Bogomol'nyi Bounds and the Supersymmetric Born-Infeld Theory

We study N=2 supersymmetric Born-Infeld-Higgs theory in 3 dimensions and derive Bogomol'nyi relations in its bosonic sector. A peculiar coupling between the Higgs and the gauge field (with dynamics determined by the Born-Infeld action) is forced by supersymmetry. The resulting equations coincide with those arising in the Maxwell-Higgs model. Concerning Bogomol'nyi bounds for the vortex energy, they are derived from the N=2 supersymmetry algebra.Comment: 24 pages, Latex fil

The Gravity dual of the Non-Perturbative N=2 N = 2 SUSY Yang-Mills Theory

The anomalous Ward identity is derived for $N = 2$ SUSY Yang-Mills theories, which is resulted out of Wrapping of $D_5$ branes on Supersymmetric two cycles. From the Ward identity One obtains the Witten-Dijkgraaf-Verlinde-Verlinde equation and hence can solve for the pre-potential. This way one avoids the problem of enhancon which maligns the non-perturbative behaviour of the Yang-Mills theory resulted out of Wrapped branes.Comment: 4 pages, LaTeX. Talk given at the IXth International Symposium on Particles, Strings and Cosmology PASCOS '03, Mumbai-India, January 3-8 2003. v2:some reference adde

HKT and OKT Geometries on Soliton Black Hole Moduli Spaces

We consider Shiraishi's metrics on the moduli space of extreme black holes. We interpret the simplification in the pattern of N-body interactions that he observed in terms of the recent picture of black holes in four and five dimensions as composites, made up of intersecting branes. We then show that the geometry of the moduli space of a class of black holes in five and nine dimensions is hyper-K\"ahler with torsion, and octonionic-K\"ahler with torsion, respectively. For this, we examine the geometry of point particle models with extended world-line supersymmetry and show that both of the above geometries arise naturally in this context. In addition, we construct a large class of hyper-K\"ahler with torsion and octonionic-K\"ahler with torsion geometries in various dimensions. We also present a brane interpretation of our results.Comment: pages 55, phyzzx, some more references have been adde

A genealogy of hacking

Hacking is now a widely discussed and known phenomenon, but remains difficult to define and empirically identify because it has come to refer to many different, sometimes incompatible, material practices. This paper proposes genealogy as a framework for understanding hacking by briefly revisiting Foucault’s concept of genealogy and interpreting its perspectival stance through the feminist materialist concept of the situated observer. Using genealogy as a theoretical frame a history of hacking will be proposed in four phases. The first phase is the ‘pre-history’ of hacking in which four core practices were developed. The second phase is the ‘golden age of cracking’ in which hacking becomes a self-conscious identity and community and is for many identified with breaking into computers, even while non-cracking practices such as free software mature. The third phase sees hacking divide into a number of new practices even while old practices continue, including the rise of serious cybercrime, hacktivism, the division of Open Source and Free Software and hacking as an ethic of business and work. The final phase sees broad consciousness of state-sponsored hacking, the re-rise of hardware hacking in maker labs and hack spaces and the diffusion of hacking into a broad ‘clever’ practice. In conclusion it will be argued that hacking consists across all the practices surveyed of an interrogation of the rationality of information techno-cultures enacted by each hacker practice situating itself within a particular techno-culture and then using that techno-culture to change itself, both in changing potential actions that can be taken and changing the nature of the techno-culture itself

Mechanisms underlying attentional set-shifting in Parkinson's disease

Patients with Parkinson's disease (PD) show impairments on tasks that require them to switch attention between two perceptual dimensions (extradimensional (ED) shifting). It has been suggested that ED shifting deficits can be caused by two separate mechanisms, 'learned irrelevance' and 'perseveration'. This study set out to test the hypothesis that enhanced learned irrelevance is present in medicated patients with PD. An enhancement of learned irrelevance in PD patients should result in increased errors on a 'deficit' shift relative to controls and decreased errors on an 'improvement' shift. A similar pair of deficit and improvement shifts were used to detect possible enhanced perseveration in patients. Instead of showing the predicted patterns of deficit and improvement, patients displayed a consistent deficit on those shifts that required that they switch their attention to a different dimension (ED shifts). In contrast, patients were not impaired on shifts that required no such shift of attention (intradimensional shifts). Although there was an increase in errors at the learned irrelevance deficit shift, a similar increase at the learned irrelevance improvement shift shows that enhanced learned irrelevance is not responsible for either of these results. Patients were no more distractible than controls, but displayed increased 'loss of set' as measured by errors generated after a rule was learned. These results point to the existence of exaggerated, rigid selective attention in patients with PD rather than a breakdown in the ability to selectively attend. There was no evidence for the existence of enhanced learned irrelevance in the patients. (C) 1999 Elsevier Science Ltd. All rights reserved.</p