Cosmological constraints on unparticle dark matter

In unparticle dark matter (unmatter) models the equation of state of the unmatter is given by $p=\rho/(2d_U+1)$, where $d_U$ is the scaling factor. Unmatter with such equations of state would have a significant impact on the expansion history of the universe. Using type Ia supernovae (SNIa), the baryon acoustic oscillation (BAO) measurements and the shift parameter of the cosmic microwave background (CMB) to place constraints on such unmatter models we find that if only the SNIa data is used the constraints are weak. However, with the BAO and CMB shift parameter data added strong constraints can be obtained. For the $\Lambda$UDM model, in which unmatter is the sole dark matter, we find that $d_U > 60$ at 95% C.L. For comparison, in most unparticle physics models it is assumed $d_U<2$. For the $\Lambda$CUDM model, in which unmatter co-exists with cold dark matter, we found that the unmatter can at most make up a few percent of the total cosmic density if $d_U<10$, thus it can not be the major component of dark matter.Comment: Replaced with revised version. BAO data is added to make a tighter constraint. Version accepted for publication on Euro.Phys.J.

Improving the Computational Thinking Pedagogical Capabilities of School Teachers

The idea of computational thinking as skills and universal competence which every child should possess emerged last decade and has been gaining traction ever since. This raises a number of questions, including how to integrate computational thinking into the curriculum, whether teachers have computational thinking pedagogical capabilities to teach children, and the important professional development and training areas for teachers. The aim of this paper is to address the strategic issues by illustrating a series of computational thinking workshops for Foundation to Year 8 teachers held at an Australian university. Data indicated that teachers\u27 computational thinking understanding, pedagogical capabilities, technological know-how and confidence can be improved in a relatively short period of time through targeted professional learning

The Nearby Supernova Factory

The Nearby Supernova Factory (SNfactory) is an ambitious project to find and study in detail approximately 300 nearby Type Ia supernovae (SNe~Ia) at redshifts 0.03<z<0.08. This program will provide an exceptional data set of well-studied SNe in the nearby smooth Hubble flow that can be used as calibration for the current and future programs designed to use SNe to measure the cosmological parameters. The first key ingredient for this program is a reliable supply of Hubble-flow SNe systematically discovered in unprecedented numbers using the same techniques as those used in distant SNe searches. In 2002, 35 SNe were found using our test-bed pipeline for automated SN search and discovery. The pipeline uses images from the asteroid search conducted by the Near Earth Asteroid Tracking group at JPL. Improvements in our subtraction techniques and analysis have allowed us to increase our effective SN discovery rate to ~12 SNe/month in 2003.Comment: 7 pages, 3 figures to be published in New Astronomy Review

