Strong Optimized Conservative Fermi-LAT Constraints on Dark Matter Models from the Inclusive Photon Spectrum

We set conservative, robust constraints on the annihilation and decay of dark matter into various Standard Model final states under various assumptions about the distribution of the dark matter in the Milky Way halo. We use the inclusive photon spectrum observed by the Fermi Gamma-ray Space Telescope through its main instrument, the Large-Area Telescope (LAT). We use simulated data to first find the "optimal" regions of interest in the gamma-ray sky, where the expected dark matter signal is largest compared with the expected astrophysical foregrounds. We then require the predicted dark matter signal to be less than the observed photon counts in the a priori optimal regions. This yields a very conservative constraint as we do not attempt to model or subtract astrophysical foregrounds. The resulting limits are competitive with other existing limits, and, for some final states with cuspy dark-matter distributions in the Galactic Center region, disfavor the typical cross section required during freeze-out for a weakly interacting massive particle (WIMP) to obtain the observed relic abundance.Comment: 24 pages + appendices and references, 13 figures, accepted by PRD. Contact authors: Andrea Massari, Eder Izaguirre, and Rouven Essi

Clustering of galaxies around GRB sight-lines

There is evidence of an overdensity of strong intervening MgII absorption line systems distributed along the lines of sight towards GRB afterglows relative to quasar sight-lines. If this excess is real, one should also expect an overdensity of field galaxies around GRB sight-lines, as strong MgII tends to trace these sources. In this work, we test this expectation by calculating the two point angular correlation function of galaxies within 120$^{\prime\prime}$ ($\sim470~h_{71}^{-1}~\mathrm{Kpc}$ at $\langle z\rangle \sim0.4$) of GRB afterglows. We compare the Gamma-ray burst Optical and Near-infrared Detector (GROND) GRB afterglow sample -- one of the largest and most homogeneous samples of GRB fields -- with galaxies and AGN found in the COSMOS-30 photometric catalog. We find no significant signal of anomalous clustering of galaxies at an estimated median redshift of $z\sim0.3$ around GRB sight-lines, down to $K_{\mathrm{AB}}<19.3$. This result is contrary to the expectations from the MgII excess derived from GRB afterglow spectroscopy, although many confirmed galaxy counterparts to MgII absorbers may be too faint to detect in our sample -- especially those at $z>1$. We note that the addition of higher sensitivity Spitzer IRAC or HST WFC3 data for even a subset of our sample would increase this survey's depth by several orders of magnitude, simultaneously increasing statistics and enabling the investigation of a much larger redshift space.}Comment: 10 pages, 6 figures. A&A accepte

GRB 091127: The cooling break race on magnetic fuel

Using high-quality, broad-band afterglow data for GRB 091127, we investigate the validity of the synchrotron fireball model for gamma-ray bursts, and infer physical parameters of the ultra-relativistic outflow. We used multi-wavelength follow-up observations obtained with GROND and the XRT onboard the Swift satellite. The resulting afterglow light curve is of excellent accuracy, and the spectral energy distribution is well-sampled over 5 decades in energy. These data present one of the most comprehensive observing campaigns for a single GRB afterglow and allow us to test several proposed emission models and outflow characteristics in unprecedented detail. Both the multi-color light curve and the broad-band SED of the afterglow of GRB 091127 show evidence of a cooling break moving from high to lower energies. The early light curve is well described by a broken power-law, where the initial decay in the optical/NIR wavelength range is considerably flatter than at X-rays. Detailed fitting of the time-resolved SED shows that the break is very smooth with a sharpness index of 2.2 +- 0.2, and evolves towards lower frequencies as a power-law with index -1.23 +- 0.06. These are the first accurate and contemporaneous measurements of both the sharpness of the spectral break and its time evolution. The measured evolution of the cooling break (nu_c propto t^-1.2) is not consistent with the predictions of the standard model, wherein nu_c propto t^-0.5 is expected. A possible explanation for the observed behavior is a time dependence of the microphysical parameters, in particular the fraction of the total energy in the magnetic field epsilon_B. This conclusion provides further evidence that the standard fireball model is too simplistic, and time-dependent micro-physical parameters may be required to model the growing number of well-sampled afterglow light curves.Comment: accepted to A&A, 13 pages, 5 figure

Analytically solvable potentials for γ\gamma-unstable nuclei

An analytical solution of the collective Bohr equation with a Coulomb-like and a Kratzer-like $\gamma-$unstable potential in quadrupole deformation space is presented. Eigenvalues and eigenfunctions are given in closed form and transition rates are calculated for the two cases. The corresponding SO(2,1)$\times$SO(5) algebraic structure is discussed.Comment: 9 pages, 4 figures in one .ps fil

Common and specific impairments in attention functioning in girls with chromosome 22q11.2 deletion, fragile X or Turner syndromes.

