Browsing Mathematics and Computer Studies (Peerreviewed publications) by Issue Date
Now showing items 120 of 44

Moishezon twistor spaces without effective divisors of degree one (prepublished 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 (Prepublished 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 BodenHu conjecture holds precisely up to rank eight (Prepublished 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 autoequivalences and the set of all tstructures ... 
On a relative FourierMukai transform on genus one fibrations
(Springer, 2006)We study relative FourierMukai transforms on genus one fibrations with section, allowing explicitly the total space of the fibration to be singular and nonprojective. 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 MordellWeil ... 
Homological algebra with locally compact abelian groups (Prepublished Version)
(Elsevier, 2007)In this article we study locally compact abelian (LCA) groups from the viewpoint of derived categories, using that their category is quasiabelian in the sense of J.P. Schneiders. We deﬁne a wellbehaved derived Homcomplex ... 
Rationality and Poincaré families for vector bundles with extra structure on a curve (Prepublished 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 (Prepublished 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 (Prepublished 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 DeligneHitchin moduli space (Prepublished 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 (Prepublished 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 Gbundles 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 (Prepublished 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.