Momentum Broadening in an Anisotropic Plasma

The rates governing momentum broadening in a quark-gluon plasma with a momentum anisotropy are calculated to leading-log order for a heavy quark using kinetic theory. It is shown how the problematic singularity for these rates at leading-oder is lifted by next-to-leading order gluon self-energy corrections to give a finite contribution to the leading-log result. The resulting rates are shown to lead to larger momentum broadening along the beam axis than in the transverse plane, which is consistent with recent STAR results. This might indicate that the quark-gluon-plasma at RHIC is not in equilibrium.Comment: 14 pages, 2 figures, uses revtex4; see source for numerics; v2: typos corrected, note added in appendix, matches published versio

Tsunamis, Viscosity and the HBT Puzzle

The equation of state and bulk and shear viscosities are shown to be able to affect the transverse dynamics of a central heavy ion collision. The net entropy, along with the femtoscopic radii are shown to be affected at the 10-20% level by both shear and bulk viscosity. The degree to which these effects help build a tsunami-like pulse is also discussed.Comment: Contribution to SQM 2007 in Levoca, Slovaki

Relativistic dissipative hydrodynamics with extended matching conditions for ultra-relativistic heavy-ion collisions

Recently we proposed a novel approach to the formulation of relativistic dissipative hydrodynamics by extending the so-called matching conditions in the Eckart frame [Phys. Rev. {\bf C 85}, (2012) 14906]. We extend this formalism further to the arbitrary Lorentz frame. We discuss the stability and causality of solutions of fluid equations which are obtained by applying this formulation to the Landau frame, which is more relevant to treat the fluid produced in ultra-relativistic heavy-ion collisions. We derive equations of motion for a relativistic dissipative fluid with zero baryon chemical potential and show that linearized equations obtained from them are stable against small perturbations. It is found that conditions for a fluid to be stable against infinitesimal perturbations are equivalent to imposing restrictions that the sound wave, $c_s$, propagating in the fluid, must not exceed the speed of light $c$, i.e., $c_s < c$. This conclusion is equivalent to that obtained in the previous paper using the Eckart frame [Phys. Rev. {\bf C 85}, (2012) 14906].Comment: 2nd version. Typos corrected. 7 pages. Contribution to The European Physical Journal A (Hadrons and Nuclei) topical issue about 'Relativistic Hydro- and Thermodynamics in Nuclear Physics

Parton radiative processes and pressure isotropization in relativistic heavy ion collisions

The impact of radiative processes on kinetic equilibration is studied via a radiative transport model. The 2 3 processes can significantly increase the level of thermalization. These processes lead to an approximate coupling constant scaling of the evolution of the pressure anisotropy qualitatively different from the case with only 2 -> 2 partonic processes. Furthermore, thermal and Color Glass Condensate motivated initial conditions are shown to share the same asymptotic evolution when 2 3 processes are included. This emphasizes the unique role of radiative processes in Quark-Gluon Plasma thermalization.Comment: Revised introduction and discussion on 3-body collisions, corrected Equation (3), updated acknowledgments and reference

Transport coefficients, spectral functions and the lattice

Transport coefficients are determined by the slope of spectral functions of composite operators at zero frequency. We study the spectral function relevant for the shear viscosity for arbitrary frequencies in weakly-coupled scalar and nonabelian gauge theories at high temperature and compute the corresponding correlator in euclidean time. We discuss whether nonperturbative values of transport coefficients can be extracted from euclidean lattice simulations.Comment: 25 pages with 7 eps figures, discussion improved, acknowledgement added; to appear in JHE

Strangeness counting in high energy collisions

The estimates of overall strange quark production in high energy e+e-, pp and ppbar collisions by using the statistical-thermal model of hadronisation are presented and compared with previous works. The parametrization of strangeness suppression within the model is discussed. Interesting regularities emerge in the strange/non-strange produced quark ratio which turns out to be fairly constant in elementary collisions while it is twice as large in SPS heavy ion collision.Comment: talk given at Strangeness in Quark Matter 98, submitted to J. Phys.

Hydrodynamics and Flow

In this lecture note, we present several topics on relativistic hydrodynamics and its application to relativistic heavy ion collisions. In the first part we give a brief introduction to relativistic hydrodynamics in the context of heavy ion collisions. In the second part we present the formalism and some fundamental aspects of relativistic ideal and viscous hydrodynamics. In the third part, we start with some basic checks of the fundamental observables followed by discussion of collective flow, in particular elliptic flow, which is one of the most exciting phenomenon in heavy ion collisions at relativistic energies. Next we discuss how to formulate the hydrodynamic model to describe dynamics of heavy ion collisions. Finally, we conclude the third part of the lecture note by showing some results from ideal hydrodynamic calculations and by comparing them with the experimental data.Comment: 40 pages, 35 figures; lecture given at the QGP Winter School, Jaipur, India, Feb.1-3, 2008; to appear in Springer Lecture Notes in Physic

Monitoring overloaded vehicles : improving traffic control centre performance by using management information systems

Decision making is an important function of management and to facilitate decision making that is relevant to any organisation, it is imperative that managers have the correct information at the right time. Since the 1990?s, the Transport Systems and Operations research group at the Council for Scientific and Industrial Research (CSIR) started developing a Management Information System to assist road traffic authorities and vehicle load control centres in decision making. A management information system is a combination of devices, software, data and procedures designed to address the collection and processing of information with the aim of providing management with relevant information for decision making purposes. This paper describes a management information system (MIS) developed and implemented in the Western Cape Province since 2006 and recently in KwaZulu-Natal in South Africa, to assist road authorities with heavy vehicle load control. Since its implementation in the Western Cape average overloads has shown reduction from 755 kg in 2006 to 529 kg in 2015, part of the reduction in average overloads can be credited to the use of the MIS. The benefits gained by the road authorities are many and includes the ability to identify operational problems in near real time; monitor scale operator?s performance; to identify problematic hauliers who overload vehicles deliberately; to monitor operational performance and schedule shifts accordingly. The management information system has proved to be successful and useful, as management is able to track irregularities and reduce corruption. Operational performance has improved as underlined by management increasingly requesting training of scale operators to bridge the gaps identified by the system.Paper presented at the 35th Annual Southern African Transport Conference 4-7 July 2016 "Transport ? a catalyst for socio-economic growth and development opportunities to improve quality of life", CSIR International Convention Centre, Pretoria, South Africa.The Minister of Transport, South AfricaTransportation Research Board of the US

High Energy Physics in Africa, Latin America and other developing regions

We summarize the current status of high energy physics (HEP) in Africa, Latin America, and other developing regionsComment: 6 pages, 2 figure