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[en] The entanglement and Renyi entropies for spherical entangling surfaces in CFTs with gravity duals can be explicitly calculated by mapping these entropies first to the thermal entropy on hyperbolic space and then, using the AdS/CFT correspondence, to the Wald entropy of topological black holes. Here we extend this idea by taking into account corrections to the Wald entropy. Using the method based on horizon symmetries and the asymptotic Cardy formula, we calculate corrections to the Wald entropy and find that these corrections are proportional to the logarithm of the area of the horizon. With the corrected expression for the entropy of the black hole, we then find corrections to the Renyi entropies. We calculate these corrections for both Einstein and Gauss-Bonnet gravity duals. Corrections with logarithmic dependence on the area of the entangling surface naturally occur at the order GD0. The entropic c-function and the inequalities of the Renyi entropy are also satisfied even with the correction terms. (orig.)
[en] We study solutions for the Klein-Gordon equation with vector and scalar potentials of the Coulomb types under the influence of noninertial effects in the cosmic string spacetime. We also investigate a quantum particle described by the Klein-Gordon oscillator in the background spacetime generated by a cosmic string. An important result obtained is that the noninertial effects restrict the physical region of the spacetime where the particle can be placed. In addition, we show that these potentials can form bound states for the Klein-Gordon equation in this kind of background. (orig.)
[en] We highlight some subtleties that affect naive implementations of quadrupolar and octupolar gravitational waveforms from numerically-integrated trajectories of three-body systems. Some of those subtleties arise from the requirement that the source be contained in its ‘coordinate near zone’ when applying the standard PN formulae for gravitational-wave emission, and from the need to use the non-linear Einstein equations to correctly derive the quadrupole emission formula. We show that some of these subtleties were occasionally overlooked in the literature, with consequences for published results. We also provide prescriptions that lead to correct and robust predictions for the waveforms computed from numerically-integrated orbits. (paper)
[en] Any inflationary model predicts the production of a stochastic gravitational-wave background. Such a signal includes unique information about the primordial mechanism that generate it, then representing a promising way of probing the inflationary physics. In this direction, upcoming and future experiments of direct gravitational-wave detection at small scales is expected to play a relevant role, providing new constraints on the features of the inflationary gravitational waves
[en] In September 2015 the Advanced LIGO detectors inaugurated the era of gravitational-wave astrophysics with the observation of GW150914. In this proceeding, I will describe the upgrade that made the detection possible, review the binary black hole observations of the first a LIGO observing run, and discuss plans for the future.
[en] Gamma-Ray Bursts are center stage in the new era of multi messenger astronomy, as their nature is probed through photons, gravitational waves (GW), neutrinos and cosmic rays. Discovered thanks to their powerful multiwavelength electromagnetic signal, they have been linked to the explosion of very massive stars ('long GRBs'), or to the coalescence of compact objects ('short GRBs')which also produce a GW signal. GRBs are also believed to be efficient particle accelerators, as required by the observation of high-energy photons up to ∼ 100GeV. Therefore, quite naturally, they have been proposed as possible sources of the mysterious ultra-high-energy cosmic rays (UHECRs), with energies above 1018 eV. However, some of the current models that simultaneously produce high electromagnetic fluxes and high-energy cosmic rays necessarily produce neutrinos as well, with a flux which appears to violate the limits recently set by the Ice Cube detector. I will review the observational features of GRBs as multi-messenger sources, as well as their link to theoretical models.
[en] We present a new simulation framework, based on the python programming language and specifically developed for X-ray polarimetric applications, called XIMPOL. Starting from an arbitrary source model (including morphological, temporal, spectral and polarimetric information), XIMPOL uses the response functions of the detector under study to produce fast and realistic observation simulations. A Chandra-to-XIMPOL converter is also available within the framework, designed to convert a real Chandra observation into a XIMPOL simulation. The generated output files can be directly fed into the standard visualization and analysis tools, including XSPEC, which make XIMPOL a useful tool not only for simulating observations of astronomical sources, but also to develop and test end-to-end analysis chains.
[en] Cosmic rays have been discovered a century ago, however, their sources remain unidentified. It is believed that the same environments that accelerate cosmic rays also produce neutrinos by hadronic interactions. Recently, the IceCube Neutrino Observatory has discovered a flux of high-energy astrophysical neutrinos, and a joint analysis with the Pierre-Auger Observatory and the Telescope Array found hints for a possible directional correlation of neutrino events and cosmic-ray events. First studies for a follow-up analysis including additional data are presented.
[en] The cosmological principle assumes that the universe is homogeneous and isotropic on cosmic scales. There exist many works testing the cosmic homogeneity and/or the cosmic isotropy of the universe in the literature. In fact, some observational hints of the cosmic anisotropy have been claimed. However, we note that the paucity of the data considered in the literature might be responsible for the ''found'' cosmic anisotropy. So, it might disappear in a large enough sample. Very recently, the Pantheon sample consisting of 1048 type Ia supernovae (SNIa) has been released, which is the largest spectroscopically confirmed SNIa sample to date. In the present work, we test the cosmic anisotropy in the Pantheon SNIa sample by using three methods, and hence the results from different methods can be cross-checked. All the results obtained by using the hemisphere comparison (HC) method, the dipole fitting (DF) method and HEALPix suggest that no evidence for the cosmic anisotropy is found in the Pantheon SNIa sample. (orig.)
[en] Shear peak statistics has gained a lot of attention recently as a practical alternative to the two-point statistics for constraining cosmological parameters. We perform a shear peak statistics analysis of the Dark Energy Survey (DES) Science Verification (SV) data, using weak gravitational lensing measurements from a 139 deg"2 field. We measure the abundance of peaks identified in aperture mass maps, as a function of their signal-to-noise ratio, in the signal-to-noise range 0 < S/N < 4 . To predict the peak counts as a function of cosmological parameters, we use a suite of N-body simulations spanning 158 models with varying Ωm and σ8, fixing w = –1, Ωb = 0.04, h = 0.7 and ns = 1, to which we have applied the DES SV mask and redshift distribution. In our fiducial analysis we measure σ8(Ωm/0.3)"0"."6 = 0.77 ± 0.07, after marginalizing over the shear multiplicative bias and the error on the mean redshift of the galaxy sample. We introduce models of intrinsic alignments, blending and source contamination by cluster members. These models indicate that peaks with S/N > 4 would require significant corrections, which is why we do not include them in our analysis. We compare our results to the cosmological constraints from the two-point analysis on the SV field and find them to be in good agreement in both the central value and its uncertainty. Lastly, we discuss prospects for future peak statistics analysis with upcoming DES data.