BACKGROUND: Chromosome 22q11.2 deletion syndrome (22q11.2DS), fragile X syndrome (FXS), and Turner syndrome (TS) are complex and variable developmental syndromes caused by different genetic abnormalities; yet, they share similar cognitive impairments in the domains of numbers, space, and time. The atypical development of foundational neural networks that underpin the attentional system is thought to result in further impairments in higher-order cognitive functions. The current study investigates whether children with similar higher-order cognitive impairments but different genetic disorders also show similar impairments in alerting, orienting, and executive control of attention. METHODS: Girls with 22q11.2DS, FXS, or TS and typically developing (TD) girls, aged 7 to 15 years, completed an attention network test, a flanker task with alerting and orienting cues. Exploration of reaction times and accuracy allowed us to test for potential commonalities in attentional functioning in alerting, orienting, and executive control. Linear regression models were used to test whether the predictors of group and chronological age were able to predict differences in attention indices. RESULTS: Girls with 22q11.2DS, FXS, or TS demonstrated unimpaired function of the alerting system and impaired function of the executive control system. Diagnosis-specific impairments were found such that girls with FXS made more errors and had a reduced orienting index, while girls with 22q11.2DS showed specific age-related deficits in the executive control system. CONCLUSIONS: These results suggest that the control but not the implementation of attention is selectively impaired in girls with 22q11.2DS, TS or FXS. Additionally, the age effect on executive control in girls with 22q11.2DS implies a possible altered developmental trajectory

Heat transport in model jammed solids

We calculate numerically the normal modes of vibrations in 3D jammed packings of soft spheres as a function of the packing fraction and obtain the energy diffusivity, a spectral measure of transport that controls sound propagation and thermal conductivity. The crossover frequency between weak and strong phonon scattering is controlled by the coordination and shifts to zero as the system is decompressed towards the critical packing fraction at which rigidity is lost. Below the crossover, the diffusivity displays a power-law divergence with inverse frequency, which suggests that the vibrational modes are primarily transverse waves, weakly scattered by disorder. Above it, a large number of modes appear whose diffusivity plateaus at a nearly constant value independent of the inter-particle potential, before dropping to zero above the Anderson localization frequency. The thermal conductivity of a marginally jammed solid just above the rigidity threshold is calculated and related to the one measured experimentally at room temperature for most glasses.Comment: 15 pages, 7 figure

An Approach to Measuring Step Excrescence Effects in the Presence of a Pressure Gradient

An experimental study was undertaken to determine the effects of step excrescences on boundary layer transition using a unique ground test facility in which the test model was propelled though still air. The models used were designed to have a nominally constant pressure gradient so that the results would be relevant to laminar flow aircraft whose wings often have long runs of mildly favorable pressure gradient. The models had an integrated continuously adjustable two-dimensional step, which could be adjusted to be forward-facing or aft-facing. The large model was used to increase the Reynolds numbers examined so that the results are applicable to laminar flow flight vehicles. Multiple measurement methods, including Preston tubes, hot wires, accelerometers, a boundary layer traverse, and static pressure taps were used to provide comparison data, and to add to the physical understanding of the results. The propelled-model test approach required that the instrumentation be self-contained and ride along with the model as the carrier vehicle moved down the test track. Due to the relatively short times available for data-taking (approximately 15-30 seconds per run), the initialization and data analysis techniques had to be tailored for this application

Impact of HIV-Associated Conditions on Mortality in People Commencing Anti-Retroviral Therapy in Resource Limited Settings

To identify associations between specific WHO stage 3 and 4 conditions diagnosed after ART initiation and all cause mortality for patients in resource-limited settings (RLS). DESIGN, SETTING: Analysis of routine program data collected prospectively from 25 programs in eight countries between 2002 and 2010

Sensitivity Projections for Dark Matter Searches with the Fermi Large Area Telescope

The nature of dark matter is a longstanding enigma of physics; it may consist of particles beyond the Standard Model that are still elusive to experiments. Among indirect search techniques, which look for stable products from the annihilation or decay of dark matter particles, or from axions coupling to high-energy photons, observations of the $\gamma$-ray sky have come to prominence over the last few years, because of the excellent sensitivity of the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope mission. The LAT energy range from 20 MeV to above 300 GeV is particularly well suited for searching for products of the interactions of dark matter particles. In this report we describe methods used to search for evidence of dark matter with the LAT, and review the status of searches performed with up to six years of LAT data. We also discuss the factors that determine the sensitivities of these searches, including the magnitudes of the signals and the relevant backgrounds, considering both statistical and systematic uncertainties. We project the expected sensitivities of each search method for 10 and 15 years of LAT data taking. In particular, we find that the sensitivity of searches targeting dwarf galaxies, which provide the best limits currently, will improve faster than the square root of observing time. Current LAT limits for dwarf galaxies using six years of data reach the thermal relic level for masses up to 120 GeV for the $b\bar{b}$ annihilation channel for reasonable dark matter density profiles. With projected discoveries of additional dwarfs, these limits could extend to about 250 GeV. With as much as 15 years of LAT data these searches would be sensitive to dark matter annihilations at the thermal relic cross section for masses to greater than 400 GeV (200 GeV) in the $b\bar{b}$ ($\tau^+ \tau^-$) annihilation channels.Comment: Updated with a few additional and corrected references; otherwise, text is identical to previous version. Submitted on behalf of the Fermi-LAT collaboration. Accepted for publication in Physics Reports, 59 pages, 34 figures; corresponding author: Eric Charles ([email protected]