Non-Isotropic Angular Distribution for Very Short-Time Gamma-Ray Bursts

While most gamma-ray bursts (GRBs) are now believed to be from cosmological distances, the origin of very short-time GRBs is still not known. In the past, we have shown that GRBs with time duration (T90) less than 100 ms may form a separate class of GRBs based on the hardness and time distribution of these events. We have also shown that the ln N ln S distribution is consistent with the expectation of quasi-Euclidean distribution of sources. In this paper, we report the study of the angular location of these GRBs showing a strong deviation from isotropy within the Galactic coordinates of plus 180 degrees < longitude < 90 degrees and -30 degrees < latitude < 30 degrees. We have studied the rest of the GRBs and do not find a similar deviation. This further indicates that the very-short GRBs likely form a separate class of GRBs, most probably from sources of Galactic or near solar origin

Prediction of Small-Scale Densities Using the Chemical and Optical Spread Functions

Development adjacency effects and optical spread in photographic systems cause difficulties in predicting small-scale densities. These effects can be quantified as spread functions. The optical spread func tion describes the light scatter of the film. The chemical spread func tion describes the lateral diffusion of development- inhibiting and dev elopment-accelerating reaction products. These spread functions can be used along with the sensitometry and covering power relationships of the system to predict small-area densities from the object exposure profile. A study based on C. N. Nelson\u27s work was undertaken to develop a math ematical model that uses the optical and chemical spread functions to predict small-area densities of an image from the original object ex posure profile. This model was developed for a fine-grain aerial dup licating film processed in KODAK D-76 (1:4). It was found that the model predicted the image profile of a log-periodic target to within 0.02 D on the peaks of the bars. However, the model overshot the edges of the bars by about -0.0$ D. This difference, even though significantly greater than the experimental error, does not affect the usefulness of this model to image quality studies

Transient Accelerated Expansion and Double Quintessence

We consider Double Quintessence models for which the Dark Energy sector consists of two coupled scalar fields. We study in particular the possibility to have a transient acceleration in these models. In both Double Quintessence models studied here, it is shown that if acceleration occurs, it is necessarily transient. We consider also the possibility to have transient acceleration in two one-field models, the Albrecht-Skordis model and the pure exponential. Using separate conservative constraints (marginalizing over the other parameters) on the effective equation of state $w_{eff}$, the relative density of the Dark Energy $\Omega_{Q,0}$ and the present age of the universe, we construct scenarios with a transient acceleration that has already ended at the present time, and even with no acceleration at all, but a less conservative analysis using the CMB data rules out the last possibility. The scenario with a transient acceleration ended by today, can be implemented for the range of cosmological parameters $\Omega_{m,0}\gtrsim 0.35$ and $h\lesssim 0.68$.Comment: Version accepted in Phys. Rev. D, 22 pages, 10 figures, 4 table

Strange Quarks Nuggets in Space: Charges in Seven Settings

We have computed the charge that develops on an SQN in space as a result of balance between the rates of ionization by ambient gammas and capture of ambient electrons. We have also computed the times for achieving that equilibrium and binding energy of the least bound SQN electrons. We have done this for seven different settings. We sketch the calculations here and give their results in the Figure and Table II; details are in the Physical Review D.79.023513 (2009).Comment: Six pages, one figure. To appear in proceedings of the 2008 UCLA coference on dark matter and dark energ

Theory and laboratory astrophysics

Science opportunities in the 1990's are discussed. Topics covered include the large scale structure of the universe, galaxies, stars, star formation and the interstellar medium, high energy astrophysics, and the solar system. Laboratory astrophysics in the 1990's is briefly surveyed, covering such topics as molecular, atomic, optical, nuclear and optical physics. Funding recommendations are given for the National Science Foundation, NASA, and the Department of Energy. Recommendations for laboratory astrophysics research are given

From heaviness to lightness during inflation

We study the quantum fluctuations of scalar fields with a variable effective mass during an inflationary phase. We consider the situation where the effective mass depends on a background scalar field, which evolves during inflation from being frozen into a damped oscillatory phase when the Hubble parameter decreases below its mass. We find power spectra with suppressed amplitude on large scales, similar to the standard massless spectrum on small scales, and affected by modulations on intermediate scales. We stress the analogies and differences with the parametric resonance in the preheating scenario. We also discuss some potentially observable consequences when the scalar field behaves like a curvaton.Comment: 23 pages; 8 figures; published versio

