Benchmark experiments with global climate models applicable to extra-solar gas giant planets in the shallow atmosphere approximation

The growing field of exoplanetary atmospheric modelling has seen little work on standardised benchmark tests for its models, limiting understanding of the dependence of results on specific models and conditions. With spatially resolved observations as yet difficult to obtain, such a test is invaluable. Although an intercomparison test for models of tidally locked gas giant planets has previously been suggested and carried out, the data provided were limited in terms of comparability. Here, the shallow PUMA model is subjected to such a test, and detailed statistics produced to facilitate comparison, with both time means and the associated standard deviations displayed, removing the time dependence and providing a measure of the variability. Model runs have been analysed to determine the variability between resolutions, and the effect of resolution on the energy spectra studied. Superrotation is a robust and reproducible feature at all resolutions

Transverse-Mass Spectra in Heavy-Ion Collisions at energies E_{lab} = 2--160 GeV/nucleon

Transverse-mass spectra of protons, pions and kaons produced in collisions of heavy nuclei are analyzed within the model of 3-fluid dynamics. It was demonstrated that this model consistently reproduces these spectra in wide ranges of incident energies E_{lab}, from 4A GeV to 160A GeV, rapidity bins and centralities of the collisions. In particular, the model describes the "step-like" dependence of kaon inverse slopes on the incident energy. The key point of this explanation is interplay of hydrodynamic expansion of the system with its dynamical freeze-out.Comment: 13 pages, 16 figures, summary is extended, version accepted by Phys. Rev.

Exploring the Expansion History of the Universe

Exploring the recent expansion history of the universe promises insights into the cosmological model, the nature of dark energy, and potentially clues to high energy physics theories and gravitation. We examine the extent to which precision distance-redshift observations can map out the history, including the acceleration-deceleration transition, and the components and equations of state of the energy density. We consider the ability to distinguish between various dynamical scalar field models for the dark energy, as well as higher dimension and alternate gravity theories. Finally, we present a new, advantageous parametrization for the study of dark energy.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Letter

Particle-Antiparticle Asymmetry Due to Non-Renormalizable Effective Interactions

We consider a model for generating a particle-antiparticle asymmetry through out-of-equilibrium decays of a massive particle due to non-renormalizable, effective interactions.Comment: preliminary version, 38 pages; LaTeX source, epsf.sty and EPS files included in tar archiv

Decaying Dark Matter from Dark Instantons

We construct an explicit, TeV-scale model of decaying dark matter in which the approximate stability of the dark matter candidate is a consequence of a global symmetry that is broken only by instanton-induced operators generated by a non-Abelian dark gauge group. The dominant dark matter decay channels are to standard model leptons. Annihilation of the dark matter to standard model states occurs primarily through the Higgs portal. We show that the mass and lifetime of the dark matter candidate in this model can be chosen to be consistent with the values favored by fits to data from the PAMELA and Fermi LAT experiments.Comment: 19 pages LaTeX, 3 eps figures. v2,v3: references adde

Classical Strongly Coupled QGP II: Screening and Equation of State

We analyze the screening and bulk energy of a classical and strongly interacting plasma of color charges, a model we recently introduced for the description of a quark-gluon plasma at T=(1-3)Tc. The partition function is organized around the Debye-Huckel limit. The linear Debye-Huckel limit is corrected by a virial expansion. For the pressure, the expansion is badly convergent even in the dilute limit. The non-linear Debye-Huckel theory is studied numerically as an alternative for moderately strong plasmas. We use Debye theory of solid to extend the analysis to the crystal phase at very strong coupling. The analytical results for the bulk energy per particle compare well with the numerical results from molecular dynamics simulation for all couplings.Comment: 9 pages, 5 figure

Sub-eV scalar dark matter through the super-renormalizable Higgs portal

The Higgs portal of the Standard Model provides the opportunity for coupling to a very light scalar field $\phi$ via the super-renormalizable operator $\phi(H^\dagger H)$. This allows for the existence of a very light scalar dark matter that has coherent interaction with the Standard Model particles and yet has its mass protected against radiative corrections. We analyze ensuing constraints from the fifth-force measurements, along with the cosmological requirements. We find that the detectable level of the fifth-force can be achieved in models with low inflationary scales, and certain amount of fine-tuning in the initial deviation of $\phi$ from its minimum.Comment: 6 pages, 3 figures. References added in the revised version

Gluon Saturation Effects in Relativistic U+U Collisions

We examine entropy production in relativistic U+U collisions on the basis of a Color Glass Condensate (CGC) type picture as implemented in the Kharzeev-Levin-Nardi model (KLN). In this framework, we find that the peak entropy density produced in tip-on-tip U+U collisions is about 30% greater than that seen in central Au+Au collisions. Although the resulting difference in the produced charged particle multiplicity between tip-on-tip and side-on-side collisions is smaller than that predicted by previous Glauber model estimates, it is still large enough to allow for experimental discrimination between average orientations of the uranium nuclei. We also point out that in the saturation/CGC approach the collision geometry plays a more important role than previously believed, and that the observed centrality dependence of the produced particle multiplicity per participant in Au+Au collisions can be qualitatively reproduced even without running coupling effects.Comment: 7 pages, including 8 figure