Perturbative corrections to the Gutzwiller mean-field solution of the Mott-Hubbard model

We study the Mott-insulator transition of bosonic atoms in optical lattices. Using perturbation theory, we analyze the deviations from the mean-field Gutzwiller ansatz, which become appreciable for intermediate values of the ratio between hopping amplitude and interaction energy. We discuss corrections to number fluctuations, order parameter, and compressibility. In particular, we improve the description of the short-range correlations in the one-particle density matrix. These corrections are important for experimentally observed expansion patterns, both for bulk lattices and in a confining trap potential.Comment: 10 pages, 10 figue

Next-to-leading order QCD corrections to hadron+jet production in pp collisions at RHIC

We compute the next-to-leading order QCD corrections to the spin-independent and spin-dependent cross-sections for the production of a single-hadron accompanied by an opposite jet in hadronic collisions. This process is being studied experimentally at RHIC, providing a new tool to unveil the polarized gluon distribution Delta g. We perform a detailed analysis of the phenomenological impact of the observable at NLO accuracy and show that the preliminary data by the STAR collaboration confirms the idea of a small gluon polarization in the 0.05<x<0.3 range.Comment: 16 pages, 11 Figures included. Minor typos correcte

Degenerate quantum gases of strontium

Degenerate quantum gases of alkaline-earth-like elements open new opportunities in research areas ranging from molecular physics to the study of strongly correlated systems. These experiments exploit the rich electronic structure of these elements, which is markedly different from the one of other species for which quantum degeneracy has been attained. Specifically, alkaline-earth-like atoms, such as strontium, feature metastable triplet states, narrow intercombination lines, and a non-magnetic, closed-shell ground state. This review covers the creation of quantum degenerate gases of strontium and the first experiments performed with this new system. It focuses on laser-cooling and evaporation schemes, which enable the creation of Bose-Einstein condensates and degenerate Fermi gases of all strontium isotopes, and shows how they are used for the investigation of optical Feshbach resonances, the study of degenerate gases loaded into an optical lattice, as well as the coherent creation of Sr_2 molecules.Comment: Review paper, 43 pages, 24 figures, 249 reference

On the nature of Thermal Diffusion in binary Lennard-Jones liquids

The aim of this study is to understand deeper the thermal diffusion transport process (Ludwig-Soret effect) at the microscopic level. For that purpose, the recently developed reverse nonequilibrium molecular dynamics method was used to calculate Soret coefficients of various systems in a systematic fashion. We studied binary Lennard-Jones (LJ) fluids near the triple point (of one of the components) in which we separately changed the ratio of one of the LJ parameters mass, atomic diameter and interaction strength while keeping all other parameters fixed and identical. We observed that the magnitude of the Soret coefficient depends on all three ratios. Concerning its sign we found that heavier species, smaller species and species with higher interaction strengths tend to accumulate in the cold region whereas the other ones (lighter, bigger or weaker bound) migrate to the hot region of our simulation cell. Additionally, the superposition of the influence of the various parameters was investigated as well as more realistic mixtures. We found that in the experimentally relevant parameter range the contributions are nearly additive and that the mass ratio often is the dominating factor.Comment: 27 pages, 9 figures, submitted to J. Chem. Phy

Changing quantum reference frames

We consider the process of changing reference frames in the case where the reference frames are quantum systems. We find that, as part of this process, decoherence is necessarily induced on any quantum system described relative to these frames. We explore this process with examples involving reference frames for phase and orientation. Quantifying the effect of changing quantum reference frames serves as a first step in developing a relativity principle for theories in which all objects including reference frames are necessarily quantum.Comment: 21 pages, 6 figures, comments welcome; v2 added some references; v3 published versio