Flamingo Vol. I N 3

Voo-Doo. Untitled. Prose. 1. Widow. Untitled. Prose. 1. Tiger. Untitled. Prose. 1. Purple Cow. Untitled. Prose. 1. Anonymous. Untitled. Prose. 1. Life. Untitled. Prose. 2. Yale Record. Untitled. Prose. 2. Voo-Doo. Untitled. Prose. 2. Sour Owl. Untitled. Prose. 2. Puppet. Untitled. Prose. 2. Sun Dial. Untitled. Prose. 2. Anonymous. Untitled. Prose. 2. Nottingham, Ruth. Teddy . Prose. 5. Grogan. Untitled. Picture. 7. Anonymous. Untitled. Prose. 7. Anonymous. An Easy One . Prose. 7. Anonymous. How Terrible! Prose. 7. Anonymous. Untitled. Prose. 7. Anonymous. Untitled. Poem. 7. F.H.G. Untitled. Picture. 7. Wood, J.E.F. When mother Went to College . Prose. 8. E.D.T. Chicago Corn Exchange . Poem. 8. Anonymous. Untitled. Prose. 8. Anonymous. Untitled. Poem. 8. Anonymous. All But . Prose. 8. R.D.B. Roscoe to The Rescue . Prose. 9. Leet, L.D. On The Efficacy of Dreams . Prose. 10. Orange Ade. The Fable of the Coffin Nailer . Prose. 11. Orange Ade. Time Wasted . Prose. 11. Orange Ade. The Americanized Boy . Prose. 11. Orange Ade. Anything to Oblige . Prose. 11. Orange Ade. Tit For Tat . Prose. 11. Orange Ade. Good Alibi . Prose. 11. Orange Ade. Untitled. Prose. 11. Grogan. Untitled. Picture. 11. Lusk, R.G. On The Absurdity of Catching Fish When A-Fishing . Prose. 12. Anonymous. Co-eds and Plain Eds in 1950 . Picture. 13. Potter, W.M. Letters of A Japanese Sandman . Prose. 13. Anonymous. Ex Facultate . Prose. 13. Anonymous. Untitled. Prose. 13. R.J.S. An Uplifting Influence . Picture. 13. Anonymous. Consider the Luxite Girl . Poem. 14. Anonymous. Shades of Orpheus . Poem. 14. Anonymous. With The Gospel Team . Poem. 14. Anonymous. Untitled. Prose. 14. Anonymous. Untitled. Poem. 14. Anonymous. A Dirty Trick . Prose. 14. Taylor, Elsie D. Vestigial Customs . Prose. 15. Anonymous. Untitled. Prose. 16. Anonymous. A New version of Anthropology . Prose. 18. Anonymous. A New version of Anthropology . Picture. 18. Anonymous. Untitled. Prose. 18. Funk, Dorothy K. Untitled. Picture. 18. Anonymous. A Deep one . Prose. 18. Anonymous. Take His Name . Prose. 18. Olney, Clarke. The Evolution of An Intellectual . Prose. 19. Anonymous. Untitled. Prose. 19. Anonymous. Untitled. Prose. 20. W.A.W. On Getting Up For Breakfast . Prose. 20. McCann. Untitled. Picture. 21. Anonymous. Untitled. Prose. 21. Anonymous. S.S.S. . Prose. 21. Anonymous. The Judge Disagreed . Prose. 21. Anonymous. The Modern Woman . Prose. 21. Anonymous. Denison Slang in Japan . Prose. 22. Anonymous. Being Specific . Prose. 22. Anonymous. Then The Fun Began . Prose. 22. Anonymous. Then The Fun Began . Prose. 22. Anonymous. Chess Nuts . Poem. 22. Anonymous. Chess Nuts . Picture. 22. Funk, Dorothy K. Untitled. Picture. 22. Anonymous. Untitled. Prose. 22. Reel, Virginia. Untitled. Prose. 22. Anonymous. Untitled. Prose. 23. Anonymous. Take This to Heart . Prose. 23. Anonymous. Stepping Out . Picture. 23. Olney, Clarke. Untitled. Picture. 23. Anonymous. To Lalage . Prose. 23. Anonymous. Untitled. Poem. 24. Anonymous. Description of the Day . Prose. 25. Anonymous. Untitled. Prose. 25. Voo-Doo. Good Bizziness . Prose. 26. Anonymous. Fore! . Prose. 26. Anonymous. Untitled. Prose. 26. Brelsford, Ernest C. Souveniring . Prose. 27. Anonymous. Untitled. Prose. 30. Burr. Sweet Dreams . Prose. 30. Jester. Untitled. Prose. 30. Judge. Untitled. Prose. 30. Goblin. Untitled. Prose. 30. Cracker. Sanitation . Poem. 32. Anonymous. Untitled. Prose. 32. Jester. Untitled. Prose. 32. Goblin. Untitled. Prose. 32. Record. Untitled. Prose. 32. Linotype. Untitled. Prose. 32. Holt, Kilburn. The Schemer\u27s Lament . Poem. 7. Owen, Ernest t. Mother . Poem. 3. Owen, Ernest T. To--- . Poem. 24

Is the evidence for dark energy secure?

