African University of Science and Technology: Recent submissions

Now showing items 361-380 of 4824

  • Groups and embeddings in SL(2, C) 

    Button, Jack (Taylor & FrancisCommunications in Algebra, 2015-10-19)
    We give results on when a finitely generated torsion free group does or does not embed in SL(2, C). For instance if we glue two copies of the figure 8 knot along its torus boundary then the fundamental group of the resulting ...

  • Automorphy of some residually dihedral Galois representations 

    Thorne, Jack Arfon (Springer, 2015-05-08)
    We establish the automorphy of some families of 2-dimensional representations of the absolute Galois group of a totally real field, which do not satisfy the so-called ‘Taylor–Wiles hypothesis’. We apply this to the problem ...

  • Invariant distributions, Beurling transforms and tensor tomography in higher dimensions 

    Paternain, Gabriel Pedro; Salo, Mikko; Uhlmann, Gunther (SpringerMathematische Annalen, 2015-02-01)
    In the recent articles [PSU13, PSU14c], a number of tensor tomography results were proved on two-dimensional manifolds. The purpose of this paper is to extend some of these methods to manifolds of any dimension. A central ...

  • Unifying Amplitude and Phase Analysis Unifying Amplitude and Phase Analysis. A Compositional Data Approach to Functional Multivariate Mixed-Effects Modeling of Mandarin Chinese 

    Hadjipantelis, PZ; Aston, John Alexander; Müller, HG; Evans, JP (Taylor & FrancisJournal of the American Statistical Association, 2015-07-06)
    Mandarin Chinese is characterized by being a tonal language; the pitch (or F0) of its utterances carries considerable linguistic information. However, speech samples from different individuals are subject to changes in ...

  • The Triviality problem for profinite completions 

    Bridson, Martin R; Wilton, Henry John (SpringerInventiones Mathematicae, 2015-02-24)
    We prove that there is no algorithm that can determine whether or not a finitely presented group has a non-trivial finite quotient; indeed, this property remains undecidable among the fundamental groups of compact, ...

  • Equidistribution of Frobenius eigenvalues 

    Thorne, Jack Arfon (Oxford JournalsInternational Mathematics Research Notices, 2015-02-09)
    We study the problem of variation of Frobenius eigenvalues on the cohomology of families of local systems of algebraic curves over finite fields.

  • Exact Lagrangian immersions with a single double point 

    Ekholm, Tobias; Smith, Ivan (American Mathematical Society, 2015-01-09)
    We show that if a closed orientable 2k-manifold K, k > 2, with Euler characteristic χ(K) ≠ -2 admits an exact Lagrangian immersion into C2k with one transverse double point and no other self intersections, then K is ...

  • Hidden states, hidden structures: Bayesian learning in time series models 

    Murphy, James Kevin (University of CambridgeDepartment of Engineering, 2014-06-10)
    This thesis presents methods for the inference of system state and the learning of model structure for a number of hidden-state time series models, within a Bayesian probabilistic framework. Motivating examples are taken ...

  • Trading to stops 

    Imkeller, Nora; Rogers, Leonard Christopher (Society for Industrial and Applied MathematicsSiam Journal on Financial Mathematics, 2014-12-16)
    The use of trading stops is a common practice in financial markets for a variety of reasons: it reduces the frequency of trading and thereby transaction costs; it provides a simple way to control losses on a given trade, ...

  • Quiver algebras as Fukaya categories 

    Smith, Ivan (Mathematical Sciences PublishersGeometry & Topology, 2015-10-20)
    We embed triangulated categories defined by quivers with potential arising from ideal triangulations of marked bordered surfaces into Fukaya categories of quasiprojective 3–folds associated to meromorphic quadratic ...

  • The contact property for magnetic flows on surfaces 

    Benedetti, Gabriele (University of CambridgeDepartment of Pure Mathematics and Mathematical StatisticsTrinity College, 2015-01-06)
    This work investigates the dynamics of magnetic flows on closed orientable Riemannian surfaces. These flows are determined by triples (M, g, σ), where M is the surface, g is the metric and σ is a 2-form on M . Such dynamical ...

  • On the Boltzmann equation, quantitative studies and hydrodynamical limits 

    Briant, Marc (University of CambridgeDepartment of Pure Mathematics and Mathematical StatisticsCambridge Centre for Analysis, 2014-11-11)
    The present thesis deals with the mathematical treatment of kinetic theory and focuses more precisely on the Boltzmann equation. We investigate several properties of the solutions to the latter equation: their positivity ...

  • Algebraic boundaries of Hilbert's SOS cones 

    Blekherman, Grigoriy; Hauenstein, Jonathan; Ottem, John Christian; Ranestad, Kristian; Sturmfels, Bernd (Cambridge University PressCompositio Mathematica, 2012-10-15)
    We study the geometry underlying the difference between nonnegative polynomials and sums of squares. The hypersurfaces that discriminate these two cones for ternary sextics and quaternary quartics are shown to be ...

  • Ample subvarieties and q-ample divisors 

    Ottem, John Christian (ElsevierAdvances in Mathematics, 2012-03-20)
    We introduce a notion of ampleness for subschemes of any codimension using the theory of q-ample line bundles. We also investigate certain geometric properties satisfied by ample subvarieties, e.g. the Lefschetz ...

  • Excitations in superfluids of atoms and polaritons 

    Pinsker, Florian (University of CambridgeDepartment of Pure Mathematics and Mathematical StatisticsSt. Edmund's College, 2014-11-11)
    This thesis is devoted to the study of excitations in atomic and polariton Bose-Einstein condensates (BEC). These two specimens are prime examples for equilibrium and non equilibrium BEC. The corresponding condensate wave ...

  • Estimate nothing 

    Duembgen, Moritz; Rogers, Leonard Christopher (Taylor & FrancisQuantitative Finance, 2014)
    In the econometrics of financial time series, it is customary to take some parametric model for the data, and then estimate the parameters from historical data. This approach suffers from several problems. Firstly, how is ...

  • Optimal investment: bounds and heuristics 

    Rogers, L. C. G.; Zaczkowski, P. (Incisive Financial PublishingJournal of Computational Finance, 2015-10-28)
    High-dimensional optimal investment/consumption problems are hard to deal with, not least because of the difficulty in characterizing the value function. This paper tries to offer ways to determine an approximately optimal ...

  • Investing and stopping 

    Duembgen, Moritz; Rogers, Leonard Christopher (Applied Probability TrustJournal of Applied Probability, 2014)
    In this paper we solve the hedge fund manager’s optimization problem in a model that allows for investors to enter and leave the fund over time depending on its performance. The manager’s payoff at the end of the year will ...

  • An explicit upper bound for the Helfgott delta in SL(2,p) 

    Button, Jack; Roney-Dougal, Colva M (ElsevierJournal of Algebra, 2014-09-23)
    Helfgott proved that there exists a δ > 0 such that if S is a symmetric generating subset of SL(2, p)containing 1 then either S^3=SL(2, p)or |S^3| ≥|S|^1+ δ. It is known that δ ≥ 1/3024. Here we show that δ ≤ (log_2 (7) ...

  • Quadratic differentials as stability conditions 

    Bridgeland, Tom; Smith, Ivan (SpringerPublications mathématiques de l'IHÉS, 2014)
    We prove that moduli spaces of meromorphic quadratic differentials with simple zeroes on compact Riemann surfaces can be identified with spaces of stability conditions on a class of CY3 triangulated categories defined using ...