11,056 research outputs found

    Ultracold atomic Bose and Fermi spinor gases in optical lattices

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    We investigate magnetic properties of Mott-insulating phases of ultracold Bose and Fermi spinor gases in optical lattices. We consider in particular the F=2 Bose gas, and the F=3/2 and F=5/2 Fermi gases. We derive effective spin Hamiltonians for one and two atoms per site and discuss the possibilities of manipulating the magnetic properties of the system using optical Feshbach resonances. We discuss low temperature quantum phases of a 87Rb gas in the F=2 hyperfine state, as well as possible realizations of high spin Fermi gases with either 6Li or 132Cs atoms in the F=3/2 state, and with 173Yb atoms in the F=5/2 state.Comment: 15 pages, 5 figures; a completely new and substantially expanded version with several errors correcte

    Properties of gas clumps and gas clumping factor in the intra cluster medium

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    The spatial distribution of gas matter inside galaxy clusters is not completely smooth, but may host gas clumps associated with substructures. These overdense gas substructures are generally a source of unresolved bias of X-ray observations towards high density gas, but their bright luminosity peaks may be resolved sources within the ICM, that deep X-ray exposures may be (already) capable to detect. In this paper we aim at investigating both features, using a set of high-resolution cosmological simulations with ENZO. First, we monitor how the bias by unresolved gas clumping may yield incorrect estimates of global cluster parameters and affects the measurements of baryon fractions by X-ray observations. We find that based on X-ray observations of narrow radial strips, it is difficult to recover the real baryon fraction to better than 10 - 20 percent uncertainty. Second, we investigated the possibility of observing bright X-ray clumps in the nearby Universe (z<=0.3). We produced simple mock X-ray observations for several instruments (XMM, Suzaku and ROSAT) and extracted the statistics of potentially detectable bright clumps. Some of the brightest clumps predicted by simulations may already have been already detected in X- ray images with a large field of view. However, their small projected size makes it difficult to prove their existence based on X-ray morphology only. Preheating, AGN feedback and cosmic rays are found to have little impact on the statistical properties of gas clumps.Comment: 17 pages, 11 figures. MNRAS accepte
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