Several kinds of astronomical observations, interpreted in the framework of the standard Friedmann-Robertson-Walker cosmology, have indicated that our universe is dominated by a Cosmological Constant. The dimming of distant Type Ia supernovae suggests that the expansion rate is accelerating, as if driven by vacuum energy, and this has been indirectly substantiated through studies of angular anisotropies in the cosmic microwave background (CMB) and of spatial correlations in the large-scale structure (LSS) of galaxies. However there is no compelling direct evidence yet for (the dynamical effects of) dark energy. The precision CMB data can be equally well fitted without dark energy if the spectrum of primordial density fluctuations is not quite scale-free and if the Hubble constant is lower globally than its locally measured value. The LSS data can also be satisfactorily fitted if there is a small component of hot dark matter, as would be provided by neutrinos of mass 0.5 eV. Although such an Einstein-de Sitter model cannot explain the SNe Ia Hubble diagram or the position of the `baryon acoustic oscillation' peak in the autocorrelation function of galaxies, it may be possible to do so e.g. in an inhomogeneous Lemaitre-Tolman-Bondi cosmology where we are located in a void which is expanding faster than the average. Such alternatives may seem contrived but this must be weighed against our lack of any fundamental understanding of the inferred tiny energy scale of the dark energy. It may well be an artifact of an oversimplified cosmological model, rather than having physical reality.Comment: 12 pages, 5 figures; to appear in a special issue of General Relativity and Gravitation, eds. G.F.R. Ellis et al; Changes: references reformatted in journal style - text unchange

Probing Dark Energy with Supernovae : Bias from the time evolution of the equation of state

Observation of thousands of type Ia supernovae should offer the most direct approach to probe the dark energy content of the universe. This will be undertaken by future large ground-based surveys followed by a space mission (SNAP/JDEM). We address the problem of extracting the cosmological parameters from the future data in a model independent approach, with minimal assumptions on the prior knowledge of some parameters. We concentrate on the comparison between a fiducial model and the fitting function and adress in particular the effect of neglecting (or not) the time evolution of the equation of state. We present a quantitative analysis of the bias which can be introduced by the fitting procedure. Such bias cannot be ignored as soon as the statistical errors from present data are drastically improved.Comment: 22 pages, 10 figures, submitted to Phys. Rev.

Geometric origin of mechanical properties of granular materials

Some remarkable generic properties, related to isostaticity and potential energy minimization, of equilibrium configurations of assemblies of rigid, frictionless grains are studied. Isostaticity -the uniqueness of the forces, once the list of contacts is known- is established in a quite general context, and the important distinction between isostatic problems under given external loads and isostatic (rigid) structures is presented. Complete rigidity is only guaranteed, on stability grounds, in the case of spherical cohesionless grains. Otherwise, the network of contacts might deform elastically in response to load increments, even though grains are rigid. This sets an uuper bound on the contact coordination number. The approximation of small displacements (ASD) allows to draw analogies with other model systems studied in statistical mechanics, such as minimum paths on a lattice. It also entails the uniqueness of the equilibrium state (the list of contacts itself is geometrically determined) for cohesionless grains, and thus the absence of plastic dissipation. Plasticity and hysteresis are due to the lack of such uniqueness and may stem, apart from intergranular friction, from small, but finite, rearrangements, in which the system jumps between two distinct potential energy minima, or from bounded tensile contact forces. The response to load increments is discussed. On the basis of past numerical studies, we argue that, if the ASD is valid, the macroscopic displacement field is the solution to an elliptic boundary value problem (akin to the Stokes problem).Comment: RevTex, 40 pages, 26 figures. Close to published paper. Misprints and minor errors correcte

Notes on a paper of Mess

These notes are a companion to the article "Lorentz spacetimes of constant curvature" by Geoffrey Mess, which was first written in 1990 but never published. Mess' paper will appear together with these notes in a forthcoming issue of Geometriae Dedicata.Comment: 26 page