8231444
Hawking Radiation from Spherically Symmetrical Gravitational Collapse to an Extremal R-N Black Hole for a Charged Scalar Field*
Si-Jie Gao has recently investigated Hawking radiation from spherically symmetrical gravitational collapse to an extremal R-N black hole for a real scalar field. Especially he estimated the upper bound for the expected number of particles in any wave packet belonging to H-out spontaneously produced from the state \0>(in), which confirms the traditional belief that extremal black holes do not radiate particles. Making some modifications, we demonstrate that the analysis can go through for a charged scalar field.
11176637
Quasinormal modes for Weyl neutrino field in RN black holes
We employ the WKB approximation up to the third order to determine the low-lying quasinormal modes for the Weyl neutrino field in RN black holes, which are the most relevant to the evolution of the field around a black hole in the intermediate stage. It is shown that the quasinormal mode frequencies for the Weyl neutrino field in RN black holes are different from those in Schwarzschild black holes owing to the charge-induced additional gravitation, and the variations of the quasinormal mode frequencies for the Weyl neutrino field are similar to those for integral spin fields in RN black holes.
118380186
Numerical evolution of multiple black holes with accurate initial data
We present numerical evolutions of three equal-mass black holes using the moving puncture approach. We calculate puncture initial data for three black holes solving the constraint equations by means of a high-order multigrid elliptic solver. Using these initial data, we show the results for three black hole evolutions with sixth-order waveform convergence. We compare results obtained with the BAM and AMSS- N C KU codes with previous results. The approximate analytic solution to the Hamiltonian constraint used in previous simulations of three black holes leads to different dynamics and waveforms. We present some numerical experiments showing the evolution of four black holes and the resulting gravitational waveform.
122607999
From binary black hole simulation to triple black hole simulation
Black hole systems are among the most promising sources for a gravitational wave detection project. Now, China is planning to construct a space-based laser interferometric detector as a follow-on mission of LISA in the near future. Aiming to provide some theoretical support to this detection project on the numerical relativity side, we focus on black hole systems simulation in this work. Considering the globular galaxy, multiple black hole systems also likely to exist in our universe and play a role as a source for the gravitational wave detector we are considering. We will give a progress report in this paper on our black hole system simulation. More specifically, we will present triple black hole simulation together with binary black hole simulation. On triple black hole simulations, one novel perturbational method is proposed.
119209594
Constructing EOB dynamics with numerical energy flux for intermediate-mass-ratio inspirals
A new scheme for computing dynamical evolutions and gravitational radiations for intermediatemass-ratio inspirals (IMRIs) based on an effective one-body (EOB) dynamics plus Teukolsky perturbation theory is built in this paper. In the EOB framework, the dynamics essentially affects the resulted gravitational waveform for binary compact star system. This dynamics includes two parts. One is the conservative part which comes from effective one-body reduction. The other part is the gravitational back reaction which contributes to the shrinking process of the inspiral of binary compact star system. Previous works used analytical waveform to construct this back reaction term. Since the analytical form is based on post-Newtonian expansion, the consistency of this term is always checked by numerical energy flux. Here we directly use numerical energy flux by solving the Teukolsky equation via the frequency-domain method to construct this back reaction term. And the conservative correction to the leading order terms in mass-ratio is included in the deformed-Kerr metric and the EOB Hamiltonian. We try to use this method to simulate not only quasi-circular adiabatic inspiral but also the nonadiabatic plunge phase. For several different spinning black holes, we demonstrate and compare the resulted dynamical evolutions and gravitational waveforms.
