General principles for the non-equilibrium relaxation of populations in quantum materials

We examine the problem of how excited populations of electrons relax after they have been excited by a pump. We include three of the most important relaxation processes: (i) impurity scattering; (ii) Coulomb scattering; and (iii) electron-phonon scattering. The relaxation of an excited population of electrons is one of the most fundamental processes measured in pump/probe experiments, but its interpretation remains under debate. We show how several common assumptions about non-equilibrium relaxation that are pervasive in the field may not hold under quite general conditions. The analysis shows that non-equilibrium relaxation is more complex than previously thought, but it yields to recently developed theoretical methods in non-equilibrium theory. In this work, we show how one can use many-body theory to properly interpret and analyze these complex systems. We focus much of the discussion on implications of these results for experiment.Comment: 13 pages, 10 figure

A method for computing chemical-equilibrium compositions of reacting-gas mixtures by reduction to a single iteration equation

Computing equilibrium chemical composition and thermodynamic properties of reacting gas mixtures by reduction to single iterative equatio

Modelling the alumina abundance of oxygen-rich evolved stars in the Large Magellanic Cloud

In order to determine the composition of the dust in the circumstellar envelopes of oxygen-rich asymptotic giant branch (AGB) stars we have computed a grid of modust radiative-transfer models for a range of dust compositions, mass-loss rates, dust shell inner radii and stellar parameters. We compare the resulting colours with the observed oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC) sample, finding good overall agreement for stars with a mid-infrared excess. We use these models to fit a sample of 37 O-rich AGB stars in the LMC with optically thin circumstellar envelopes, for which 5$-$35-$\mu$m Spitzer infrared spectrograph (IRS) spectra and broadband photometry from the optical to the mid-infrared are available. From the modelling, we find mass-loss rates in the range $\sim 8\times10^{-8}$ to $5\times10^{-6}$ M$_{\odot}\ \mathrm{yr}^{-1}$, and we show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron provides a good fit to the observed spectra. Furthermore, we show from dust models that the AKARI [11]$-$[15] versus [3.2]$-$[7] colour-colour diagram, is able to determine the fractional abundance of alumina in O-rich AGB stars.Comment: 22 pages, 17 figures, accepted MNRA

Flamingo Vol. IX N 3

Anonymous. Untitled. Prose. 1. Anonymous. Untitled. Prose. 2. Anonymous. Untitled. Prose. 3. Ollapod, Cornell. Untitled. Prose. 3. Anonymous. Untitled. Prose. 4. Anonymous. Untitled. Prose. 5. Smith, Reed. Untitled. Cartoon. 8. Anonymous. Gripes and Groans . Prose. 9. J.C.K. You Disgraceful Being, She Said . Picture. 10. Anonymous. Untitled. Prose. 10. Anonymous. Homecoming . Prose. 1. Anonymous. My Girl . Prose. 1. McDonald, George. Untitled. Picture. 11. O\u27Dell, Dorothy. Edifying Adventures of Alice (In Wonderland) . Prose. 12. Anonymous. I. Though Stuff . Prose. 12. Anonymous. Untitled. Prose. 12. Anonymous. Untitled. Prose. 15. Anonymous. Hi-Glims of Denison\u27s History . Prose. 16. Anonymous. Hi-Glims of Denison\u27s History . Picture. 16. Anonymous. Untitled. Prose. 16. Anonymous. Geography of a Single Woman\u27s Life . Prose. 16. Anonymous. II. Hard-Up Stuff . Prose. 16. Anonymous. Fraternity Bridge . Prose. 16. Anonymous. Introducing-Miss 1931 . Prose. 17. Anonymous. III. Big (Bad) Stuff) . Prose. 18. Anonymous. Untitled. Prose. 18. Anonymous. With Horseradish honors . Prose. 18. Anonymous. It\u27s Best Friends . Prose. 18. Anonymous. Table Talk . Prose. 19. Anonymous. Untitled. Prose. 19. Anonymous. IV. Blankety-Blank Stuff . Prose. 19. Anonymous. V. Mighty (Old) Stuff). Prose. 20. Anonymous. Untitled. Prose. 20. Anonymous. Untitled. Prose. 21. Anonymous. Homecoming . Picture. 21. Shiokawa, Richard K. Untitled. Picture. 21. Anonymous. Ain\u27t It So . Prose. 21. Anonymous. book Nook . Prose. 22. Anonymous. Untitled. Prose. 26. Life. Untitled. Prose. 26. Wampus. Untitled. Prose. 26. Anonymous. Untitled. Prose. 27. Gargoyle. Untitled. Prose. 27. Froth. Untitled. Prose. 27. Anonymous. Untitled. Prose. 28. Texas Ranger. Untitled. Prose. 28. Medley. Untitled. Prose. 28. Gargoyle. Untitled. Prose. 29. Cracker. Untitled. Prose. 29. Harvard Lampoon. Untitled. Prose. 29. Texas Ranger. Untitled. Prose. 29. Frivol. Untitled. Prose. 29. Princeton Tiger. Untitled. Prose. 30. Barnacle. Untitled. Prose. 30. Beanpot. Untitled. Prose. 30. Gargoyle. Untitled. Prose. 30. Pup. Untitled. Prose. 31. Pennsylvania Punch Bowl. Untitled. Prose. 31. Penn State Froth. Untitled. Prose. 31. Anonymous. Untitled. Prose. 32. Gargoyle. Untitled. Prose. 32. Smrcina, Orville. Things That Freshmen Do Know . Picture. 13

On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer IRS and Infrared Space Observatory SWS spectra of 217 oxygen-rich asymptotic giant branch stars and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally-rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 microns. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ~10^-9 solar masses/year. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-micron feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-micron band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.Comment: Accepted for publication in MNRAS, 24 pages, 16 figure