Browsing Department of Mathematics and Computer Studies by Issue Date
Now showing items 1-20 of 50
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Moishezon twistor spaces without effective divisors of degree one (pre-published version)
(Universität Kaiserslautern, 1995)We study simply connected compact twistor spaces Z of positive type. Assuming that the fundamental linear system j \Gamma 1 2 Kj is at least a pencil, we prove the following theorem: the existence of an irreducible curve ... -
Generalized vector bundles on curves (Pre-published version)
(de Gruyter, 1998)In their paper [14] G. Harder and M.S. Narasimhan (and independently D. Quillen) have constructed a canonical flag of subbundles on any vector bundle on a complete smooth algebraic curve over a field. This flag measures ... -
Twistor spaces with a pencil of fundamental divisors
(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 ... -
Existence of twistor spaces of algebraic dimension two over the connected sum of four complex projective planes
(American Mathematical Society, 1999)We prove the existence of twistor spaces of algebraic dimension two over the connected sum of four complex projective planes 4CP2. These are the rst examples of twistor spaces of algebraic dimension two over a ... -
Stability of Arakelov bundles and tensor products without global sections
(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 Boden-Hu conjecture holds precisely up to rank eight (Pre-published version)
(Springer Verlag, 2004) -
Moduli schemes of generically simple Azumaya modules
(Documenta Mathematica, 2005)Let A be an Azumaya algebra over a smooth projective variety X or more generally, a torsion free coherent sheaf of algebras over X whose generic fiber is a central simple algebra. We show that generically simple torsion ... -
Derived categories of irreducible projective curves of arithmetic genus one
(Cambridge Journals, 2006)We investigate the bounded derived category of coherent sheaves on irreducible singular projective curves of arithmetic genus one. A description of the group of exact auto-equivalences and the set of all t-structures ... -
On a relative Fourier-Mukai transform on genus one fibrations
(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 ... -
Solving cubic equations in two variables
(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 ... -
Homological algebra with locally compact abelian groups (Pre-published Version)
(Elsevier, 2007)In this article we study locally compact abelian (LCA) groups from the viewpoint of derived categories, using that their category is quasi-abelian in the sense of J.-P. Schneiders. We define a well-behaved derived Hom-complex ... -
Rationality and Poincaré families for vector bundles with extra structure on a curve (Pre-published version)
(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. ... -
Elliptic curves – an introduction
(Irish Mathematical Society, 2007) -
Minimizing oblique errors for robust estimating
(Irish Mathematical Society, 2008)The slope of the best fit line from minimizing the sum of the squared oblique errors is shown to be the root of a polynomial of degree four. We introduce a median estimator for the slope and, using a case study, we show ... -
On semistable vector bundles over curves (Pre-published version)
(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; ... -
Some moduli stacks of symplectic bundles on a curve are rational (Pre-published version)
(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 ⊗ ... -
Torelli theorem for the Deligne-Hitchin moduli space (Pre-published version)
(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 ... -
Poincaré families and automorphisms of principal bundles on a curve (Pre-published version)
(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 ... -
Ireland's participation in the 50th international mathematical olympiad
(Irish Mathematical Society, 2009)The 50th International Mathematical Olympiad (IMO) took place in Bremen (Germany) from 12th July until 22nd July 2009. With 565 participants (59 of whom were girls) from 104 countries, this was the IMO with the largest ... -
The moduli stack of vector bundles on a curve (Pre-published Version)
(Ramanujan Mathematical Society, 2010)This expository text tries to explain brie y and not too technically the notions of stack and algebraic stack, emphasizing as an example the moduli stack of vector bundles on an algebraic curve.