Invariants of the single impurity Anderson model and implications for conductance functionals

An exact relation between the conductance maximum $G_0$ at zero temperature and a ratio of lead densities is derived within the framework of the single impurity Anderson model: $G_0={\mathfrak R}[n] \frac{2e^2}{h}$, where ${\mathfrak R}[n]=4\Delta N_{{\cal L},x} \Delta N_{{\cal R},x}/(\Delta N_{{\cal L},x}+\Delta N_{{\cal R},x})^2$ and $\Delta N_{{\cal L},x}$, $\Delta N_{{\cal R},x}$ denote the excess density in the left/right lead at distance $x$ due to the presence of the impurity at the origin, $x=0$. The relation constitutes a parameter-free expression of the conductance of the model in terms of the ground state density that generalizes an earlier result to the generic case of asymmetric lead couplings. It turns out that the specific density ratio, ${\mathfrak R}[n]$, is independent of the distance to the impurity $x$, the (magnetic) band-structure and filling fraction of the contacting wires, the strength of the onsite interaction, the gate voltage and the temperature. Disorder induced backscattering in the contacting wires has an impact on ${\mathfrak R}$ that we discuss. Our result suggests that it should be possible, in principle, to determine experimentally the peak conductance of the Anderson impurity by performing a combination of measurements of ground-state densities.Comment: 5 pages, 3 figures, accepted by EP

Book Review: governance in pacific Asia: political economy and development from Japan to Burma

In his latest book, Peter Ferdinand discusses the increasing economic integration of the Pacific Asian region as well as its impact on global affairs. Kent Deng is impressed by the breadth of the book’s coverage and the way it rethinks the once narrowly conceived boundaries of Asia

Cold atoms in cavity-generated dynamical optical potentials

We review state-of-the-art theory and experiment of the motion of cold and ultracold atoms coupled to the radiation field within a high-finesse optical resonator in the dispersive regime of the atom-field interaction with small internal excitation. The optical dipole force on the atoms together with the back-action of atomic motion onto the light field gives rise to a complex nonlinear coupled dynamics. As the resonator constitutes an open driven and damped system, the dynamics is non-conservative and in general enables cooling and confining the motion of polarizable particles. In addition, the emitted cavity field allows for real-time monitoring of the particle's position with minimal perturbation up to sub-wavelength accuracy. For many-body systems, the resonator field mediates controllable long-range atom-atom interactions, which set the stage for collective phenomena. Besides correlated motion of distant particles, one finds critical behavior and non-equilibrium phase transitions between states of different atomic order in conjunction with superradiant light scattering. Quantum degenerate gases inside optical resonators can be used to emulate opto-mechanics as well as novel quantum phases like supersolids and spin glasses. Non-equilibrium quantum phase transitions, as predicted by e.g. the Dicke Hamiltonian, can be controlled and explored in real-time via monitoring the cavity field. In combination with optical lattices, the cavity field can be utilized for non-destructive probing Hubbard physics and tailoring long-range interactions for ultracold quantum systems.Comment: 55 page review pape

Risk preferences and development revisited

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The social dynamics of heterogeneous innovation ecosystems : Effects of openness on community–firm relations

In this article, we develop a programmatic notion of innovation ecosystems, which emphasizes the analysis of different forms of distributed innovation without reducing the perspective to the role of a focal organization. It highlights relationships between communities and corporate firms as nexus for distributed innovation and elaborates how different facets of openness shape the dynamic of the ecosystem. Thus, our model allows for the analysis and comparison of a broad scope of constellations, their particular coordinating mechanisms as well as related advantages and disadvantages. We apply this framework to two specific cases of distributed innovation, the RepRap 3D printer and the ARA modular smartphone, in order to delineate how differences in the forms of openness affect the prevalent relationships between communities and firms as well as the constituting functions of their particular innovation ecosystem

Swirl Boundary Layer at the Inlet of a Rotating Circular Cone

International audienceWhen a fluid enters a rotating pipe, a swirl boundary layer with thickness of $δ_S$ appears at the wall and interacts with the axial momentum boundary layer with thickness of $δ$. The swirl is produced by the wall shear stress and not due to kinematic reasons as by a turbomachine. In the center of the pipe, the fluid is swirl-free and is accelerated due to axial boundary layer growth. Below a critical flow number $ϕ < ϕ_c$, there is flow separation, known in the turbomachinery context as part load recirculation. Previous work analyses the flow at the inlet of a rotating circular pipe. For a systematic approach to a turbomachine, the influence of the turbine's and pump's function, schematically fulfilled by a diffuser and a nozzle, on the evolution of the swirl and flow separation is to analyse. The radius of the rotating pipe depends linearly on the axial coordinate, yielding a rotating circular cone. The swirl evolution depends on the Reynolds number, flow number, axial coordinate and apex angle. The influence of the la er is the paper's main task. The circumferential velocity component is measured applying 1D Laser Doppler Anemometry to investigate the swirl evolution