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Search Results: 1 - 10 of 6109 matches for " Chris Fullwood "
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Internet Access by People with Intellectual Disabilities: Inequalities and Opportunities
Darren Chadwick,Caroline Wesson,Chris Fullwood
Future Internet , 2013, DOI: 10.3390/fi5030376
Abstract: This review gives an overview of the societal inequalities faced by people with intellectual disabilities, before focusing specifically on challenges people face accessing the Internet. Current access will be outlined along with the societal, support and attitudinal factors that can hinder access. Discussion of carer views of Internet use by people with intellectual disabilities will be covered incorporating consideration of the tension between protection, self-determination and lifestyle issues and gaining Internet access. We will address how impairment related factors may impede access and subsequently discuss how supports may be used to obfuscate impairments and facilitate access. We will move on from this to critically describe some of the potential benefits the Internet could provide to people with intellectual disabilities, including the potential for self-expression, advocacy and developing friendships. Finally, strategies to better include people with intellectual disabilities online will be given along with future research suggestions.
On generalized Sethi-Vafa-Witten formulas
James Fullwood
Mathematics , 2011, DOI: 10.1063/1.3628633
Abstract: We present a formula for computing proper pushforwards of classes in the Chow ring of a projective bundle under the projection $\pi:\Pbb(\Escr)\rightarrow B$, for $B$ a non-singular compact complex algebraic variety of any dimension. Our formula readily produces generalizations of formulas derived by Sethi,Vafa, and Witten to compute the Euler characteristic of elliptically fibered Calabi-Yau fourfolds used for F-theory compactifications of string vacua. The utility of such a formula is illustrated through applications, such as the ability to compute the Chern numbers of any non-singular complete intersection in such a projective bundle in terms of the Chern class of a line bundle on $B$.
On Euler polynomials for projective hypersurfaces
James Fullwood
Mathematics , 2014,
Abstract: For every positive integer $n\in \mathbb{Z}_+$ we define an `Euler polynomial' $\mathscr{E}_n(t)\in \mathbb{Z}[t]$, and observe that for a fixed $n$ all Chern numbers (as well as other numerical invariants) of all smooth hypersurfaces in $\mathbb{P}^n$ may be recovered from the single polynomial $\mathscr{E}_n(t)$. More generally, we show that all Chern classes of hypersurfaces in a smooth variety may be recovered from its top Chern class.
On characteristic classes of singular hypersurfaces and involutive symmetries of the Chow group
James Fullwood
Mathematics , 2014,
Abstract: For any algebraic scheme $X$ and every $(n,\mathscr{L})\in \mathbb{Z}\times \text{Pic}(X)$ we define an associated involution of its Chow group $A_*X$, and show that certain characteristic classes of (possibly singular) hypersurfaces in a smooth variety are interchanged via these involutions. For $X=\mathbb{P}^N$ we show that such involutions are induced by involutive correspondences.
On tadpole relations via Verdier specialization
James Fullwood
Mathematics , 2015,
Abstract: Using the construct of "Verdier specialization", we provide a purely mathematical derivation of Chern class identities which upon integration yield the D3-brane tadpole relations coming from the equivalence between F-theory and associated weakly coupled type IIB orientifold limits. In particular, we find that all Chern class identities associated with weak coupling limits appearing in the physics literature are manifestations of a relative version of Verdier's specialization formula.
On Milnor classes via invariants of singular subschemes
James Fullwood
Mathematics , 2013,
Abstract: We derive a formula for the Milnor class of scheme-theoretic global complete intersections (with arbitrary singularities) in a smooth variety in terms of the Segre class of its singular scheme. In codimension one the formula recovers a formula of Aluffi for the Milnor class of a hypersurface.
On CSM classes via Chern-Fulton classes of f-schemes
James Fullwood,Dongxu Wang
Mathematics , 2015,
Abstract: The Chern-Fulton class is a generalization of Chern class to the realm of arbitrary embeddable schemes. While Chern-Fulton classes are sensitive to non-reduced scheme structure, they are not sensitive to possible singularities of the underlying support, thus at first glance are not interesting from a singularity theory viewpoint. However, we introduce a class of formal objects which we think of as `fractional schemes', or f-schemes for short, and then show that when one broadens the domain of Chern-Fulton classes to f-schemes one may indeed recover singularity invariants of varieties and schemes. More precisely, we show that for almost all global complete intersections, their Chern-Schwartz-Macpherson classes may be computed via Chern-Fulton classes of f-schemes.
On Hirzebruch invariants of elliptic fibrations
James Fullwood,Mark van Hoeij
Mathematics , 2011,
Abstract: We compute all Hirzebruch invariants $\chi_q$ for $D_5$, $E_6$, $E_7$ and $E_8$ elliptic fibrations of every dimension. A single generating series $\chi(t,y)$ is produced for each family of fibrations such that the coefficient of $t^{k}y^{q}$ encodes $\chi_q$ over a base of dimension $k$, solely in terms of invariants of the base of the fibration.
On stringy invariants of GUT vacua
James Fullwood,Mark van Hoeij
Mathematics , 2012,
Abstract: We investigate aspects of certain stringy invariants of singular elliptic fibrations which arise in engineering Grand Unified Theories in F-theory. In particular, we exploit the small resolutions of the total space of these fibrations provided recently in the physics literature to compute `stringy characteristic classes', and find that numerical invariants obtained by integrating such characteristic classes are predetermined by the topology of the base of the elliptic fibration. Moreover, we derive a simple (dimension independent) formula for pushing forward powers of the exceptional divisor of a blowup, which one may use to reduce any integral (in the sense of Chow cohomology) on a small resolution of a singular elliptic fibration to an integral on the base. We conclude with a speculatory note on the cohomology of small resolutions of GUT vacua, where we conjecture that certain simple formulas for their Hodge numbers may be given solely in terms of the first Chern class and Hodge numbers of the base.}
D5 elliptic fibrations: non-Kodaira fibers and new orientifold limits of F-theory
Mboyo Esole,James Fullwood,Shing-Tung Yau
Mathematics , 2011,
Abstract: A D5 elliptic fibration is a fibration whose generic fiber is modeled by the complete intersection of two quadric surfaces in P3. They provide simple examples of elliptic fibrations admitting a rich spectrum of singular fibers (not all on the list of Kodaira) without introducing singularities in the total space of the fibration and therefore avoiding a discussion of their resolutions. We study systematically the fiber geometry of such fibrations using Segre symbols and compute several topological invariants. We present for the first time Sen's (orientifold) limits for D5 elliptic fibrations. These orientifolds limit describe different weak coupling limits of F-theory to type IIB string theory giving a system of three brane-image-brane pairs in presence of a Z_2 orientifold. The orientifold theory is mathematically described by the double cover the base of the elliptic fibration. Such orientifold theories are characterized by a transition from a semi-stable singular fiber to an unstable one. In this paper, we describe the first example of a weak coupling limit in F-theory characterized by a transition to a non-Kodaira (and non-ADE) fiber. Inspired by string dualities, we obtain non-trivial topological relations connecting the elliptic fibration and the different loci that appear in its weak coupling limit. Mathematically, these are surprising relations relating the total Chern class of the D5 elliptic fibration and those of different loci that naturally appear in the weak coupling limit. We work in arbitrary dimension and our results don't assume the Calabi-Yau condition.
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