We analyze a recently proposed method to create fractional quantum Hall ͑FQH͒ states of atoms confined in optical lattices ͓A. Sørensen et al., Phys. Rev. Lett. 94, 086803 ͑2005͔͒. Extending the previous work, we investigate conditions under which the FQH effect can be achieved for bosons on a lattice with an effective magnetic field and finite on-site interaction. Furthermore, we characterize the ground state in such systems by calculating Chern numbers which can provide direct signatures of topological order and explore regimes where the characterization in terms of wave-function overlap fails. We also discuss various issues which are relevant for the practical realization of such FQH states with ultracold atoms in an optical lattice, including the presence of a long-range dipole interaction which can improve the energy gap and stabilize the ground state. We also investigate a detection technique based on Bragg spectroscopy to probe these systems in an experimental realization.

We discuss the scattering of photons from a three-level emitter in a one-dimensional waveguide, where the transport is governed by the interference of spontaneously emitted and directly transmitted waves. The scattering problem is solved in closed form for different level structures. Several possible applications are discussed: The state of the emitter can be switched deterministically by Raman scattering, thus enabling applications in quantum computing such as a single photon transistor. An array of emitters gives rise to a photonic band gap structure, which can be tuned by a classical driving laser. A disordered array leads to Anderson localization of photons, where the localization length can again be controlled by an external driving.

The purpose of this study was to monitor current and predict future rates of inbreeding in the Danish dairy breeds. Calves born from 1999 until 2003 and registered as Danish Holstein (1,883,983), Danish Jersey (336,966), or Danish Red (261,047) were reference populations. Average complete generation equivalent was approximately 7. For calves born in 2003, average inbreeding was 3.9, 3.4, and 1.4% for Holstein, Jersey, and Danish Red, respectively. In recent years, effective population sizes were 49, 53, and 47, respectively. Based on coancestry statistics, future effective population sizes will be 43, 42, and 51, respectively. The effective number of founders, effective number of ancestors, and effective number of founder genomes were calculated. These measures of genetic diversity were all low for Holstein and Jersey and somewhat larger for Danish Red. The most important ancestors of Danish Holstein were Elevation (13.8%), Chief (10.9%), and Bell (8.5%). The most important ancestor of Danish Red was Momentum (9.4%), a Red Holstein-Friesian. The most important ancestor for Danish Jersey was FYN Lemvig (12.1%) with a large number of progeny in the reference population. The results of this study indicate the necessity for active management of the rate of inbreeding in the future.

Increased rates of inbreeding are one side effect of breeding programmes designed to give genetic progress for traits of economic importance in livestock. Inbreeding leads to inbreeding depression for traits showing dominance, and will ultimately lead to a decrease in genetic variance within populations. Here we review theoretical and experimental literature from animal breeding, evolutionary biology and conservation genetics on the consequences of inbreeding in terms of trait means and genetic and environmental variance components. The genetic background for these effects is presented and the experimental literature interpreted in relation to them. Furthermore, purging of deleterious alleles and the variable nature of effects of inbreeding on populations are discussed. Based on the literature, we conclude that inbreeding in animal breeding must be controlled very effi ciently to maintain long-term sustainable livestock production in the future. The tools to do this effi ciently exist, and much can be learnt on inbreeding from the literature in fi elds only distantly related to animal breeding. ), and in the evolution of behavioural mechanisms for avoiding mating between close relatives in animals (Pusey and Wolf, 1996). These adaptations illustrate the importance of inbreeding as an evolutionary force.

We present the first experimental realization of coherent Bragg scattering off a one-dimensional system-two strings of atoms strongly coupled to a single photonic mode-realized by trapping atoms in the evanescent field of a tapered optical fiber, which also guides the probe light. We report nearly 12% power reflection from strings containing only about 1000 cesium atoms, an enhancement of 2 orders of magnitude compared to reflection from randomly positioned atoms. This result paves the road towards collective strong coupling in 1D atom-photon systems. Our approach also allows for a straightforward fiber connection between several distant 1D atomic crystals.