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Search Results: 1 - 10 of 191513 matches for " D. Strickland "
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Starburst-driven galactic superwinds
D. K. Strickland
Physics , 2001,
Abstract: I provide an observational review of the properties of starburst-driven galactic superwinds, focusing mainly on recent results pertinent to the transport of metals and energy into the IGM. Absorption-line studies are providing rich kinematic information on both neutral and ionized gas in superwinds, with observed mass flow rates similar to the star formation rate and outflow velocities comparable to or greater than the escape velocity. FUSE observations of the Ovi doublet provide previously unattainable information regarding outflow velocities and radiative cooling rates in hot gas at T \sim 3\times 10^{5} K. Emission from gas at temperatures of 10^{4} K and \sim 5 \times 10^{6} K is now being studied with unprecedented spatial resolution using HST and Chandra, tracing the complex interaction of the still-invisible wind of SN-ejecta with the ambient ISM entrained into these outflows. I discuss the implications of these observations for our understanding of starburst-driven outflows.
Starburst-driven galactic winds: I. Energetics and intrinsic X-ray emission
D. K. Strickland,I. R. Stevens
Physics , 2000, DOI: 10.1046/j.1365-8711.2000.03391.x
Abstract: We have performed an extensive hydrodynamical parameter study of starburst-driven galactic winds, motivated by the latest observation data on the best-studied starburst galaxy M82. We study how the wind dynamics, morphology and X-ray emission depend on the host galaxy's ISM distribution, starburst star formation history and strength, and presence and distribution of mass-loading by dense clouds. We find that the soft X-ray emission from galactic winds comes from low filling factor (ff < 2 per cent) gas, which contains only a small fraction (f < 10 per cent) of the mass and energy of the wind, irrespective of whether the wind models are strongly mass-loaded or not. X-ray observations of galactic winds therefore do not directly probe the gas that contains the majority of the energy, mass or metal-enriched gas in the outflow. The soft X-ray emission comes from gas at a wide range different temperatures and densities. Estimates of the physical properties of the hot gas in starburst galaxies, based on fitting the standard simple spectral models to existing X-ray spectra, should therefore be treated with extreme suspicion. The majority of the thermal and kinetic energy of these winds is in a volume filling hot, T approx 10^7 K, component which is extremely difficult to probe observationally due to its low density and hence low emissivity. Most of the total energy is in the kinetic energy of this hot gas, a factor which must be taken into account when attempting to constrain wind energetics observationally. We also find that galactic winds are efficient at transporting large amounts of energy out of the host galaxy, in contrast to their inefficiency at transporting mass out of star-forming galaxies. (Abridged)
The influence of strong magnetic fields on proto-quark stars
V. Dexheimer,D. P. Menezes,M. Strickland
Physics , 2012, DOI: 10.1088/0954-3899/41/1/015203
Abstract: We analyze different stages of magnetized quark star evolution incorporating baryon number conservation and using an anisotropic energy momentum tensor. The first stages of the evolution are simulated through the inclusion of trapped neutrinos and fixed entropy per particle, while in the last stage the star is taken to be deleptonized and cold. We find that, although strong magnetic fields modify quark star masses, the evolution of isolated stars needs to be constrained by fixed baryon number, which necessarily lowers the possible star masses. Moreover, magnetic field effects, measured by the difference between the parallel and perpendicular pressures, are more pronounced in the beginning of the star evolution, when there is a larger number of charged leptons and up quarks. We also show that having a spatially varying magnetic field allows for larger magnetic fields to be supported.
Limb-Darkening Coefficients for Eclipsing White Dwarfs
A. Gianninas,B. D. Strickland,Mukremin Kilic,P. Bergeron
Physics , 2013, DOI: 10.1088/0004-637X/766/1/3
Abstract: We present extensive calculations of linear and non-linear limb-darkening coefficients as well as complete intensity profiles appropriate for modeling the light-curves of eclipsing white dwarfs. We compute limb-darkening coefficients in the Johnson-Kron-Cousins UBVRI photometric system as well as the Large Synoptic Survey Telescope (LSST) ugrizy system using the most up-to-date model atmospheres available. In all, we provide the coefficients for seven different limb-darkening laws. We describe the variations of these coefficients as a function of the atmospheric parameters, including the effects of convection at low effective temperatures. Finally, we discuss the importance of having readily available limb-darkening coefficients in the context of present and future photometric surveys like the LSST, Palomar Transient Factory, and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). The LSST, for example, may find ~10^5 eclipsing white dwarfs. The limb-darkening calculations presented here will be an essential part of the detailed analysis of all of these systems.
