Astrophysics and Astronomy Commons^™

Magnetization Precession And Domain-Wall Structure In Cobalt-Ruthenium-Cobalt Trilayers, Zhen Li, Ralph Skomski, Sy-Hwang Liou, Steven Michalski, Mircea Chipara, Roger D. Kirby

Physics & Astronomy Faculty Publications

The magnetization dynamics of Co(5 nm)/Ru/Co(5 nm) trilayers with Ru thicknesses from 0.3–0.6 nm is experimentally and theoretically investigated. The coupling between the Co layers is antiferromagnetic (AFM) and yields a stable AFM domain structure with frozen domain walls. Comparing high-resolution magnetic force microscopy (MFM) and pump-probe measurements, we analyze the behavior of the films for different field-strength regimes. For moderate magnetic fields, pump-probe measurements provide dynamic characterization of the coupled precessional modes in the GHz range. The dynamics at small fields is realized by the pinning of AFM domain walls at inhomogeneities. The MFM images yield a domain-wall width …

Thermal Reaction Wave Simulation Using Micro And Macro Scale Interaction Model, Andrei A. Markov, Igor A. Filimonov, Karen S. Martirosyan

Physics & Astronomy Faculty Publications

The thermal wave, propagating in a cylindrical tube, is numerically simulated. The technique is developed in order to provide the scale capturing as well as the stable algorithm for numerical simulation of the combustion wave. Based on the model kinetics scheme, the fields of temperature, mass fractions, and particle radius are presented for the various values of similarity parameters of the problem. The highly accurate method enables to control scales interaction and justifies various flow structures. The phase composition, structure, and morphology of the condensed product as well as the rate of the oxidation and phase transition are predicted using …

Fine-Scale Structures In Saturn's Rings Waves, Wakes And Ghosts, Kevin Baille

Electronic Theses and Dissertations

The Cassini mission provided wonderful tools to explore Saturn, its satellites and its rings system. The UVIS instrument allowed stellar occultation observations of structures in the rings with the best resolution available (around 10 meters depending on geometry and navigation), bringing our understanding of the physics of the rings to the next level. In particular, we have been able to observe, dissect, model and test the interactions between the satellites and the rings. We first looked at kilometer-wide structures generated by resonances with satellites orbiting outside the main rings. The observation of structures in the C ring and their association …

Magnetic-Field Induced Stability In Two-Flavor Color Superconductivity, Churna B. Bhandari

Open Access Theses & Dissertations

It has long been understood that the ground state of a superdense quark system, a Fermi liquid of weakly interacting quarks, is unstable with respect to the formation of diquark condensates. This nonperturbative phenomenon is essentially equivalent to the Cooper instability of conventional BCS superconductivity. As the quark pairs have nonzero color charge, this kind of superconductivity breaks the SU(3) color gauge symmetry, thus it is called color superconductivity. A peculiar feature of spin-zero color superconductivity is the lack of Meissner effect for a combination of the regular electromagnetic field and one of the gluon fields. This combination behaves as …

Combustion Of Lunar Regolith Mixed With Energetic Additives: Thermodynamic Calculations And Experimental Studies, Francisco Alvarez

Open Access Theses & Dissertations

The future of space exploration will require longer missions in order to better understand the conditions of near-Earth celestial objects, like the Moon or Mars. Future space missions will require the development of goods, such as propulsion fuel and structural materials, produced using the extraterrestrial resources available. The area that develops these technologies is called In-Situ Resource Utilization (ISRU). ISRU allows reducing the payload, and as a consequence reduces the energy consumption and cost of space travel. The production of structural materials on the Moon can be accomplished using Self-Propagating High-Temperature Synthesis (SHS). This work describes the combination of ISRU …

The Fossil Record Of Two-Phase Galaxy Assembly: Kinematics And Metallicities In The Nearest S0 Galaxy, J, A, Arnold, Aaron J. Romanowsky, J. P. Brodie, L. Chomiuk, L. R. Spitler, J. Strader, A. J. Benson, D. A. Forbes

Faculty Publications

We present a global analysis of kinematics and metallicity in the nearest S0 galaxy, NGC 3115, along with implications for its assembly history. The data include high-quality wide-field imaging from Suprime-Cam on the Subaru telescope, and multi-slit spectra of the field stars and globular clusters (GCs) obtained using Keck-DEIMOS/LRIS and Magellan-IMACS. Within two effective radii, the bulge (as traced by the stars and metal-rich GCs) is flattened and rotates rapidly (v/σ gsim 1.5). At larger radii, the rotation declines dramatically to v/σ ~ 0.7, but remains well aligned with the inner regions. The radial decrease in characteristic metallicity of both …

