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arXiv:0710.1630 [ps, pdf, other] :
Title: What do WMAP and SDSS really tell about inflation?
Authors: Julien Lesgourgues, , Alexei A. Starobinsky, Wessel Valkenburg
Comments: 5 pages, 3 figures. Numerical module available at this http URL
We derive new constraints on the Hubble function H(phi) and subsequently on the inflationary potential V(phi) from WMAP 3-year data combined with the Sloan Luminous Red Galaxy survey (SDSS-LRG), using a new methodology which appears to be more generic, conservative and model-independent than in most of the recent literature, since it depends neither on the slow-roll approximation, nor on any extrapolation scheme for the potential beyond the observable e-fold range, nor on additional assumptions about initial conditions for the inflaton velocity. This last feature represents the main improvement of this work, and is made possible by the reconstruction of H(phi) prior to V(phi). Our results only rely on the assumption that within the observable range, corresponding to ~ 10 e-folds, inflation is not interrupted and the function H(phi) is smooth enough for being Taylor-expanded at order one, two or three. We conclude that the variety of potentials allowed by the data is still large. However, it is clear that the first two slow-roll parameters are really small while the validity of the slow-roll expansion beyond them is not established. |
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arXiv:0710.1302 [ps, pdf, other] :
Title: Enhanced Non-Gaussianity from Excited Initial States
Authors: Andrew J. Tolley, R. Holman
Comments: 31 pages, 1 figure
We use the techniques of effective field theory in an expanding universe to examine the effect of choosing an excited inflationary initial state built over the Bunch-Davies state on the CMB bi-spectrum. We find that even for Hadamard states, there are unexpected enhancements in the bi-spectrum for certain configurations in momentum space due to interactions of modes in the early stages of inflation. These enhancements can be parametrically larger than the standard ones and are potentially observable in current and future data. These initial state effects have a characteristic signature in $l$-space which distinguishes them from the usual contributions, with the enhancement being most pronounced for configurations corresponding to flattened triangles for which two momenta are collinear. |
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arXiv:0710.1303 [ps, pdf, other] :
Title: Testing Reionization with Gamma Ray Burst Absorption Spectra
Author: S. Gallerani, R. Salvaterra, A. Ferrara, T. Roy Choudhury
Comments: 5 pages, 3 figures, submitted to MNRAS
We propose a novel method to study cosmic reionization using absorption line spectra of high-redshift Gamma Ray Burst (GRB) afterglows. We show that the time evolution and the statistics of the dark portions (gaps) in the observed spectra taken during the first days after the GRB explosion represent exquisite tools to discriminate among different reionization models. We then compute the probability to find the largest gap in a given width range for burst afterglows of observed J-band flux F_J, and redshift z_GRB. We show that different reionization scenarios populate the (F_J,z_GRB) plane in a very different way, allowing to distinguish among different reionization histories. We provide here useful plots that allow a very simple and direct comparison between observations and model results. Finally, we apply our methods to GRB050904 detected at z=6.29 whose largest gap is found to be almost equal to 65 angstrom. We show that the observation of this burst provides strong indications of a highly ionized intergalactic medium at z=6, with an estimated mean neutral hydrogen fraction x_HI=7.0 \pm 4.0 10^-4 along the line of sight towards GRB050904. |
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arXiv:0710.1646 [ps, pdf, other] :
Title: AMIGA, Auger Muons and Infill for the Ground Array
Authors: A. Etchegoyen [Pierre Auger Collaboration]
Comments: 4 pages, 3 figures, ICRC 2007 #1307
The Pierre Auger Observatory is planned to be upgraded so that the energy spectrum of cosmic rays can be studied down to 0.1 EeV and the muon component of showers can be determined. The former will lead to a spectrum measured by one technique from 0.1 EeV to beyond 100 EeV while the latter will aid identification of the primary particles. These enhancements consist of three high elevation telescopes (HEAT) and an infilled area having both surface detectors and underground muon counters (AMIGA). The surface array of the Auger Observatory will be enhanced over a 23.5 km2 area by 85 detector pairs laid out as a graded array of water-Cherenkov detectors and 30 m2 buried muon scintillator counters. The spacings in the array will be 433 and 750 m. The muon detectors will comprise highly segmented scintillators with optical fibres ending on multi-anode phototubes. The AMIGA complex will be centred 6.0 km away from the fluorescence detector installation at Coihueco and will be overlooked by the HEAT telescopes. We describe the design features of the AMIGA enhancement. |
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arXiv:0710.1767 [ps, pdf, other] :
Title: Primary particle acceleration above 100 TeV in the shell-type Supernova Remnant RX J1713.7--3946 with deep H.E.S.S. observations
Authors: D. Berge et al. [H.E.S.S. Collaboration]
Comments: 4 pages, 3 figures, proceedings of the 30th ICRC, Merida, Mexico, 2007
