, 2009)
      Fix integers g ≥ 3 and r ≥ 2, with r ≥ 3 if g = 3. Given a compact connected Riemann surface X of genus g, let M DH (X) denote the corresponding SL(r,C) Deligne–Hitchin moduli space. We prove that the complex analytic ...
    • Trace forms of symbol algebras (Pre-published version) 

      Flatley, Ronan (World Scientific Publishing Complany, 2012)
      Let S be a symbol algebra. The trace form of S is computed and it is shown how this form can be used to determine whether S is a division algebra or not. In addition, the exterior powers of the trace form of S are computed.
    • Twistor spaces with a pencil of fundamental divisors 

      Kreussler, Bernd (Documenta Mathematica, 1999)
      In this paper simply connected twistor spaces Z containing a pencil of fundamental divisors are studied. The Riemannian base for such spaces is diffeomorphic to the connected sum nCP2 . We obtain for n 5 a complete ...