Star Clusters In M31: Old Clusters With Bar Kinematics, H. Morrison, N. Caldwell, R. P. Schiavon, E. Athanassoula, Aaron J. Romanowsky, P. Harding

Faculty Publications

We analyze our accurate kinematical data for the old clusters in the inner regions of M31. These velocities are based on high signal-to-noise Hectospec data. The data are well suited for analysis of M31's inner regions because we took particular care to correct for contamination by unresolved field stars from the disk and bulge in the fibers. The metal-poor clusters show kinematics that are compatible with a pressure-supported spheroid. The kinematics of metal-rich clusters, however, argue for a disk population. In particular the innermost region (inside 2 kpc) shows the kinematics of the x 2 family of bar periodic orbits, …

Evidence For Two Phases Of Galaxy Formation From Radial Trends In The Globular Cluster System Of Ngc 1407, D. A. Forbes, L. R. Spitler, J. Strader, Aaron J. Romanowsky, J. P. Brodie, C. Foster

Faculty Publications

Here we present the colours of individual globular clusters (GCs) around the massive elliptical galaxy NGC 1407 out to a projected galactocentric radius of 140 kpc or 17 galaxy effective radii (Re). Such data are a proxy for the halo metallicity. We find steep, and similar, metallicity gradients of ∼−0.4 dex dex−1 for both the blue (metal poor) and red (metal rich) GC subpopulations within 5–8.5 Re (40–70 kpc). At larger radii the mean GC colours (metallicity) are constant. A similar behaviour is seen in a wide-field study of M87's GC system, and in our own Galaxy. We interpret these …

The Dark Halo Of He Hydra I Galaxy Cluster: Core, Cusp, Cosmological? Dynamics Of Ngc 3311 And Its Globular Cluster System, T. Richtler, R. Salinas, I. Misgeld, M. Hilker, G.K. T. Hau, Aaron J. Romanowsky, Y. Schuberth, M. Spolaor

Faculty Publications

Context. Some galaxy clusters exhibit shallow or even cored dark matter density profiles in their central regions rather than the predicted steep or cuspy profiles, conflicting with the standard understanding of dark matter. NGC 3311 is the central cD galaxy of the Hydra I cluster (Abell 1060). Aims. We use globular clusters around NGC 3311, combined with kinematical data of the galaxy itself, to investigate the dark matter distribution in the central region of Hydra I. Methods. Radial velocities of 118 bright globular clusters, based on VLT/VIMOS mask spectroscopy, are used to calculate velocity dispersions which are well defined out …

The Search For The Missing Mantles Of Differentiated Asteroids: Evidence From Taxonomic A-Class Asteroids And Olivine-Dominated Achondrite Meteorites, Michael Peter Lucas

USF Tampa Graduate Theses and Dissertations

The apparent rarity of taxonomic A-class asteroids poses a significant paradox for understanding asteroid differentiation and the dynamical evolution of the early solar system. Based on results from asteroid taxonomic surveys, and on the abundances and mineralogy of different achondrite meteorites, it appears that olivine-dominated mantle remnants are missing from both the asteroid population and in meteorite collections. Several scenarios to explain this paradox have been proposed: (1) olivine mantle material has been stripped away by collisions and only remains as small fragments (< ~5 km), (2) A-class asteroids are abundant but have been altered in some way masking their presence, or (3) differentiated asteroids did not form thick olivine-rich mantles.

We have approached these questions through the collection of taxonomic and observational data on known A-class …

Why Is An Einstein Ring Blue?, Jonathan Blackledge

Articles

Albert Einstein predicted the existence of `Einstein rings' as a consequence of his general theory of relativity. The phenomenon is a direct result of the idea that if a mass warps space-time then light (and other electromagnetic waves) will be `lensed' by the strong gravitational field produced by a large cosmological body such as a galaxy. Since 1998, when the first complete Einstein ring was observed, many more complete or partially complete Einstein rings have been observed in the radio and infrared spectra, for example, and by the Hubble Space Telescope in the optical spectrum. However, in the latter case, …

Grb071028b, A Burst Behind Large Amounts Of Dust In An Unabsorbed Galaxy, C. Clemens, J. Greiner, T. Krühler, D. Pierini, S. Savaglio, S. Klose, P.M.J. Afonso, R. Filgas, F.E. Olivares, A. Rau, P. Schady, A. Rossi, A. Küpcü Yoldas, Adria Updike, A. Yoldas

Arts & Sciences Faculty Publications

No abstract provided.

Grb 091127: The Cooling Break Race On Magnetic Fuel, R. Filgas, J. Greiner, P. Schady, T. Krühler, Adria Updike, S. Klose, M. Nardini, D.A. Kann, A. Rossi, V. Sudilovsky, P.M.J. Afonso, C. Clemens, J. Elliott, A. Nicuesa Guelbenzu, F. Olivares E., A. Rau

Arts & Sciences Faculty Publications

No abstract provided.

