Exploring QCD with Heavy Ion Collisions

After decades of painstaking research, the field of heavy ion physics has reached an exciting new era. Evidence is mounting that we can create a high temperature, high density, strongly interacting ``bulk matter'' state in the laboratory -- perhaps even a quark-gluon plasma. This strongly interacting matter is likely to provide qualitative new information about the fundamental strong interaction, described by Quantum Chromodynamics (QCD). These lectures provide a summary of experimental heavy ion research, with particular emphasis on recent results from RHIC (Relativistic Heavy Ion Collider) at Brookhaven National Laboratory. In addition, we will discuss what has been learned so far and the outstanding puzzles.Comment: 30 pages, invited Heavy Ion Summary Lectures at the Lake Louise Winter Institute, February 2003, Lake Louise, Alberta, Canad

Finite-volume Hyperbolic 3-Manifolds contain immersed Quasi-Fuchsian surfaces

The paper contains a new proof that a complete, non-compact hyperbolic $3$-manifold $M$ with finite volume contains an immersed, closed, quasi-Fuchsian surface.Comment: Final version to appear in AGT. Some typos corrected, particularly def (3.6). Rewording of 4 paragraphs in proof of (4.2) for added clarity. Final section added comparing this paper to the approach of Masters and Zhan

Direct gamma and gamma-jet measurement capability of ATLAS for Pb+Pb collisions

The ATLAS detector at the LHC is capable of efficiently separating photons and neutral hadrons based on their shower shapes over a wide range in eta, phi, ET, either in addition to or instead of isolation cuts. This provides ATLAS with a unique strength for direct photon and gamma-jet physics as well as access to the unique capability to measure non-isolated photons from fragmentation or from the medium. We present a first look at the ATLAS direct photon measurement capabilities in Pb+Pb and, for reference, p+p collisions at sqrt(sNN)=5.5 TeV over the region |eta|<2.4.Comment: 4 pages, 4 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, 2009, updated to remove draft linenumbering. No other change

Conservative Subgroup Separability For Surfaces With Boundary

If F is a surface with boundary, then a finitely generated subgroup without peripheral elements of G = {\pi}_1(F) can be separated from finitely many other elements of G by a finite index subgroup of G corresponding to a finite cover F' with the same number of boundary components as F

Charging of ice-vapor interfaces

International audienceThe time resolved chemical composition of aerosol particles, formed by the oxidation of alpha-pinene has been investigated by liquid chromatography/mass spectrometry (LC-MS) using negative and positive ionisation methods (ESI(-) and APCI(+)). The experiments were performed at the EUPHORE facility in Valencia (Spain) under various experimental conditions, including dark ozone reactions, photosmog experiments with low NOx mixing ratios and reaction with OH radicals in the absence of NOx (H2O2-photolysis). Particles were sampled on PTFE filters at different stages of the reaction and extracted with methanol. The predominant products from alpha-pinene in the particulate phase are cis-pinic acid, cis-pinonic acid and hydroxy-pinonic acid isomers. Another major compound with molecular weight 172 was detected, possibly a hydroxy-carboxylic acid. These major compounds account for 50% to 80% of the identified aerosol products, depending on the time of sampling and type of experiment. In addition, more than 20 different products have been detected and structures have been tentatively assigned based on their molecular weight and responses to the different ionisation modes. The different experiments performed showed that the aerosol formation is mainly caused by the ozonolysis reaction. The highest aerosol yields were observed in the dark ozone experiments, for which also the highest ratios of mass of identified products to the formed aerosol mass were found (30% to 50%, assuming a density of 1 g cm-3)

Tropical cirrus and water vapor: an effective Earth infrared iris feedback?

International audienceWe revisit a model of feedback processes proposed by Lindzen et al. (2001), in which an assumed 22% reduction in the area of tropical high clouds per degree of sea surface temperature increase produces negative feedbacks associated with upper tropospheric water vapor and cloud radiative effects. We argue that the water vapor feedback is overestimated in Lindzen et al. (2001) by at least 60%, and that the high cloud feedback should be small. Although not mentioned by Lindzen et al, tropical low clouds make a significant contribution to their negative feedback, which is also overestimated. Using more realistic parameters in the model of Lindzen et al., we obtain a feedback factor in the range of ?0.15 to ?0.51, compared to their larger negative feedback factor of ?0.45 to ?1.03