The shell-type supernova remnant RX J1713.7--3946 was observed during three years with the H.E.S.S. Cherenkov telescope system. The first observation campaign in 2003 yielded the first-ever resolved TeV gamma-ray image. Follow-up observations in 2004 and 2005 revealed the very-high-energy gamma-ray morphology with unprecedented precision and enabled spatially resolved spectral studies. Combining the data of three years, we obtain significantly increased statistics and energy coverage of the gamma-ray spectrum as compared to earlier H.E.S.S. results. We present the analysis of the data of different years separately for comparison and demonstrate that the telescope system operates stably over the course of three years. When combining the data sets, a gamma-ray image is obtained with a superb angular resolution of 0.06 degrees. The combined spectrum extends over three orders of magnitude, with significant gamma-ray emission approaching 100 TeV. For realistic scenarios of very-high-energy gamma-ray production, the measured gamma-ray energies imply efficient particle acceleration of primary particles, electrons or protons, to energies exceeding 100 TeV in the shell of RX J1713.7--3946. |
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arXiv:0710.1856 [ps, pdf, other] :
Title: Impact of Dark Matter Annihilation on the High-Redshift Intergalactic Medium
Authors: Leonid Chuzhoy
Comments: 4 pages, 6 figures
We reexamine the impact of dark matter (DM) annihilation on the intergalactic medium, taking into account the clumping of DM particles. We find that if the DM annihilation rate is close to the upper limit inferred from the WMAP observations, sigma v /m_X<~10^-25 cm^-3 s^-1 GeV^-1, where sigma is the annihilation cross-section, v is the relative velocity and m_X is the mass of the colliding particles, then DM annihilation can make a major contribution (tau_e>~0.05) to the reionization of the Universe. Further, if the annihilation rate is above ~10^-28 cm^-3 s^-1 GeV^-1, it can significantly raise the gas temperature prior to reionization, thus leaving a potentially detectable imprint on the cosmological 21-cm signal. |
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arXiv:0710.2246 [ps, pdf, other] :
Title: Probing the Slope of Cluster Mass Profile with Gravitational Rings: Application to Abell 1689
Authors: H. Tu, M. Limousin, B. Fort, C. G. Shu, J. F. Sygnet, E. Jullo, J. -P. Kneib, J. Richard
Comments: Submitted to MNRAS. Article with full resolution figures available at this http URL
The strong lensing modelling of gravitational ``rings'' formed around massive galaxies has been shown to be sensitive to the amplitude of the external shear produced by nearby mass condensations. In current wide field surveys, it is now possible to find out a large number of rings, typically 10 gravitational rings per square degree. We propose here, to systematically study gravitational rings around galaxy clusters to probe the cluster mass profile beyond the cluster strong lensing regions. For cluster of galaxies with multiple arc systems, we show that rings found at various distances from the cluster centre can improve the modelling by constraining the slope of the cluster mass profile. We outline the principle of the method with simple numerical simulations and we apply it to 3 rings discovered recently in Abell~1689. In particular, the lens modelling of the 3 ring confirms the cluster is bimodal, and favors a slope of the mass profile steeper than isothermal at a cluster radius $\sim 300 \kpc/h$. These results are compared with previous lens modelling of Abell~1689 including weak lensing analysis. Because of the complexity of the mass distribution in Abell~1689, we argue that in order to accurately measure the cluster mass profile with the ring method, it would be better to detect and to study more simple and relaxed clusters with rings. |
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arXiv:0710.2252 [ps, pdf, other] :
Title: The Spectrum of 1ES0229 + 200 and the Cosmic Infrared Background
Authors: F.W. Stecker, S.T. Scully
Comments: 3 pages, 1 figure, submitted to Astron. & Astrophys
We examine the effect of gamma-ray absorption by the extragalactic infrared radiation on intrinsic spectra predicted for 1ES0229+200 and compare our results with the observational data. We find agreement with our previous results on the shape of the IR spectral energy distribution (SED), contrary to the recent assertion of the HESS group. Our analysis indicates that 1ES0229+200 has a very hard intrinsic spectrum with a spectral index between 1.1 +/- 0.3 and 1.5 +/- 0.3 in the energy range between ~0.5 TeV and ~15 TeV. Under the assumptions that (1) the SED models of Stecker, Malkan & Scully (2006) are reasonable as derived from numerous detailed IR observations, and (2) spectral indexes in the range 1 < \Gamma < 1.5 have been shown to be obtainable from relativistic shock acceleration under the astrophysical conditions extant in blazar flares (Stecker, Baring & Summerlin 2007), the fits to the observations of 1ES0229+200 using our previous IR SEDs are consistent with both the IR and gamma-ray observations. Our analysis presents evidence indicating that the energy spectrum of relativistic particles in 1ES0229+200 is produced by relativistic shock acceleration, producing an intrinsic gamma-ray spectrum with index 1 < \Gamma < 1.5 and with no evidence of a peak in the SED up to energies ~15 TeV. |
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