119188076
Reinvestigation of moving punctured black holes with a new code
We report on our code, in which the moving puncture method is applied and an adaptive/fixed mesh refinement is implemented, and on its preliminary performance on black hole simulations. Based on the Baumgarte-Sharpiro-Shibata-Nakamura (BSSN) formulation, up-to-date gauge conditions and the modifications of the formulation are also implemented and tested. In this work, we present our primary results about the simulation of a single static black hole, of a moving single black hole, and of the head-on collision of a binary black hole system. For the static punctured black hole simulations, different modifications of the BSSN formulation are applied. It is demonstrated that both the currently used sets of modifications lead to a stable evolution. For cases of a moving punctured black hole with or without spin, we search for viable gauge conditions and study the effect of spin on the black hole evolution. Our results confirm previous results obtained by other research groups. In addition, we find a new gauge condition, which has not yet been adopted by any other researchers, which can also give stable and accurate black hole evolution calculations. We examine the performance of the code for the head-on collision of a binary black hole system, andmore » the agreement of the gravitational waveform it produces with that obtained in other works. In order to understand qualitatively the influence of matter on the binary black hole collisions, we also investigate the same head-on collision scenarios but perturbed by a scalar field. The numerical simulations performed with this code not only give stable and accurate results that are consistent with the works by other numerical relativity groups, but also lead to the discovery of a new viable gauge condition, as well as clarify some ambiguities in the modification of the BSSN formulation. These results demonstrate that this code is reliable and ready to be used in the study of more realistic astrophysical scenarios and of numerical relativity.« less
117245675
Ultra High Energy nt Detection Using Air Shower Fluorescence/Cerenkov Light Detector
The possibility of using air shower fluorescence/Cerenkov light detectors for ντ detection has been explored. A detector of this type is proposed to be set in the shadow of Mt. Wheeler Peak in Nevada, USA. The ντ to shower conversion probability density is calculated over an energy range from 1 PeV to 10 EeV. The number of showers converted from ντ ’s are estimated according to several models of neutrino sources.
122890389
GMF model dependence of correlations between BL Lacs and ultra high energy cosmic rays
Some studies suggested that there exists a correlation between locations of BL Lacertae objects (BL Lacs) and arrival directions of ultra high energy cosmic rays (UHECRs). Especially by assuming the primary particles charged +1 and using a galactic magnetic field (GMF) model to calculate deflections of the UHECRs, the significance of correlation can be improved. A new GMF model is constructed by incorporating all progresses in the GMF measurements in recent years and use it to a thorough study of the deflections of the UHECRs measured by the AGASA experiment. Compared with other models, the GFM model dependence of the correlation between the LTHECRs and the selected BL Lacs is studied. It turns out that only specific one of those GMF models makes the correlation significant, even if the GMF models are not very different. The UHECR deflections are also different depending on which GMF model is used. It indicates that the significance of the correlation, suggested in those studies, is strongly depending on GMF models. Great improvement in statistics may help to suppress the sensitivity to GMF models. (C) 2007 Elsevier B.V. All rights reserved.
15235119
The correlations between BL Lacs and ultra-high-energy cosmic rays deflected by using different GMF models
Some studies suggested that a correlation between locations of BL Lacertae objects (BL Lacs) and the arrival directions of the ultrahigh energy cosmic rays (UHECRs) exists. Especially by assuming the primary particles charged +1 and using a galactic magnetic field (GMF) model to calculate the deflections of the UHECRs, the significance of correlation is improved. We construct a new GMF model by incorporating all progresses in the GMF measurements in recent years. Based on a thorough study of the deflections of the UHECRs measured by the AGASA experiment, we study the GFM model dependence of the correlation between the UHECRs and the selected BL Lacs using the new model together with others. It turns out that only specific one of those GMF models makes the correlation significant, even if neither GMF models themselves nor deflections of the UHECRs are not significantly different. It suggests that the significance of the correlation, calculated using a method suggested in those studies, is intensively depending on the GMF model. Great improvement in statistics may help to suppress the sensitivity to the GMF models.
129754741
Meteorological Effects on the Trigger Rate of Air Showers Observed with the Tibet Air Shower Array
26918473
Geometry and optics calibration for air fluorescence detectors using star light
Abstract The high resolution Fly’s Eye (HiRes) detector in Dugway, Utah, is an air fluorescence detector designed for the measurement of the energy and arrival direction of cosmic ray particles with energy E >10 18 eV. HiRes monitors the night sky for fluorescence light from air shower cascades induced by cosmic ray primaries. The light is collected by mirrors and projected onto arrays of photomultiplier tubes that provide an image of the air shower. HiRes is an astronomical instrument, and the accuracy of the mirror pointing and understanding of the optical properties of the mirror–camera units is crucial. We present a method to cross-check and monitor the mirror pointing by using star light. A star crossing the field of view of a photomultiplier tube causes a temporary increase in the total light detected by the tube. Using UV bright stars, we analyze the pointing accuracy of the HiRes 2 detector, and evaluate the shape of a point-like object as a function of distance to the mirror axis.