The chromo-weibel instability
Strickland, Michael;
Brazilian Journal of Physics , 2007, DOI: 10.1590/S0103-97332007000500021
Abstract: i discuss the physics of non-abelian plasmas which are locally anisotropic in momentum space. such momentum-space anisotropies are generated by the rapid longitudinal expansion of the matter created in the first 1 fm/c of an ultrarelativistic heavy ion collision. in contrast to locally isotropic plasmas anisotropic plasmas have a spectrum of soft unstable modes which are characterized by exponential growth of transverse chromo-magnetic/-electric fields at short times. this instability is the qcd analogue of the weibel instability of qed. parametrically the chromo-weibel instability provides the fastest method for generation of soft background fields and dominates the short-time dynamics of the system. the existence of the chromo-weibel instability has been proven using diagrammatic methods, transport theory, and numerical solution of classical yang-mills fields. i review the results obtained from each of these methods and discuss the numerical techniques which are being used to determine the late-time behavior of plasmas subject to a chromo-weibel instability.
Thermalization and the chromo-Weibel instability
Strickland, Michael
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/0954-3899/34/8/S31
Abstract: Despite the apparent success of ideal hydrodynamics in describing the elliptic flow data which have been produced at Brookhaven National Lab's Relativistic Heavy Ion Collider, one lingering question remains: is the use of ideal hydrodynamics at times t < 1 fm/c justified? In order to justify its use a method for rapidly producing isotropic thermal matter at RHIC energies is required. One of the chief obstacles to early isotropization/thermalization is the rapid longitudinal expansion of the matter during the earliest times after the initial nuclear impact. As a result of this expansion the parton distribution functions become locally anisotropic in momentum space. In contrast to locally isotropic plasmas anisotropic plasmas have a spectrum of soft unstable modes which are characterized by exponential growth of transverse chromo-magnetic/-electric fields at short times. This instability is the QCD analogue of the Weibel instability of QED. Parametrically the chromo-Weibel instability provides the fastest method for generation of soft background fields and dominates the short-time dynamics of the system.
On The Necessity Of The Best (Possible) World
Strickland, Lloyd
Ars Disputandi : the Online Journal for Philosophy of Religion , 2005,
Abstract: Many have argued that if God exists then he must necessarily create the best possible world (hereafter: bpw), which entails that the bpw necessarily exists, and is therefore the only possible world. But without any scope for comparison, the superlative term ¢ € best ¢ € is clearly inappropriate and so the bpw cannot be the bpw at all! As such, it must be impossible for God to create it. Hence if God exists then he must of necessity make something that is impossible to create! Because of its conclusion, I call this the repugnant argument. I consider a number of possible responses to this argument.
Thermal Upsilon(1s) and chi_b1 suppression in sqrt(s_NN)=2.76 TeV Pb-Pb collisions at the LHC
Michael Strickland
Physics , 2011, DOI: 10.1103/PhysRevLett.107.132301
Abstract: I compute the thermal suppression of the Upsilon(1s) and chi_b1 states in sqrt(s_NN)=2.76 TeV Pb-Pb collisions. Using the suppression of each of these states I estimate the total R_AA for the Upsilon(1s) state as a function of centrality, rapidity, and transverse momentum. I find less suppression of the chi_b1 state than would be traditionally assumed; however, my final results for the total Upsilon(1s) suppression are in good agreement with recent preliminary CMS data.
Anisotropic Hydrodynamics: Three lectures
Michael Strickland
Physics , 2014, DOI: 10.5506/APhysPolB.45.2355
Abstract: Anisotropic hydrodynamics is a non-perturbative reorganization of relativistic hydrodynamics that takes into account the large momentum-space anisotropies generated in ultrarelativistic heavy-ion collisions. As a result, it allows one to extend the regime of applicability of hydrodynamic treatments to situations that can be quite far from isotropic thermal equilibrium. In this paper, I review the material presented in a series of three introductory lectures. I review the derivation of ideal and second-order viscous hydrodynamics from kinetic theory. I then show how to extend the methods used to a system that can be highly anisotropic in local-rest-frame momenta. I close by discussing recent work on this topic and then present an outlook to the future.
Anisotropic Hydrodynamics: Motivation and Methodology
Michael Strickland
Physics , 2014, DOI: 10.1016/j.nuclphysa.2014.01.013
Abstract: In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can been made around an anisotropic background, and the resulting dynamical framework has been dubbed "anisotropic hydrodynamics." I also discuss expectations for the degree of momentum-space anisotropy of the quark gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.
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