Braiding of non-Abelian anyons using pairwise interactions

The common approach to topological quantum computation is to implement quantum gates by adiabatically moving non-Abelian anyons around each other. Here we present an alternative perspective based on the possibility of realizing the exchange (braiding) operators of anyons by adiabatically varying pairwise interactions between them rather than their positions. We analyze a system composed by four anyons whose couplings define a T-junction and we show that the braiding operator of two of them can be obtained through a particular adiabatic cycle in the space of the coupling parameters. We also discuss how to couple this scheme with anyonic chains in order to recover the topological protection.Comment: 8 pages, 7 figures. Errors corrected, clarifications and comments adde

Web Auctions in Europe

This paper argues that a better understanding of the business model of web auctions can be reached if we adopt a broader view and provide empirical research from different sites. In this paper the business model of web auctions is refined into four dimensions. These are auction model, motives, exchange processes, and stakeholders. One of the objects of this research is to redefine the blurry concept of the business model by analyzing one business model, the web auction model. We show in this research the complexity and diversity of factors contributing to the success of the web auction model. By generalizing the results to the level of business model we also show how complex and diverse business models can be. Motivated by the lack of empirically grounded justification for the mixed business results of web auctions, this paper adopts a qualitative approach that includes telephone interviews with web auctions developed in different European countries.exchange processes;stakeholders;Web auctions

The A&A Experience With Impact Factors

There is a widespread impression that the scientific journal "Astronomy & Astrophysics" (A&A) has a smaller impact, as measured by citations to articles, than some of the other major astronomy journals. This impression was apparently supported - and probably created - by the Journal Citation Report (JCR), which is prepared annually by the Institute of Scientific Information (ISI) Web of Knowledge. The published poor impact factor of A&A was in fact wrong and was due to a serious flaw in the method used by ISI Web of Knowledge to determine it. The resulting damage inflicted upon A&A by the JCR is incalculable.Comment: 4 pages, to be published in A. Heck (ed.) "Organizations and Strategies in Astronomy, Vol. 5" (Kluwer, 2004

Large Surveys in Cosmology: The Changing Sociology

Galaxy redshift surveys and Cosmic Microwave Background experiments are undertaken with larger and larger teams, in a fashion reminiscent of particle physics experiments and the human genome projects. We discuss the role of young researchers, the issue of multiple authorship, and ways to communicate effectively in teams of tens to hundreds of collaborators.Comment: Invited article for "Organizations and Strategies in Astronomy II", ed. A. Heck, Kluwer Acad. Publ., in press (7 pages, no figures

New Symbolic Tools for Differential Geometry, Gravitation, and Field Theory

DifferentialGeometry is a Maple software package which symbolically performs fundamental operations of calculus on manifolds, differential geometry, tensor calculus, Lie algebras, Lie groups, transformation groups, jet spaces, and the variational calculus. These capabilities, combined with dramatic recent improvements in symbolic approaches to solving algebraic and differential equations, have allowed for development of powerful new tools for solving research problems in gravitation and field theory. The purpose of this paper is to describe some of these new tools and present some advanced applications involving: Killing vector fields and isometry groups, Killing tensors and other tensorial invariants, algebraic classification of curvature, and symmetry reduction of field equations.Comment: 42 page

Topologically protected charge transfer along the edge of a chiral p\textit{p}-wave superconductor

The Majorana fermions propagating along the edge of a topological superconductor with $p_x+ip_y$ pairing deliver a shot noise power of $\frac{1}{2}\times e^2/h$ per eV of voltage bias. We calculate the full counting statistics of the transferred charge and find that it becomes trinomial in the low-temperature limit, distinct from the binomial statistics of charge-$e$ transfer in a single-mode nanowire or charge-$2e$ transfer through a normal-superconductor interface. All even-order correlators of current fluctuations have a universal quantized value, insensitive to disorder and decoherence. These electrical signatures are experimentally accessible, because they persist for temperatures and voltages large compared to the Thouless energy.Comment: 5 pages, 4 figures. v3 [post-publication]: added an appendix on the effect of a tunnel barrier at the normal-superconductor contac

