Transforming Development? The Role of Philanthropic Foundations in International Development Cooperation

This study by an independent think tank in Germany takes a look at the role of philanthropic foundations on the international development scene

Semiclassical transport in nearly symmetric quantum dots. I. Symmetry breaking in the dot

We apply the semiclassical theory of transport to quantum dots with exact and approximate spatial symmetries; left-right mirror symmetry, up-down mirror symmetry, inversion symmetry, or fourfold symmetry. In this work—the first of a pair of articles—we consider (a) perfectly symmetric dots and (b) nearly symmetric dots in which the symmetry is broken by the dot's internal dynamics. The second article addresses symmetry-breaking by displacement of the leads. Using semiclassics, we identify the origin of the symmetry-induced interference effects that contribute to weak localization corrections and universal conductance fluctuations. For perfect spatial symmetry, we recover results previously found using the random-matrix theory conjecture. We then go on to show how the results are affected by asymmetries in the dot, magnetic fields, and decoherence. In particular, the symmetry-asymmetry crossover is found to be described by a universal dependence on an asymmetry parameter gamma_asym. However, the form of this parameter is very different depending on how the dot is deformed away from spatial symmetry. Symmetry-induced interference effects are completely destroyed when the dot's boundary is globally deformed by less than an electron wavelength. In contrast, these effects are only reduced by a finite amount when a part of the dot's boundary smaller than a lead-width is deformed an arbitrarily large distance

Semiclassical transport in nearly symmetric quantum dots II: symmetry-breaking due to asymmetric leads

In this work - the second of a pair of articles - we consider transport through spatially symmetric quantum dots with leads whose widths or positions do not obey the spatial symmetry. We use the semiclassical theory of transport to find the symmetry-induced contributions to weak localization corrections and universal conductance fluctuations for dots with left-right, up-down, inversion and four-fold symmetries. We show that all these contributions are suppressed by asymmetric leads, however they remain finite whenever leads intersect with their images under the symmetry operation. For an up-down symmetric dot, this means that the contributions can be finite even if one of the leads is completely asymmetric. We find that the suppression of the contributions to universal conductance fluctuations is the square of the suppression of contributions to weak localization. Finally, we develop a random-matrix theory model which enables us to numerically confirm these results.Comment: (18pages - 9figures) This is the second of a pair of articles (v3 typos corrected - including in equations

A hierarchical equations of motion (HEOM) analog for systems with delay: illustrated on inter-cavity photon propagation

Over the last two decades, the hierarchical equations of motion (HEOM) of Tanimura and Kubo have become the equation of motion-based tool for numerically exact calculations of system-bath problems. The HEOM is today generalized to many cases of dissipation and transfer processes through an external bath. In spatially extended photonic systems, the propagation of photons through the bath leads to retardation/delays in the coupling of quantum emitters. Here, the idea behind the HEOM derivation is generalized to the case of photon retardation and applied to the simple example of two dielectric slabs. The derived equations provide a simple reliable framework for describing retardation and may provide an alternative to path integral treatments

Global Health Warning: Definitions Wield Power Comment on “Navigating Between Stealth Advocacy and Unconscious Dogmatism: The Challenge of Researching the Norms, Politics and Power of Global Health”

Gorik Ooms recently made a strong case for considering the centrality of normative premises to analyzing and understanding the underappreciated importance of the nexus of politics, power and process in global health. This critical commentary raises serious questions for the practice and study of global health and global health governance. First and foremost, this commentary underlines the importance of the question of what is global health, and why as well as how does this definition matter? This refocuses discussion on the importance of definitions and how they wield power. It also re-affirms the necessity of a deeper analysis and understanding of power and how it affects and shapes the practice of global health

Penguin Effects in Bd0→J/ψKS0B_d^0\to J/ψK^0_S and Bs0→J/ψφB_s^0\to J/ψφ

Controlling the contributions from doubly Cabibbo-suppressed penguin topologies in the decays $B_d^0\to J/\psi K^0_S$ and $B_s^0\to J/\psi\phi$ is mandatory to reach the highest possible precision in the measurement of the $B^0_q$--$\bar B^0_q$ ($q=d,s$) mixing phases $\phi_d$ and $\phi_s$. The penguin contributions can be determined using a strategy based on the $SU(3)$ flavour symmetry of QCD. Using the latest experimental data, we update our combined analysis of the decays $B_d^0\to J/\psi K^0_S$, $B_s^0\to J/\psi\phi$ and their control channels $B_s^0\to J/\psi K^0_S$, $B_d^0\to J/\psi \pi^0$ and $B_d^0\to J/\psi \rho^0$. This allows us to simultaneously determine the penguin parameters and both mixing phases. We discuss how the branching fractions of these decays can be used to probe the size of non-factorisable $SU(3)$-breaking effects, which form the main theoretical uncertainty associated with our $SU(3)$-based strategy, and provide new insights into the factorisation approach