Lattice Simulations with Chemical Potential

After giving an overview of recently invented methods for simulating lattice QCD at small mu/T, we discuss some results for bulk thermodynamic quantities of QCD matter coming from those methods. We focus on the transition line and the critical endpoint in the QCD phase diagram.Comment: Invited talk given at the Strong and Electroweak Matter 2004, Helsinki, Finland 16-19 June 200

Radiation and particle detector and amplifier

A radiation or charged particle detector is described which incorporates a channel multiplier structure to amplify the detected rays or particles. The channel multiplier structure has a support multiplying element with a longitudinal slot along one side. The element supports a pair of plates positioned contiguous with the slot. The plates funnel the particles or rays to be detected into the slotted aperture and the element, thus creating an effectively wide aperture detector of the windowless type

Star/horizon simulator used to test space guidance system

Star/horizon simulator is used for alignment and optical plus photoelectric tests of the sextant for the Apollo guidance and navigation system optical unit assembly. The unit is basically a refractive collimator with a two inch objective lens system and a twenty-four inch focal length

Market Share Dynamics in a Model with Search and Word-of-Mouth Communication

This paper analyzes price competition in an infinitely repeated duopoly game. In each period, consumers remember the existence and location of their previous supplier. New information is gathered via search or word-of-mouth communication. Market outcomes are history-dependent, and the Markov perfection refinement is used to narrow the set of equilibria. Firms are shown to use mixed pricing strategies in equilibrium. The resulting price dispersion generates non-trivial market share dynamics. The goal of the paper is to characterize these dynamics, and to reveal the driving forces behind them

Thermodynamics of (2+1)-flavor QCD

We report on the status of our QCD thermodynamics project. It is performed on the QCDOC machine at Brookhaven National Laboratory and the APEnext machine at Bielefeld University. Using a 2+1 flavor formulation of QCD at almost realistic quark masses we calculated several thermodynamical quantities. In this proceeding we show the susceptibilites of the chiral condensate and the Polyakov loop, the static quark potential and the spatial string tension.Comment: To appear in the proceedings of International Conference on Strong and Electroweak Matter (SEWM 2006), Upton, New York, 10-13 May 200

Computing infrastructure issues in distributed communications systems : a survey of operating system transport system architectures

The performance of distributed applications (such as file transfer, remote login, tele-conferencing, full-motion video, and scientific visualization) is influenced by several factors that interact in complex ways. In particular, application performance is significantly affected both by communication infrastructure factors and computing infrastructure factors. Several communication infrastructure factors include channel speed, bit-error rate, and congestion at intermediate switching nodes. Computing infrastructure factors include (among other things) both protocol processing activities (such as connection management, flow control, error detection, and retransmission) and general operating system factors (such as memory latency, CPU speed, interrupt and context switching overhead, process architecture, and message buffering). Due to a several orders of magnitude increase in network channel speed and an increase in application diversity, performance bottlenecks are shifting from the network factors to the transport system factors.This paper defines an abstraction called an "Operating System Transport System Architecture" (OSTSA) that is used to classify the major components and services in the computing infrastructure. End-to-end network protocols such as TCP, TP4, VMTP, XTP, and Delta-t typically run on general-purpose computers, where they utilize various operating system resources such as processors, virtual memory, and network controllers. The OSTSA provides services that integrate these resources to support distributed applications running on local and wide area networks.A taxonomy is presented to evaluate OSTSAs in terms of their support for protocol processing activities. We use this taxonomy to compare and contrast five general-purpose commercial and experimental operating systems including System V UNIX, BSD UNIX, the x-kernel, Choices, and Xinu

QCD Thermodynamics with an almost realistic quark mass spectrum

We will report on the status of a new large scale calculation of thermodynamic quantities in QCD with light up and down quarks corresponding to an almost physical light quark mass value and a heavier strange quark mass. These calculations are currently being performed on the QCDOC Teraflops computers at BNL. We will present new lattice calculations of the transition temperature and various susceptibilities reflecting properties of the chiral transition. All these quantities are of immediate interest for heavy ion phenomenology.Comment: 10 pages, 4 figures, talk presented at the Particles and Nuclei International Conference, October 24-28, 2005, Santa Fe, NM, US

Temperature, chemical potential and the rho meson

We describe some applications of the Dyson-Schwinger equations at nonzero-(T,mu). Employing a simple model dressed-gluon propagator we determine the boundary of the deconfinement phase transition and the medium dependence of rho-meson properties. We introduce an extension to describe the time-evolution of scalar and vector self energies.Comment: 6 pages, LaTeX with 3 EPS figures; Contribution to the 'International Workshop XXVIII on Gross Properties of Nuclei and Nuclear Excitations', Hirschegg, Austria, 16-22.01.200

The Timing of Climate Agreements under Multiple Externalities

We study the potential of cooperation in global emission abatements with multiple externalities. Using a two-country model without side-payments, we identify the strategic effects under different timing regimes of cooperation. We obtain a positive complementarity effect of long-term cooperation in abatement on R&D levels that boosts potential bene?t of long-term cooperation and a redistributive effect that destabilizes long-term cooperation when countries are asymmetric. We show that whether and what type of cooperation is sustainable, depends crucially on the kind rather than on the magnitude of asymmetries