The search for DM in nearby dSph galaxies with MAGIC: candidates, results and prospects

At present, dwarf spheroidal galaxies satellites of the Milky Way may represent the best astrophysical objects for dark matter (DM) searches with gamma-ray telescopes. They present the highest mass-to-light ratios known in the Universe. Furthermore, many of them are near enough from the Earth to be able to yield high predicted DM annihilation fluxes that might be observed by current gamma-ray instruments like MAGIC. The picture has become even better with the recent discovery of new dwarfs. These new objects are expected to yield even higher DM annihilation fluxes, since most of them are nearer than the previously known dwarfs and are even more DM dominated systems. Here a tentative list of the best candidates is given. The observational results obtained with MAGIC from the Draco dwarf as well as the observation of other dwarfs carried out by other Cherenkov telescopes are presented as well. Finally, we discuss the detection prospects of such kind of objects in the context of DM searches.Comment: To appear in the proceedings of the 8th UCLA Dark Matter Symposium, Marina del Rey, USA, 20-22 February 200

Unusual Intron Conservation near Tissue-Regulated Exons Found by Splicing Microarrays

Alternative splicing contributes to both gene regulation and protein diversity. To discover broad relationships between regulation of alternative splicing and sequence conservation, we applied a systems approach, using oligonucleotide microarrays designed to capture splicing information across the mouse genome. In a set of 22 adult tissues, we observe differential expression of RNA containing at least two alternative splice junctions for about 40% of the 6,216 alternative events we could detect. Statistical comparisons identify 171 cassette exons whose inclusion or skipping is different in brain relative to other tissues and another 28 exons whose splicing is different in muscle. A subset of these exons is associated with unusual blocks of intron sequence whose conservation in vertebrates rivals that of protein-coding exons. By focusing on sets of exons with similar regulatory patterns, we have identified new sequence motifs implicated in brain and muscle splicing regulation. Of note is a motif that is strikingly similar to the branchpoint consensus but is located downstream of the 5′ splice site of exons included in muscle. Analysis of three paralogous membrane-associated guanylate kinase genes reveals that each contains a paralogous tissue-regulated exon with a similar tissue inclusion pattern. While the intron sequences flanking these exons remain highly conserved among mammalian orthologs, the paralogous flanking intron sequences have diverged considerably, suggesting unusually complex evolution of the regulation of alternative splicing in multigene families

A WIMP detector with two-phase xenon

Abstract We describe an important new technique to search for WIMPs. This technique employs a method of background discrimination using double phase xenon as detector target. We describe the construction of a two-phase, 1-kg xenon detector. The detector will be installed at the underground laboratory in the Mt. Blanc tunnel, which provides a low background rate. A comparison between the sensitivity curve of our detector and the theoretical events limit from SUSY calculations is presented

Excluding Electroweak Baryogenesis in the MSSM

In the context of the MSSM the Light Stop Scenario (LSS) is the only region of parameter space that allows for successful Electroweak Baryogenesis (EWBG). This possibility is very phenomenologically attractive, since it allows for the direct production of light stops and could be tested at the LHC. The ATLAS and CMS experiments have recently supplied tantalizing hints for a Higgs boson with a mass of ~ 125 GeV. This Higgs mass severely restricts the parameter space of the LSS, and we discuss the specific predictions made for EWBG in the MSSM. Combining data from all the available ATLAS and CMS Higgs searches reveals a tension with the predictions of EWBG even at this early stage. This allows us to exclude EWBG in the MSSM at greater than (90) 95% confidence level in the (non-)decoupling limit, by examining correlations between different Higgs decay channels. We also examine the exclusion without the assumption of a ~ 125 GeV Higgs. The Higgs searches are still highly constraining, excluding the entire EWBG parameter space at greater than 90% CL except for a small window of m_h ~ 117 - 119 GeV.Comment: 24 Pages, 4 Figures (v3: fixed typos, minor corrections, added references