Nominal rigidities and the optimal rate of inflation

This paper analyses two reasons why inflation may interfere with price adjustment so as to create inefficiencies in resource allocation at low rates of inflation. The first argument is that the higher the rate of inflation the lower the likelihood that downward nominal rigidities are binding (the Tobin argument) which implies a non-linear Phillips-curve. The second argument is that low inflation strengthens nominal price rigidities and thus impairs the flexibility of the price system resulting in a less efficient resource allocation. It is argued that inflation can be too low from a welfare point of view due to the presence of nominal rigidities, but the quantitative importance is an open question

Modeling a striped pseudogap state

We study the electronic structure within a system of phase-decoupled one-dimensional superconductors coexisting with stripe spin and charge density wave order. This system has a nodal Fermi surface (Fermi arc) in the form of a hole pocket and an antinodal pseudogap. The spectral function in the antinodes is approximately particle-hole symmetric contrary to the gapped regions just outside the pocket. We find that states at the Fermi energy are extended whereas states near the pseudogap energy have localization lengths as short as the inter-stripe spacing. We consider pairing which has either local d-wave or s-wave symmetry and find similar results in both cases, consistent with the pseudogap being an effect of local pair correlations. We suggest that this state is a stripe ordered caricature of the pseudogap phase in underdoped cuprates with coexisting spin-, charge-, and pair-density wave correlations. Lastly, we also model a superconducting state which 1) evolves smoothly from the pseudogap state, 2) has a signature subgap peak in the density of states, and 3) has the coherent pair density concentrated to the nodal region.Comment: 12 pages, 12 figures, extended discussion, added references; v3, added figure of antinodal spectra for normal/pseudo/sc state

Magnetic and superfluid phases of confined fermions in two-dimensional optical lattices

We examine antiferromagnetic and d-wave superfluid phases of cold fermionic atoms with repulsive interactions in a two-dimensional optical lattice combined with a harmonic trapping potential. For experimentally realistic parameters, the trapping potential leads to the coexistence of magnetic and superfluid ordered phases with the normal phase. We study the intriguing shell structures arising from the competition between the magnetic and superfluid order as a function of the filling fraction. In certain cases antiferromagnetism induce superfluidity by charge redistributions. We furthermore demonstrate how these shell structures can be detected as distinct anti-bunching dips and pairing peaks in the density-density correlation function probed in expansion experiments.Comment: 4 pages, 3 figure

Taxes and employment - is there a Scandinavia puzzle ?

Recent debates have suggested that taxation is very detrimental to labour force participation and employment. However, some countries - notably the Scandinavian - stand out as contradictions to this view since they have managed to sustain high labour force participation despite high tax rates and a generous social safety net.This paper considers the experience of European countries and Scandinavia compared to the US and asks whether Scandinavian countries are outliers. First, it is argued that the simple "tax argument" does not capture the European experience since labour force participation for some age groups is at the same or a higher level than the US. Second, it is argued that even though the social safety net is generous in Scandinavian countries, it is also very employment conditional. It is shown that these conditionalities can make high labour force participation consistent with a high marginal effective taxation of labour, and that it on the margin lowers the marginal costs of public funds. The design of the social safety net is therefore important in accounting for the Scandinavian experience.Taxes and employment, is there a Scandinavia puzzle? taxation of labour, employment, labour force participation, social safety net, Andersen

Optimization of slender wings for center-of-pressure shift due to change in Mach number

It is observed that the center of pressure on a wing shifts as the Mach number is changed. Such shifts are in general undesirable and are sometimes compensated for by actively shifting the center of gravity of the aircraft or by using active stability controls. To avoid this complication, it is desirable to design the wings of a high speed aircraft so as to minimize the extent of the center-of-pressure shifts. This, together with a desire to minimize the center-of-pressure shifts in missile control surfaces, provides the motivation for this project. There are many design parameters which affect center-of-pressure shifts, but it is expected that the largest effects are due to the wing planform. Thus, for the sake of simplicity, this study is confined to an investigation of thin, flat, (i.e., no camber or twist), relatively slender, pointed wings flying at a small angle of attack. Once the dependence of the center of pressure on planform and Mach number is understood, we can expect to investigate the sensitivity of the center-of-pressure shifts to various other parameters

Wage formation and European integration

European integration is likely to affect labour market performance through various routes. One important channel is the effects product market integration has on labour markets. This paper reviews how product market integration may strengthen labour market interdependencies between integrating economies and therefore affect both the level of employment and the flexibility by which wages adjust to shocks.integration, european integration, labour market performance, product market integration, wage formation, wages, employment, Andersen

Spin dynamics in the stripe phase of the cuprates

Within a model that supports stripe spin and charge order coexisting with a d$_{x^2-y^2}$-wave superconducting phase, we study the self-consistently obtained electronic structure and the associated transverse dynamical spin susceptibility. In the coexisting phase of superconducting and static stripe order, the resulting particle-hole continuum can strongly damp parts of the low-energy spin wave branches. This provides insight into recent inelastic neutron scattering data revealing the dispersion of the low-energy collective magnetic modes of lanthanum based cuprate superconductors.Comment: 4 pages, 3 figure

Pinning of stripes by local structural distortions in cuprate high-Tc superconductors

We study the spin-density wave (stripe) instability in lattices with mixed low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) crystal symmetry. Within an explicit mean-field model it is shown how local LTT regions act as pinning centers for static stripe formation. We calculate the modulations in the local density of states near these local stripe regions and find that mainly the coherence peaks and the van Hove singularity (VHS) are spatially modulated. Lastly, we use the real-space approach to simulate recent tunneling data in the overdoped regime where the VHS has been detected by utilizing local normal state regions.Comment: Conference proceedings for Stripes1

Macroeconomics - Which Way Now?

Recent developments in macroeconomics are reviewed, and it is argued that a better understanding of the role of market failures and institutions is a major achievement. The insights in when and how policy intervention may be called for have thus been improved. However, the progress does not imply that we are approaching a situation where business cycles can be “controlled”; rather it implies that we better understand why this would be very difficult if not impossible.