On The Nature Of The Extremely Fast Optical Rebrightening Of The Afterglow Of Grb 081029, M. Nardini, J. Greiner, T. Krühler, R. Filgas, S. Klose, P. Afonso, C. Clemens, A. N. Guelbenzu, F. Olivares E., A. Rau, A. Rossi, Adria Updike, A. Küpcü Yoldas, A. Yoldas, D. Burlon, J. Elliott, D. A. Kann

Arts & Sciences Faculty Publications

Context. After the launch of the Swift satellite, the gamma-ray burst (GRB) optical light-curve smoothness paradigm has been questioned thanks to the faster and better sampled optical follow-up, which has unveiled a very complex behaviour. This complexity is triggering the interest of the whole GRB community. The GROND multi-channel imager is used to study optical and near-infrared (NIR) afterglows of GRBs with unprecedented optical and near-infrared temporal and spectral resolution. The GRB 081029 has a very prominent optical rebrightening event and is an outstanding example of the application of the multi-channel imager to GRB afterglows. Aims. Here we exploit the …

Photometric Redshifts For Gamma-Ray Burst Afterglows From Grond And Swift/Uvot, T. Krühler, P. Schady, J. Greiner, P. Afonso, E. Bottacini, C. Clemens, R. Filgas, S. Klose, T. S. Koch, A. Küpcü-Yoldas, S. R. Oates, F. Olivares E., M. J. Page, S. Mcbreen, M. Nardini, A. Nicuesa Guelbenzu, A. Rau, P. W.A. Roming, A. Rossi, Adria Updike, A. Yoldas

Arts & Sciences Faculty Publications

No abstract provided.

The Seds And Host Galaxies Of The Dustiest Grb Afterglows, T. Krühler, J. Greiner, P. Schady, S. Savaglio, P. M.J. Afonso, C. Clemens, J. Elliott, R. Filgas, D. Gruber, D. A. Kann, S. Klose, A. Küpcü-Yoldas, S. Mcbreen, F. Olivares, D. Pierini, A. Rau, A. Rossi, M. Nardini, A. Nicuesa Guelbenzu, V. Sudilovsky, Adria Updike

Arts & Sciences Faculty Publications

No abstract provided.

Spitzer 24Μm Survey For Dust Disks Around Hot White Dwarfs, You-Hua Chu, Kate Y.L. Su, Jana Bilikova, Robert A. Gruendl, Orsola De Marco, Martin A. Guerrero, Adria Updike, Kevin Volk, Thomas Rauch

Arts & Sciences Faculty Publications

No abstract provided.

Precise Measurements Of Beam Spin Asymmetries In Semi-Inclusive Π0 Production, M. Aghasyan, H. Avakian, P. Rossi, E. De Sanctis, D. Hasch, M. Mirazita, D. Adikaram, M. J. Amaryan, M. Anghinolfi, H. Baghdasaryan, R. P. Bennett, S. Bültmann, G. E. Dodge, C. E. Hyde, A. Klein, S. E. Kuhn, M. Mayer, H. Seraydaryan, L. B. Weinstein

Physics Faculty Publications

We present studies of single-spin asymmetries for neutral pion electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV polarized electrons from an unpolarized hydrogen target, using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. A substantial sin phi(h) amplitude has been measured in the distribution of the cross section asymmetry as a function of the azimuthal angle φh of the produced neutral pion. The dependence of this amplitude on Bjorken x and on the pion transverse momentum is extracted with significantly higher precision than previous data and is compared to model calculations. (C) 2011 Elsevier B.V.

Evolution Of The Differential Transverse Momentum Correlation Function With Centrality In Au + Au Collisions At √Snn = 200 Gev, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arhipkin, G. S. Averichev, S. Bültmann, D. Plyku

Physics Faculty Publications

We present first measurements of the evolution of the differential transverse momentum correlation function, C, with collision centrality in Au + Au interactions at √^sNN = 200 GeV. This observable exhibits a strong dependence on collision centrality that is qualitatively similar to that of number correlations previously reported. We use the observed longitudinal broadening of the near-side peak of C with increasing centrality to estimate the ratio of the shear viscosity to entropy density, η / s , of the matter formed in central Au + Au interactions. We obtain an upper limit estimate of η / s …

Photon Impact Factor In The Next-To-Leading Order, Ian Balitsky, Giovanni A. Chirilli

Physics Faculty Publications

An analytic coordinate-space expression for the next-to-leading order photon impact factor for small-x deep inelastic scattering is calculated using the operator expansion in Wilson lines.