Optimal Monetary Policy, Commitment, and Imperfect Credibility

In the conventional optimal monetary policy framework, two key assumptions underline the full commitment solution : Monetary authority is perfectly credible, and can commit for an infinite number of periods. Using a baseline forward-looking model, this study explores the implications of relaxing these assumptions in turn. First, finite lasting commitments are introduced using a stochastic exogenous process that generates policy reoptimizations. As a consequence, monetary policy is characterized with a continuum from pure discretion to full commitment. Second, we solve the optimal and robust targeting rules when the central bank confronts imperfect and/or uncertain credibility. Imperfect credibility is defined as a situation in which the private sector expects the commitment regime to end sooner than that is intended by the policy maker. The results indicate that, under imperfect credibility, optimal policy becomes observationally closer to the discretionary solution, the more being so as the degree of uncertainty rises. These findings may be insightful for explaining the observed near-discretionary behavior of the central banks, which indeed operate under imperfect credibility.Optimal Monetary Policy, Stabilization Bias, Imperfect Credibility, Discretion, Commitment

Turkish Experience With Implicit Inflation Targeting

This paper describes the challenges faced during the implementation of implicit inflation targeting in Turkey and evaluates the transition process to full-fledged inflation targeting. Using this background, the paper draws lessons for similar countries considering inflation targeting as a monetary policy regime. We argue that, the strategy of starting inflation targeting with an "implicit" version and gradually converging to full-fledged targeting can be a viable option when certain set of conditions is not satisfied. We conjecture, however, that implementing a "light" version?namely implicit inflation targeting?does not necessarily mean that the system would be exempt from all the prerequisites. In the Turkish case, for example, institutional independence and political support seem to have been the fundamental conditions for initiating the process of inflation targeting.Implicit inflation targeting, Price stability, Turkey

Credit Cards: Weapons for Domestic Violence

The objectives of this study were to describe the intra-specific variation in herbicide response of weed populations when subjected to new vs. well-established herbicides, and to assess distributions of logLD(50)- and logGR(50)-estimates as a potential indicator for early resistance detection. Seeds of two grass weeds (Alopecurus myosuroides, Apera spica-venti) were collected in southern Sweden, mainly in 2002. In line with the objectives of the study, the collections sites were not chosen for noted herbicide failures nor for detected herbicide resistance, but solely for the presence of the target species. For each species, seedlings were subjected to two herbicides in dose-response experiments in a greenhouse. One herbicide per species was recently introduced and the other had been on the market for control of the species for a decade, with several reports of resistance in the literature. Fresh weight of plants and a visual vigour score were used to estimate GR(50) and LD50, respectively. Resistance to fenoxaprop-P-ethyl in A. myosuroides was indicated by the LD50-estimates to be present in frequencies sufficient to affect the population-level response in 9 of 29 samples, and was correlated to response to flupyrsulfuron, while low susceptibility to isoproturon in A. spica-venti populations was not linked to the response to sulfosulfuron. In the study as a whole, the magnitude of the estimated herbicide susceptibility ranges differed irrespective of previous exposure. No consistent differences were found in the distribution of LD50-estimates for new and "old" herbicides, and normality in the distribution of estimates could not be assumed for a non-exposed sample, even in the absence of an indication of cross-resistance.Original Publication:Liv A Espeby, Hakan Fogelfors and Per Milberg, Susceptibility variation to new and established herbicides: Examples of inter-population sensitivity of grass weeds, 2011, CROP PROTECTION, (30), 4, 429-435.http://dx.doi.org/10.1016/j.cropro.2010.12.022Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com

Spin-orbit interaction in quantum dots in the presence of exchange correlations

We discuss the problem of spin-orbit interaction in a 2D chaotic or diffusive quantum dot in the presence of exchange correlations. Spin-orbit scattering breaks spin rotation invariance, and in the crossover regime between different symmetries of the spin-orbit coupling, the problem has no closed solution. A conventional choice of a many-particle basis in a numerical diagonalization is the set of Slater determinants built from the single-particle eigenstates of the one-body Hamiltonian (including the spin-orbit terms). We develop a different approach based on the use of a good-spin many-particle basis that is composed of the eigenstates of the universal Hamiltonian in the absence of spin-orbit scattering. We introduce a complete labelling of this good-spin basis and use angular momentum algebra to calculate in closed form the matrix elements of the spin-orbit interaction in this basis. Spin properties, such as the ground-state spin distribution and the spin excitation function, are easily calculated in this basis.Comment: 14 pages, 3 figure

Stochastic Differential Equations for Quantum Dynamics of Spin-Boson Networks

The quantum dynamics of open many-body systems poses a challenge for computational approaches. Here we develop a stochastic scheme based on the positive P phase-space representation to study the nonequilibrium dynamics of coupled spin-boson networks that are driven and dissipative. Such problems are at the forefront of experimental research in cavity and solid state realizations of quantum optics, as well as cold atom physics, trapped ions and superconducting circuits. We demonstrate and test our method on a driven, dissipative two-site system, each site involving a spin coupled to a photonic mode, with photons hopping between the sites, where we find good agreement with Monte Carlo Wavefunction simulations. In addition to numerically reproducing features recently observed in an experiment [Phys. Rev. X 4, 031043 (2014)], we also predict a novel steady state quantum dynamical phase transition for an asymmetric configuration of drive and dissipation.Comment: 15 pages, 8 figure