Analysis of the sensor characteristics of the Galileo dust detector with collimated Jovian dust stream particles

The Dust Detector System onboard Galileo records dust impacts in the Jupiter system. Impact events are classified into four quality classes. Class 3 -- our highest quality class -- has always been noise-free and, therefore, contains only true dust impacts. Depending on the noise environment, class 2 are dust impacts or noise. Within $20 R_J$ from Jupiter (Jupiter radius, $R_J = 71,492 km$) class 2 shows clear indications for contamination by noise. We analyse the dust data from Galileo's prime Jupiter mission (1996 and 1997), separate dust impacts from noise events and derive a complete denoised set of Galileo dust data (class 2 and class 3). Collimated streams of nanometer-sized dust particles which have been detected throughout the Jovian system (Gr\"un et al. 1998, JGR, 103, 20011-20022) are used to analyse the sensitive area and the field of view of the dust detector itself. The sensitive area for stream particles which trigger class 3 events is $110 \pm 37 cm^2$. This is almost a factor of ten smaller than the total sensitive area for class 2 impacts (1,000 cm^2). Correspondingly, the field of view of the detector for class 3 stream particles is reduced from $140^{\circ}$ to $96^{\circ}$. The magnetometer boom and other instruments on board Galileo cause a significant shadowing of the field of view of the dust sensor. Our analysis is supplementary to ground calibrations of the dust instrument because the low masses and high speeds of the stream particles could not be achieved in the laboratory. Our new results have important consequences for the analysis of dust in the Jupiter system.Comment: Planetary and Space Science, accepted, 11 figures, 3 table

Single fermion manipulation via superconducting phase differences in multiterminal Josephson junctions

We show how the superconducting phase difference in a Josephson junction may be used to split the Kramers degeneracy of its energy levels and to remove all the properties associated with time reversal symmetry. The superconducting phase difference is known to be ineffective in two-terminal short Josephson junctions, where irrespective of the junction structure the induced Kramers degeneracy splitting is suppressed and the ground state fermion parity must stay even, so that a protected zero-energy Andreev level crossing may never appear. Our main result is that these limitations can be completely avoided by using multi-terminal Josephson junctions. There the Kramers degeneracy breaking becomes comparable to the superconducting gap, and applying phase differences may cause the change of the ground state fermion parity from even to odd. We prove that the necessary condition for the appearance of a fermion parity switch is the presence of a "discrete vortex" in the junction: the situation when the phases of the superconducting leads wind by $2\pi$. Our approach offers new strategies for creation of Majorana bound states as well as spin manipulation. Our proposal can be implemented using any low density, high spin-orbit material such as InAs quantum wells, and can be detected using standard tools.Comment: Source code available as ancillary files. 10 pages, 7 figures. v2: minor changes, published versio

Durability testing at 5 atmospheres of advanced catalysts and catalyst supports for gas turbine engine combustors

The durability of CATCOM catalysts and catalyst supports was experimentally demonstrated in a combustion environment under simulated gas turbine engine combustor operating conditions. A test of 1000 hours duration was completed with one catalyst using no. 2 diesel fuel and operating at catalytically-supported thermal combustion conditions. The performance of the catalyst was determined by monitoring emissions throughout the test, and by examining the physical condition of the catalyst core at the conclusion of the test. Tests were performed periodically to determine changes in catalytic activity of the catalyst core. Detailed parametric studies were also run at the beginning and end of the durability test, using no. 2 fuel oil. Initial and final emissions for the 1000 hours test respectively were: unburned hydrocarbons (C3 vppm):0, 146, carbon monoxide (vppm):30, 2420; nitrogen oxides (vppm):5.7, 5.6