TARGET2 Unlimited: monetary policy implications of asymmetric liquidity management within the Euro area. CEPS Policy Brief No. 248, 13 July 2011

This paper analyses the implications of a continued divergence of TARGET2 balances for monetary policy in the euro area. The accumulation of TARGET2 claims (liabilities) would make the ECB’s liquidity management asymmetric once the TARGET2 claims in core countries have crowded out central bank credit in those regions. Then while providing scarce liquidity to banks in countries with TARGET2 liabilities, the ECB will need to absorb excess liquidity in countries with TARGET2 claims. We discuss three alternatives and their implications for absorbing excess liquidity in core regions: 1) using market-based measures might accelerate the capital flight from periphery to core countries and would add to the accumulation of risky assets by the ECB; 2) conducting non-market based measures, such as imposing differential (unremunerated) reserve requirements, would distort banking markets and would support the development of shadow banking; and 3) staying passive would lead to decreasing interest rates in core Europe entailing inflationary pressure and overinvestment in those regions and possibly future instability of the banking system

The Role of Spatial Coherence and Orbital Angular Momentum of Light in Astronomy

The orbital angular momentum (OAM) of light is potentially interesting for astronomical study of rotating objects such as black holes, but the effect of reduced spatial coherence of astronomical light sources such as stars is largely unknown. In a lab-scale experiment, we find that the detected OAM spectrum depends strongly on the position of the light-twisting object along the line of sight. We develop a simple intuitive model to predict the influence of reduced spatial coherence in astronomical observations, and discuss line-of-sight and intensity issues.Comment: updated versio

Local structural excitations in model glasses

Structural excitations of model Lennard-Jones glass systems are investigated using the Activation-Relaxation-Technique (ART), which explores the potential energy landscape of a local minimum energy configuration by converging to a nearby saddle-point configuration. Performing ART results in a distribution of barrier energies that is single-peaked for well relaxed samples. The present work characterises such atomic scale excitations in terms of their local structure and environment. It is found that, at zero applied stress, many of the identified events consist of chain-like excitations that can either be extended or ring-like in their geometry. The location and activation energy of these saddle-point structures are found to correlate with the type of atom involved, and with spatial regions that have low shear moduli and are close to the excess free volume within the configuration. Such correlations are however weak and more generally the identified local structural excitations are seen to exist throughout the model glass sample. The work concludes with a discussion within the framework of $\alpha$ and $\beta$ relaxation processes that are known to occur in the under-cooled liquid regime.Comment: 34 Pages, 13 Figure

Four-photon orbital angular momentum entanglement

Quantum entanglement shared between more than two particles is essential to foundational questions in quantum mechanics, and upcoming quantum information technologies. So far, up to 14 two-dimensional qubits have been entangled, and an open question remains if one can also demonstrate entanglement of higher-dimensional discrete properties of more than two particles. A promising route is the use of the photon orbital angular momentum (OAM), which enables implementation of novel quantum information protocols, and the study of fundamentally new quantum states. To date, only two of such multidimensional particles have been entangled albeit with ever increasing dimensionality. Here we use pulsed spontaneous parametric downconversion (SPDC) to produce photon quadruplets that are entangled in their OAM, or transverse-mode degrees of freedom; and witness genuine multipartite Dicke-type entanglement. Apart from addressing foundational questions, this could find applications in quantum metrology, imaging, and secret sharing.Comment: 5 pages, 4 figure

Ensemble versus individual system in quantum optics

Modern techniques allow experiments on a single atom or system, with new phenomena and new challenges for the theoretician. We discuss what quantum mechanics has to say about a single system. The quantum jump approach as well as the role of quantum trajectories are outlined and a rather sophisticated example is given.Comment: Fundamental problems in quantum theory workshop, invited lecture. 11 pages Latex + 7 figures. To appear in Fortschr. d. Physi

Shear-band arrest and stress overshoots during inhomogeneous flow in a metallic glass

At the transition from a static to a dynamic deformation regime of a shear band in bulk metallic glasses, stress transients in terms of overshoots are observed. We interpret this phenomenon with a repeated shear-melting transition and are able to access a characteristic time for a liquidlike to solidlike transition in the shear band as a function of temperature, enabling us to understand why shear bands arrest during inhomogenous serrated flow in bulk metallic glasses

Detuning effects in the one-photon mazer

The quantum theory of the mazer in the non-resonant case (a detuning between the cavity mode and the atomic transition frequencies is present) is written. The generalization from the resonant case is far from being direct. Interesting effects of the mazer physics are pointed out. In particular, it is shown that the cavity may slow down or speed up the atoms according to the sign of the detuning and that the induced emission process may be completely blocked by use of a positive detuning. It is also shown that the detuning adds a potential step effect not present at resonance and that the use of positive detunings defines a well-controlled cooling mechanism. In the special case of a mesa cavity mode function, generalized expressions for the reflection and transmission coefficients have been obtained. The general properties of the induced emission probability are finally discussed in the hot, intermediate and cold atom regimes. Comparison with the resonant case is given.Comment: 9 pages, 8 figure

Sub-nanometer free electrons with topological charge

The holographic mask technique is used to create freely moving electrons with quantized angular momentum. With electron optical elements they can be focused to vortices with diameters below the nanometer range. The understanding of these vortex beams is important for many applications. Here we present a theory of focused free electron vortices. The agreement with experimental data is excellent. As an immediate application, fundamental experimental parameters like spherical aberration and partial coherence are determined.Comment: 4 pages, 5 figure

Natuurlijk een veilige kust

Als je bij zwaar weer over het strand wandelt, ervaar je de krachten van wind en zee aan den lijve. Als je dan bedenkt dat ruim 9 miljoen Nederlanders beneden de zeespiegel leven, besef je hoe kwetsbaar we eigenlijk zijn. Robuuste zeerepen, sterke zeedijken en met dammen afgesloten zeearmen houden de zee buiten de deur. Als we duinen en dijken blijven verhogen neemt de kans op een overstroming weliswaar af, maar mocht de zeewering onverhoopt doorbreken, dan zullen de gevolgen groter zijn dan ooit. Het is daarom tijd voor een duurzame benadering die ons minder kwetsbaar maakt. Dat kan door met de natuur mee te werke