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Building an alternative social currency: Dematerialising and rematerialising digital money across media
This paper reports on the user experience and design of physical and digital forms of a mixed-media local currency. We reconceive digitally mediated transactions as social interactions and report on the development of conceptual designs informed by user research and interactive workshops. Our findings show that use is strongly tied to conceptions of locality and community, markers of identity, information exchange and the digital and physical forms as tools for shaping interactions. The form of the currency can make the invisible visible, exposing our identities and values, business models, and the details of the transactions themselves. Our analysis stresses the need to provide opportunities for extending social interaction, making more local connections and deriving the best value from those connections, without insulating individuals from each other, or from the wider geographical context. Themes that emerged from the user research were visualized as conceptual designs for digitally augmented media, allowing us to explore the monetary transaction at three levels: the material, as interaction between two parties, and the context of the transaction.The RCUK Digital Economy theme (EP/K012304/1)
The radial structure of protostellar accretion disks: influence of jets
The radial structure of accretion disks is a fundamental issue regarding star
and planet formation. Many theoretical studies, focussing on different aspects
such as e.g. disk emissivity or ionization, have been conducted in the context
of the Standard Accretion Disk (SAD) model, where no jet is present. We wish to
calculate the structure of YSO accretion disks in an approach that takes into
account the presence of the protostellar jets. The radial structure of these
Jet Emitting Disks (JED) should then be compared to that of standard accretion
disks. The analytical treatment used in this work is very similar to that of
standard accretion disks but is using the parameter space of Magnetised
Accretion-Ejection Structures that include the jet torque on the underlying
disk. In this framework, the analytical expressions of key quantities, such as
mid-plane temperatures, surface densities or disk aspect ratio are derived. It
is found that JEDs present a structure very different from the SADs and that
can be observationally tested. The implications on planet formation in the
inner regions of accretion disks are briefly discussed. We also supply sets of
analytical formulae, valid in different opacity regimes, for the disk
quantities. These expressions can be readily used for any work where the disk
structure is needed as an input for the model.Comment: 11 pages, 4 figures. Accepted for publication in A&
Are Magnetic Wind-Driving Disks Inherently Unstable?
There have been claims in the literature that accretion disks in which a
centrifugally driven wind is the dominant mode of angular momentum transport
are inherently unstable. This issue is considered here by applying an
equilibrium-curve analysis to the wind-driving, ambipolar diffusion-dominated,
magnetic disk model of Wardle & Konigl (1993). The equilibrium solution curves
for this class of models typically exhibit two distinct branches. It is argued
that only one of these branches represents unstable equilibria and that a real
disk/wind system likely corresponds to a stable solution.Comment: 5 pages, 2 figures, to be published in ApJ, vol. 617 (2004 Dec 20).
Uses emulateapj.cl
Magnetically Defined Qubits on 3D Topological Insulators
We explore potentials that break time-reversal symmetry to confine the
surface states of 3D topological insulators into quantum wires and quantum
dots. A magnetic domain wall on a ferromagnet insulator cap layer provides
interfacial states predicted to show the quantum anomalous Hall effect (QAHE).
Here we show that confinement can also occur at magnetic domain
heterostructures, with states extended in the inner domain, as well as
interfacial QAHE states at the surrounding domain walls. The proposed geometry
allows the isolation of the wire and dot from spurious circumventing surface
states. For the quantum dots we find that highly spin-polarized quantized QAHE
states at the dot edge constitute a promising candidate for quantum computing
qubits.Comment: 5 pages, 4 figure
Global-String and Vortex Superfluids in a Supersymmetric Scenario
The main goal of this work is to investigate the possibility of finding the
supersymmetric version of the U(1)-global string model which behaves as a
vortex-superfluid. To describe the superfluid phase, we introduce a
Lorentz-symmetry breaking background that, in an approach based on
supersymmetry, leads to a discussion on the relation between the violation of
Lorentz symmetry and explicit soft supersymmetry breakings. We also study the
relation between the string configuration and the vortex-superfluid phase. In
the framework we settle down in terms of superspace and superfields, we
actually establish a duality between the vortex degrees of freedom and the
component fields of the Kalb-Ramond superfield. We make also considerations
about the fermionic excitations that may appear in connection with the vortex
formation.Comment: 9 pages. This version presented the relation between Lorentz symmetry
violation by the background and the appearance of terms that explicitly break
SUS
Mobi algebra as an abstraction to the unit interval and its comparison to rings
We introduce a new algebraic structure, called mobi algebra, consisting of three constants and one ternary operation. The canonical example of a mobi algebra is the unit interval with the three constants 0, 1, and 1/2 and the ternary operation given by the formula x−yx+yz. We study some of its properties and prove that every unitary ring with one half uniquely determines and is uniquely determined by a mobi algebra with one double. Another algebraic structure, called involutive medial monoid (IMM), is considered to establish the passage between rings and mobi algebras.info:eu-repo/semantics/publishedVersio
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