Waiting time distribution for trains of quantized electron pulses

We consider a sequence of quantized Lorentzian pulses of non-interacting electrons impinging on a quantum point contact (QPC) and study the waiting time distribution (WTD), for any transmission and any number of pulses. As the degree of overlap between the electronic wave functions is tuned, the WTD reveals how the correlations between particles are modified. In the weak overlap regime, the WTD is made of several equidistant peaks, separated by the same period as the incoming pulses, contained in an almost exponentially decaying envelope. In the other limit, the WTD of a single quantum channel subjected to a constant voltage is recovered. In both cases, the WTD stresses the difference between the fluctuations induced by the scatterer and the ones encoded in the incoming quantum state. A clear cross-over between these two situations is studied with numerical and analytical calculations based on scattering theory.Comment: 12 pages, 4 figure

Distributions of electron waiting times in quantum-coherent conductors

The distribution of electron waiting times is useful to characterize quantum transport in mesoscopic structures. Here we consider a generic quantum-coherent conductor consisting of a mesoscopic scatterer in a two-terminal setup. We extend earlier results for single-channel conductors to setups with several (possibly spin-degenerate) conduction channels and we discuss the effect of a finite electronic temperature. We present detailed investigations of the electron waiting times in a quantum point contact as well as in two mesoscopic interferometers with energy-dependent transmissions: a Fabry-P\'erot interferometer and a Mach-Zehnder interferometer. We show that the waiting time distributions allow us to determine characteristic features of the scatterers, for instance the number of resonant levels in the Fabry-P\'erot interferometer that contribute to the electronic transport.Comment: 13 pages, 11 figure

A Constrained Object Model for Configuration Based Workflow Composition

Automatic or assisted workflow composition is a field of intense research for applications to the world wide web or to business process modeling. Workflow composition is traditionally addressed in various ways, generally via theorem proving techniques. Recent research observed that building a composite workflow bears strong relationships with finite model search, and that some workflow languages can be defined as constrained object metamodels . This lead to consider the viability of applying configuration techniques to this problem, which was proven feasible. Constrained based configuration expects a constrained object model as input. The purpose of this document is to formally specify the constrained object model involved in ongoing experiments and research using the Z specification language.Comment: This is an extended version of the article published at BPM'05, Third International Conference on Business Process Management, Nancy Franc

Fingerprints of Majorana fermions in current-correlations measurements from a superconducting tunnel microscope

We compute various current correlation functions of electrons flowing from a topological nanowire to the tip of a superconducting scanning tunnel microscope and identify fingerprints of a Majorana bound state. In particular, the spin resolved cross-correlations are shown to display a clear distinction between the presence of a such an exotic state (negative correlations) and an Andreev bound state (positive correlations). Similarity and differences with measurements with a normal tunnel microscope are also discussed, like the robustness to finite temperature for instance.Comment: 7 pages, 2 figure

A quantum magnetic RC circuit

We propose a setup that is the spin analog of the charge-based quantum RC circuit. We define and compute the spin capacitance and the spin resistance of the circuit for both ferromagnetic (FM) and antiferromagnetic (AF) systems. We find that the antiferromagnetic setup has universal properties, but the ferromagnetic setup does not. We discuss how to use the proposed setup as a quantum source of spin excitations, and put forward a possible experimental realization using ultracold atoms in optical lattices

On the subject matter of international relations

This article deals with the subject matter of International Relations as an academic discipline. It addresses the issue of whether and how one or many realms could legitimately be claimed as the discipline’s prime subject. It first raises a number of problems associated with both identifying the subject matter of IR and ‘labelling’ the discipline in relation to competing terms and disciplines, followed by a discussion on whether, and to what degree, IR takes its identity from a confluence of disciplinary traditions or from a distinct methodology. It then outlines two possibilities that would lead to identifying IR as a discipline defined by a specific realm in distinction to other disciplines: (1) the ‘international’ as a specific realm of the social world, functionally differentiated from other realms; (2) IR as being about everything in the social world above a particular scale. The final section discusses the implications of these views for the study of International Relations

Structural changes in EC trade intensities

The European Economic Community has now been in existence for about 20 years. Five years have elapsed since it was enlarged. What progress have the member countries made in the integration of their foreign trade? What would be the repercussions of a southward extension of the EC to take in Greece, Portugal and Spain

Youth culture and European integration in Germany: Back to European basics?

Basándose en datos de la encuesta respresentativa sobre los jóvenes en Alemania, este artículo destaca tendencias significativas en las actitudes hacia la integracíon europea a lo largo de un periodo relativamente corto. La investigación de estas actitudes cambiantes hace pensar que estos cambios podrían señalar más que una simple reacción a corto plazo hacia acontecimientos políticos singulares una reorientación hacia la emergente conceptualización de la integracíon europea como un proyecto de paz.Using data of a representative survey among young people in Germany, the present article detects significant shifts in attitudes towards European integration over a relatively short time-span. Surveying these changing attitudes, the article explores the idea that these changing attitudes could signal more than mere short-term reactions to singular political events, but rather point to a reorientation towards the initial conceptualization of European integration as a peace project