A study of specific learning difficulties in tertiary education

This study is unique in investigating instances of Specific Learning Difficulties (Dyslexia) among mature students in British institutes of tertiary education. Despite growing awareness of this condition, it is only during the last thirty years that cases of dyslexia among adults have been distinguished from aphasia. Assessments were conducted using a structured questionnaire, psychometric tests, measures of attainment, vocational interest and personality. Test results provided support for the view that dyslexia is characterised by a discrepancy between language skills and intellectual ability accompanied by measurable cognitive differences. Significant differences were found on tests of short term memory, while spelling difficulties were the most enduring form of written language difficulty. Differences found on measures of personality, are thought to reflect an interaction between personality and coping strategies. Most subjects had felt constrained to take Jobs with a low interest level, ie. they had compromised their vocational interests and subsequently achieved lower socio-economic status than their fathers. The investigation into the provision made by British universities revealed that very few have any formal policy for dealing with dyslexic students. Most were unable to state what course support or examination concessions were available. In a study of factors related to modality, dyslexic students took longer to read material and remembered less than other groups. When using multi-modal material dyslexic subjects remembered more but must reconcile improving their recall ability with the expense of spending more time. In a second study of factors thought to influence the marking of scripts It was found that higher marks were not awarded to typewritten scripts free from spelling errors. Changes in format only influenced the focus of the tutors' comments. The conclusions are that dyslexia does not improve spontaneously, the dyslexic child is likely to become a dyslexic adult who will continue to experience difficulties with language skills, especially spelling, while the individuals educational, social and occupational ambitions are likely to be compromised because of their specific learning difficulties

Dyons and S-Duality in N=4 Supersymmetric Gauge Theory

We analyze the spectrum of dyons in N=4 supersymmetric Yang-Mills theory with gauge group SU(3) spontaneously broken down to U(1)xU(1). The Higgs fields select a natural basis of simple roots. Acting with S-duality on the W-boson states corresponding to simple roots leads to an orbit of BPS dyon states that are magnetically charged with respect to one of the U(1)'s. The corresponding monopole solutions can be obtained by embedding SU(2) monopoles into SU(3) and the S-duality predictions reduce to the SU(2) case. Acting with S-duality on the W-boson corresponding to a non-simple root leads to an infinite set of new S-duality predictions. The simplest of these corresponds to the existence of a harmonic form on the moduli space of SU(3) monopoles that have magnetic charge (1,1) with respect to the two U(1)'s. We argue that the moduli space is given by R^3x(R^1xM)/Z_2, where M is Euclidean Taub-NUT space, and that the latter admits the appropriate normalizable harmonic two form. We briefly discuss the generalizations to other gauge groups.Comment: 13 pages (Harvmac b), discrete identification corrected, reference adde

A supersymmetric black ring

A new supersymmetric black hole solution of five-dimensional supergravity is presented. It has an event horizon of topology S1xS2. This is the first example of a supersymmetric, asymptotically flat black hole of non-spherical topology. The solution is uniquely specified by its electric charge and two independent angular momenta. These conserved charges can be arbitrarily close, but not exactly equal, to those of a supersymmetric black hole of spherical topology.Comment: 4 pages, 1 figure. v2: Comment about chiral null models remove

D-brane Solitons in Supersymmetric Sigma-Models

Massive D=4 N=2 supersymmetric sigma models typically admit domain wall (Q-kink) solutions and string (Q-lump) solutions, both preserving 1/2 supersymmetry. We exhibit a new static 1/4 supersymmetric `kink-lump' solution in which a string ends on a wall, and show that it has an effective realization as a BIon of the D=4 super DBI-action. It is also shown to have a time-dependent Q-kink-lump generalization which reduces to the Q-lump in a limit corresponding to infinite BI magnetic field. All these 1/4 supersymmetric sigma-model solitons are shown to be realized in M-theory as calibrated, or `Q-calibrated', M5-branes in an M-monopole background.Comment: 16 pages, 3 figures, Late

Vortex Strings and Four-Dimensional Gauge Dynamics

We study the low-energy quantum dynamics of vortex strings in the Higgs phase of N=2 supersymmetric QCD. The exact BPS spectrum of the stretched string is shown to coincide with the BPS spectrum of the four-dimensional parent gauge theory. Perturbative string excitations correspond to bound W-bosons and quarks while the monopoles appear as kinks on the vortex string. This provides a physical explanation for an observation by N. Dorey relating the quantum spectra of theories in two and four dimensions.Comment: 23 pages, 1 figure. v2: Two extra appendices included: one on the brane construction, the other describing the potential on the vortex moduli space. Two figures added. Typos corrected and references added. v3: BPS nature of quarks correcte

Supersymmetric black rings and three-charge supertubes

We present supergravity solutions for 1/8-supersymmetric black supertubes with three charges and three dipoles. Their reduction to five dimensions yields supersymmetric black rings with regular horizons and two independent angular momenta. The general solution contains seven independent parameters and provides the first example of non-uniqueness of supersymmetric black holes. In ten dimensions, the solutions can be realized as D1-D5-P black supertubes. We also present a worldvolume construction of a supertube that exhibits three dipoles explicitly. This description allows an arbitrary cross-section but captures only one of the angular momenta.Comment: 59 pages, 6 figures; v2: minor correction