Angular asymmetries as a probe for anomalous contributions to HZZ vertex at the LHC

In this article, the prospects for studying the tensor structure of the HZZ vertex with the LHC experiments are presented. The structure of tensor couplings in Higgs di-boson decays is investigated by measuring the asymmetries and by studing the shapes of the final state angular distributions. The expected background contributions, detector resolution, and trigger and selection efficiencies are taken into account. The potential of the LHC experiments to discover sizeable non-Standard Model contributions to the HZZ vertex with $300\;{\rm fb}^{-1}$ and $3000\;{\rm fb}^{-1}$ is demonstrated.Comment: 9 pages, 8 figures; added 3 references for section 1; added 3 references, added missing unit GeV in Table III and 4 clarifying sentences to the tex

Universal Quantum Computation in a Neutral Atom Decoherence Free Subspace

In this paper, we propose a way to achieve protected universal computation in a neutral atom quantum computer subject to collective dephasing. Our proposal relies on the existence of a Decoherence Free Subspace (DFS), resulting from symmetry properties of the errors. After briefly describing the physical system and the error model considered, we show how to encode information into the DFS and build a complete set of safe universal gates. Finally, we provide numerical simulations for the fidelity of the different gates in the presence of time-dependent phase errors and discuss their performance and practical feasibility.Comment: 7 pages, 8 figure

Adiabatic Elimination in a Lambda System

This paper deals with different ways to extract the effective two-dimensional lower level dynamics of a lambda system excited by off-resonant laser beams. We present a commonly used procedure for elimination of the upper level, and we show that it may lead to ambiguous results. To overcome this problem and better understand the applicability conditions of this scheme, we review two rigorous methods which allow us both to derive an unambiguous effective two-level Hamiltonian of the system and to quantify the accuracy of the approximation achieved: the first one relies on the exact solution of the Schrodinger equation, while the second one resorts to the Green's function formalism and the Feshbach projection operator technique.Comment: 14 pages, 3 figure

Error correction in ensemble registers for quantum repeaters and quantum computers

We propose to use a collective excitation blockade mechanism to identify errors that occur due to disturbances of single atoms in ensemble quantum registers where qubits are stored in the collective population of different internal atomic states. A simple error correction procedure and a simple decoherence-free encoding of ensemble qubits in the hyperfine states of alkali atoms are presented.Comment: 4 pages, 2 figure

Delayed soft X-ray emission lines in the afterglow of GRB 030227

Strong, delayed X-ray line emission is detected in the afterglow of GRB 030227, appearing near the end of the XMM-Newton observation, nearly twenty hours after the burst. The observed flux in the lines, not simply the equivalent width, sharply increases from an undetectable level (<1.7e-14 erg/cm^2/s, 3 sigma) to 4.1e-14 erg/cm^2/s in the final 9.7 ks. The line emission alone has nearly twice as many detected photons as any previous detection of X-ray lines. The lines correspond well to hydrogen and/or helium-like emission from Mg, Si, S, Ar and Ca at a redshift z=1.39. There is no evidence for Fe, Co or Ni--the ultimate iron abundance must be less than a tenth that of the lighter metals. If the supernova and GRB events are nearly simultaneous there must be continuing, sporadic power output after the GRB of a luminosity >~5e46 erg/s, exceeding all but the most powerful quasars.Comment: Submitted to ApJL. 14 pages, 3 figures with AASLaTe

Inducing spin-dependent tunneling to probe magnetic correlations in optical lattices

We suggest a simple experimental method for probing antiferromagnetic spin correlations of two-component Fermi gases in optical lattices. The method relies on a spin selective Raman transition to excite atoms of one spin species to their first excited vibrational mode where the tunneling is large. The resulting difference in the tunneling dynamics of the two spin species can then be exploited, to reveal the spin correlations by measuring the number of doubly occupied lattice sites at a later time. We perform quantum Monte Carlo simulations of the spin system and solve the optical lattice dynamics numerically to show how the timed probe can be used to identify antiferromagnetic spin correlations in optical lattices.Comment: 5 pages, 5 figure

ISO far-infrared observations of rich galaxy clusters II. Sersic 159-03

The far-infrared emission from rich galaxy clusters is investigated. Maps have been obtained by ISO at 60, 100, 135, and 200 microns using the PHT-C camera. Ground based imaging and spectroscopy were also acquired. Here we present the results for the cooling flow cluster Sersic 159-03. An infrared source coincident with the dominant cD galaxy is found. Some off-center sources are also present, but without any obvious counterparts.Comment: 6 pages, 4 postscript figures, accepted for publication in `Astronomy and Astrophysics

Computer model for simulating the long-term dynamics of annual weeds under different cultivation practices

A model is being developed which describes the population dynamics of annual weeds and how it is affected by crop rotation, cultivation practices and weed control. The model aims to predict the development of a certain weed species in order to plan crop rotation and cultivation practices to minimize the risk of proliferation. The model does not predict the exact number of weeds expected to be found in a certain year or crop, but rather the general development over a number of years. The model includes documented knowledge, as well as informal expert knowledge, on seed survival in the soil, seed placement in soil after tillage, seed germination with respect to placement in soil, time of year and tillage, weed development in response to crop competitiveness and seed production of the weeds. The model is at present only accounting for the development of one weed species at a time, and only a few weed species are parameterised. However, the model can easily be extended with more weed species, crops and cultivation practices. Model predictions should match what knowledgeable weed scientists already know, perhaps with a little new insight